1
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Tran M, Agostinetti P, Aiello G, Avramidis K, Baiocchi B, Barbisan M, Bobkov V, Briefi S, Bruschi A, Chavan R, Chelis I, Day C, Delogu R, Ell B, Fanale F, Fassina A, Fantz U, Faugel H, Figini L, Fiorucci D, Friedl R, Franke T, Gantenbein G, Garavaglia S, Granucci G, Hanke S, Hogge JP, Hopf C, Kostic A, Illy S, Ioannidis Z, Jelonnek J, Jin J, Latsas G, Louche F, Maquet V, Maggiora R, Messiaen A, Milanesio D, Mimo A, Moro A, Ochoukov R, Ongena J, Pagonakis I, Peponis D, Pimazzoni A, Ragona R, Rispoli N, Ruess T, Rzesnicki T, Scherer T, Spaeh P, Starnella G, Strauss D, Thumm M, Tierens W, Tigelis I, Tsironis C, Usoltceva M, Van Eester D, Veronese F, Vincenzi P, Wagner F, Wu C, Zeus F, Zhang W. Status and future development of Heating and Current Drive for the EU DEMO. Fusion Engineering and Design 2022. [DOI: 10.1016/j.fusengdes.2022.113159] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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2
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Di Siena A, Bilato R, Görler T, Navarro AB, Poli E, Bobkov V, Jarema D, Fable E, Angioni C, Kazakov YO, Ochoukov R, Schneider P, Weiland M, Jenko F. New High-Confinement Regime with Fast Ions in the Core of Fusion Plasmas. Phys Rev Lett 2021; 127:025002. [PMID: 34296928 DOI: 10.1103/physrevlett.127.025002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 04/15/2021] [Accepted: 06/07/2021] [Indexed: 06/13/2023]
Abstract
The key result of the present work is the theoretical prediction and observation of the formation of a new type of transport barrier in fusion plasmas, called F-ATB (fast ion-induced anomalous transport barrier). As demonstrated through state-of-the-art global electrostatic and electromagnetic simulations, the F-ATB is characterized by a full suppression of the turbulent transport-caused by strongly sheared, axisymmetric E×B flows-and an increase of the neoclassical counterpart, albeit keeping the overall fluxes at significantly reduced levels. The trigger mechanism is shown to be a mainly electrostatic resonant interaction between suprathermal particles, generated via ion-cyclotron-resonance heating, and plasma microturbulence. These findings are obtained by realistic simulations of the ASDEX Upgrade discharge No. 36637-properly designed to maximized the beneficial role of the wave-particle resonance interaction-which exhibits the expected properties of improved confinement produced by energetic particles.
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Affiliation(s)
- A Di Siena
- The University of Texas at Austin, 201 E 24th Street, Austin, Texas 78712, USA
| | - R Bilato
- Max Planck Institute for Plasma Physics, Boltzmannstr 2, Garching 85748, Germany
| | - T Görler
- Max Planck Institute for Plasma Physics, Boltzmannstr 2, Garching 85748, Germany
| | - A Bañón Navarro
- Max Planck Institute for Plasma Physics, Boltzmannstr 2, Garching 85748, Germany
| | - E Poli
- Max Planck Institute for Plasma Physics, Boltzmannstr 2, Garching 85748, Germany
| | - V Bobkov
- Max Planck Institute for Plasma Physics, Boltzmannstr 2, Garching 85748, Germany
| | - D Jarema
- Max Planck Institute for Plasma Physics, Boltzmannstr 2, Garching 85748, Germany
| | - E Fable
- Max Planck Institute for Plasma Physics, Boltzmannstr 2, Garching 85748, Germany
| | - C Angioni
- Max Planck Institute for Plasma Physics, Boltzmannstr 2, Garching 85748, Germany
| | - Ye O Kazakov
- Laboratory for Plasma Physics, LPP-ERM/KMS, TEC Partner, Brussels 1000, Belgium
| | - R Ochoukov
- Max Planck Institute for Plasma Physics, Boltzmannstr 2, Garching 85748, Germany
| | - P Schneider
- Max Planck Institute for Plasma Physics, Boltzmannstr 2, Garching 85748, Germany
| | - M Weiland
- Max Planck Institute for Plasma Physics, Boltzmannstr 2, Garching 85748, Germany
| | - F Jenko
- Max Planck Institute for Plasma Physics, Boltzmannstr 2, Garching 85748, Germany
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3
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Schmidt BS, Salewski M, Reman B, Dendy RO, Moseev D, Ochoukov R, Fasoli A, Baquero-Ruiz M, Järleblad H. Determining 1D fast-ion velocity distribution functions from ion cyclotron emission data using deep neural networks. Rev Sci Instrum 2021; 92:053528. [PMID: 34243325 DOI: 10.1063/5.0041456] [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: 12/23/2020] [Accepted: 04/26/2021] [Indexed: 06/13/2023]
Abstract
