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Gunasekaran P, Hwang YS, Lee GH, Park J, Kim JG, La YK, Park NY, Kothandaraman R, Yim MS, Choi J, Kim HN, Park IY, Lee SJ, Kim MH, Cha-Molstad H, Shin SY, Ryu EK, Bang JK. Degradation of Polo-like Kinase 1 by the Novel Poly-Arginine N-Degron Pathway PROTAC Regulates Tumor Growth in Nonsmall Cell Lung Cancer. J Med Chem 2024; 67:3307-3320. [PMID: 38105611 DOI: 10.1021/acs.jmedchem.3c01493] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
Polo-like kinase 1 (PLK1), which is crucial in cell cycle regulation, is considered a promising anticancer drug target. Herein, we present the N-degron pathway-based proteolysis targeting chimera (PROTAC) for PLK1 degradation, targeting the Polo-box domain (PBD). We identified DD-2 as the most potent PROTAC that selectively induces PLK1 degradation in cancer cells, including HeLa and nonsmall cell lung cancer (NSCLC), through the N-degron pathway. DD-2 exhibited significant in vitro anticancer effects, inducing G2/M arrest and apoptosis in HeLa and NSCLC cell lines. DD-2 showed significant tumor growth inhibition in a xenograft mouse model using HeLa and NSCLC cell lines, highlighting its potential in cancer treatment. Furthermore, the combination of DD-2 with tyrosine kinase inhibitor (TKI), osimertinib, effectively suppressed tumor growth in double-mutated H1975 cell lines, emphasizing DD-2's potential in combination cancer therapies. Collectively, this study demonstrates the potential of the N-degron pathway, especially using DD-2, for targeted cancer therapies.
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Affiliation(s)
- Pethaiah Gunasekaran
- Division of Magnetic Resonance, Korea Basic Science Institute (KBSI), Ochang, Chungbuk 28119, Republic of Korea
- Dandicure Inc, Ochang, Chungbuk 28119, Republic of Korea
| | - Yeon Sil Hwang
- Division of Magnetic Resonance, Korea Basic Science Institute (KBSI), Ochang, Chungbuk 28119, Republic of Korea
- Dandicure Inc, Ochang, Chungbuk 28119, Republic of Korea
| | - Gong-Hyeon Lee
- Dandicure Inc, Ochang, Chungbuk 28119, Republic of Korea
| | - Jaehui Park
- College of Pharmacy, Chungbuk National University, Cheongju, Chungbuk 28160, Republic of Korea
| | - Jung Gi Kim
- Nucleic Acid Therapeutics Research Center, Korea Research Institute of Bioscience and Biotechnology, 30 Yeongudanji-ro, Ochang, Cheongwon, Chungbuk 28116, Republic of Korea
| | - Yeo Kyung La
- Division of Magnetic Resonance, Korea Basic Science Institute (KBSI), Ochang, Chungbuk 28119, Republic of Korea
| | - Nam Yeong Park
- Division of Magnetic Resonance, Korea Basic Science Institute (KBSI), Ochang, Chungbuk 28119, Republic of Korea
| | | | - Min Su Yim
- Division of Vaccine Development Coordination, Center for Vaccine Research, National Institute of Infectious Diseases, National Institute of Health, Korea Disease Control and Prevention Agency, Cheongju 28159, Republic of Korea
| | - Joonhyeok Choi
- Division of Magnetic Resonance, Korea Basic Science Institute (KBSI), Ochang, Chungbuk 28119, Republic of Korea
| | - Hak Nam Kim
- Division of Magnetic Resonance, Korea Basic Science Institute (KBSI), Ochang, Chungbuk 28119, Republic of Korea
| | - Il Yeong Park
- College of Pharmacy, Chungbuk National University, Cheongju, Chungbuk 28160, Republic of Korea
| | - Soo Jae Lee
- College of Pharmacy, Chungbuk National University, Cheongju, Chungbuk 28160, Republic of Korea
| | - Mi-Hyun Kim
- Department of Internal Medicine, Pusan National University School of Medicine and Biomedical Research Institute, Pusan National University Hospital, Busan 49241, Republic of Korea
| | - Hyunjoo Cha-Molstad
- Nucleic Acid Therapeutics Research Center, Korea Research Institute of Bioscience and Biotechnology, 30 Yeongudanji-ro, Ochang, Cheongwon, Chungbuk 28116, Republic of Korea
| | - Song Yub Shin
- Department of Cellular and Molecular Medicine, School of Medicine, Chosun University, Gwangju 61452, Republic of Korea
| | - Eun Kyoung Ryu
- Division of Magnetic Resonance, Korea Basic Science Institute (KBSI), Ochang, Chungbuk 28119, Republic of Korea
- Department of Bio-Analytical Science, University of Science & Technology, Daejeon 34113, Republic of Korea
| | - Jeong Kyu Bang
- Division of Magnetic Resonance, Korea Basic Science Institute (KBSI), Ochang, Chungbuk 28119, Republic of Korea
- Dandicure Inc, Ochang, Chungbuk 28119, Republic of Korea
- Department of Bio-Analytical Science, University of Science & Technology, Daejeon 34113, Republic of Korea
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Gunasekaran P, Lee GH, Hwang YS, Koo BC, Han EH, Bang G, La YK, Park S, Kim HN, Kim MH, Bang JK, Ryu EK. An investigation of Plk1 PBD inhibitor KBJK557 as a tumor growth suppressor in non-small cell lung cancer. J Anal Sci Technol 2022. [DOI: 10.1186/s40543-022-00345-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/09/2022] Open
Abstract
AbstractLung cancer is the second most commonly reported type of cancer worldwide. Approximately 80–85% of lung cancer occurrences are accounted by non-small cell lung cancer (NSCLC). Polo-like kinase-1 (Plk1) plays multiple roles in cell cycle progression and its overexpression is observed in majority of malignancies, including NSCLC. A combination of frontline drugs and inhibitors targeting the Plk kinase domain (KD) has been used to overcome drug resistance in NSCLC. Plk1 KD inhibitors are highly prone to cross-reactivity with similar kinases, eventually leading to undesirable side effects. Moreover, there have been no reports of Plk1 PBD inhibitors showing antitumorigenic effects on NSCLC cells or animal models so far. To address this issue herein, for the first time, our recently reported Plk1 PBD inhibitor KBJK557 was evaluated for the anticancer potential against NSCLC cells. KBJK557 displayed notable cytotoxic effects in A549, PC9, and H1975 cells. Mechanistic investigations revealed that KBJK557-treated cells underwent G2/M cell cycle arrest, triggering subsequent apoptosis. In vivo antitumorigenic activity in xenograft mice model demonstrates that KBJK557-treated mice showed a considerable decrease in tumor size, proving the significances of Plk1 in lung cancer. Collectively, this study demonstrates that KBJK557 can serve as a promising drug candidate for treating the lung cancer through Plk1 PBD inhibition.
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Jang JY, Lim S, Kim S, Lee MW, Kim YG, Sung C, Hwang YS. Development of a soft x-ray (SXR) array diagnostic system on versatile experiment spherical torus (VEST). Rev Sci Instrum 2022; 93:093506. [PMID: 36182494 DOI: 10.1063/5.0101883] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Accepted: 07/27/2022] [Indexed: 06/16/2023]
Abstract
A new soft x-ray (SXR) array diagnostic system has been developed on versatile experiment spherical torus (VEST) for measurements of 2D SXR emissivity profile and identification of poloidal mode structure. Through tomographic inversion techniques, 2D SXR emissivity profile can be acquired from the line-integrated SXR data, which enables the visualization of mode structure of plasma instability, such as the magnetohydrodynamics mode. The SXR array diagnostic system consists of two 20-channel arrays positioned at the middle and the top on the same poloidal plane for horizontal and vertical lines of sight, respectively. Each array of the diagnostic system uses absolute extreme ultraviolet photodiode array as the detector. To apply appropriate filters (up to four) for different energy regimes without breaking the vacuum, a filter wheel and its rotatable vacuum feed-through are installed behind the pinhole. SXR data are acquired with a digitizer at the sampling rate of up to 125 MHz. Finally, we discuss initial measurement data obtained from Ohmic plasma in VEST.
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Affiliation(s)
- Jae Young Jang
- Department of Energy Systems Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - Soobin Lim
- Department of Energy Systems Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - Seongcheol Kim
- Department of Energy Systems Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - M W Lee
- Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
| | - Young-Gi Kim
- Korea Research Institute of Standards and Science, Daejeon 34113, Republic of Korea
| | - C Sung
- Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
| | - Y S Hwang
- Department of Energy Systems Engineering, Seoul National University, Seoul 08826, Republic of Korea
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Kim JY, Choi J, Hwang YS, Chung KJ. High-magnetic-confinement mode in partially magnetized E×B plasmas. Phys Rev E 2022; 105:L053202. [PMID: 35706243 DOI: 10.1103/physreve.105.l053202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Accepted: 04/17/2022] [Indexed: 06/15/2023]
Abstract
The suppression of the gradient-drift driven instability and the transition to the high-magnetic-confinement mode are experimentally observed in a cylindrical partially magnetized E×B plasma using an additional biasable electrode installed at the radial edge. When a positive voltage is applied to the electrode, an electron-loss channel forms in its direction, breaking the spatially symmetric nonambipolar flow. Finally, in the steady state, the plasma density tends to peak in the plasma core, approaching plasma densities that are four times larger than those observed in the case where the instability is the strongest. A high-magnetic-confinement mode with a reduced edge-to-center density ratio of 0.16 is observed, which demonstrates that the saturation of magnetic confinement due to the gradient-drift driven instability can be prevented by an asymmetric nonambipolar flow.
