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Jiang S, Li W, He Z, Jia Q, Wang L. Intrinsically reducing divergence angle of Cherenkov radiation from dielectric capillary. OPTICS LETTERS 2020; 45:5416-5419. [PMID: 33001908 DOI: 10.1364/ol.401947] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 08/24/2020] [Indexed: 06/11/2023]
Abstract
Narrow-band terahertz (THz) Cherenkov radiation can be excited as a relativistic electron bunch passes through the dielectric capillary with sub-millimeter radius. However, due to the diffraction effect, the radiation will enter free space with a large divergence angle, which makes it difficult to collect the radiation energy efficiently. In this Letter, to deal with this challenge, we propose to add a new dielectric layer, which satisfies a special relationship with the electron velocity, between the metal coating and original dielectric layer in the capillary. According to numerical simulation and theoretical analysis results, the divergence angle of radiation is significantly suppressed, and the peak power density is also enhanced by over two orders. As a result, the transmission efficiency from the radiation source to the optical system can be increased to over 90%. We expect that this method will provide a new way to generate THz Cherenkov radiation.
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O'Shea BD, Andonian G, Barber SK, Clarke CI, Hoang PD, Hogan MJ, Naranjo B, Williams OB, Yakimenko V, Rosenzweig JB. Conductivity Induced by High-Field Terahertz Waves in Dielectric Material. PHYSICAL REVIEW LETTERS 2019; 123:134801. [PMID: 31697514 DOI: 10.1103/physrevlett.123.134801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Indexed: 06/10/2023]
Abstract
An intense, subpicosecond, relativistic electron beam traversing a dielectric-lined waveguide generates very large amplitude electric fields at terahertz (THz) frequencies through the wakefield mechanism. In recent work employing this technique to accelerate charged particles, the generation of high-power, narrow-band THz radiation was demonstrated. The radiated waves contain fields with measured amplitude exceeding 2 GV/m, orders of magnitude greater than those available by other THz generation techniques at a narrow bandwidth. For fields approaching the GV/m level, a strong damping has been observed in SiO_{2}. This wave attenuation with an onset near 850 MV/m is consistent with changes to the conductivity of the dielectric lining and is characterized by a distinctive latching mechanism that is reversible on longer timescales. We describe the detailed measurements that serve to clarify the underlying physical mechanisms leading to strong field-induced damping of THz radiation (hω=1.59 meV, f=0.38 THz) in SiO_{2}, a bulk, wide band-gap (8.9 eV) dielectric.
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Affiliation(s)
- B D O'Shea
- UCLA Department of Physics and Astronomy, 405 Hilgard Avenue, Los Angeles, California 90095, USA
- SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - G Andonian
- UCLA Department of Physics and Astronomy, 405 Hilgard Avenue, Los Angeles, California 90095, USA
| | - S K Barber
- UCLA Department of Physics and Astronomy, 405 Hilgard Avenue, Los Angeles, California 90095, USA
- Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720, USA
| | - C I Clarke
- SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - P D Hoang
- UCLA Department of Physics and Astronomy, 405 Hilgard Avenue, Los Angeles, California 90095, USA
| | - M J Hogan
- SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - B Naranjo
- UCLA Department of Physics and Astronomy, 405 Hilgard Avenue, Los Angeles, California 90095, USA
| | - O B Williams
- UCLA Department of Physics and Astronomy, 405 Hilgard Avenue, Los Angeles, California 90095, USA
| | - V Yakimenko
- SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - J B Rosenzweig
- UCLA Department of Physics and Astronomy, 405 Hilgard Avenue, Los Angeles, California 90095, USA
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Li W, Lu Y, He Z, Jia Q, Wang L. Harmonics generation of a terahertz wakefield free-electron laser from a dielectric loaded waveguide excited by a direct current electron beam. OPTICS LETTERS 2016; 41:2458-2461. [PMID: 27244388 DOI: 10.1364/ol.41.002458] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We propose to generate high-power terahertz (THz) radiation from a cylindrical dielectric loaded waveguide (DLW) excited by a direct-current electron beam with the harmonics generation method. The DLW supports a discrete set of modes that can be excited by an electron beam passing through the structure. The interaction of these modes with the co-propagating electron beam results in micro-bunching and the coherent enhancement of the wakefield radiation, which is dominated by the fundamental mode. By properly choosing the parameters of DLW and beam energy, the high order modes can be the harmonics of the fundamental one; thus, high frequency radiation corresponding to the high order modes will benefit from the dominating bunching process at the fundamental eigenfrequency and can also be coherently excited. With the proposed method, high power THz radiation can be obtained with an easily achievable electron beam and a large DLW structure.