The relationship between simulated ion cyclotron emission (ICE) signals s and the corresponding 1D velocity distribution function fv⊥ of the fast ions triggering the ICE is modeled using a two-layer deep neural network. The network architecture (number of layers and number of computational nodes in each layer) and hyperparameters (learning rate and number of learning iterations) are fine-tuned using a bottom-up approach based on cross-validation. Thus, the optimal mapping gs;θ of the neural network in terms of the number of nodes, the number of layers, and the values of the hyperparameters, where θ is the learned model parameters, is determined by comparing many different configurations of the network on the same training and test set and choosing the best one based on its average test error. The training and test sets are generated by computing random ICE velocity distribution functions f and their corresponding ICE signals s by modeling the relationship as the linear matrix equation Wf = s. The simulated ICE signals are modeled as edge ICE signals at LHD. The network predictions for f based on ICE signals s are on many simulated ICE signal examples closer to the true velocity distribution function than that obtained by 0th-order Tikhonov regularization, although there might be qualitative differences in which features one technique is better at predicting than the other. Additionally, the network computations are much faster. Adapted versions of the network can be applied to future experimental ICE data to infer fast-ion velocity distribution functions.
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Affiliation(s)
- B S Schmidt
- Department of Physics, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - M Salewski
- Department of Physics, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - B Reman
- Laboratoire Plasma et Conversion d'Energie, Université Toulouse, Toulouse, France
| | - R O Dendy
- Centre for Fusion, Space and Astrophysics, University of Warwick, Coventry, United Kingdom
| | - D Moseev
- Max-Planck-Institut für Plasmaphysik, Greifswald, Garching, Germany
| | - R Ochoukov
- Max-Planck-Institut für Plasmaphysik, Greifswald, Garching, Germany
| | - A Fasoli
- École Polytechnique Fédérale de Lausanne, Swiss Plasma Center, Lausanne, Switzerland
| | - M Baquero-Ruiz
- École Polytechnique Fédérale de Lausanne, Swiss Plasma Center, Lausanne, Switzerland
| | - H Järleblad
- Department of Physics, Technical University of Denmark, Kgs. Lyngby, Denmark
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4
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Usoltceva M, Bobkov V, Faugel H, Franke T, Kostic A, Maggiora R, Milanesio D, Maquet V, Ochoukov R, Tierens W, Zeus F, Zhang W. DEMO ion cyclotron heating: Status of ITER-type antenna design. Fusion Engineering and Design 2021. [DOI: 10.1016/j.fusengdes.2021.112269] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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5
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Moseev D, Ochoukov R, Bobkov V, Dendy RO, Faugel H, Hartmann D, Kallmeyer JP, Lansky J, Laqua HP, Marsen S, McClements KG, Nielsen SK, Reintrog A, Salewski M, Schmidt BS, Schulz T, Stange T. Development of the ion cyclotron emission diagnostic for the W7-X stellarator. Rev Sci Instrum 2021; 92:033546. [PMID: 33820048 DOI: 10.1063/5.0040944] [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: 12/17/2020] [Accepted: 03/08/2021] [Indexed: 06/12/2023]
Abstract
An ion cyclotron emission (ICE) diagnostic is prepared for installation into the W7-X stellarator, with the aim to be operated in the 2022 experimental campaign. The design is based on the successful ICE diagnostic on the ASDEX Upgrade tokamak. The new diagnostic consists of four B-dot probes, mounted about 72° toroidally away (one module) from the neutral beam injector, with an unobstructed plasma view. Two of the B-dot probes are oriented parallel to the local magnetic field, aimed to detect fast magnetosonic waves. The remaining two probes are oriented poloidally, with the aim to detect slow waves. The radio frequency (RF) signals picked up by the probes are transferred via 50 Ω vacuum-compatible coaxial cables to RF detectors. Narrow band notch filters are used to protect the detectors from possible RF waves launched by the W7-X antenna. The signal will be sampled with a four-channel fast analog-to-digital converter with 14 bit depth and 1 GSample/s sampling rate. The diagnostic's phase-frequency characteristic is properly measured in order to allow measuring the wave vectors of the picked up waves.