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Affiliation(s)
- June Young Kim
- Department of Nuclear Engineering, Seoul National University, Seoul, Korea
| | - Jaeyoung Choi
- Department of Nuclear Engineering, Seoul National University, Seoul, Korea
| | - Y S Hwang
- Department of Nuclear Engineering, Seoul National University, Seoul, Korea
| | - Kyoung-Jae Chung
- Department of Nuclear Engineering, Seoul National University, Seoul, Korea
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Kim JY, Lee HC, Go G, Choi YH, Hwang YS, Chung KJ. Exploring the nonextensive thermodynamics of partially ionized gas in magnetic field. Phys Rev E 2021; 104:045202. [PMID: 34781524 DOI: 10.1103/physreve.104.045202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2021] [Accepted: 09/21/2021] [Indexed: 11/07/2022]
Abstract
Contrary to classical thermodynamics, which deals with systems in thermal equilibrium, partially ionized gases generally do not reach thermal equilibrium. Nonextensive statistical mechanics has helped extend classical thermodynamics to nonequilibrium ionized gas. However, the fundamental question on whether the statistics of non-Maxwellian electrons satisfy the laws of thermodynamics has not been resolved. Here, we verify the thermodynamic laws of reversible and adiabatic processes for a magnetically expanding ionized gas. Together with the experimental evidence of the non-Maxwellian electron distribution, the κ distribution, which measures the thermal equilibrium states, shows the Tsallis entropy to be nearly constant and the polytropic index to be close to adiabatic values along a divergent magnetic field. These results verify that the collisionless magnetic expansion of a nonequilibrium plasma is reversible and adiabatic, and an isentropic process is the origin of the high-energy tail of the energy distribution far downstream.
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Affiliation(s)
- June Young Kim
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - Hyo-Chang Lee
- Korea Research Institute of Standards and Science, Daejeon 34113, Republic of Korea.,Department of Electrical Engineering, Hanyang University, Seoul 04763, Republic of Korea
| | - Geunwoo Go
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - Yeong Hwan Choi
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - Y S Hwang
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - Kyoung-Jae Chung
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, Republic of Korea
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Ham S, Ryu J, Park S, Chung KJ, Ghim YC, Woo HJ, Hwang YS. Development of a filtered AXUV diode array for X-pinch soft x-ray spectra in the energy range of 1-10 keV. Rev Sci Instrum 2021; 92:053509. [PMID: 34243284 DOI: 10.1063/5.0034638] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Accepted: 04/12/2021] [Indexed: 06/13/2023]
Abstract
We develop a filtered absolute extreme ultraviolet (AXUV) diode array to measure the time evolution of the soft x-ray spectrum in the energy range of 1-10 keV. AXUV-HS5, the detector, has a fast rise time of 0.7 ns, a wide energy detection range, and high accessibility. We use Geant4 simulations to design an appropriate filter set for flat-and-sharp virtual channels (VCs), where a filter with no spectral edge removes large tails of the response curves. A Levenberg-Marquardt (LM) method, sensitive to the expected spectral function, is improved to reliably generate a continuous radiation spectrum, by utilizing spectral information from the least-squares (LS) method that reconstructs a discrete spectrum with low spectral resolution directly from the VCs. We test the filtered AXUV diode array on an X-pinch device with a peak current of 140 kA at Seoul National University; the array with ten channels is installed in a vacuum chamber. For a two-wire 40 μm stainless steel X-pinch, x-ray power, radiation temperature, and the reconstructed x-ray spectrum are obtained from the filtered AXUV diode array by the combined LS-LM method.
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Affiliation(s)
- Seunggi Ham
- Department of Energy Systems Engineering, Seoul National University, Seoul 08826, South Korea
| | - Jonghyeon Ryu
- Department of Energy Systems Engineering, Seoul National University, Seoul 08826, South Korea
| | - Sungbin Park
- Department of Energy Systems Engineering, Seoul National University, Seoul 08826, South Korea
| | - Kyoung-Jae Chung
- Department of Energy Systems Engineering, Seoul National University, Seoul 08826, South Korea
| | - Y-C Ghim
- Department of Nuclear and Quantum Engineering, KAIST, Daejeon 34141, South Korea
| | - H J Woo
- Agency for Defense Development, Daejeon 34186, South Korea
| | - Y S Hwang
- Department of Energy Systems Engineering, Seoul National University, Seoul 08826, South Korea
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Ryu J, Ham S, Lee J, Park J, Park S, Choi Y, Woo HJ, Lee K, Ghim YC, Hwang YS, Chung KJ. A modular X-pinch device for versatile X-pinch experiments at Seoul National University. Rev Sci Instrum 2021; 92:053533. [PMID: 34243305 DOI: 10.1063/5.0041306] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 03/31/2021] [Indexed: 06/13/2023]
Abstract
This paper describes an X-pinch device recently developed at Seoul National University (SNU). The SNU X-pinch device is designed and fabricated to accommodate various diagnostics as well as conduct versatile experiments. It is easy to change the capacitance of the pulse generator because the capacitor bank has a modular design without insulation oil or gas. This allows us to perform a variety of experiments with a wide capacitance range from 80 to 800 nF. The operating voltage of the SNU X-pinch device is controlled from 20 to 100 kV by adjusting the gas pressure inside a triggered spark-gap switch. Triggering of the spark-gap switch is synchronized with the operation of a pulsed laser to diagnose the X-pinch plasma at the proper time. A large vacuum chamber precisely machined from an aluminum mono-block is attached to the top of the pulse generator. It is designed to accommodate not only various X-pinch loads but also various diagnostic apparatus such as optical components. Initial experiments with the SNU X-pinch device have successfully generated x rays with wires of various materials and sizes. The device will be used not only to explore the dynamics of X-pinch plasmas but also as a test stand for diagnostics of high-energy-density plasmas.
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Affiliation(s)
- Jonghyeon Ryu
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - Seunggi Ham
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - Juhyeong Lee
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - JongYoon Park
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - Sungbin Park
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - YeongHwan Choi
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - H J Woo
- Agency for Defense Development, Daejeon 34186, Republic of Korea
| | - Kern Lee
- Agency for Defense Development, Daejeon 34186, Republic of Korea
| | - Y-C Ghim
- Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
| | - Y S Hwang
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - Kyoung-Jae Chung
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, Republic of Korea
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Jang JY, Ko WH, Li Y, von Hellermann M, Shi Y, Hwang YS. Development of an ultrafast charge exchange spectroscopy system on the KSTAR tokamak. Rev Sci Instrum 2021; 92:053525. [PMID: 34243333 DOI: 10.1063/5.0043824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 04/21/2021] [Indexed: 06/13/2023]
Abstract
An ultrafast charge exchange spectroscopy (UFCES) system has been designed for measuring fluctuations in ion temperature and toroidal rotation velocity. The UFCES on the KSTAR tokamak is a powerful tool for investigating plasma instabilities and long-wavelength turbulence related to ion temperature gradient and flow. The UFCES system is designed to measure the C VI line (n = 8 → 7, λ0 = 529.05 nm) from the charge exchange reaction between a deuterium-heating neutral beam and the intrinsic carbon impurity in KSTAR. The ion temperature and toroidal rotation velocity at two radial positions will be observed simultaneously with UFCES. The key difference between the UFCES system and conventional charge exchange spectrometers is the application of high-throughput collection optics, a high-efficiency transmission grating combined with prisms, and a high-speed detector. We use a comprehensive spectrum simulation code with input parameters of KSTAR's plasmas and a neutral beam injection system to estimate the performance of the designed UFCES system. The results simulated with the code show that the diagnostic achieves a turbulence-relevant time resolution of 10 µs with a high enough signal-to-noise ratio. Furthermore, a preliminary test is performed using a complementary metal-oxide semiconductor camera and Ne spectral lamp to confirm the linear dispersion and curvature radius.
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Affiliation(s)
- Jae Young Jang
- Department of Energy Systems Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - Won-Ha Ko
- Korea Institute of Fusion Energy, Daejeon 34133, Republic of Korea
| | - Yingying Li
- ENN Science and Technology Development Co., Ltd., Langfang 065001, China
| | - Manfred von Hellermann
- Diagnostic Team, ITER Organization, Route Vinon sur Verdon, St. Paul Lez Durance, 13067, France
| | - Yuejiang Shi
- ENN Science and Technology Development Co., Ltd., Langfang 065001, China
| | - Y S Hwang
- Department of Energy Systems Engineering, Seoul National University, Seoul 08826, Republic of Korea
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Yim MS, Hwang YS, Bang JK, Jung DW, Kim JM, Yi GR, Lee G, Ryu EK. Morphologically homogeneous, pH-responsive gold nanoparticles for non-invasive imaging of HeLa cancer. Nanomedicine 2021; 34:102394. [PMID: 33857687 DOI: 10.1016/j.nano.2021.102394] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Revised: 03/15/2021] [Accepted: 03/22/2021] [Indexed: 01/02/2023]
Abstract
Gold nanoparticles (AuNPs) have been widely used as nanocarriers in drug delivery to improve the efficiency of chemotherapy treatment and enhance early disease detection. The advantages of AuNPs include their excellent biocompatibility, easy modification and functionalization, facile synthesis, low toxicity, and controllable particle size. This study aimed to synthesize a conjugated citraconic anhydride link between morphologically homogeneous AuNPs and doxorubicin (DOX) (DOX-AuNP). The carrier was radiolabeled for tumor diagnosis using positron emission tomography (PET). The systemically designed DOX-AuNP was cleaved at the citraconic anhydride linker site under the mild acidic conditions of a cancer cell, thereby releasing DOX. Subsequently, the AuNPs aggregated via electrostatic attraction. HeLa cancer cells exhibited a high uptake of the radiolabeled DOX-AuNP. Moreover, PET tumor images were obtained using radiolabeled DOX-AuNP in cancer xenograft mouse models. Therefore, DOX-AuNP is expected to provide a valuable insight into the use of radioligands to detect tumors using PET.