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Ribič PR. Can a metal surface repel electric charges? PHYSICAL REVIEW LETTERS 2012; 109:244801. [PMID: 23368328 DOI: 10.1103/physrevlett.109.244801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2012] [Indexed: 06/01/2023]
Abstract
We show that the interaction between a surface and a charge packet moving parallel to it can become repulsive above a critical relativistic energy. We find that this is true for a lossless dielectric surface and also for a Drude metallic surface--in apparent contrast with such common notions as image charge. This counterintuitive phenomenon occurs for packets larger in the transverse than in the longitudinal (parallel to the motion) direction. The repulsion does not occur for a point charge that is instead attracted at all energies. In addition to the above attractive or repulsive transverse force, there is a longitudinal decelerating force, which for a dielectric corresponds to the Čerenkov effect. Once again, the behavior of a line packet differs from that of a point charge: for a packet with infinite transverse size, the decelerating field decreases to zero as the relativistic factor γ → ∞, whereas, for a point charge, the asymptotic value is finite. These findings have a potential impact not only on fundamental electrodynamics but also on accelerator physics and electron spectroscopy.
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Affiliation(s)
- Primož Rebernik Ribič
- Faculté des Sciences de Base, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
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Proposal for generation of high-intensity monochromatic Cherenkov radiation in THz range by femtosecond electron bunches in impurity-doped semiconductor tube. Radiat Phys Chem Oxf Engl 1993 2011. [DOI: 10.1016/j.radphyschem.2011.07.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Tyukhtin AV, Galyamin SN. Vavilov-Cherenkov radiation in passive and active media with complex resonant dispersion. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2008; 77:066606. [PMID: 18643389 DOI: 10.1103/physreve.77.066606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2007] [Revised: 04/21/2008] [Indexed: 05/26/2023]
Abstract
Some of the problems with the theory of moving charge radiation in media with frequency dispersion are analyzed. First, some general properties of the integrals for field components are described. The results are applied to the cases of passive and active media. In one instance, the field of a charge moving in passive media with an arbitrary number of resonances is considered. Components of the field have been presented as a sum of the "quasi-Coulomb" field, the wave field, and the "plasma trace." In another example, the case of an active medium with two resonant frequencies is considered. It has been demonstrated that radiation is amplified even with a purely real refractive index if the following conditions are fulfilled: the "lower" resonance is active, the "upper" one is passive, and the charge movement velocity lies within a certain range. Efficient algorithms for the computation of fields in the cases of passive and active media have been developed.
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Affiliation(s)
- Andrey V Tyukhtin
- Radiophysics Department, St. Petersburg University, 1 Ulyanovskaya, St. Petersburg, 198504, Russia
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Mizrahi A, Schächter L. Optical Bragg accelerators. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2004; 70:016505. [PMID: 15324182 DOI: 10.1103/physreve.70.016505] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2003] [Revised: 01/26/2004] [Indexed: 05/24/2023]
Abstract
It is demonstrated that a Bragg waveguide consisting of a series of dielectric layers may form an excellent optical acceleration structure. Confinement of the accelerating fields is achieved, for both planar and cylindrical configurations by adjusting the first dielectric layer width. A typical structure made of silica and zirconia may support gradients of the order of 1 GV/m with an interaction impedance of a few hundreds of ohms and with an energy velocity of less than 0.5c. An interaction impedance of about 1000 Omega may be obtained by replacing the Zirconia with a (fictitious) material of epsilon=25. Special attention is paid to the wake field developing in such a structure. In the case of a relatively small number of layers, it is shown that the total electromagnetic power emitted is proportional to the square of the number of electrons in the macrobunch and inversely proportional to the number of microbunches; this power is also inversely proportional to the square of the internal radius of the structure for a cylindrical structure, and to the width of the vacuum core in a planar structure. Quantitative results are given for a higher number of dielectric layers, showing that in comparison to a structure bounded by metallic walls, the emitted power is significantly smaller due to propagation bands allowing electromagnetic energy to escape.
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Affiliation(s)
- Amit Mizrahi
- Department of Electrical Engineering, Technion-IIT, Haifa 32000, Israel
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Xiao L, Gai W, Sun X. Field analysis of a dielectric-loaded rectangular waveguide accelerating structure. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2002; 65:016505. [PMID: 11800802 DOI: 10.1103/physreve.65.016505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2001] [Revised: 07/02/2001] [Indexed: 05/23/2023]
Abstract
Recently, there has been some interest in planar or rectangular dielectric accelerating structures for future high-gradient linear accelerators. In this paper, we present a detailed analysis of the modes of a dielectric-loaded rectangular waveguide accelerating structure based on a circuit model approximation and mode matching method. In general, the acceleration field in a synchronous acceleration mode is nonuniform in the two transverse dimensions. We show, however, that by using a series of rectangular structures successively rotated by 90 degrees, the net accelerating force can be made almost uniform. Characteristic parameters such as R/Q, group velocity, and attenuation constant for X- and W-band accelerators are calculated. The longitudinal wakefields experienced by a relativistic charged particle beam in these structures are also presented. These analytical results are also compared with numerical calculations using the MAFIA code suite demonstrating the validity of our analytic approach.
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Affiliation(s)
- Liling Xiao
- High Energy Physics Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
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