IPAC2016 - List of Authors (Ohgaki, H.)

Paper	Title	Page
MOPOW018	Feasibility Study of Photocathode Opearation of Thermionic RF Gun at KU-FEL	754
	H. Zen, T. Kii, K. Masuda, K. Morita, T. Murata, T. Nogi, H. Ohgaki, S. Suphakul, K. Torgasin Kyoto University, Kyoto, Japan R. Kuroda AIST, Tsukuba, Ibaraki, Japan
	Kyoto University Free Electron Laser (KU-FEL) is a mid-infrared FEL driven by a compact linac utilizinig a thermionic RF gun as its electron source. Recently we succeeded in operating KU-FEL with photocathode operation of the RF gun by using the thermionic cathode (LaB6) as a photocathode. The performance of KU-FEL under the thermionic cathode and photocathode operation will be reported. In addition, some recent application experiment results will also be presented in this presentation. H. Zen, et al., Infrared Phys. Techn. 51 (2008) 382.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW018
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TUPOW008	Generation of Short Bunch Electron Beam from Compact Accelerator for Terahertz Radiation	1757
	S. Suphakul, T. Kii, K. Masuda, K. Morita, H. Ohgaki, K. Torgasin, H. Zen Kyoto University, Kyoto, Japan
	We are developing a new compact accelerator system to generate a high power terahertz (THz) radiation at the Institute of Advanced Energy, Kyoto University. THz radiations are produced by injecting ultra-short and intense electron pulses to a short plannar undulator. The bunch compression characteristic by the newly installed chicane was investigated by observation of a coherent part of an optical transition radiation (OTR). As the result, the chicane can compress the electron bunch at the laser injection phase from 10 to 40 degree. The beam energy and relative rms energy spread were also measured and the results were 4.6 MeV and 1.3 %, respectively.
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TUPOY046	Study on NRF-CT Imaging by Laser Compton Backscattering Gamma-rays in UVSOR	2007
	H. Ohgaki, I. Daito, T. Kii, H. Zen Kyoto University, Kyoto, Japan T. Hayakawa, T. Shizuma JAEA, Ibaraki-ken, Japan M. Katoh, J. Yamazaki UVSOR, Okazaki, Japan Y. Taira, H. Toyokawa AIST, Ibaraki, Japan
	Funding: This work was supported by JSPS KAKENHI Grant Number 26289363, 24340060 and the Joint Studies Program (2014) of the Institute for Molecular Science. Monochromatic gamma-ray beam in MeV energy region is suitable for non-destructive inspection of high density and massive objects because of its high penetrability. A specific nuclide can be detected by the process of Nuclear Resonance Fluorescence (NRF). A non-destructive inspection of Special Nuclear Materials hidden in a container cargo using NRF is proposed by Bertozzi. Non-destructive detection of Pu inside of a spent nuclear fuel rod is also proposed for management of radioactive wastes, nuclear material accounting and safeguards. We have developed 2D NRF imaging by using quasi-monochromatic gamma-ray beam in MeV energy region generated by Laser Compton Backscattering (LCS) method** and proposed to develop an NRF-CT image in the ELI-NP where a high intensity LCS beam can be available in near future. To demonstrate and finalize the measurement system of the NRF-CT imaging by using LCS gamma-ray beam, we have started a study on NRF-CT imaging at the new LCS beamline in UVSOR. The LCS beamline can generate 5.4 MeV LCS gamma-rays with a flux of 1×10⁷ photons/s. We have measured the 5.291 MeV NRF gamma-rays from a lead target in this beamline and tried to take a NRF-CT image. * W. Bertozzi et al., Nucl. Inst. Meth. B241, 820-825 (2005). B. Ludewigt et al., Proc. of 2010 ANS meeting (2010). * H. Toyokawa et al., JJAP, 50, 100209 (2011).
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WEOAB03	Photoemission Properties of LaB6 and CeB6 Under Various Temperature and Incident Photon Energy Conditions	2088
SUPSS038	use link to see paper's listing under its alternate paper code
	K. Morita, T. Katsurayama, T. Kii, K. Masuda, T. Murata, K. Nagasaki, T. Nogi, H. Ohgaki, S. Suphakul, K. Torgasin, H. Yamashita, H. Zen Kyoto University, Kyoto, Japan
	Recently, thermionic cathode materials such as LaB6, Ir5Ce and dispenser cathodes have been also used as photocathode since they have low work function, reasonably high quantum efficiency, and long lifetime,. However, the effect of cathode temperature and laser wavelength on quantum efficiency is known only for limited conditions. Although it is expected to be able to lengthen the required wavelength of photocathode drive laser by heating cathodes, laser with photon energy under the work function has not been tested. Revealing them enables us to design the cost minimum accelerators. In this research, photoemission properties of LaB6 and CeB6 with various excitation photon energies will be investigated under various temperatures of the materials. Those materials have similar work function, but CeB6 have one order of magnitude smaller Richardson constant than LaB6*. By comparing photoemission properties of these materials, impact of Richardson constant on the photoemission properties will be investigated. S. Thorin et al. Proc of FEL2009, 310 D. Satoh et al. Proc of IPAC2014, 679 * J.M. Lafferty, J. Appl. Phys. 22, (1951), 299
	Slides WEOAB03 [0.996 MB]
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Paper