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Affiliation(s)
- Min Su Yim
- Division of Bioconvergence Analysis, Korea Basic Science Institute, Cheongju, Republic of Korea
| | - Yeon Sil Hwang
- Division of Bioconvergence Analysis, Korea Basic Science Institute, Cheongju, Republic of Korea
| | - Jeong Kyu Bang
- Division of Bioconvergence Analysis, Korea Basic Science Institute, Cheongju, Republic of Korea; Bio-Analytical Science, University of Science and Technology, Daejeon, Republic of Korea
| | - Dae-Woong Jung
- Korea Basic Science Institute, Daejeon, Republic of Korea; Department of Chemical Engineering, Sungkyunkwan University, Suwon, Republic of Korea
| | - Jun Min Kim
- Korea Basic Science Institute, Daejeon, Republic of Korea; Department of Chemical Engineering, Sungkyunkwan University, Suwon, Republic of Korea
| | - Gi-Ra Yi
- Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea
| | - Gaehang Lee
- Korea Basic Science Institute, Daejeon, Republic of Korea.
| | - Eun Kyoung Ryu
- Division of Bioconvergence Analysis, Korea Basic Science Institute, Cheongju, Republic of Korea; Bio-Analytical Science, University of Science and Technology, Daejeon, Republic of Korea.
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Kim JH, Kim YG, Kim D, Lee JH, Hwang YS. Radial profile measurement with an improved 1 kHz Thomson scattering system on Versatile Experiment Spherical Torus. Rev Sci Instrum 2021; 92:043549. [PMID: 34243449 DOI: 10.1063/5.0043792] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 04/03/2021] [Indexed: 06/13/2023]
Abstract
A Thomson scattering (TS) system has been utilized to measure the electron temperature and density of the core region of Versatile Experiment Spherical Torus (VEST). Recently, the laser injection system is successfully upgraded adopting the burst laser with the repetition rate of 1 kHz and the energy of 2 J. Furthermore, improved collection optics with additional polychromators and a 32-channel fast digitizer are prepared to observe the fast time evolution of radial profiles. This improvement is essential to study fast phenomena such as internal reconnection event (IRE). We increase the TS signal and reduce the stray light by introducing new filters having better optical properties such as high optical density at 1064 nm, transmission, and reflectance. Moreover, the optimum reverse bias voltages are newly set to make the system operational independent of the background radiation. As a result, 1 kHz radial profiles of the core electron temperature and density are measured for the first time, showing characteristics of IREs in VEST.
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Affiliation(s)
- Jung-Hwa Kim
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - Young-Gi Kim
- United Kingdom Atomic Energy Authority, Culham Science Centre, Abingdon, Oxon OX14 3DB, United Kingdom
| | - Doyeon Kim
- Center for Relativistic Laser Science, Institute for Basic Science, Gwangju 61005, Republic of Korea
| | - Jong-Ha Lee
- Korea Institute of Fusion Energy, Daejeon 34133, Republic of Korea
| | - Y S Hwang
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, Republic of Korea
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11
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Choi S, Lee DG, Woo HJ, Hong SH, Ham S, Ryu J, Chung KJ, Hwang YS, Ghim YC. Data analysis scheme for correcting general misalignments of an optics configuration for a voltage measurement system based on the Pockels electro-optic effect. Rev Sci Instrum 2021; 92:043105. [PMID: 34243378 DOI: 10.1063/5.0040467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2020] [Accepted: 04/03/2021] [Indexed: 06/13/2023]
Abstract
Having a sub-ns response time and not requiring physical contacts to the measurement points, a voltage measurement system based on the Pockels electro-optic effect, referred to as a PE (Pockels effect)-based voltmeter, is widely used for pulsed high voltage devices such as accelerators and X-pinch systems. To correct for the misalignment of a Pockels cell and the transmittance ratio of a beam splitter, a polar-coordinate-based data analysis scheme has been proposed. This scheme also overcomes a limitation on the measurable range of a PE-based voltmeter without ambiguity and can measure the half-wave voltage of a Pockels cell. We present an improved polar-coordinate-based data analysis scheme using an ellipse fitting method, which can correct for misalignments of all the optics components of a PE-based voltmeter while keeping the advantages of the previous scheme. We show the results of the improved data analysis scheme for measuring a slowly modulated voltage up to approximately 5 kV in about 30 s and a pulsed high voltage up to 7 kV with a rise time of less than 20 ns.
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Affiliation(s)
- Seongmin Choi
- Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, South Korea
| | - Dong-Geun Lee
- Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, South Korea
| | - H J Woo
- Agency for Defense Development, Daejeon 34186, South Korea
| | - S H Hong
- Agency for Defense Development, Daejeon 34186, South Korea
| | - Seunggi Ham
- Department of Energy Systems Engineering, Seoul National University, Seoul 08826, South Korea
| | - Jonghyeon Ryu
- Department of Energy Systems Engineering, Seoul National University, Seoul 08826, South Korea
| | - Kyoung-Jae Chung
- Department of Energy Systems Engineering, Seoul National University, Seoul 08826, South Korea
| | - Y S Hwang
- Department of Energy Systems Engineering, Seoul National University, Seoul 08826, South Korea
| | - Y-C Ghim
- Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, South Korea
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12
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Choe K, Kim D, Chung KJ, Hwang YS. Improved gating device of time-of-flight ion mass analyzer for ion sources. Rev Sci Instrum 2019; 90:033305. [PMID: 30927787 DOI: 10.1063/1.5088576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Accepted: 03/06/2019] [Indexed: 06/09/2023]
Abstract
A gating device is a critical component in a time-of-flight (TOF) ion mass analyzer for identifying ion species extracted from ion sources according to their mass-to-charge ratio. It consists of several concentric ring electrodes to deflect as many ions as possible within a very short gate time, thus increasing the ion current collected in a Faraday cup. In this study, we further improve the ion collection efficiency of the gating device by minimizing potential distortion along the paths of ions, by modifying the structure of gate electrodes and applying a bipolar gate pulse on them. Using the improved gating device, we find that the ion beam current increased by nearly 50% compared to the conventional one without changing the noise level. The improved TOF system is well applied to identify the spectrum of ion species extracted from a cold cathode Penning ion source, depending on the operating conditions.
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Affiliation(s)
- Kyumin Choe
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, South Korea
| | - DongHwan Kim
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, South Korea
| | - Kyoung-Jae Chung
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, South Korea
| | - Y S Hwang
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, South Korea
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13
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Ham S, Britun N, Kim D, Kim Y, Oh SG, Hwang YS. Design of an imaging Fabry-Pérot interferometer for the VEST edge plasma temperature measurement. Rev Sci Instrum 2018; 89:10D108. [PMID: 30399804 DOI: 10.1063/1.5038927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 07/24/2018] [Indexed: 06/08/2023]
Abstract
A new technique for gas temperature determination in fusion plasmas based on time- and space-resolved imaging interferometry is presented. The proposed imaging interferometer includes a multi-channel optical fiber bundle, a pair of flat mirrors, collimating lenses, and a fast camera for registration of interferometry fringes. The technique is applied for ion temperature measurements in the Versatile Experiment Spherical Torus (VEST) tokamak located at the Seoul National University. The multi-channel operation regime of the interferometer is studied by simulations. The first experimental two-channel results obtained using the Hα emission line from the VEST plasma edge are presented and analyzed. The mentioned apparatus is suggested to be especially useful for the multi-point time-resolved characterization of the non-repetitive processes in low-temperature regions of fusion plasmas.
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Affiliation(s)
- Seunggi Ham
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, South Korea
| | - Nikolay Britun
- Chimie des Interactions Plasma Surface (CHIPS), CIRMAP, Université de Mons, 23 Place du Parc, B-7000 Mons, Belgium
| | - Doyeon Kim
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, South Korea
| | - Yoosung Kim
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, South Korea
| | - Soo-Ghee Oh
- Department of Physics, Ajou University, Suwon 16499, South Korea
| | - Y S Hwang
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, South Korea
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14
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Yang J, Kim Y, Jeong WI, Hwang YS. Simple and accurate method of diamagnetic flux measurement in Versatile Experimental Spherical Torus (VEST). Rev Sci Instrum 2018; 89:103508. [PMID: 30399825 DOI: 10.1063/1.5041517] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Accepted: 10/03/2018] [Indexed: 06/08/2023]
Abstract
Diamagnetic flux is measured accurately in the Versatile Experiment Spherical Torus by simply measuring the change in the toroidal field (TF) coil current without additional poloidal loops. Stray couplings mainly with the plasma current (since poloidal field coils are aligned well to the TF coils) are compensated for, resulting in the minimum measurable flux of ±0.2 mWb determined mainly by the finite sensitivity of the TF coil current sensor, implying that the accuracy of this simple method can be improved by measuring the TF coil current change with a higher sensitivity. The poloidal beta is derived from the measured diamagnetic flux with the consideration of the low aspect ratio geometry. The poloidal beta and the plasma stored energy derived from the measurement are in good agreement with those from the equilibrium reconstruction, and the energy confinement time derived from the measurement is consistent with the L mode scaling.
