| Paper | Title | Page |
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| TUP019 | Regime of Multi-Stage Non-Resonant Trapping in Free Electron Lasers | 83 |
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Funding: This work is supported by the RFBR (grants #18-02-40009, #18-02-00765) and by the IAP RAS Project 0035-2019-0001. We describe three works united by the idea of the non-resonant regime [1] providing an effective trapping in a beam with a great energy spread. In this regime, the "bucket" corresponding to the resonant electron-wave interaction passes through the electron layer on the energy-phase plane and traps a fraction of electrons. (I) Operability of this regime was demonstrated in the high-efficient 0.8 MeV Ka-band FEM-amplifier [2]. (II) In short-wavelength FELs the multi-stage trapping in several consecutive sections can be organized [3]. In each section a small e-beam fraction is trapped due to a weak electron-wave interaction. However, repetition of this process from section to section involves in the interaction almost the whole e-beam. We describe efficiency enhancement and improving the frequency wave spectrum in multi-stage SASE FELs. (III) The multi-stage amplification of a single-frequency wave signal can provide cooling of the electron bunch. In this regime, tapering of every section is provided such that the "bucket" goes from maximal initial electron energy down to the minimal one and moves down energies of trapped electrons. [1] A.Savilov et al., Nucl. Instr. Meth. A, vol. 507, p.158, 2003 [2] A.Kaminsky et al., Int. Conf. IRMMW-THz 2018, art. 4057938 [3] S.Kuzikov, A.Savilov, Phys. Plasmas, vol. 25, p.113114, 2018 |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP019 | |
| About • | paper received ※ 14 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019 | |
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| TUP020 | Terahertz Free Electron Maser Based on Excitation of a Talbot-Type Super-Mode in an Oversized Microwave System | 87 |
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Funding: The work is supported by the Russian Science Foundation, Project # 19-12-00212. A natural problem arising in the case of realization of a THz FEM with a high-current relativistic e-beam is an inevitable use of an oversized microwave system, which characteristic transverse size significantly exceeds the wavelength of the operating wave. In this situation, it becomes difficult to provide selective excitation of a chosen transverse mode of the operating cavity. Our basic idea is to give up working on a fixed transverse mode. Instead, we propose to work on a supermode, which is a fixed set of several transverse modes of an oversized wavegude. We propose to use the Talbot effect [1,2,3] as a way to create an oversized microwave system of an electron maser that provides a high Q-factor for this supermode. On the basis of a multi-mode set of self-consistent equations of the electron-wave interaction we demonstrate the possibility of the selective self-excitation of the supermode both in the simplest 2-D model and in the detailed modeling of a THz FEM fed by a 10 MeV / 2 kA / 200 e-beam based on excitation of a Talbot-type supermode at a frequency close to 2 THz. The calculated efficiency at the level of 5-10% corresponds to the GW level of the output power. [1] L. A. Rivlin, Laser Focus, p. 82, 1981 [2] G. G. Denisov, D. A. Lukovnikov, M. Yu. Shmelyov, Digest of 18 Int. Conf. on IR MM Waves, p. 485, 1993 [3] V. L. Bratman et al., Nucl. Instr. Meth. Phys. Res. A, vol. 407, pp. 40-44, 1998 |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP020 | |
| About • | paper received ※ 14 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019 | |
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| TUP021 | Development of Powerful Long-Pulse Terahertz Band FELs Based on Linear Induction Accelerators | 91 |
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Funding: This work was supported by the Russian Scientific Foundation (RSCF), grant No. 19-12-00212. The paper is devoted to development of high-power long-pulse THz-band FELs based on new generation of linear induction accelerators which have been elaborated recently at Budker Institute (Novosibirsk). These accelerators generate microsecond electron beams with current at kA-level and energy of 2 to 5 MeV (with a possibility to increase electrons energy up to 20 MeV). Based on this beam, we initiated a new project of multi-MW long-pulse FEL operating in the frequency range of 1 to 10 THz using a wiggler period of 3 to 6 cm. For this FEL oscillator, we suggest a hybrid planar two-mirror resonator consisting of an upstream highly selective advanced Bragg reflector and a downstream weakly reflecting conventional Bragg reflector. Simulations demonstrate that the advanced Bragg reflector based on coupling of propagating and quasi-cutoff waves ensures the mode control at the values of the gap between the corrugated plates forming such resonator up to 20 wavelengths. Simulations of the FEL driven by electron beam generated by the LIU¿2 in the frame of both averaged approach and 3D PIC code demonstrate that the THz radiation power can reach the level of 10 to 20 MW. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP021 | |
| About • | paper received ※ 28 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019 | |
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| THP060 | Development of RF-Undulators and Powering Sources for Compact Efficient Compton FEL-Scattrons | 704 |
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| Conception of Compton-type FELs operating up to X-ray band is under development currently at IAP RAS (N.Novgorod). This concept is aimed at reducing energy of a driving relativistic electron beam and thereby increasing efficiency of the electron-wave interaction in FEL, as well as achieving relative compactness of the generator. The basis of this concept is RF-undulators of a new type - the so-called ’flying’ undulators. Results of current research of these RF-undulators, their simulations and ’cold’ tests in the Ka-band are presented. For powering RF-undulators spatially-extended narrow-band Cerenkov masers are developed in the specified frequency range. In order to achieve the required sub-gigawatt power level of the pumping wave in a strongly oversized oscillator, we exploit the original idea of using two-dimensional distributed feedback implemented in the 2D doubly-periodical slow-wave structures. The design parameters of Ka-band surface-wave oscillator intended for powering RF-undulators, results of its simulation and initial experimental studies are discussed. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP060 | |
| About • | paper received ※ 15 August 2019 paper accepted ※ 25 August 2019 issue date ※ 05 November 2019 | |
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