Title

Page

Feasibility Study of Photocathode Opearation of Thermionic RF Gun at KU-FEL

754

H. Zen, T. Kii, K. Masuda, K. Morita, T. Murata, T. Nogi, H. Ohgaki, S. Suphakul, K. Torgasin
Kyoto University, Kyoto, Japan
R. Kuroda
AIST, Tsukuba, Ibaraki, Japan

Kyoto University Free Electron Laser (KU-FEL) is a mid-infrared FEL driven by a compact linac utilizinig a thermionic RF gun as its electron source*. Recently we succeeded in operating KU-FEL with photocathode operation of the RF gun by using the thermionic cathode (LaB6) as a photocathode. The performance of KU-FEL under the thermionic cathode and photocathode operation will be reported. In addition, some recent application experiment results will also be presented in this presentation.
*H. Zen, et al., Infrared Phys. Techn. 51 (2008) 382.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW018

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TUPOW008

Generation of Short Bunch Electron Beam from Compact Accelerator for Terahertz Radiation

1757

S. Suphakul, T. Kii, K. Masuda, K. Morita, H. Ohgaki, K. Torgasin, H. Zen
Kyoto University, Kyoto, Japan

We are developing a new compact accelerator system to generate a high power terahertz (THz) radiation at the Institute of Advanced Energy, Kyoto University. THz radiations are produced by injecting ultra-short and intense electron pulses to a short plannar undulator. The bunch compression characteristic by the newly installed chicane was investigated by observation of a coherent part of an optical transition radiation (OTR). As the result, the chicane can compress the electron bunch at the laser injection phase from 10 to 40 degree. The beam energy and relative rms energy spread were also measured and the results were 4.6 MeV and 1.3 %, respectively.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW008

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TUPOY046

Study on NRF-CT Imaging by Laser Compton Backscattering Gamma-rays in UVSOR

2007

H. Ohgaki, I. Daito, T. Kii, H. Zen
Kyoto University, Kyoto, Japan
T. Hayakawa, T. Shizuma
JAEA, Ibaraki-ken, Japan
M. Katoh, J. Yamazaki
UVSOR, Okazaki, Japan
Y. Taira, H. Toyokawa
AIST, Ibaraki, Japan

Funding: This work was supported by JSPS KAKENHI Grant Number 26289363, 24340060 and the Joint Studies Program (2014) of the Institute for Molecular Science.
Monochromatic gamma-ray beam in MeV energy region is suitable for non-destructive inspection of high density and massive objects because of its high penetrability. A specific nuclide can be detected by the process of Nuclear Resonance Fluorescence (NRF). A non-destructive inspection of Special Nuclear Materials hidden in a container cargo using NRF is proposed by Bertozzi*. Non-destructive detection of Pu inside of a spent nuclear fuel rod is also proposed for management of radioactive wastes, nuclear material accounting and safeguards**. We have developed 2D NRF imaging by using quasi-monochromatic gamma-ray beam in MeV energy region generated by Laser Compton Backscattering (LCS) method*** and proposed to develop an NRF-CT image in the ELI-NP where a high intensity LCS beam can be available in near future. To demonstrate and finalize the measurement system of the NRF-CT imaging by using LCS gamma-ray beam, we have started a study on NRF-CT imaging at the new LCS beamline in UVSOR. The LCS beamline can generate 5.4 MeV LCS gamma-rays with a flux of 1×10⁷ photons/s. We have measured the 5.291 MeV NRF gamma-rays from a lead target in this beamline and tried to take a NRF-CT image.
* W. Bertozzi et al., Nucl. Inst. Meth. B241, 820-825 (2005).
** B. Ludewigt et al., Proc. of 2010 ANS meeting (2010).
*** H. Toyokawa et al., JJAP, 50, 100209 (2011).

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOY046

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WEOAB03

Photoemission Properties of LaB6 and CeB6 Under Various Temperature and Incident Photon Energy Conditions

2088

SUPSS038

use link to see paper's listing under its alternate paper code

K. Morita, T. Katsurayama, T. Kii, K. Masuda, T. Murata, K. Nagasaki, T. Nogi, H. Ohgaki, S. Suphakul, K. Torgasin, H. Yamashita, H. Zen
Kyoto University, Kyoto, Japan

Recently, thermionic cathode materials such as LaB6, Ir5Ce and dispenser cathodes have been also used as photocathode since they have low work function, reasonably high quantum efficiency, and long lifetime*,**. However, the effect of cathode temperature and laser wavelength on quantum efficiency is known only for limited conditions. Although it is expected to be able to lengthen the required wavelength of photocathode drive laser by heating cathodes, laser with photon energy under the work function has not been tested. Revealing them enables us to design the cost minimum accelerators. In this research, photoemission properties of LaB6 and CeB6 with various excitation photon energies will be investigated under various temperatures of the materials. Those materials have similar work function, but CeB6 have one order of magnitude smaller Richardson constant than LaB6***. By comparing photoemission properties of these materials, impact of Richardson constant on the photoemission properties will be investigated.
* S. Thorin et al. Proc of FEL2009, 310
** D. Satoh et al. Proc of IPAC2014, 679
*** J.M. Lafferty, J. Appl. Phys. 22, (1951), 299

Slides WEOAB03 [0.996 MB]

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEOAB03

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