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Affiliation(s)
- J Yang
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Y Kim
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - W I Jeong
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Y S Hwang
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
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15
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Jo J, Cheon M, Kim J, Lim S, Isobe M, Ogawa K, Nishitani T, Park S, Murata I, Chung KJ, Hwang YS. Initial operation results of NE213 scintillation detector for time-resolved measurements on triton burnup in KSTAR. Rev Sci Instrum 2018; 89:10I118. [PMID: 30399758 DOI: 10.1063/1.5039308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 07/29/2018] [Indexed: 06/08/2023]
Abstract
In time-resolved measurement for triton burnup in Korea Superconducting Tokamak Advanced Research (KSTAR) deuterium plasmas, an NE213 liquid scintillation detector was installed and operated during the 2017 KSTAR campaign. The detector is composed of an NE213 scintillator (50 mm in diameter and 10 mm in thickness) and a photomultiplier tube (PMT). The PMT anode signal was processed under a data acquisition system which contains a field programmable gate array circuit and pulse processing software that is capable of discriminating gamma-ray and neutron pulse signals. In order to determine an appropriate threshold level for the 14 MeV neutron signal resulting from triton burnup, the NE213 scintillation detector was calibrated by using d-d and d-t neutron generators at the National Fusion Research Institute and Intense 14 MeV Neutron Source Facility, OKTAVIAN, Osaka University, Japan. The detector was installed on KSTAR with a 10 mm thick soft-iron stray magnetic field shield and a radiation shield which consists of 100 mm thick lead blocks and 200 mm thick borated polyethylene blocks. A discrimination range for d-t neutron was determined based on test results from neutron generators and KSTAR. Data points selected from the discrimination range were consistent with the classical triton confinement characteristics. In conclusion, under condition of an input counting rate of 1.9 × 105 counts per second (CPS), the detector is able to measure triton burnup signals up to 500 CPS for various plasma parameters.
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Affiliation(s)
- Jungmin Jo
- Department of Energy Systems Engineering, Seoul National University, Seoul 151-744, South Korea
| | - MunSeong Cheon
- National Fusion Research Institute, Daejeon, South Korea
| | - Junghee Kim
- National Fusion Research Institute, Daejeon, South Korea
| | - Soobin Lim
- Department of Energy Systems Engineering, Seoul National University, Seoul 151-744, South Korea
| | - M Isobe
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki-shi, Japan
| | - K Ogawa
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki-shi, Japan
| | - T Nishitani
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki-shi, Japan
| | - Seugil Park
- National Fusion Research Institute, Daejeon, South Korea
| | - I Murata
- Division of Sustainable Energy and Environmental Engineering, Graduate School of Engineering, Osaka University, Osaka, Japan
| | - Kyoung-Jae Chung
- Department of Energy Systems Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Y S Hwang
- Department of Energy Systems Engineering, Seoul National University, Seoul 151-744, South Korea
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16
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Jo J, Cheon M, Kim J, An Y, Park S, Chung KJ, Hwang YS. Characterization of photo-multiplier tube as ex-vessel radiation detector in tokamak. Rev Sci Instrum 2017; 88:093503. [PMID: 28964183 DOI: 10.1063/1.5000857] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 08/18/2017] [Indexed: 06/07/2023]
Abstract
Feasibility of using conventional photo-multiplier tubes (PMTs) without a scintillator as an ex-vessel radiation detector in a tokamak environment is studied. Basic irradiation tests using standard gamma ray sources and a d-d neutron generator showed that the PMT is responding both to gamma photons and neutrons, possibly due to the direct generation of secondary electrons inside the PMT by the impingement of high energy photons. Because of the selective sensitivity of the PMT to hard x-ray and neutrons in ohmic and neutral beam injected plasmas, respectively, it is shown that the PMT with certain configuration can be utilized either to monitor the fluctuation in the fusion neutron generation rate or to study the behavior of runaway electrons in tokamaks.
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Affiliation(s)
- Jungmin Jo
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, South Korea
| | - MunSeong Cheon
- National Fusion Research Institute, Daejeon 34133, South Korea
| | - Junghee Kim
- National Fusion Research Institute, Daejeon 34133, South Korea
| | - YoungHwa An
- National Fusion Research Institute, Daejeon 34133, South Korea
| | - Seungil Park
- National Fusion Research Institute, Daejeon 34133, South Korea
| | - Kyoung-Jae Chung
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, South Korea
| | - Y S Hwang
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, South Korea
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17
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Jo J, Cheon M, Kim JY, Rhee T, Kim J, Shi YJ, Isobe M, Ogawa K, Chung KJ, Hwang YS. Triton burnup measurements in KSTAR using a neutron activation system. Rev Sci Instrum 2016; 87:11D828. [PMID: 27910448 DOI: 10.1063/1.4961273] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Measurements of the time-integrated triton burnup for deuterium plasma in Korea Superconducting Tokamak Advanced Research (KSTAR) have been performed following the simultaneous detection of the d-d and d-t neutrons. The d-d neutrons were measured using a 3He proportional counter, fission chamber, and activated indium sample, whereas the d-t neutrons were detected using activated silicon and copper samples. The triton burnup ratio from KSTAR discharges is found to be in the range 0.01%-0.50% depending on the plasma conditions. The measured burnup ratio is compared with the prompt loss fraction of tritons calculated with the Lorentz orbit code and the classical slowing-down time. The burnup ratio is found to increase as plasma current and classical slowing-down time increase.
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Affiliation(s)
- Jungmin Jo
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - MunSeong Cheon
- National Fusion Research Institute, Daejeon 34133, South Korea
| | - Jun Young Kim
- Korea University of Science and Technology, Daejeon 34133, South Korea
| | - T Rhee
- National Fusion Research Institute, Daejeon 34133, South Korea
| | - Junghee Kim
- National Fusion Research Institute, Daejeon 34133, South Korea
| | - Yue-Jiang Shi
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - M Isobe
- National Institute for Fusion Science, Toki-shi, Japan
| | - K Ogawa
- National Institute for Fusion Science, Toki-shi, Japan
| | - Kyoung-Jae Chung
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Y S Hwang
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
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18
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Kim Y, Shi YJ, Yang JH, Kim S, Kim YG, Dang JJ, Yang S, Jo J, Oh SG, Chung KJ, Hwang YS. Electron density profile measurements from hydrogen line intensity ratio method in Versatile Experiment Spherical Torus. Rev Sci Instrum 2016; 87:11E540. [PMID: 27910347 DOI: 10.1063/1.4960535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Electron density profiles of versatile experiment spherical torus plasmas are measured by using a hydrogen line intensity ratio method. A fast-frame visible camera with appropriate bandpass filters is used to detect images of Balmer line intensities. The unique optical system makes it possible to take images of Hα and Hβ radiation simultaneously, with only one camera. The frame rate is 1000 fps and the spatial resolution of the system is about 0.5 cm. One-dimensional local emissivity profiles have been obtained from the toroidal line of sight with viewing dumps. An initial result for the electron density profile is presented and is in reasonable agreement with values measured by a triple Langmuir probe.
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Affiliation(s)
- YooSung Kim
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Yue-Jiang Shi
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Jeong-Hun Yang
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - SeongCheol Kim
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Young-Gi Kim
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Jeong-Jeung Dang
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Seongmoo Yang
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Jungmin Jo
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Soo-Ghee Oh
- Division of Energy Systems Research, Ajou University, Suwon 442-749, South Korea
| | - Kyoung-Jae Chung
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Y S Hwang
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
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19
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Kim Y, Shi YJ, Yang JH, Kim S, Kim YG, Dang JJ, Yang S, Jo J, Oh SG, Chung KJ, Hwang YS. Publisher's Note: "Electron density profile measurements from hydrogen line intensity ratio method in Versatile Experiment Spherical Torus" [Rev. Sci. Instrum. 87, 11E540 (2016)]. Rev Sci Instrum 2016; 87:11F906. [PMID: 27910682 DOI: 10.1063/1.4964512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Affiliation(s)
- YooSung Kim
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Yue-Jiang Shi
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Jeong-Hun Yang
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - SeongCheol Kim
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Young-Gi Kim
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Jeong-Jeung Dang
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Seongmoo Yang
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Jungmin Jo
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Soo-Ghee Oh
- Division of Energy Systems Research, Ajou University, Suwon 442-749, South Korea
| | - Kyoung-Jae Chung
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Y S Hwang
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
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20
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Dang JJ, Chung KJ, Hwang YS. A simple spectroscopic method to determine the degree of dissociation in hydrogen plasmas with wide-range spectrometer. Rev Sci Instrum 2016; 87:053503. [PMID: 27250419 DOI: 10.1063/1.4948919] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
A new and simple method for determining the degree of dissociation in hydrogen plasmas is presented. In this method, wide-range spectrum covering from an atomic H-γ line (434.05 nm) to molecular Fulcher-α band (600-640 nm) is measured simultaneously by a wide-range miniature spectrometer. Since the wide-range spectrum measured by the miniature spectrometer is too broadened to resolve respective lines in the Fulcher-α band, a synthetic spectrum method is applied to improve the accuracy in the Q-branch of Fulcher-α band intensity measurement. In order to reduce the influence from other transitions or anomalous P- and R-branch of Fulcher-α spectrum, the Fulcher-α spectra of which vibrational states are higher than 1 (υ ≥ 1) are synthesized using the rotational temperature obtained by the 0-0 Fulcher-α spectrum. The degree of dissociation is determined from the intensity ratio between H-γ line and the synthesized Fulcher-α band spectrum. A comparative study carried out in a volume-produced negative hydrogen ion source shows that the degree of dissociation determined by this method agrees well with the measured values using a spectrometer with high spectral resolution. The present method is expected to be useful to characterize the plasma sources with molecular species since it provides important parameters for understanding neutral particle behaviors.
