FEL2012 - List of Authors (Zen, H.)

Paper

Title

Page

Development of Multi-bunch Laser System for Photocathode RF Gun in KU - FEL

173

K. Shimahashi, Y.W. Choi, H. Imon, T. Kii, R. Kinjo, T. Konstantin, K. Masuda, H. Negm, H. Ohgaki, K. Okumura, M. Omer, S. Shibata, K. Yoshida, H. Zen
Kyoto University, Institute for Advanced Energy, Kyoto, Japan
R. Kuroda
AIST, Tsukuba, Ibaraki, Japan

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

T. Konstantin, Y.W. Choi, H. Imon, T. Kii, R. Kinjo, K. Masuda, K. Nagasaki, H. Negm, H. Ohgaki, K. Okumura, M. Omer, S. Shibata, K. Shimahashi, M. Takasaki, K. Yoshida, H. Zen
Kyoto University, Institute for Advanced Energy, Kyoto, Japan

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

WEOB03

Laser-induced CSR : Seeding of the Microbunching Instability in Storage Rings

E. Roussel, S. Bielawski, C. Evain, C. Szwaj, T. Tanikawa
PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France
M. Adachi, M. Katoh
UVSOR, Okazaki, Japan
M. Hosaka, N. Yamamoto
Nagoya University, Nagoya, Japan
M. Le Parquier
CERLA, Villeneuve d'Ascq, France
H. Zen
Kyoto University, Institute for Advanced Energy, Kyoto, Japan

Microbunching instability arises both in Linear Free Electron Laser and in storage rings due to the interaction of the electrons with their own radiation, mainly in dipoles (bending magnets in storage rings and chicanes in linear FEL). This instability leads to the formation of micro-structures in the longitudinal phase-space (typically in the mm range in the longitudinal profile) and limits the performances of these accelerator based ligth sources. We show that the interaction of the electron bunch with an external laser pulse, whose envelope is modulated at a Terahertz frequency (associated to mm wavelength), allows to investigate the dynamics of electron bunches in storage rings during the micro-bunching instability. Here, we achieve experiments at UVSOR-II* around the CSR instability threshold. We also perform numerical calculations using a one-dimensional Fokker-Planck-Vlasov modeling taking into account CSR wakefield. This seeding mechanism highlights that CSR depends on the wakefields for some ranges of excited wavenumber.
* C. Evain et al., Phys. Rev. ST Accel. Beams 13, 090703 (2010); S. Bielawski et al., Nature Physics 4, 390 (2008).

Slides WEOB03 [2.523 MB]

WEPD38

Improvement of KU-FEL Performance by Replacing Undulator and Optical Cavity

449

H. Zen, M. A. Bakr, Y.W. Choi, H. Imon, T. Kii, R. Kinjo, T. Konstantin, K. Masuda, H. Negm, H. Ohgaki, K. Okumura, M. Omer, S. Shibata, K. Shimahashi, K. Yoshida
Kyoto University, Institute for Advanced Energy, Kyoto, Japan

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)

WEPD41

Construction and Commissioning of Coherent Light Source Experiment Station at UVSOR

460

S. Tanaka, M. Adachi, K. Hayashi, M. Katoh, S.I. Kimura, E. Nakamura, J. Yamazaki
UVSOR, Okazaki, Japan
M. Hosaka, Y. Taira, Y. Takashima, N. Yamamoto
Nagoya University, Nagoya, Japan
T. Takahashi
Kyoto University, Research Reactor Institute, Osaka, Japan
H. Zen
Kyoto University, Institute for Advanced Energy, Kyoto, Japan

At UVSOR, Coherent light source technologies, such as resonator free electron laser, coherent harmonic generation and coherent synchrotron radiation via laser modulation, have been developed parasitically by using an undulator and a beam-line normally used for photo-electron spectroscopy. Under Quantum Beam Technology Program of MEXT in Japan, we started constructing a new experiment station dedicated for the coherent light source developments. We created a new straight section by moving the injection line. Two identical undulators 1m long were constructed and installed there. A buncher magnet was constructed and installed between the undulators to form an optical klystron. Two beam-lines, BL1U and BL1B, were constructed, the former of which is for free electron laser and coherent harmonic generation and the later for the coherent synchrotron radiation in the terahertz range. The laser system was reinforced and new laser transport line was constructed. The generation of coherent synchrotron radiation by laser modulation was already tested. The construction of the optical cavity for the free electron laser will start in this year.

