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Nagai, Ryoji; Hajima, Ryoichi; Shizuma, Toshiyuki; Mori, Michiaki; Akagi, Tomoya*; Kosuge, Atsushi*; Honda, Yosuke*; Araki, Sakae*; Terunuma, Nobuhiro*; Urakawa, Junji*
Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1328 - 1330, 2015/09
Accelerator and laser technologies required for laser Compton scattering (LCS) photon source based on an energy-recovery linac (ERL) have been developed at the Compact ERL (cERL) facility. A high-flux, energy tunable, and monochromatic photon source such as the ERL-based LCS photon source is necessary for nondestructive assay of nuclear materials. For the demonstration of the ERL-based LCS photon generation, a laser enhancement cavity was installed at the recirculation loop of the cERL. The electron beam energy, the laser wavelength, and the collision angle are 20 MeV, 1064 nm, and 18 
, respectively. The calculated maximum energy of the LCS photons is about 7 keV. A silicon drift detector (SDD) with active area of 17 mm
placed 16.6 m from the collision point was used for observation of the LCS photons. As a result of the measurement, the flux on the detector, central energy, and energy width of the LCS photons were obtained as 1200/s, 6.91 keV, and 81 eV, respectively.
Nagai, Ryoji; Hajima, Ryoichi; Mori, Michiaki; Shizuma, Toshiyuki; Akagi, Tomoya*; Araki, Sakae*; Honda, Yosuke*; Kosuge, Atsushi*; Terunuma, Nobuhiro*; Urakawa, Junji*
Proceedings of 6th International Particle Accelerator Conference (IPAC '15) (Internet), p.1607 - 1609, 2015/06
Accelerator and laser technologies required for laser Compton scattering (LCS) photon source based on an energy-recovery linac (ERL) have been developed at the Compact ERL (cERL) facility. A high-flux, energy tunable, and monochromatic photon source such as the ERL-based LCS photon source is necessary for nondestructive assay of nuclear materials. For the demonstration of the ERL-based LCS photon generation, a laser enhancement cavity was installed at the recirculation loop of the cERL. The electron beam energy, the laser wavelength, and the collision angle are 20 MeV, 1064 nm, and 18 deg., respectively. The calculated maximum energy of the LCS photons is about 7 keV. A silicon drift detector (SDD) with active area of 17 mm placed 16.6 m from the collision point was used for observation of the LCS photons. As a result of the measurement, the flux on the detector, central energy, and energy width of the LCS photons were obtained as 1200 /s, 6.91 keV, and 81 eV, respectively.
Nagai, Ryoji; Hajima, Ryoichi; Mori, Michiaki; Shizuma, Toshiyuki; Akagi, Tomoya*; Kosuge, Atsushi*; Honda, Yosuke*; Urakawa, Junji*
Proceedings of 11th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1328 - 1331, 2014/10
A high intensity 
-ray source from the laser Compton scattering (LCS) by an electron beam in an energy-recovery linac (ERL) is a key technology for a nondestructive assay system to identify nuclear materials. In order to demonstrate accelerator and laser technologies required for a LCS photon generation, a LCS photon source is under construction at the Compact ERL (cERL). The LCS photon source consists of a mode-locked fiber laser and a laser enhancement cavity. A beamline and an experimental hatch are also under construction. The commissioning of the LCS photon source will be started in February 2015 and LCS photon generation is scheduled in March 2015.
Nagai, Ryoji; Hajima, Ryoichi; Mori, Michiaki; Shizuma, Toshiyuki; Akagi, Tomoya*; Kosuge, Atsushi*; Honda, Yosuke*; Urakawa, Junji*
Proceedings of 11th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.839 - 842, 2014/10
In order to demonstrate accelerator and laser technologies required for a laser Compton scattering (LCS) photon generation, a LCS photon source is under construction at the Compact ERL (cERL). We considered the flux monitors for the adjustment LCS photon source. A thin scintillator detector and a silicon drift detector are employed as flux monitors and are installed at the upstream part of the LCS beamline. The background signal level due to the bremsstrahlung of the electron beam was measured by a CsI(pure) scintillator. In the result of the measurement, the background signal is acceptable level for the flux monitors.