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Affiliation(s)
- Jeong-Jeung Dang
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, South Korea
| | - Kyoung-Jae Chung
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, South Korea
| | - Y S Hwang
- Department of Nuclear Engineering, Seoul National University, Seoul 08826, South Korea
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21
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Cho WH, Dang JJ, Kim JY, Chung KJ, Hwang YS. Optimization of plasma parameters with magnetic filter field and pressure to maximize H⁻ ion density in a negative hydrogen ion source. Rev Sci Instrum 2016; 87:02B136. [PMID: 26932018 DOI: 10.1063/1.4935230] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Transverse magnetic filter field as well as operating pressure is considered to be an important control knob to enhance negative hydrogen ion production via plasma parameter optimization in volume-produced negative hydrogen ion sources. Stronger filter field to reduce electron temperature sufficiently in the extraction region is favorable, but generally known to be limited by electron density drop near the extraction region. In this study, unexpected electron density increase instead of density drop is observed in front of the extraction region when the applied transverse filter field increases monotonically toward the extraction aperture. Measurements of plasma parameters with a movable Langmuir probe indicate that the increased electron density may be caused by low energy electron accumulation in the filter region decreasing perpendicular diffusion coefficients across the increasing filter field. Negative hydrogen ion populations are estimated from the measured profiles of electron temperatures and densities and confirmed to be consistent with laser photo-detachment measurements of the H(-) populations for various filter field strengths and pressures. Enhanced H(-) population near the extraction region due to the increased low energy electrons in the filter region may be utilized to increase negative hydrogen beam currents by moving the extraction position accordingly. This new finding can be used to design efficient H(-) sources with an optimal filtering system by maximizing high energy electron filtering while keeping low energy electrons available in the extraction region.
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Affiliation(s)
- Won-Hwi Cho
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Jeong-Jeung Dang
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - June Young Kim
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Kyoung-Jae Chung
- SNU Division of Graduate Education for Sustainabilization of Foundation Energy, Seoul National University, Seoul, South Korea
| | - Y S Hwang
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
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22
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Kim JY, Cho WH, Dang JJ, Chung KJ, Hwang YS. Electron cyclotron resonance heating by magnetic filter field in a negative hydrogen ion source. Rev Sci Instrum 2016; 87:02B117. [PMID: 26931999 DOI: 10.1063/1.4933090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The influence of magnetic filter field on plasma properties in the heating region has been investigated in a planar-type inductively coupled radio-frequency (RF) H(-) ion source. Besides filtering high energy electrons near the extraction region, the magnetic filter field is clearly observed to increase the electron temperature in the heating region at low pressure discharge. With increasing the operating pressure, enhancement of electron temperature in the heating region is reduced. The possibility of electron cyclotron resonance (ECR) heating in the heating region due to stray magnetic field generated by a filter magnet located at the extraction region is examined. It is found that ECR heating by RF wave field in the discharge region, where the strength of an axial magnetic field is approximately ∼4.8 G, can effectively heat low energy electrons. Depletion of low energy electrons in the electron energy distribution function measured at the heating region supports the occurrence of ECR heating. The present study suggests that addition of axial magnetic field as small as several G by an external electromagnet or permanent magnets can greatly increase the generation of highly ro-vibrationally excited hydrogen molecules in the heating region, thus improving the performance of H(-) ion generation in volume-produced negative hydrogen ion sources.
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Affiliation(s)
- June Young Kim
- Department of Nuclear Engineering, Seoul National University, Seoul 151-742, South Korea
| | - Won-Hwi Cho
- Department of Nuclear Engineering, Seoul National University, Seoul 151-742, South Korea
| | - Jeong-Jeung Dang
- Department of Nuclear Engineering, Seoul National University, Seoul 151-742, South Korea
| | - Kyoung-Jae Chung
- Department of Nuclear Engineering, Seoul National University, Seoul 151-742, South Korea
| | - Y S Hwang
- Department of Nuclear Engineering, Seoul National University, Seoul 151-742, South Korea
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23
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Yang J, Lee JW, Jung BK, Chung KJ, Hwang YS. Development of internal magnetic probe for current density profile measurement in Versatile Experiment Spherical Torus. Rev Sci Instrum 2014; 85:11D809. [PMID: 25430222 DOI: 10.1063/1.4886429] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
An internal magnetic probe using Hall sensors to measure a current density profile directly with perturbation of less than 10% to the plasma current is successfully operated for the first time in Versatile Experiment Spherical Torus (VEST). An appropriate Hall sensor is chosen to produce sufficient signals for VEST magnetic field while maintaining the small size of 10 mm in outer diameter. Temperature around the Hall sensor in a typical VEST plasma is regulated by blown air of 2 bars. First measurement of 60 kA VEST ohmic discharge shows a reasonable agreement with the total plasma current measured by Rogowski coil in VEST.
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Affiliation(s)
- J Yang
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - J W Lee
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - B K Jung
- SNU Division of Graduate Education for Sustainabilization of Foundation Energy, Seoul National University, Seoul 151-744, South Korea
| | - K J Chung
- SNU Division of Graduate Education for Sustainabilization of Foundation Energy, Seoul National University, Seoul 151-744, South Korea
| | - Y S Hwang
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
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24
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Park YS, Lee Y, Dang JJ, Chung KJ, Hwang YS. Operating conditions for the generation of stable anode spot plasma in front of a positively biased electrode. Rev Sci Instrum 2014; 85:02A508. [PMID: 24593431 DOI: 10.1063/1.4857215] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Stability of an anode spot plasma, which is an additional high density plasma generated in front of a positively biased electrode immersed in ambient plasma, is a critical issue for its utilization to various types of ion sources. In this study, operating conditions for the generation of stable anode spot plasmas are experimentally investigated. Diagnostics of the bias current flowing into the positively biased electrode and the properties of ambient plasma reveal that unstable nature of the anode spot is deeply associated with the reduction of double layer potential between the anode spot plasma and the ambient plasma. It is found that stability of the anode spot plasma can be improved with increasing the ionization rate in ambient plasma so as to compensate the loss of electrons across the double layer or with enlarging the area of the biased electrode to prevent electron accumulation inside the anode spot. The results obtained from the present study give the guideline for operating conditions of anode spot plasmas as an ion source with high brightness.
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Affiliation(s)
- Yeong-Shin Park
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Yuna Lee
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Jeong-Jeung Dang
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Kyoung-Jae Chung
- Center for Advance Research in Fusion Reactor Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Y S Hwang
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
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25
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Lee Y, Chung KJ, Park YS, Hwang YS. Investigation of helium ion production in constricted direct current plasma ion source with layered-glows. Rev Sci Instrum 2014; 85:02C105. [PMID: 24593635 DOI: 10.1063/1.4852298] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Generation of helium ions is experimentally investigated with a constricted direct current (DC) plasma ion source operated at layered-glow mode, in which electrons could be accelerated through multiple potential structures so as to generate helium ions including He(2+) by successive ionization collisions in front of an extraction aperture. The helium discharge is sustained with the formation of a couple of stable layers and the plasma ball with high density is created near the extraction aperture at the operational pressure down to 0.6 Torr with concave cathodes. The ion beam current extracted with an extraction voltage of 5 kV is observed to be proportional to the discharge current and inversely proportional to the operating pressure, showing high current density of 130 mA/cm(2) and power density of 0.52 mA/cm(2)/W. He(2+) ions, which were predicted to be able to exist due to multiple-layer potential structure, are not observed. Simple calculation on production of He(2+) ions inside the plasma ball reveals that reduced operating pressure and increased cathode area will help to generate He(2+) ions with the layered-glow DC discharge.