WEPD46

Pulse Structure Measurement of Near-Infrared FEL in Burst-Mode Operation of LEBRA Linac

472

K. Nakao, K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nogami, T. Sakai, T. Tanaka
LEBRA, Funabashi, Japan
H. Zen
Kyoto University, Institute for Advanced Energy, Kyoto, Japan

The near-infrared free electron laser (FEL) at the Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University has been provided for scientific studies in various fields since 2003. Improvement in the electron beam injector system for the LEBRA 125MeV electron linac made possible to accelerate the electron beam in three different modes, full-bunch mode, superimpose mode and burst mode. FEL lasing in the second and the third modes was achieved in 2011. The FEL pulse lengths in the full-bunch mode and the burst mode, measured at an FEL wavelength of 1600 nm with autocorrelation method using a Michelson interferometer, were approximately 100 fs and 180 fs, respectively. The FEL gain in the burst mode was apparently much higher than that in the full-bunch mode. Although the autocorrelation method provides only a rough estimate, the burst-mode FEL pulse structure was suggested to be different from the full bunch mode.

WEPD65

Design and Numerical Simulation of THz-FEL Amplifier in Kyoto University

519

M. A. Bakr, Y.W. Choi, T. Kii, R. Kinjo, K. Masuda, H. Negm, H. Ohgaki, M. Omer, K. Shimahashi, K. Yoshida, H. Zen
Kyoto University, Institute for Advanced Energy, Kyoto, Japan
M. A. Bakr
Assiut University, Assiut, Egypt

Design of a compact and economic THz free-electron laser (FEL) amplifier, which consists of a BNL-type 1.6 cells photocathode radio frequency gun, Solenoid, transport line and short undulator, has been studied at Kyoto University. The electron beam energy to obtain FEL with a wavelength of the range 150~400 μm was calculated to be 4.1~7.0 MeV for a bunch charge of 1.0 nC/bunch. The numerical calculations of the electron beam from the RF gun up to the undulator entrance are carried out using Parmela code and the FEL properties from the undulator will be simulated using GENESIS 1.3. The expected FEL spectral was estimated using 4~5 undulator periods with ~30 cm length and 0.3 T magnetic field. Details of the design concept, numerical calculations and results will be presented in the conference.

THOA03

Use of Fringe-Resolved Autocorrelation for the diagnosis of the wavelength stability of a FEL

Y. Qin, T. Kii, T. Nakajima, H. Ohgaki, X. Wang, H. Zen
Kyoto University, Institute for Advanced Energy, Kyoto, Japan

For the spectroscopic applications of a FEL it is very important to monitor its wavelength stability. The most straightforward way is to take a laser spectrum at once with an array-type photodetector. This, however, is not an easy task at the wavelength regions (<190 nm or >1100 nm) where a Si-based array-type photodetector does not work. An alternative method has to be developed. In this paper we propose to use the autocorrelation setup, which is usually used to measure the pulse duration, to monitor the wavelength stability of a FEL. During the numerical simulation to demonstrate the above idea, we have included various kinds of instabilities such as the central wavelength, intensity, and pulse duration as well as the chirps. Our results show that we can estimate the stability of the wavelength from the width of the upper envelope of fringe-resolved autocorrelation (FRAC) signals: Given the same pulse duration the FEL pulse with larger wavelength instability results narrower envelope width of FRAC signals. Based on this fact, the FRAC can be used as a tool to diagnose the wavelength stability in the wavelength region where a direct spectrum measurement is not possible.