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Affiliation(s)
- D Moseev
- Max-Planck-Institut für Plasmaphysik, Greifswald, Garching, Germany
| | - R Ochoukov
- Max-Planck-Institut für Plasmaphysik, Greifswald, Garching, Germany
| | - V Bobkov
- Max-Planck-Institut für Plasmaphysik, Greifswald, Garching, Germany
| | - R O Dendy
- Centre for Fusion, Space and Astrophysics, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - H Faugel
- Max-Planck-Institut für Plasmaphysik, Greifswald, Garching, Germany
| | - D Hartmann
- Max-Planck-Institut für Plasmaphysik, Greifswald, Garching, Germany
| | - J-P Kallmeyer
- Max-Planck-Institut für Plasmaphysik, Greifswald, Garching, Germany
| | - J Lansky
- Hochschule Stralsund, Stralsund, Germany
| | - H P Laqua
- Max-Planck-Institut für Plasmaphysik, Greifswald, Garching, Germany
| | - S Marsen
- Max-Planck-Institut für Plasmaphysik, Greifswald, Garching, Germany
| | - K G McClements
- Culham Centre for Fusion Energy, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB, United Kingdom
| | - S K Nielsen
- Department of Physics, Technical University of Denmark, Kgs., Lyngby, Denmark
| | - A Reintrog
- Max-Planck-Institut für Plasmaphysik, Greifswald, Garching, Germany
| | - M Salewski
- Department of Physics, Technical University of Denmark, Kgs., Lyngby, Denmark
| | - B S Schmidt
- Department of Physics, Technical University of Denmark, Kgs., Lyngby, Denmark
| | - T Schulz
- Max-Planck-Institut für Plasmaphysik, Greifswald, Garching, Germany
| | - T Stange
- Max-Planck-Institut für Plasmaphysik, Greifswald, Garching, Germany
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Ochoukov R, Dreval M, Bobkov V, Faugel H, Herrmann A, Kammerloher L, Leitenstern P. Publisher's Note: "Ion temperature measurement techniques using fast sweeping retarding field analyzer (RFA) in strongly intermittent ASDEX Upgrade tokamak plasmas" [Rev. Sci. Instrum. 91, 063506 (2020)]. Rev Sci Instrum 2020; 91:079902. [PMID: 32752790 DOI: 10.1063/5.0019839] [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] [Received: 06/25/2020] [Indexed: 06/11/2023]
Affiliation(s)
- R Ochoukov
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany
| | - M Dreval
- Institute of Plasma Physics, National Science Center Kharkov Institute of Physics and Technology, Kharkov 61108, Ukraine
| | - V Bobkov
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany
| | - H Faugel
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany
| | - A Herrmann
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany
| | - L Kammerloher
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany
| | - P Leitenstern
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany
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Ochoukov R, Dreval M, Bobkov V, Faugel H, Herrmann A, Kammerloher L, Leitenstern P. Ion temperature measurement techniques using fast sweeping retarding field analyzer (RFA) in strongly intermittent ASDEX Upgrade tokamak plasmas. Rev Sci Instrum 2020; 91:063506. [PMID: 32611035 DOI: 10.1063/5.0010788] [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: 04/15/2020] [Accepted: 05/28/2020] [Indexed: 06/11/2023]
Abstract
This manuscript presents a new method of interpreting the ion temperature (Ti) measurement with a retarding field analyzer (RFA) that accounts for the intermittent/turbulent nature of the scrape off layer (SOL) plasmas in tokamaks. Fast measurements and statistical methods are desirable for an adequate description of random fluctuations caused by such intermittent events as edge localized modes (ELMs) and blobs. We use a RFA that can sweep its current-voltage (I-V) characteristics with up to 10 kHz. The RFA uses an electronics compensation stage to subtract the capacitive pickup due to the finite connecting cable capacitance, which greatly improves the signal-to-noise ratio. In the 10 kHz case, a single I-V characteristic is obtained in time, which is an order of magnitude faster than the ELM cycle. The fast sweeping frequency allows us to reconstruct the Ti probability density function (PDF), which we use as the Ti representation. The boundary conditions that we place on the I-V characteristics when calculating the Ti values impact the resulting Ti PDF. If the boundaries are insensitive to the plasma fluctuations, then the most probable Ti value of the PDF (20 eV-25 eV) is similar to the Ti value obtained via the classical conditional averaging method (20 eV-27 eV). However, if the boundary conditions follow the fluctuations, then the PDF-based method gives a substantially higher most probable Ti value (35 eV-60 eV). Overall, we show that a fast sweeping RFA diagnostic should be used in intermittent SOL plasmas to reconstruct the PDF for accurate Ti measurements.