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Affiliation(s)
- Yuna Lee
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Kyoung-Jae Chung
- Center for Advance Research in Fusion Reactor Engineering, Seoul National University, Seoul 151-744, South Korea
| | | | - Y S Hwang
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
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26
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Jung BK, Dang JJ, An YH, Chung KJ, Hwang YS. Development of a novel radio-frequency negative hydrogen ion source in conically converging configuration. Rev Sci Instrum 2014; 85:02B112. [PMID: 24593552 DOI: 10.1063/1.4830424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Volume-produced negative ion source still requires enhancement of current density with lower input RF (radio-frequency) power in lower operating pressure for various applications. To confirm recent observation of efficient negative ion production with a short cylindrical chamber with smaller effective plasma size, the RF-driven transformer-coupled plasma H(-) ion source at Seoul National University is modified by adopting a newly designed quartz RF window to reduce the chamber length. Experiments with the reduced chamber length show a few times enhancement of H(-) ion beam current compared to that extracted from the previous chamber design, which is consistent with the measured H(-) ion population. Nevertheless, decrease in H(-) ion beam current observed in low pressure regime below ∼5 mTorr owing to insufficient filtering of high energy electrons in the extraction region needs to be resolved to address the usefulness of electron temperature control by the change of geometrical configuration of the discharge chamber. A new discharge chamber with conically converging configuration has been developed, in which the chamber diameter decreases as approaching to the extraction region away from the planar RF antenna such that stronger filter magnetic field can be utilized to prohibit high energy electrons from transporting to the extraction region. First experimental results for the H(-) ion beam extraction with this configuration show that higher magnetic filter field makes peak negative beam currents happen in lower operating pressure. However, overall decrease in H(-) ion beam current due to the change of chamber geometry still requires further study of geometrical effect on particle transport and optimization of magnetic field in this novel configuration.
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Affiliation(s)
- B K Jung
- Department of Nuclear Engineering, Seoul National University, Seoul 151-742, South Korea
| | - J J Dang
- Department of Nuclear Engineering, Seoul National University, Seoul 151-742, South Korea
| | - Y H An
- Department of Nuclear Engineering, Seoul National University, Seoul 151-742, South Korea
| | - K J Chung
- Center for Advance Research in Fusion Reactor Engineering, Seoul National University, Seoul 151-742, South Korea
| | - Y S Hwang
- Department of Nuclear Engineering, Seoul National University, Seoul 151-742, South Korea
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Choe K, Jung B, Chung KJ, Hwang YS. Development of a radio frequency ion source with multi-helicon plasma injectors for neutral beam injection system of Versatile Experiment Spherical Torus. Rev Sci Instrum 2014; 85:02B318. [PMID: 24593595 DOI: 10.1063/1.4852276] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Despite of high plasma density, helicon plasma has not yet been applied to a large area ion source such as a driver for neutral beam injection (NBI) system due to intrinsically poor plasma uniformity in the discharge region. In this study, a radio-frequency (RF) ion source with multi-helicon plasma injectors for high plasma density with good uniformity has been designed and constructed for the NBI system of Versatile Experiment Spherical Torus at Seoul National University. The ion source consists of a rectangular plasma expansion chamber (120 × 120 × 120 mm(3)), four helicon plasma injectors with annular permanent magnets and RF power system. Main feature of the source is downstream plasma confinement in the cusp magnetic field configuration which is generated by arranging polarities of permanent magnets in the helicon plasma injectors. In this paper, detailed design of the multi-helicon plasma injector and plasma characteristics of the ion source are presented.
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Affiliation(s)
- Kyumin Choe
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Bongki Jung
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Kyoung-Jae Chung
- Center for Advance Research in Fusion Reactor Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Y S Hwang
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
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Chung KJ, Jung BK, An Y, Dang JJ, Hwang YS. Effects of discharge chamber length on the negative ion generation in volume-produced negative hydrogen ion source. Rev Sci Instrum 2014; 85:02B119. [PMID: 24593559 DOI: 10.1063/1.4842316] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
In a volume-produced negative hydrogen ion source, control of electron temperature is essential due to its close correlation with the generation of highly vibrationally excited hydrogen molecules in the heating region as well as the generation of negative hydrogen ions by dissociative attachment in the extraction region. In this study, geometric effects of the cylindrical discharge chamber on negative ion generation via electron temperature changes are investigated in two discharge chambers with different lengths of 7.5 cm and 11 cm. Measurements with a radio-frequency-compensated Langmuir probe show that the electron temperature in the heating region is significantly increased by reducing the length of the discharge chamber due to the reduced effective plasma size. A particle balance model which is modified to consider the effects of discharge chamber configuration on the plasma parameters explains the variation of the electron temperature with the chamber geometry and gas pressure quite well. Accordingly, H(-) ion density measurement with laser photo-detachment in the short chamber shows a few times increase compared to the longer one at the same heating power depending on gas pressure. However, the increase drops significantly as operating gas pressure decreases, indicating increased electron temperatures in the extraction region degrade dissociative attachment significantly especially in the low pressure regime. It is concluded that the increase of electron temperature by adjusting the discharge chamber geometry is efficient to increase H(-) ion production as long as low electron temperatures are maintained in the extraction region in volume-produced negative hydrogen ion sources.
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Affiliation(s)
- Kyoung-Jae Chung
- Center for Advance Research in Fusion Reactor Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Bong-Ki Jung
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - YoungHwa An
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Jeong-Jeung Dang
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
| | - Y S Hwang
- Center for Advance Research in Fusion Reactor Engineering, Seoul National University, Seoul 151-744, South Korea
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Hwang YS, Schultz GW, Mulla MS. Structure-activity relationship of unsaturated fatty acids as mosquito ovipositional repellents. J Chem Ecol 2013; 10:145-51. [PMID: 24318236 DOI: 10.1007/bf00987651] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/1982] [Revised: 04/04/1983] [Indexed: 11/25/2022]
Abstract
Various straight-chain unsaturated fatty acids from C14 to C24 were evaluated for their ovipositional repellency against gravid females of the southern house mosquitoCulex quinquefasciatus Say, and the relationship between the structures of the fatty acids and their ovipositional repellency was determined. A double bond withZ configuration was prerequisite for an unsaturated fatty acid to be highly repellent;E isomers were less active or even inactive. No relationship was found between the repellency and the number of double bonds in the unsaturated fatty acids. In C18 monounsaturated fatty acids, (Z)-9 acid was more active than (Z)-11 and (Z)-6 acids, indicating that a double bond at the 9 position rendered an acid highly repellent. Among (Z)-9-alkenoic acids of different chain lengths, the most repellent was C18 acid which was also more active than (Z)-11-C20, (Z)-13-C22, and (Z)-15-C24 acids. Oleic[(Z)-9-octadecenoic]acid, which met all these criteria, was the most ovipositionally repellent among the unsaturated fatty acids tested.
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Affiliation(s)
- Y S Hwang
- Department of Entomology, University of California, 92521, Riverside, California
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Hwang YS, Tsai HY, Chen HY, Wei HW, Lin JH, Liu HL. SU-E-I-59: Patient-Based Average Glandular Dose Estimations in Taiwan. Med Phys 2013. [DOI: 10.1118/1.4814169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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31
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Jeong-hun Y, Chung KJ, An Y, Jung BK, Jo JG, Hwang YS. Design of a dual sensor probe array for internal field measurement in Versatile Experiment Spherical Torus. Rev Sci Instrum 2012; 83:10D721. [PMID: 23126895 DOI: 10.1063/1.4739224] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
A dual sensor probe array is designed and constructed for internal magnetic field measurement at Versatile Experiment Spherical Torus (VEST) at the Seoul National University. Simultaneous use of Hall sensors and chip inductors allows cross-calibration among the measurements and compensation for each other's weaknesses while their small sizes are expected to cause only mild plasma perturbations. Calibration of the dual sensor probe array, using a Helmholtz coil, shows good sensitivity for the magnetic field measurement of the VEST. Prior to Ohmic start-up, the magnetic field structure inside the vacuum chamber is measured by using the calibrated probe array. The dual sensor probe array is expected to be useful in analyzing the temporal magnetic field structure change during the magnetic reconnection and in reconstruction of the current profile during the discharge of the VEST device.
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Affiliation(s)
- Yang Jeong-hun
- Department of Nuclear Engineering, Seoul National University, South Korea
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Park YS, Lee Y, Kim YJ, Park MJ, Moon DW, Chung KJ, Hwang YS. Brightness enhancement of plasma ion source by utilizing anode spot for nano applications. Rev Sci Instrum 2012; 83:02B313. [PMID: 22380292 DOI: 10.1063/1.3672472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Anode spots are known as additional discharges on positively biased electrode immersed in plasmas. The anode spot plasma ion source (ASPIS) has been investigated as a high brightness ion source for nano applications such as focused ion beam (FIB) and nano medium energy ion scattering (nano-MEIS). The generation of anode spot is found to enhance brightness of ion beam since the anode spot increases plasma density near the extraction aperture. Brightness of the ASPIS has been estimated from measurement of emittance for total ion beam extracted through sub-mm aperture. The ASPIS is installed to the FIB system. Currents and diameters of the focused beams with∕without anode spot are measured and compared. As the anode spot is turned on, the enhancement of beam current is observed at fixed diameter of the focused ion beam. Consequently, the brightness of the focused ion beam is enhanced as well. For argon ion beam, the maximum normalized brightness of 12,300 A∕m(2) SrV is acquired. The ASPIS is applied to nano-MEIS as well. The ASPIS is found to increase the beam current density and the power efficiency of the ion source for nano-MEIS. From the present study, it is shown that the ASPIS can enhance the performance of devices for nano applications.