Slides THOA03 [1.580 MB]

THPD05

Observation of High Harmonic Generation from 6H-SiC Irradiated by MIR-FEL

555

K. Yoshida, Y.W. Choi, H. Imon, T. Kii, R. Kinjo, K. Komai, K. Masuda, H. Negm, H. Ohgaki, K. Okumura, M. Omer, S. Shibata, K. Shimahashi, H. Zen
Kyoto University, Institute for Advanced Energy, Kyoto, Japan

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

THPD08

Pit Formation on Dental Hard Tissues Using Two Different Free Electron Laser Sources, LEBRA-FEL and KU-FEL

563

T. Sakae
Nihon University School of Dentistry at Matsudo, Matsudo-shi, Japan
K. Hayakawa, Y. Hayakawa, M. Inagaki, T. Kuwada, K. Nakao, K. Nogami, I. Sato, T. Tanaka
LEBRA, Funabashi, Japan
T. Kii, H. Ohgaki, H. Zen
Kyoto University, Institute for Advanced Energy, Kyoto, Japan

Funding: This study was supported by a Grant for Supporting Project for Strategic Research by MEXT, Japan (S0801032) and by the ZE Research Program, IIAE, Kyoto University (A-17).
According to the increased usage and demands of lasers in dentistry, research and development of the more reliable and functional lasers are needed. In the case of caries treatment, the lasers generated by commercial apparatus are not enough to dig the dental enamel and/or dentin tissues. Our previous studies showed that FEL generated at LEBRA has a potential to form pits on these dental hard tissues easily, and that the effective wavelength depends on the tissue types sensitively at about 3000 nm. To progress the FEL study on dental tissues, it is needed to spread the range of wavelengths more than that at LEBRA, between 2000 and 6000 nm. The newly established KU-FEL is able to generate the FEL of wavelength between 5000 and 13000 nm. Combining the two FEL sources, we found a new result that the dental hard tissues were easily dug by 7800 nm KU-FEL, which wavelength has not been presumed before. In the combination of LEBRA-FEL and KU-FEL, the wider knowledge on the FEL action on dental tissues will be achieved.

Paper	Title	Page
MOPD57	Development of Multi-bunch Laser System for Photocathode RF Gun in KU - FEL	173
	K. Shimahashi, Y.W. Choi, H. Imon, T. Kii, R. Kinjo, T. Konstantin, K. Masuda, H. Negm, H. Ohgaki, K. Okumura, M. Omer, S. Shibata, K. Yoshida, H. Zen Kyoto University, Institute for Advanced Energy, Kyoto, Japan R. Kuroda AIST, Tsukuba, Ibaraki, Japan
	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
	T. Konstantin, Y.W. Choi, H. Imon, T. Kii, R. Kinjo, K. Masuda, K. Nagasaki, H. Negm, H. Ohgaki, K. Okumura, M. Omer, S. Shibata, K. Shimahashi, M. Takasaki, K. Yoshida, H. Zen Kyoto University, Institute for Advanced Energy, Kyoto, Japan
	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

WEOB03	Laser-induced CSR : Seeding of the Microbunching Instability in Storage Rings
	E. Roussel, S. Bielawski, C. Evain, C. Szwaj, T. Tanikawa PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France M. Adachi, M. Katoh UVSOR, Okazaki, Japan M. Hosaka, N. Yamamoto Nagoya University, Nagoya, Japan M. Le Parquier CERLA, Villeneuve d'Ascq, France H. Zen Kyoto University, Institute for Advanced Energy, Kyoto, Japan
	Microbunching instability arises both in Linear Free Electron Laser and in storage rings due to the interaction of the electrons with their own radiation, mainly in dipoles (bending magnets in storage rings and chicanes in linear FEL). This instability leads to the formation of micro-structures in the longitudinal phase-space (typically in the mm range in the longitudinal profile) and limits the performances of these accelerator based ligth sources. We show that the interaction of the electron bunch with an external laser pulse, whose envelope is modulated at a Terahertz frequency (associated to mm wavelength), allows to investigate the dynamics of electron bunches in storage rings during the micro-bunching instability. Here, we achieve experiments at UVSOR-II* around the CSR instability threshold. We also perform numerical calculations using a one-dimensional Fokker-Planck-Vlasov modeling taking into account CSR wakefield. This seeding mechanism highlights that CSR depends on the wakefields for some ranges of excited wavenumber. * C. Evain et al., Phys. Rev. ST Accel. Beams 13, 090703 (2010); S. Bielawski et al., Nature Physics 4, 390 (2008).
	Slides WEOB03 [2.523 MB]