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Affiliation(s)
- R Ochoukov
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany
| | - M Dreval
- Institute of Plasma Physics, National Science Center Kharkov Institute of Physics and Technology, Kharkov 61108, Ukraine
| | - V Bobkov
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany
| | - H Faugel
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany
| | - A Herrmann
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany
| | - L Kammerloher
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany
| | - P Leitenstern
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany
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Kostic A, Crombé K, Dux R, Griener M, Ochoukov R, Shesterikov I, Suárez López G, Usoltceva M, Casagrande R, Martin EH, Noterdaeme JM. Polarization Stark spectroscopy for spatially resolved measurements of electric fields in the sheaths of ICRF antenna. Rev Sci Instrum 2019; 90:123101. [PMID: 31893862 DOI: 10.1063/1.5123659] [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: 08/08/2019] [Accepted: 11/10/2019] [Indexed: 06/10/2023]
Abstract
A multichannel spectroscopic diagnostic based on the Stark effect on helium lines was developed and implemented in IShTAR (Ion Cyclotron Sheath Test ARrangement) to measure the spatial distribution of electric fields across the radio frequency sheaths of the ion cyclotron antenna. Direct measurements of the DC electric fields in the antenna sheaths are an important missing component in understanding the antenna-plasma edge interactions in magnetically confined fusion plasmas since they will be used to benchmark theoretical models against real antenna operation. Along with the high-resolution Czerny-Turner monochromator and a detector with an intensifier, the hardware relies on the 2 chained set of linear-to-linear fiber bundles that provide seven optical channels capable of resolving an 8.4 mm region in the vicinity of the antenna's box. The diagnostic is supported with local helium gas puff, enabling it to operate in nonhelium plasmas. Spatially resolved electric field was measured for two discharge configurations, one with and one without the ICRF antenna. The results show a clear difference in the shape of the DC electric field's spatial profile for the two cases studied, with the elevated values when the ICRF antenna was operating. This demonstrates the ability of the diagnostic to measure even small relative changes in the intensity of the electric field.
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Affiliation(s)
- A Kostic
- Department of Applied Physics, Ghent University, 9000 Ghent, Belgium
| | - K Crombé
- Department of Applied Physics, Ghent University, 9000 Ghent, Belgium
| | - R Dux
- Max-Planck-Institut für Plasmaphysik, 85748 Garching, Germany
| | - M Griener
- Max-Planck-Institut für Plasmaphysik, 85748 Garching, Germany
| | - R Ochoukov
- Max-Planck-Institut für Plasmaphysik, 85748 Garching, Germany
| | - I Shesterikov
- Max-Planck-Institut für Plasmaphysik, 85748 Garching, Germany
| | - G Suárez López
- Max-Planck-Institut für Plasmaphysik, 85748 Garching, Germany
| | - M Usoltceva
- Department of Applied Physics, Ghent University, 9000 Ghent, Belgium
| | - R Casagrande
- Department of Applied Physics, Ghent University, 9000 Ghent, Belgium
| | - E H Martin
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
| | - J-M Noterdaeme
- Department of Applied Physics, Ghent University, 9000 Ghent, Belgium
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9
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Faugel H, Ochoukov R, Bobkov V, Fünfgelder H, Noterdaeme J, Aguiam D, Dux R. An overview of the in-vessel ICRF-diagnostics in the ASDEX Upgrade tokamak. Fusion Engineering and Design 2019. [DOI: 10.1016/j.fusengdes.2019.04.040] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Shesterikov I, Crombe K, Kostic A, Sitnikov DA, Usoltceva M, Ochoukov R, Heuraux S, Moritz J, Faudot E, Fischer F, Faugel H, Fünfgelder H, Siegl G, Noterdaeme JM. IShTAR: A test facility to study the interaction between RF wave and edge plasmas. Rev Sci Instrum 2019; 90:083506. [PMID: 31472664 DOI: 10.1063/1.5092431] [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: 02/11/2019] [Accepted: 07/25/2019] [Indexed: 06/10/2023]
Abstract
Existence of high electric fields near an RF antenna launcher causes a number of parasitic phenomena, such as arcing and impurity release, which seriously deteriorate the performance of an Ion Cyclotron Range of Frequencies (ICRF) heating scheme in fusion devices. Limited accessibility of the near antenna region in large-scale fusion experiments significantly complicates the associated experimental studies. The IShTAR test facility has been developed with the requirement to provide a better accessibility and diagnosability of plasmas in the direct vicinity of an ICRF antenna. The purpose of this work is to give a detailed description on the experimental setup and the available diagnostics. Furthermore, the paper will demonstrate the capability of the experiment to study phenomena near an ICRF antenna launcher which are relevant for large-scale fusion ion cyclotron resonance heating systems.