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Affiliation(s)
- Yeong-Shin Park
- Department of Nuclear Engineering, Seoul National University, Seoul 151-742, South Korea
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Lee Y, Park YS, Jo JG, Yang JJ, Hwang YS. Beam current enhancement of microwave plasma ion source utilizing double-port rectangular cavity resonator. Rev Sci Instrum 2012; 83:02B316. [PMID: 22380295 DOI: 10.1063/1.3673625] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Microwave plasma ion source with rectangular cavity resonator has been examined to improve ion beam current by changing wave launcher type from single-port to double-port. The cavity resonators with double-port and single-port wave launchers are designed to get resonance effect at TE-103 mode and TE-102 mode, respectively. In order to confirm that the cavities are acting as resonator, the microwave power for breakdown is measured and compared with the E-field strength estimated from the HFSS (High Frequency Structure Simulator) simulation. Langmuir probe measurements show that double-port cavity enhances central density of plasma ion source by modifying non-uniform plasma density profile of the single-port cavity. Correspondingly, beam current from the plasma ion source utilizing the double-port resonator is measured to be higher than that utilizing single-port resonator. Moreover, the enhancement in plasma density and ion beam current utilizing the double-port resonator is more pronounced as higher microwave power applied to the plasma ion source. Therefore, the rectangular cavity resonator utilizing the double-port is expected to enhance the performance of plasma ion source in terms of ion beam extraction.
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Affiliation(s)
- Yuna Lee
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
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An Y, Cho W, Chung KJ, Lee K, Jang S, Lee SG, Hwang YS. Wave frequency dependence of H- ion production and extraction in a transformer coupled plasma H- ion source at SNU. Rev Sci Instrum 2012; 83:02A727. [PMID: 22380236 DOI: 10.1063/1.3678659] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The effect of rf wave frequencies on the production of H(-) ion is investigated in a transformer coupled plasma H(-) ion source at Seoul National University. A Langmuir probe is installed to measure the plasma density and temperature, and these plasma parameters are correlated to the extracted H(-) beam currents at various frequencies. The Langmuir probe is also used to measure the density of H(-) ions at the ion source by generating photodetachment with an Nd:YAG laser. The extracted H(-) currents decrease to a minimum value until 13 MHz and then, increase as the driving frequency increases from 13 MHz while the relative H(-) population measured by photodetachment monotonically decreases as the driving rf frequency increases from 11 MHz to 15 MHz. A potential well formed at the extraction region at high frequencies of more than 13 MHz is considered responsible for the increased H(-) beam extraction even with a lower photodetachment signal. The variation in the driving rf frequency not only affects the density and temperature of the plasma but also modifies the plasma potential with the existence of a filtering magnetic field and consequently, influences the extracted H(-) current through the extraction as well as formation of H(-) ions.
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Affiliation(s)
- YoungHwa An
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
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35
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Jung BK, Chung KJ, Dang JJ, Hwang YS. Study on monatomic fraction improvement with alumina layer on metal electrode in hydrogen plasma ion source. Rev Sci Instrum 2012; 83:02B314. [PMID: 22380293 DOI: 10.1063/1.3673007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
A high monatomic beam fraction is an important factor in a hydrogen ion source to increase the application efficiency. The monatomic fraction of hydrogen plasmas with different plasma electrode materials is measured in a helicon plasma ion source, and aluminum shows the highest value compared to that with the other metals such as copper and molybdenum. Formation of an aluminum oxide layer on the aluminum electrode is determined by XPS analysis, and the alumina layer is verified as the high monatomic fraction. Both experiments and numerical simulations conclude that a low surface recombination coefficient of the alumina layer on the plasma electrode is one of the most important parameters for increasing the monatomic fraction in hydrogen plasma ion sources.
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Affiliation(s)
- Bong-Ki Jung
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea
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36
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Park YS, Lee Y, Chung KJ, Hwang YS. Characterization of plasma ion source utilizing anode spot with positively biased electrode for stable and high-current ion beam extraction. Rev Sci Instrum 2011; 82:123303. [PMID: 22225211 DOI: 10.1063/1.3664616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The operating conditions of a rf plasma ion source utilizing a positively biased electrode have been investigated to develop a stably operating, high-current ion source. Ion beam characteristics such as currents and energies are measured and compared with bias currents by varying the bias voltages on the electrode immersed in the ambient rf plasma. Current-voltage curves of the bias electrode and photographs confirm that a small and dense plasma, so-called anode spot, is formed near an extraction aperture and plays a key role to enhance the performance of the plasma ion source. The ion beam currents from the anode spot are observed to be maximized at the optimum bias voltage near the knee of the characteristic current-voltage curve of the anode spot. Increased potential barrier to obstruct beam extraction is the reason for the reduction of the ion beam current in spite of the increased bias current indicating the density of the anode spot. The optimum bias voltage is measured to be lower at higher operating pressure, which is favorable for stable operation without severe sputtering damage on the electrode. The ion beam current can be further enhanced by increasing the power for the ambient plasma without increasing the bias voltage. In the same manner, noble gases with higher atomic number as a feedstock gas are preferable for extracting higher beam current more stably. Therefore, performance of the plasma ion source with a positively biased electrode can be enhanced by controlling the operating conditions of the anode spot in various manners.
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Affiliation(s)
- Yeong-Shin Park
- Department of Nuclear Engineering, Seoul National University, Seoul 151-742, South Korea
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37
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Lim BC, Ki CS, Cho A, Hwang H, Kim KJ, Hwang YS, Kim YE, Yun JY, Jeon BS, Lim YH, Paek SH, Chae JH. Pantothenate kinase-associated neurodegeneration in Korea: recurrent R440P mutation in PANK2 and outcome of deep brain stimulation. Eur J Neurol 2011; 19:556-61. [PMID: 22103354 DOI: 10.1111/j.1468-1331.2011.03589.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND AND PURPOSE The purpose of this study was to evaluate the mutation status of PANK2 among Korean patients with pantothenate kinase-associated neurodegeneration (PKAN) and to document the outcome of pallidal deep brain stimulation (DBS). METHODS Direct sequencing and deletion/duplication analysis of PANK2 were conducted in 12 patients (11 unrelated) with PKAN, diagnosed on the basis of extrapyramidal dysfunction and the 'eye-of-the-tiger sign' on brain magnetic resonance imaging (MRI). Pallidal DBS was conducted in four patients, and the outcomes were measured using the Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS). RESULTS A PANK2 mutation was identified in both alleles in all patients. The most prevalent mutation was c.1319G>C (p.R440P) in 8/22 mutated alleles (36%). An intragenic deletion ranging from exons 2 to 4 was found in one allele (1/22, 4.5%) using deletion/duplication analysis. The outcome of pallidal DBS was favorable in two patients with atypical PKAN and moderate severity of dystonia. However, two patients with typical PKAN and relatively severe symptoms showed variable responses. CONCLUSIONS The c.1319G>C (p.R440P) mutation appears to be a founder genotype among Korean patients with PKAN. Furthermore, this study provides additional data for the recent international effort to evaluate the efficacy of pallidal DBS in the treatment of patients with PKAN.
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Affiliation(s)
- B C Lim
- Department of Pediatrics, Seoul National University College of Medicine, Seoul National University Children's Hospital, Seoul, Korea.
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Hahm C, Huh J, Hwang YS, Choi HJ, Yang HJ, Chung WS. A case of Plasmodium vivax with unusual enlarged gametocytes. Int J Lab Hematol 2010; 33:e1-2. [PMID: 21054814 DOI: 10.1111/j.1751-553x.2010.01272.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Juhn JW, Lee KC, Hwang YS, Domier CW, Luhmann NC, Leblanc BP, Mueller D, Gates DA, Kaita R. Fringe-jump corrected far infrared tangential interferometer/polarimeter for a real-time density feedback control system of NSTX plasmas. Rev Sci Instrum 2010; 81:10D540. [PMID: 21033892 DOI: 10.1063/1.3492381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The far infrared tangential interferometer/polarimeter (FIReTIP) of the National Spherical Torus Experiment (NSTX) has been set up to provide reliable electron density signals for a real-time density feedback control system. This work consists of two main parts: suppression of the fringe jumps that have been prohibiting the plasma density from use in the direct feedback to actuators and the conceptual design of a density feedback control system including the FIReTIP, control hardware, and software that takes advantage of the NSTX plasma control system (PCS). By investigating numerous shot data after July 2009 when the new electronics were installed, fringe jumps in the FIReTIP are well characterized, and consequently the suppressing algorithms are working properly as shown in comparisons with the Thomson scattering diagnostic. This approach is also applicable to signals taken at a 5 kHz sampling rate, which is a fundamental constraint imposed by the digitizers providing inputs to the PCS. The fringe jump correction algorithm, as well as safety and feedback modules, will be included as submodules either in the gas injection system category or a new category of density in the PCS.
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Affiliation(s)
- J-W Juhn
- Department of Nuclear Engineering, Seoul National University, Seoul 151-744, Korea.
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Hong IS, Park BS, Jang JH, Kwon HJ, Cho YS, Hwang YS. Design and construction of a compact microwave proton source for a proton linac. Rev Sci Instrum 2010; 81:02A314. [PMID: 20192335 DOI: 10.1063/1.3271170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A 100 MeV, 20 mA proton linear accelerator is being developed by the Proton Engineering Frontier Project at the Korea Atomic Energy Research Institute. 20 MeV acceleration system using radio frequency quadrupole and drift tube linac was already developed and has been tested. To operate this acceleration system with a long time, more reliable proton source is needed. A compact microwave proton source was proposed and has been designed and constructed as a prototype ion source for the 100 MeV proton linear accelerator. The design of microwave power injection system is based on the microwave proton injector at LANL and CEA. The wave power from a 2.45 GHz, 2 kW magnetron source is introduced into a compact plasma chamber with 7 cm diameter and 5 cm length through a standard tapered, double-ridged waveguide (WRD250) and a quartz window. The microwave power supply is installed on high voltage platform. Axial magnetic fields up to 1 kG can be provided with a water-cooled solenoid coil. A single-hole three electrode extraction system is designed for an extraction current up to 30 mA at a 50 kV extraction voltage. The design and initial operations of the proton source are presented.