WEPD38	Improvement of KU-FEL Performance by Replacing Undulator and Optical Cavity	449
	H. Zen, M. A. Bakr, Y.W. Choi, H. Imon, T. Kii, R. Kinjo, T. Konstantin, K. Masuda, H. Negm, H. Ohgaki, K. Okumura, M. Omer, S. Shibata, K. Shimahashi, K. Yoshida Kyoto University, Institute for Advanced Energy, Kyoto, Japan
	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)

WEPD41	Construction and Commissioning of Coherent Light Source Experiment Station at UVSOR	460
	S. Tanaka, M. Adachi, K. Hayashi, M. Katoh, S.I. Kimura, E. Nakamura, J. Yamazaki UVSOR, Okazaki, Japan M. Hosaka, Y. Taira, Y. Takashima, N. Yamamoto Nagoya University, Nagoya, Japan T. Takahashi Kyoto University, Research Reactor Institute, Osaka, Japan H. Zen Kyoto University, Institute for Advanced Energy, Kyoto, Japan
	At UVSOR, Coherent light source technologies, such as resonator free electron laser, coherent harmonic generation and coherent synchrotron radiation via laser modulation, have been developed parasitically by using an undulator and a beam-line normally used for photo-electron spectroscopy. Under Quantum Beam Technology Program of MEXT in Japan, we started constructing a new experiment station dedicated for the coherent light source developments. We created a new straight section by moving the injection line. Two identical undulators 1m long were constructed and installed there. A buncher magnet was constructed and installed between the undulators to form an optical klystron. Two beam-lines, BL1U and BL1B, were constructed, the former of which is for free electron laser and coherent harmonic generation and the later for the coherent synchrotron radiation in the terahertz range. The laser system was reinforced and new laser transport line was constructed. The generation of coherent synchrotron radiation by laser modulation was already tested. The construction of the optical cavity for the free electron laser will start in this year.

WEPD46	Pulse Structure Measurement of Near-Infrared FEL in Burst-Mode Operation of LEBRA Linac	472
	K. Nakao, K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nogami, T. Sakai, T. Tanaka LEBRA, Funabashi, Japan H. Zen Kyoto University, Institute for Advanced Energy, Kyoto, Japan
	The near-infrared free electron laser (FEL) at the Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University has been provided for scientific studies in various fields since 2003. Improvement in the electron beam injector system for the LEBRA 125MeV electron linac made possible to accelerate the electron beam in three different modes, full-bunch mode, superimpose mode and burst mode. FEL lasing in the second and the third modes was achieved in 2011. The FEL pulse lengths in the full-bunch mode and the burst mode, measured at an FEL wavelength of 1600 nm with autocorrelation method using a Michelson interferometer, were approximately 100 fs and 180 fs, respectively. The FEL gain in the burst mode was apparently much higher than that in the full-bunch mode. Although the autocorrelation method provides only a rough estimate, the burst-mode FEL pulse structure was suggested to be different from the full bunch mode.