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Affiliation(s)
- I Shesterikov
- Max-Planck-Institut für Plasmaphysik, D-85748 Garching, Germany
| | - K Crombe
- Ghent University, Department of Applied Physics, B-9000 Gent, Belgium
| | - A Kostic
- Max-Planck-Institut für Plasmaphysik, D-85748 Garching, Germany
| | - D A Sitnikov
- National Science Center "Kharkov Institute of Physics and Technology," Institute of Plasma Physics, 61108, Kharkov, Ukraine
| | - M Usoltceva
- Max-Planck-Institut für Plasmaphysik, D-85748 Garching, Germany
| | - R Ochoukov
- Max-Planck-Institut für Plasmaphysik, D-85748 Garching, Germany
| | - S Heuraux
- Institute Jean Lamour, F-54011 Nancy, France
| | - J Moritz
- Institute Jean Lamour, F-54011 Nancy, France
| | - E Faudot
- Institute Jean Lamour, F-54011 Nancy, France
| | - F Fischer
- Max-Planck-Institut für Plasmaphysik, D-85748 Garching, Germany
| | - H Faugel
- Max-Planck-Institut für Plasmaphysik, D-85748 Garching, Germany
| | - H Fünfgelder
- Max-Planck-Institut für Plasmaphysik, D-85748 Garching, Germany
| | - G Siegl
- Max-Planck-Institut für Plasmaphysik, D-85748 Garching, Germany
| | - J-M Noterdaeme
- Max-Planck-Institut für Plasmaphysik, D-85748 Garching, Germany
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Ochoukov R, Bobkov V, Chapman B, Dendy R, Dunne M, Faugel H, García-Muñoz M, Geiger B, Hennequin P, McClements KG, Moseev D, Nielsen S, Rasmussen J, Schneider P, Weiland M, Noterdaeme JM. Observations of core ion cyclotron emission on ASDEX Upgrade tokamak. Rev Sci Instrum 2018; 89:10J101. [PMID: 30399687 DOI: 10.1063/1.5035180] [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: 06/08/2023]
Abstract
The B-dot probe diagnostic suite on the ASDEX Upgrade tokamak has recently been upgraded with a new 125 MHz, 14 bit resolution digitizer to study ion cyclotron emission (ICE). While classic edge emission from the low field side plasma is often observed, we also measure waves originating from the core with fast fusion protons or beam injected deuterons being a possible emission driver. Comparing the measured frequency values with ion cyclotron harmonics present in the plasma places the origin of this emission on the magnetic axis, with the fundamental hydrogen/second deuterium cyclotron harmonic matching the observed values. The actual values range from ∼27 MHz at the on-axis toroidal field BT = -1.79 T to ∼40 MHz at BT = -2.62 T. When the magnetic axis position evolves during this emission, the measured frequency values track the changes in the estimated on-axis cyclotron frequency values. Core ICE is usually a transient event lasting ∼100 ms during the neutral beam startup phase. However, in some cases, core emission occurs in steady-state plasmas and lasts for longer than 1 s. These observations suggest an attractive possibility of using a non-perturbing ICE-based diagnostic to passively monitor fusion alpha particles at the location of their birth in the plasma core, in deuterium-tritium burning devices such as ITER and DEMO.
