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| MOAAU02 |
First Lasing of MIR-FEL at Kyoto University
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4 |
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- H. Ohgaki, K. Higashimura, T. Kii, R. Kinjo, K. Masuda, T. Yamazaki, K. Yoshikawa, H. Zen
Kyoto IAE, Kyoto
- Y. U. Jeong
KAERI, Daejon
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First lasing of Mid-Infrared Free Electron Laser was achieved at Institute of Advanced Energy (IAE), Kyoto University. The FEL driver, KU-FEL*, consists of a 4.5 cell thermionic RF gun, a 3-m S-band accelerator tube, and a 1.6-m plane undulator. The 25 MeV electron beam of 17 A peak current was employed for the lasing experiment. A beam loading compensation method with RF amplitude and phase control has been applied both for the RF gun and for the accelerator tube to extend the macro-pulse duration against the back bombardment effect in the thermionic RF gun. As a result the electron beam with about 6 micro-s duration has been available for the lasing experiment. About 106 times large light output than that from the spontaneous light was observed with a liq. N2 cooled IR detector. The FEL gain was 16% which was estimated from the exponential growth of the light and this shows good agreement with a gain simulation.
* H. Ohgaki et al., "Design studies of IR-FEL system at IAE, Kyoto University", Nucl. Instrum. Methods in Phys. Res. A, vol.507, pp.150-153 (2003)
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Slides
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| MOPPH046 |
Phase Stability of a Microtron Driving a Terahertz FEL
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79 |
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- G. M. Kazakevich, V. M. Pavlov
BINP SB RAS, Novosibirsk
- Y. U. Jeong, B. C. Lee
KAERI, Daejon
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Phase stability of bunches accelerated by a magnetron-driven microtron-injector of a terahertz Free Electron Laser (FEL) has been studied to optimize the microtron regimes providing good operation of the FEL. The study is based on a simulation of the beam dynamics in the microtron considering 2-D motion of the electrons in the median plane. This allows the computation of the first harmonic of the current loading the accelerating cavity and the current as well. The time-dependent current has been used to calculate the frequency deviations caused by the incremental loading in the coupled accelerating and magnetron cavities. Further computations using the 2-D simulation show noticeable phase oscillation of the accelerated bunch leaving the microtron on the macro-pulse front. The phase oscillation is in agreement with measured one and affects the lasing in the microtron-based FEL. Optimization of the microtron regimes allows one to minimize the effect. As a result the terahertz microtron-based FEL provides radiated macro-pulse energy up to 0.2 mJ in the range of 100-350 μm with good stability. Results of the simulation and the measurements are presented in this article.
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| TUAAU03 |
Design Study on THz Seeded FEL Using Photocathode RF Gun and Short Period Undulator
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196 |
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- T. Kii, K. Higashimura, R. Kinjo, K. Masuda, H. Ohgaki, H. Zen
Kyoto IAE, Kyoto
- Y. U. Jeong
KAERI, Daejon
- R. Kuroda
AIST, Tsukuba, Ibaraki
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A compact, high-power, narrowband, tunable coherent light source in THz regime will be a quite useful tool for bimolecular science and advanced imaging for security and so on. In this work, we propose a compact seeded THz (frequency:0.5 – 2 THz) high-gain single pass free electron laser (FEL) amplifier using a multi-bunch photocathode RF gun* and a compact hybrid staggered undulator** and injection-seeded terahertz parametric generator (IS-TPG)***. The proposed configuration has following advantages: 1. The Fourier transform limit of the THz seeded pulse can overcome the disadvantage of broad spectrum of a self-amplified spontaneous emission (SASE). 2. The resonant FEL wavelength can be rapidly controlled by changing solenoid current of the staggered undulator. 3. The single pass configuration without optical cavity mirrors helps to achieve the rapid frequency tuning. In the conference, the detailed design and numerical estimation will be discussed.
* R. Kuroda, et al., International Journal of Modern Physics B, vol. 21, pp.488 (2007)
** S. Sasaki, Proc. of PAC 2005, pp. 982 (2005)
*** K. Kawase, et al., APL, vol. 80, pp. 195 (2002)
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Slides
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| THAAU03 |
A Bulk High-Tc Superconductor Staggered Array Undulator
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473 |
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- R. Kinjo, K. Higashimura, T. Kii, K. Masuda, K. Nagasaki, H. Ohgaki, H. Zen
Kyoto IAE, Kyoto
- Y. U. Jeong
KAERI, Daejon
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Development of short-period undulators is one of the most intensive interests in FEL research, with reduced energy requirements and accordingly reduced cost for electron linacs, which is supposed to expand the use of FELs in diverse applications. In this context, we propose use of high-Tc superconducting magnets in the hybrid staggered-array undulator configuration*. The reason for the choice of the configuration is that magnetization of the superconducting magnets can be performed by a single solenoid, since the magnetization direction of the magnets to be set are all in the axial direction. The present undulator is expected to show such advantages as a short period with high magnetic induction by the superconducting magnets, and a rapid control of undulator fields and the resultant FEL wavelength by means of the solenoid current. In this paper, we discuss the results from characteristic analyses to show the potential advantages of the present undulator, by the use of a magnetic field solver taking into account the distinctive magnetic field distribution induced by high-Tc superconducting magnets. Also presented are the measurement results of undulator fields in a prototype.
* S. Sasaki, Proceedings of 2005 PAC, pp. 982-984 (2005)
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Slides
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