WEPD65	Design and Numerical Simulation of THz-FEL Amplifier in Kyoto University	519
	M. A. Bakr, Y.W. Choi, T. Kii, R. Kinjo, K. Masuda, H. Negm, H. Ohgaki, M. Omer, K. Shimahashi, K. Yoshida, H. Zen Kyoto University, Institute for Advanced Energy, Kyoto, Japan M. A. Bakr Assiut University, Assiut, Egypt
	Design of a compact and economic THz free-electron laser (FEL) amplifier, which consists of a BNL-type 1.6 cells photocathode radio frequency gun, Solenoid, transport line and short undulator, has been studied at Kyoto University. The electron beam energy to obtain FEL with a wavelength of the range 150~400 μm was calculated to be 4.1~7.0 MeV for a bunch charge of 1.0 nC/bunch. The numerical calculations of the electron beam from the RF gun up to the undulator entrance are carried out using Parmela code and the FEL properties from the undulator will be simulated using GENESIS 1.3. The expected FEL spectral was estimated using 4~5 undulator periods with ~30 cm length and 0.3 T magnetic field. Details of the design concept, numerical calculations and results will be presented in the conference.

THOA03	Use of Fringe-Resolved Autocorrelation for the diagnosis of the wavelength stability of a FEL
	Y. Qin, T. Kii, T. Nakajima, H. Ohgaki, X. Wang, H. Zen Kyoto University, Institute for Advanced Energy, Kyoto, Japan
	For the spectroscopic applications of a FEL it is very important to monitor its wavelength stability. The most straightforward way is to take a laser spectrum at once with an array-type photodetector. This, however, is not an easy task at the wavelength regions (<190 nm or >1100 nm) where a Si-based array-type photodetector does not work. An alternative method has to be developed. In this paper we propose to use the autocorrelation setup, which is usually used to measure the pulse duration, to monitor the wavelength stability of a FEL. During the numerical simulation to demonstrate the above idea, we have included various kinds of instabilities such as the central wavelength, intensity, and pulse duration as well as the chirps. Our results show that we can estimate the stability of the wavelength from the width of the upper envelope of fringe-resolved autocorrelation (FRAC) signals: Given the same pulse duration the FEL pulse with larger wavelength instability results narrower envelope width of FRAC signals. Based on this fact, the FRAC can be used as a tool to diagnose the wavelength stability in the wavelength region where a direct spectrum measurement is not possible.
	Slides THOA03 [1.580 MB]

THPD05	Observation of High Harmonic Generation from 6H-SiC Irradiated by MIR-FEL	555
	K. Yoshida, Y.W. Choi, H. Imon, T. Kii, R. Kinjo, K. Komai, K. Masuda, H. Negm, H. Ohgaki, K. Okumura, M. Omer, S. Shibata, K. Shimahashi, H. Zen Kyoto University, Institute for Advanced Energy, Kyoto, Japan
	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

THPD08	Pit Formation on Dental Hard Tissues Using Two Different Free Electron Laser Sources, LEBRA-FEL and KU-FEL	563
	T. Sakae Nihon University School of Dentistry at Matsudo, Matsudo-shi, Japan K. Hayakawa, Y. Hayakawa, M. Inagaki, T. Kuwada, K. Nakao, K. Nogami, I. Sato, T. Tanaka LEBRA, Funabashi, Japan T. Kii, H. Ohgaki, H. Zen Kyoto University, Institute for Advanced Energy, Kyoto, Japan
	Funding: This study was supported by a Grant for Supporting Project for Strategic Research by MEXT, Japan (S0801032) and by the ZE Research Program, IIAE, Kyoto University (A-17). According to the increased usage and demands of lasers in dentistry, research and development of the more reliable and functional lasers are needed. In the case of caries treatment, the lasers generated by commercial apparatus are not enough to dig the dental enamel and/or dentin tissues. Our previous studies showed that FEL generated at LEBRA has a potential to form pits on these dental hard tissues easily, and that the effective wavelength depends on the tissue types sensitively at about 3000 nm. To progress the FEL study on dental tissues, it is needed to spread the range of wavelengths more than that at LEBRA, between 2000 and 6000 nm. The newly established KU-FEL is able to generate the FEL of wavelength between 5000 and 13000 nm. Combining the two FEL sources, we found a new result that the dental hard tissues were easily dug by 7800 nm KU-FEL, which wavelength has not been presumed before. In the combination of LEBRA-FEL and KU-FEL, the wider knowledge on the FEL action on dental tissues will be achieved.