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Affiliation(s)
- I S Hong
- Proton Engineering Frontier Project, Korea Atomic Energy Research Institute, Daejeon 305-353, Republic of Korea.
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An Y, Jung B, Hwang YS. Enhanced surface production in H- ion sources by introducing a negatively biased secondary electrode. Rev Sci Instrum 2010; 81:02A702. [PMID: 20192372 DOI: 10.1063/1.3273059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A transformer coupled plasma negative hydrogen ion source with an external rf antenna has been developed at SNU, which is capable of continuous operation with long lifetime. A positively biased plasma electrode (PE) has been successfully used for the optimization of H(-) extraction. With molybdenum-coated stainless steel PE, the enhancement of H(-) production at the electrode surface was observed at the bias voltage lower than the plasma potential. However, the low bias voltage is unfavorable to H(-) beam extraction since the negative ions are repelled. A second electrode is inserted in front of the PE to enhance H(-) production at the electrode surface without impeding beam extraction. By biasing the secondary electrode (SE) more negatively, H(-) production is clearly enhanced although the SE itself reduces H(-) beam currents because of suppressed electron transport in front of the PE. In this configuration enhancement of surface productions is most pronounced in tantalum electrode among various electrode materials.
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Affiliation(s)
- YoungHwa An
- Department of Nuclear Engineering, Seoul National University, Seoul 151-742, Republic of Korea
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Park YS, Hwang YS. Enhancement in ion beam current with layered-glows in a constricted dc plasma ion source. Rev Sci Instrum 2010; 81:02B309. [PMID: 20192432 DOI: 10.1063/1.3271252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
High current mode has been discovered and investigated in a constricted dc plasma ion source. As discharge currents exceed a certain threshold, voltage to sustain the constricted dc plasma suddenly falls down to almost half of the value. In this sense, constricted dc plasmas can be sustained at much higher current than in conventional mode operation at a fixed discharge voltage. Phenomenally, several discrete layered-glows are created between an anode glow and a cathode glow. The layers are thin and divided by dark spaces where charged particles can be accelerated. In this high current mode, ion beam current density is about 100 times higher than in conventional mode at the same voltage. It is noteworthy that lower gas pressure is desirable to sustain the layered-glow mode, which is also profitable for ion source in terms of differential pumping. Ion current density exceeds 300 mA/cm(2) at low discharge power of 175 W where ion density of plasma ball is estimated to be over 3.7x10(12) cm(-3).
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Affiliation(s)
- Yeong-Shin Park
- Department of Nuclear Engineering, Seoul National University, Seoul 151-742, Republic of Korea
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Tsai HY, Liu HL, Hwang YS, Chen CC. SU-FF-I-72: Evaluation and Comparison of Image Quality Figures for Digital Mammography. Med Phys 2009. [DOI: 10.1118/1.3181192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Hwang YS, Choi BH. Preface: Proceedings of the 12th International Conference on Ion Sources. Jeju, Korea, 26-31 August 2007. Rev Sci Instrum 2008; 79:02A101. [PMID: 18315090 DOI: 10.1063/1.2838248] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Affiliation(s)
- Y S Hwang
- Department of Nuclear Engineering, Seoul National University, Seoul, Korea.
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Chung KJ, Jung SW, Choe JM, Kim GH, Hwang YS. Self-consistent circuit model for plasma source ion implantation. Rev Sci Instrum 2008; 79:02C502. [PMID: 18315245 DOI: 10.1063/1.2816792] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
A self-consistent circuit model which can describe the dynamic behavior of the entire pulsed system for plasma source ion implantation has been developed and verified with experiments. In the circuit model, one-dimensional fluid equations of plasma sheath have been numerically solved with self-consistent boundary conditions from the external circuit model including the pulsed power system. Experiments have been conducted by applying negative, high-voltage pulses up to -10 kV with a capacitor-based pulse modulator to the planar target in contact with low-pressure argon plasma produced by radio-frequency power at 13.56 MHz. The measured pulse voltage and current waveforms as well as the sheath motion have shown good agreements with the simulation results.
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Affiliation(s)
- Kyoung-Jae Chung
- Department of Nuclear Engineering, Seoul National University, Gwanak-Gu, Seoul, Republic of Korea
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Abstract
OBJECTIVE To present our experience with vagus nerve stimulation (VNS) and to evaluate the long-term efficacy and safety of the procedure in pediatric intractable epilepsy. METHODS This study included sixteen patients, who were implanted with a vagus nerve stimulator and could be followed up for at least more than 12 months in two epilepsy centers. Data including seizure frequency, EEG, quality of life measures and adverse events were prospectively filed over a 5-year period. RESULTS VNS resulted in a > 50% reduction in seizure frequency in 50.0% (8/16) of children with 31.3% (5/16) of patients achieving a > 90% reduction. Additionally, enhancements in quality of life were as follows: memory in 50.0% (8/16), mood in 62.5% (10/16), behavior in 68.8% (11/16), alertness in 68.8% (11/16), achievement in 37.5% (6/16), and verbal skills in 43.8% (7/16) of the patients. Adverse events included hoarseness in two patients, dyspnea during sleep in two patients, and sialorrhea in one patient. However, these events were tolerable or could be controlled by the adjustment of output currents. In one patient, wound revision was required. CONCLUSION Our data supports the role of VNS as an alternative therapy for pediatric intractable epilepsy.
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Affiliation(s)
- H C Kang
- Department of Pediatrics, Epilepsy Center, Inje University College of Medicine, Sanggye Paik Hospital, Korea
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Cheon MS, Juhn JW, Hwang YS. Design of Stark-tuned far-infrared laser with circular hollow waveguide. Appl Opt 2006; 45:7131-6. [PMID: 16946793 DOI: 10.1364/ao.45.007131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
A novel design of a Stark-tuned far-infrared laser using a circular hollow dielectric waveguide is proposed, and its characteristics are studied. Supplementary electrodes are inserted inside the circular hollow dielectric tube to suppress charge accumulation while keeping field uniformity. In what is believed to be a new design, the mode property is found to be improved, and the angular dependency of the attenuation loss according to the beam polarization is estimated to be much smaller than that of the conventional rectangular hybrid waveguide design. In this new design, DeltaM=0 far-infrared (FIR) transition as well as DeltaM=+/-1 transition can be observed, and the power enhancement for the DeltaM=0 FIR transition is expected.
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Affiliation(s)
- M S Cheon
- Department of Nuclear Engineering, Seoul National University, Korea.
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Park SI, Oh JH, Hwang YS, Kim SJ, Chang JW. Electrical stimulation of the anterior cingulate cortex in a rat neuropathic pain model. Acta Neurochir Suppl 2006; 99:65-71. [PMID: 17370767 DOI: 10.1007/978-3-211-35205-2_13] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
BACKGROUND Electrical stimulation is currently employed to treat several neurological conditions, including pain and Parkinson's disease. It is one of several minimally invasive alternatives to drug treatments for painful conditions. A number of studies have shown that the anterior cingulate cortex (ACC) plays an important role in the processing of pain and pain modulation. The purpose of this study is to investigate these neuropathic pain-relieving effects by delivering electrical stimulation into the ACC of rat models. METHODS Following the approval of the AAALAC and the Guidelines and Regulations for Use and Care of Animals in Yonsei University, rats were subjected to surgery under pentobarbital anesthesia (50 mg/kg, i.p.) to produce neuropathic pain. Electrodes were bilaterally implanted into the ACC with a metal holder for the electrical stimulation. The effect of the electrical stimulation of the ACC on the rat neuropathic pain model was measured by the von Frey test. FINDINGS The effect of electrical stimulation of the ACC on neuropathic pain was shown during stimulation at 30, 40, 50, and 60 min, and at 10 min after stimulation. In the pain ACC stimulation group, the response of mechanical allodynia was significantly reduced during the time of ACC electrical stimulation. CONCLUSION The mechanical allodynia of the neuropathic pain could be modulated by ACC electrical stimulation.
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Affiliation(s)
- S I Park
- School of Electrical & Computing Engineering, Seoul National University, Seoul, Korea
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Abstract
Spectral analysis of heart rate variability provides a probe to assess the function of the sympathetic and parasympathetic nervous systems. Time-frequency analysis of heart rate variability is useful for investigating autonomic nervous function in patients with syncope or non-sustained ventricular tachycardia, or in anaesthesia, etc. In this paper, we developed an algorithm for continuous and online analysis of heart rate variability. The algorithm was simulated and evaluated in MATLAB, and implemented on the digital signal processor. The electrocardiogram signals from MIT/BIH arrhythmia database and one patient with syncope demonstrate the capability of the proposed method in the continuous and online analysis of heart rate variability.
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Affiliation(s)
- H L Chan
- Department of Electrical Engineering, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-Shan, Tao-Yuan, Taiwan.
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