FEL2012 - List of Authors (Nakao, K.)

Paper	Title	Page
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.

WEPD48	Development of Intense Terahertz-wave Coherent Synchrotron Radiations at LEBRA	480
	N. Sei, H. Ogawa AIST, Tsukuba, Ibaraki, Japan K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, T. Tanaka LEBRA, Funabashi, Japan
	Funding: This work was supported by JSPS Grant-in-Aid for Challenging Exploratory Research 2365696. Nihon University and AIST have jointly developed intense terahertz-wave coherent synchrotron radiations at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University. Because a bunch length is short and a charge is large in an electron beam of a linac to saturate free-electron laser (FEL) power, the electron beam of the linac in an FEL facility is suitable for generating intense coherent radiations generally. Therefore, we launched a development of a THz-wave source with using an upstream bending magnet located in the FEL beam line. Recently, Nihon University developed 'burst mode operation', in which two or three electron bunches were included at an interval of 22.4 or 44.8 ns [1]. The electric charge in the micropulse was high (several hundreds pC) in the burst mode, so generation and observation of the coherent synchrotron radiation became easy. We have already measured the intense THz-wave from LEBRA and confirmed it to be the coherent synchrotron radiation (CSR). It was also found that CSR might have serious influence on a high-energy electron beam. In the presentation, we will report the characteristics of the CSR at LEBRA. E-mail address: sei.n@aist.go.jp 1. K. Nakao et al., Lasing of near infrared FEL with the burst-mode beam at LEBRA, Proceedings of FEL11, Shanghai, China, (2011).

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

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.

WEPD48

Development of Intense Terahertz-wave Coherent Synchrotron Radiations at LEBRA

480

N. Sei, H. Ogawa
AIST, Tsukuba, Ibaraki, Japan
K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, T. Tanaka
LEBRA, Funabashi, Japan

Funding: This work was supported by JSPS Grant-in-Aid for Challenging Exploratory Research 2365696.
Nihon University and AIST have jointly developed intense terahertz-wave coherent synchrotron radiations at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University. Because a bunch length is short and a charge is large in an electron beam of a linac to saturate free-electron laser (FEL) power, the electron beam of the linac in an FEL facility is suitable for generating intense coherent radiations generally. Therefore, we launched a development of a THz-wave source with using an upstream bending magnet located in the FEL beam line. Recently, Nihon University developed 'burst mode operation', in which two or three electron bunches were included at an interval of 22.4 or 44.8 ns [1]. The electric charge in the micropulse was high (several hundreds pC) in the burst mode, so generation and observation of the coherent synchrotron radiation became easy. We have already measured the intense THz-wave from LEBRA and confirmed it to be the coherent synchrotron radiation (CSR). It was also found that CSR might have serious influence on a high-energy electron beam. In the presentation, we will report the characteristics of the CSR at LEBRA.
E-mail address: sei.n@aist.go.jp
1. K. Nakao et al., Lasing of near infrared FEL with the burst-mode beam at LEBRA, Proceedings of FEL11, Shanghai, China, (2011).

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.