| Paper | Title | Page |
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| MOPD57 | Development of Multi-bunch Laser System for Photocathode RF Gun in KU - FEL | 173 |
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| We have been developing mid-infrared FEL (MIR-FEL) system, KU-FEL (Kyoto University-FEL), which utilizes a 4.5-cell S-band thermionic RF gun, in Institute of Advanced Energy, Kyoto University. We plan to introduce a BNL-type 1.6-cell photocathode RF gun to generate higher peak power MIR-FEL. The purpose of this work is to develop the multi-bunch laser system which excites the photocathode in the RF gun. The target values of the system are bunch number of 300 and pulse energy of 10 uJ perμpulse in 266 nm. The laser system consists of a mode-locked Nd:YVO4 laser as the oscillator, an acousto-optic modulator, a laser beam pointing stabilization system, a flash lamp pumped amplifier and 4th harmonic generation crystals. We will report the current status of multi-bunch laser in this conference. | ||
| TUPD41 | Practical Design of Resonance Frequency Tuning System for Coaxial RF Cavity for Thermionic Triode RF Gun | 333 |
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The FEL radiation production requires temporal stability of electron beam energy. The latter depends directly on the quality of electron gun. The KUFEL(Kyoto University- FEL) facility uses a thermionic 4.5 cell S-band RF gun for electron beam generation. The main disadvantage of using a thermionic RF gun is the effect of backstreaming electrons, which heats up the cathode material during operation and causes energy drop. An additional cavity, triode cavity, for RF gun was designed and fabricated in order to control the electron injection and to mitigate the amount of backstreaming electrons(*). The quality factor and the coupling coefficient of the triode cavity with the RF feed coaxial cable were designed to ensure the induction of the required cavity voltage and a wide frequency acceptance(***). The corresponded simulations show the power reduction of back streaming electrons for 80% as well as peak current enhancement without emittance degradation(**,***). However the fabricated prototype didn't match the designed parameters as tested at low power(****). In this work we report the strategies for correction of deviation from simulated and tested parameters of triode cavity.
* K.Masuda et al. Prc. FEL 2009, Liverpool ** K.Masuda et al. Prc. FEL 2006, Berlin *** T. Shiiyama et al. Prc. FEL 2007, Novosibirsk **** M.Takasaki et al. Prc. FEL 2010, Malmö |
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| WEPD38 | Improvement of KU-FEL Performance by Replacing Undulator and Optical Cavity | 449 |
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A mid-infrared FEL named as KU-FEL (Kyoto University FEL) has been developed for energy related sciences*. The FEL achieved first lasing and saturation in 2008**,***. However, the tunable range was limited from 10 to 13 micro-m because of insufficient macro-pulse duration of e-beam and FEL gain. The undulator of KU-FEL has been replaced with the undulator which was previously used for ERL-FEL in JAEA. The optical cavity has been replaced with optimized one. In addition the diameter of the coupling hole on the upstream cavity mirror has been reduced from 2 to 1 mm for reducing cavity loss. After installation, the tunable range of KU-FEL has been improved to 5-15 micro-m. Estimated FEL gain is greater than 30%, which was 1.5 times larger than original configuration.
*H. Zen, et al., Infrared Physics and Technology, Vol. 51, Issue 5, p.382 (2008) **H. Ohgaki, et al., Proc. of FEL08, p.4 (2008) ***H. Ohgaki, et al., Proc. of FEL09, p.572 (2009) |
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| THPD05 | Observation of High Harmonic Generation from 6H-SiC Irradiated by MIR-FEL | 555 |
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Silicon Carbide (SiC) is attractive as the next generation power devices, heat resistance material and so on. In addition, 6H-SiC is investigated as the material for high harmonic generation [1]. For verifying the possibility of high harmonic generation by 6H-SiC irradiated by MIR-FEL, we measured the emission spectrum from 6H-SiC irradiated by MIR-FEL whose center wavelength was 7.8 μm. As the result, we clearly observed the emissions at 963 nm, 861 nm and 775 nm, which correspond to harmonics of 8th, 9th and 10th wavelength respectively. In this meeting, we will present and discuss about the high harmonic generation introduced by MIR-FEL.
[1] Hiroaki Sato, Makoto Abe, Ichiro Shoji, Jun Suda, and Takashi Kondo, J. Opt. Soc. Am. B, Vol. 26, No. 10(2009), 1892-1896 |
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