| Paper | Title | Page |
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| MOPGW061 | Radiation from a Dielectrically Loaded Waveguide with Open End | 228 |
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Funding: Work supported by Russian Science Foundation (Grant No. 18-72-10137). Open-ended waveguide structures with dielectric loading excited by specially prepared electron bunches are considered as promising candidates for development of contemporary sources of Terahertz (THz) radiation. Despite of the fact that both ordinary vacuum THz devices (e.g., backward wave oscillator) are widely available and other mechanisms for THz generation are discussed, beam driven sources are still extremely attractive due to the extraordinary peak power of THz radiation*. In this report, we study electromagnetic (EM) field produced by a charged particle bunch exiting an open-ended circular waveguide with dielectric filling placed inside collinear vacuum waveguide of a larger radius. Based on the previously developed theory**, we mainly investigate Cherenkov radiation generated penetrated vacuum regions of the structure due to the diffraction mechanism. We pay attention to the case of a train of short bunches resulting in high-order Cherenkov modes excitation. We also develop analytical procedure allowing performing the limiting process to the case of infinite radius of the outer waveguide. * B.D. O’Shea et al., Nature Communications, Vol. 7, P. 12763, (2016). ** S.N. Galyamin et al., J. Instrumentation, Vol. 13, P. C02012 (2018). |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW061 | |
| About • | paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019 | |
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| TUPRB035 | Stimulated Emission of THz Coherent Diffraction Radiation in an Optical Cavity by a Multibunch Electron Beam | 1763 |
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Funding: JSPS KAKENHI Accelerator-based terahertz (THz) radiation has been expected to realize a high-power broad-band source. Employing a low-emittance and short-bunch electron beam at a high repetition rate, a scheme to resonantly excite optical cavity modes of THz spectrum range via coherent diffraction radiation has been proposed. The confocal cavity design is the special case that resonance conditions of all the eigen modes coincide, resulting in realizing broad-band excitation. But in general cases of non-confocal cavities, the resonance condition depends on the mode, and the resonance peak becomes wide and weak. We performed an experiment with a non-confocal cavity as a follow-up experiment of that we have done with a confocal cavity. The result confirmed that the confocal design is the key for a broad-band source. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB035 | |
| About • | paper received ※ 26 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | |
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| WEPGW077 | Recent Results using Incoherent Cherenkov Diffraction Radiation for Non-Invasive Beam Diagnostics | 2654 |
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| When a relativistic charged particle travels at a short distance from the surface of dielectric material Cherenkov Diffraction Radiation (ChDR) is produced inside the dielectric. Recent observation of incoherent ChDR in the visible spectrum has opened the possibility of using this radiation for non-invasive beam size and position measurements. An experimental test to study this technique for highly directional beam position measurement has been initiated on the CLEAR facility at CERN, whilst another experimental investigation is underway at the Accelerator Test Facility 2 (ATF2) at KEK, Japan, to measure the resolution limit of ChDR for beam imaging diagnostics. This contribution presents the latest experimental results from both of these test facilities. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW077 | |
| About • | paper received ※ 01 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019 | |
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| WEPTS055 | Energy Modulation of Electron Beam in Corrugated Dielectric Waveguide | 3248 |
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Energy modulated electron beams have a wide range of applications in accelerator physics, for example they can serve as drivers in resonant wakefield acceleration schemes. A strong wakefield induced energy modulation can be produced using a dielectric lined waveguide, the resultant micro-bunched beam is capable of producing coherent terahertz radiation *. We report on observation of energy modulation due to self-wakefields in a few picosecond duration and ~1 nC charge electron bunches of LUCX facility at KEK. To produce the modulation, we used a corrugated dielectric waveguide with an inner radius of 2 mm and a period of corrugation of 10 mm. In this case, the period of corrugation is longer than the wavelength of the main accelerating mode. We show electromagnetic simulations of on-axis electric fields leading to an optimisation of the corrugation period allowing to enhance the accelerating/decelerating fields compared to dielectric lined waveguides with a constant inner radius.
* S. Antipov et al., Experimental observation of energy modulation in electron beams passing though terahertz dielectric wakefield structures, PRL 108, 144801 (2012). |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS055 | |
| About • | paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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