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Affiliation(s)
- R Ochoukov
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, D-85748 Garching, Germany
| | - V Bobkov
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, D-85748 Garching, Germany
| | - B Chapman
- Centre for Fusion, Space and Astrophysics, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - R Dendy
- Centre for Fusion, Space and Astrophysics, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - M Dunne
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, D-85748 Garching, Germany
| | - H Faugel
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, D-85748 Garching, Germany
| | - M García-Muñoz
- FAMN Department, Faculty of Physics, University of Seville, 41012 Seville, Spain
| | - B Geiger
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, D-85748 Garching, Germany
| | - P Hennequin
- Laboratoire de Physique des Plasmas, Ecole Polytechnique, 91128 Palaiseau, France
| | - K G McClements
- CCFE, Culham Science Center, Abingdon, Oxfordshire OX14 3DB, United Kingdom
| | - D Moseev
- Max Planck Institute for Plasma Physics, Wendelsteinstr. 1, 17491 Greifswald, Germany
| | - S Nielsen
- Department of Physics, Technical University of Denmark, Fysikvej, b. 309, DK-2800 Kongens Lyngby, Denmark
| | - J Rasmussen
- Department of Physics, Technical University of Denmark, Fysikvej, b. 309, DK-2800 Kongens Lyngby, Denmark
| | - P Schneider
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, D-85748 Garching, Germany
| | - M Weiland
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, D-85748 Garching, Germany
| | - J-M Noterdaeme
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, D-85748 Garching, Germany
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12
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Kostic A, Dux R, Crombé K, Nikiforov A, Ochoukov R, Shesterikov I, Martin EH, Noterdaeme JM. Development of a spectroscopic diagnostic tool for electric field measurements in IShTAR (Ion cyclotron Sheath Test ARrangement). Rev Sci Instrum 2018; 89:10D115. [PMID: 30399884 DOI: 10.1063/1.5039321] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [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: 06/08/2018] [Indexed: 06/08/2023]
Abstract
IShTAR, Ion cyclotron Sheath Test ARrangement, is a linear device dedicated to the investigation of the edge plasma-ICRF (Ion Cyclotron Range of Frequencies) antenna interactions in tokamak edge-like conditions and serves as a platform for a diagnostic development for measuring the electric fields in the vicinity of ICRF antennas. We present here our progress in the development of an optical emission spectroscopy method for measuring the electric fields which concentrates on the changes in the helium spectral line profiles introduced by the external electrical field, i.e., the Stark effect. To be able to fully control the operating parameters, at the first stage of the study, the measurements are conducted on a planar electrode installed in the centre of the plasma column in IShTAR's helicon plasma source. At the second stage, the measurements are performed in the vicinity of IShTAR's ICRF antenna.
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Affiliation(s)
- A Kostic
- Department of Applied Physics, Ghent University, Ghent, Belgium
| | - R Dux
- Max-Planck-Institut für Plasmaphysik, Garching, Germany
| | - K Crombé
- Department of Applied Physics, Ghent University, Ghent, Belgium
| | - A Nikiforov
- Department of Applied Physics, Ghent University, Ghent, Belgium
| | - R Ochoukov
- Max-Planck-Institut für Plasmaphysik, Garching, Germany
| | - I Shesterikov
- Max-Planck-Institut für Plasmaphysik, Garching, Germany
| | - E H Martin
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
| | - J-M Noterdaeme
- Department of Applied Physics, Ghent University, Ghent, Belgium
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13
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Usoltceva M, Faudot E, Ledig J, Devaux S, Heuraux S, Zadvitskiy GV, Ochoukov R, Moritz J, Crombé K, Noterdaeme JM. Theory of a cylindrical Langmuir probe parallel to the magnetic field and its calibration with interferometry. Rev Sci Instrum 2018; 89:10J124. [PMID: 30399937 DOI: 10.1063/1.5038666] [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: 05/04/2018] [Accepted: 07/04/2018] [Indexed: 06/08/2023]
Abstract
A theory for data interpretation is presented for a cylindrical Langmuir probe in plasma parallel to the magnetic field direction. The theory is tested in a linear low-temperature plasma device Aline, in a capacitive radio-frequency (RF) discharge. The probe is placed on a 3D manipulator, and a position scan is performed. To exclude strong RF perturbations, the probe is RF compensated. Using the theory, electron densities are obtained from the current at the plasma potential, where no sheath is present. Results are calibrated by line-integrated density measurements of a 26.5 GHz microwave interferometer. Reasonable agreement is observed for probe and interferometer measurements. Furthermore, preceding, more general probe theory is compared to the one developed in the current work and the application limits are discussed.
