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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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| 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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| TUPPH052 |
Beam Loading Compensation by RF Detuning in a Thermionic RF Gun
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367 |
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- H. Zen, K. Higashimura, T. Kii, R. Kinjo, K. Masuda, H. Ohgaki
Kyoto IAE, Kyoto
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The thermionic RF gun is suitable to realize a compact and economical free electron laser, because it doesn’t require a buncher system or a high power laser system. However, due to the back bombardment effect, the beam current increases and the beam energy decreases during macro-pulse duration. To overcome the effect, some cures have been introduced e.g. the sweep magnet* and the RF amplitude control**. Recently we found a new method to mitigate the energy decrease by analytical and numerical investigations of the beam loading effect in our RF gun. When the frequency of the RF power to the gun is detuned to higher frequency (several hundred kHz) than the resonant frequency of the cavity, the energy degradation of the electron beam is mitigated. The effectiveness of the detuning method has been confirmed with the experiment. In the conference, results of the analysis and the experiment will be presented.
* C. B. Mckee, et al., NIM A, vol.304, pp.386-391 (1991)
** N. Okawachi, et al., Proceedings of FEL 2006, pp.664-667 (2006)
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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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