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Affiliation(s)
| | - E Faudot
- Université de Lorraine, 54506 Vandœuvre-lès-Nancy, France
| | - J Ledig
- Université de Lorraine, 54506 Vandœuvre-lès-Nancy, France
| | - S Devaux
- Université de Lorraine, 54506 Vandœuvre-lès-Nancy, France
| | - S Heuraux
- Université de Lorraine, 54506 Vandœuvre-lès-Nancy, France
| | - G V Zadvitskiy
- Université de Lorraine, 54506 Vandœuvre-lès-Nancy, France
| | - R Ochoukov
- Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching, Germany
| | - J Moritz
- Université de Lorraine, 54506 Vandœuvre-lès-Nancy, France
| | - K Crombé
- Ghent University, 9000 Ghent, Belgium
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14
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Ochoukov R, Bobkov V, Faugel H, Fünfgelder H, Jacquot J, Noterdaeme JM, Suárez López G. ICRF wave field measurements in the presence of scrape off layer turbulence on the ASDEX Upgrade tokamak (invited). Rev Sci Instrum 2016; 87:11D301. [PMID: 27910344 DOI: 10.1063/1.4960148] [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: 06/06/2023]
Abstract
A new array of B-dot probes was installed on ASDEX Upgrade. The purpose of the new diagnostic is to study Ion Cyclotron Range-off Frequencies (ICRF) wave field distributions in the evanescent scrape-off layer (SOL) plasma region on the low field side of ASDEX Upgrade. The vacuum measurements (no gas, BT = 0 T) reveal ICRF wave field measurements consistent with the profiles expected from the newly installed 3-strap ICRF antennas outside the antenna box: the shape of the toroidal distribution of both the amplitude and the phase is the same for the case of only the central straps being active, as for the case of only the side straps being active. These profiles become strongly modified during plasma operations. The modifications can be separated into two types: "Inter-edge localized mode (ELM)" and "During-ELM" periods. The phase distribution of the ICRF wave fields remains well-defined during the Inter-ELM period; however, it becomes more spread out over the entire 360° range during ELMs. The observed modulations cannot be explained by the observed changes in the ICRF power, as monitored in the transmission line. However, they are consistent with ICRF coupling changes introduced by plasma filaments: the plasma density perturbations due to the filaments are high enough to change the nature of the fast ICRF wave field from evanescent to propagating. The coverage of the present diagnostic is being expanded to include both the low field side and the high field side probes. Additionally, a manipulator probe head is being developed to measure ICRF wave field radial profiles across the SOL region.
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Affiliation(s)
- R Ochoukov
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany
| | - V Bobkov
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany
| | - H Faugel
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany
| | - H Fünfgelder
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany
| | - J Jacquot
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany
| | - J-M Noterdaeme
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany
| | - G Suárez López
- Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany
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15
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Ochoukov R, Bobkov V, Faugel H, Fünfgelder H, Noterdaeme JM. A new B-dot probe-based diagnostic for amplitude, polarization, and wavenumber measurements of ion cyclotron range-of frequency fields on ASDEX Upgrade. Rev Sci Instrum 2015; 86:115112. [PMID: 26628177 DOI: 10.1063/1.4935833] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [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 B-dot probe-based diagnostic has been installed on an ASDEX Upgrade tokamak to characterize ion cyclotron range-of frequency (ICRF) wave generation and interaction with magnetized plasma. The diagnostic consists of a field-aligned array of B-dot probes, oriented to measure fast and slow ICRF wave fields and their field-aligned wavenumber (k(//)) spectrum on the low field side of ASDEX Upgrade. A thorough description of the diagnostic and the supporting electronics is provided. In order to compare the measured dominant wavenumber of the local ICRF fields with the expected spectrum of the launched ICRF waves, in-air near-field measurements were performed on the newly installed 3-strap ICRF antenna to reconstruct the dominant launched toroidal wavenumbers (k(tor)). Measurements during a strap current phasing scan in tokamak discharges reveal an upshift in k(//) as strap phasing is moved away from the dipole configuration. This result is the opposite of the k(tor) trend expected from in-air near-field measurements; however, the near-field based reconstruction routine does not account for the effect of induced radiofrequency (RF) currents in the passive antenna structures. The measured exponential increase in the local ICRF wave field amplitude is in agreement with the upshifted k(//), as strap phasing moves away from the dipole configuration. An examination of discharges heated with two ICRF antennas simultaneously reveals the existence of beat waves at 1 kHz, as expected from the difference of the two antennas' operating frequencies. Beats are observed on both the fast and the slow wave probes suggesting that the two waves are coupled outside the active antennas. Although the new diagnostic shows consistent trends between the amplitude and the phase measurements in response to changes applied by the ICRF antennas, the disagreement with the in-air near-field measurements remains. An electromagnetic model is currently under development to address this issue.
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Affiliation(s)
- R Ochoukov
- Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching, Germany
| | - V Bobkov
- Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching, Germany
| | - H Faugel
- Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching, Germany
| | - H Fünfgelder
- Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching, Germany
| | - J-M Noterdaeme
- Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching, Germany
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16
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Brunner D, LaBombard B, Ochoukov R, Whyte D. Scanning ion sensitive probe for plasma profile measurements in the boundary of the Alcator C-Mod tokamak. Rev Sci Instrum 2013; 84:053507. [PMID: 23742551 DOI: 10.1063/1.4807699] [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: 06/02/2023]
Abstract
A new Ion Sensitive Probe head has been created for the outer-midplane scanning probe system on the Alcator C-Mod tokamak. The new probe head contains three elements: an ion sensitive probe to measure ion temperature and plasma potential, a Langmuir probe to measure electron temperature, density, and floating potential, and a second Langmuir probe to measure ion saturation current and the density fluctuations arising from ''blob'' events. The ion sensitive probe current is normalized to this measurement to reduced deleterious effects of the strong fluctuations. Design of the high heat flux probe (>100 MW/m(2)) and initial results are presented.
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Affiliation(s)
- D Brunner
- PSFC, MIT, Cambridge, Massachusetts 02139, USA
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17
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Brunner D, LaBombard B, Ochoukov R, Whyte D. Scanning retarding field analyzer for plasma profile measurements in the boundary of the Alcator C-Mod tokamak. Rev Sci Instrum 2013; 84:033502. [PMID: 23556816 DOI: 10.1063/1.4793785] [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: 06/02/2023]
Abstract
A new Retarding Field Analyzer (RFA) head has been created for the outer-midplane scanning probe system on the Alcator C-Mod tokamak. The new probe head contains back-to-back retarding field analyzers aligned with the local magnetic field. One faces "upstream" into the field-aligned plasma flow and the other faces "downstream" away from the flow. The RFA was created primarily to benchmark ion temperature measurements of an ion sensitive probe; it may also be used to interrogate electrons. However, its construction is robust enough to be used to measure ion and electron temperatures up to the last-closed flux surface in C-Mod. A RFA probe of identical design has been attached to the side of a limiter to explore direct changes to the boundary plasma due to lower hybrid heating and current drive. Design of the high heat flux (>100 MW∕m(2)) handling probe and initial results are presented.
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Affiliation(s)
- D Brunner
- MIT PSFC Cambridge, Massachusetts 02139, USA
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18
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Ochoukov R, Whyte DG, Lipschultz B, Labombard B, Wukitch S. Interpretation and implementation of an ion sensitive probe as a plasma potential diagnostic. Rev Sci Instrum 2010; 81:10E111. [PMID: 21033976 DOI: 10.1063/1.3483192] [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
An ion sensitive probe (ISP) is developed as a robust diagnostic for measuring plasma potentials (Φ(P)) in magnetized plasmas. The ISP relies on the large difference between the ion and electron gyroradii (ρ(i)/ρ(e)∼60) to reduce the electron collection at a collector recessed behind a separately biased wall distance ∼ρ(i). We develop a new ISP method to measure the plasma potential that is independent of the precise position and shape of the collector. Φ(P) is found as the wall potential when charged current to the probe collector vanishes during the voltage sweep. The plasma potentials obtained from the ISP match Φ(P) measured with an emissive probe over a wide range of plasma conditions in a small magnetized plasma.
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Affiliation(s)
- R Ochoukov
- PSFC, MIT, 77 Mass. Avenue, Cambridge, Massachusetts 02139, USA.
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