Tanaka, Momoko; Ochi, Yoshihiro; Kosuge, Atsushi; Okada, Hajime; Mori, Michiaki; Kiriyama, Hiromitsu; Tsubouchi, Masaaki; Nagashima, Keisuke
JAEA-Conf 2014-001, p.32 - 33, 2014/09
We have constructed a high power kHz laser system using Yb:YAG thin-disk as a gain medium for a driver laser of THz wave generation. A 4-bounce regenerative amplifier is constructed and output energy up to 10 mJ is obtained. Using compressed pulse, we demonstrated THz wave generation with LiNbO
crystal.
Nagai, Ryoji; Hajima, Ryoichi; Mori, Michiaki; Shizuma, Toshiyuki; Akagi, Tomoya*; Honda, Yosuke*; Kosuge, Atsushi*; Urakawa, Junji*
Proceedings of 5th International Particle Accelerator Conference (IPAC '14) (Internet), p.1940 - 1942, 2014/07
In order to demonstrate required accelerator and laser technologies for a high intensity -ray source from the laser Compton scattering (LCS), an LCS photon source and the peripheral equipment are under construction at the Compact ERL (cERL) at High Energy Accelerator Research Organization (KEK). The LCS photon source by an electron beam in the energy-recovery linac (ERL) is a key technology for a nondestructive assay system to identify nuclear species. The LCS photon source and the peripheral equipment consist of a mode-locked fiber laser, laser enhancement cavity, beamline, and experimental hatch. The commissioning of the LCS photon source will be started in February 2015.
Kiriyama, Hiromitsu; Mori, Michiaki; Suzuki, Masayuki*; Daito, Izuru*; Okada, Hajime; Ochi, Yoshihiro; Tanaka, Momoko; Sato, Masatoshi*; Tamaoki, Yoshinori*; Yoshii, Takehiro*; et al.
Reza Kenkyu, 42(6), p.441 - 447, 2014/06
We describe three specific high power laser systems that are being developed in our laboratory for many applications in high field science, nonlinear optics and material processing. We report on a femtosecond petawatt-class Ti:sapphire chirped-pulse amplification laser system that can produce a pulse energy of 20 J of 40 fs pulse duration, a picosecond high intensity Yb:YAG chirped-pulse amplification laser system that can generate a pulse energy of 100 mJ of 0.5 ps pulse duration, and a nanosecond high repetition rate Nd:YAG laser system that can provide an average power of 360 W with a pulse duration of 30 ns delivered at a 1 kHz repetition rate. We discuss the basic design aspects and present the results from our experimental investigations of these laser systems.
-ray beams to nondestructive detection and assay of nuclear materialHajima, Ryoichi; Hayakawa, Takehito; Shizuma, Toshiyuki; Angell, C.; Nagai, Ryoji; Nishimori, Nobuyuki; Sawamura, Masaru; Matsuba, Shunya; Kosuge, Atsushi*; Mori, Michiaki; et al.
European Physical Journal; Special Topics, 223(6), p.1229 - 1236, 2014/05
Times Cited Count：18 Percentile：49.02(Physics, Multidisciplinary)-raysKosuge, Atsushi; Mori, Michiaki; Okada, Hajime; Hajima, Ryoichi; Nagashima, Keisuke
Optics Express (Internet), 22(6), p.6613 - 6619, 2014/03
Times Cited Count：2 Percentile：13.46(Optics)Nowadays, generation of energy-tunable, monochromatic -rays is needed to establish a nondestructive assay method of nuclear fuel materials. The -rays are generated by collision of laser photons stored in a cavity and relativistic electrons. We propose a configuration of an enhancement cavity capable of performing polarization control fabricated by a combination of a four-mirror ring cavity with a small spot inside a cavity and a three-mirror of reflective optics as an image inverter for polarization-selectable -rays. The image inverter introduces a phase shift of specific polarization which can be used to generate an error signal to lock an optical cavity at a resonance condition.
Nagashima, Keisuke; Kosuge, Atsushi; Ochi, Yoshihiro; Tanaka, Momoko
Optics Express (Internet), 21(16), p.18640 - 18645, 2013/07
Times Cited Count：14 Percentile：59.39(Optics)A novel method for increasing diffraction efficiency of transmission gratings is proposed. In this method, dielectric multilayers are inserted between a grating region and a substrate. These multilayers work as an anti-reflection coating for the transmission grating. It is presented that a grating with 1740 grooves/mm has the diffraction efficiency over 99% using this anti-reflection coating.
Kiriyama, Hiromitsu; Shimomura, Takuya; Mori, Michiaki; Nakai, Yoshiki*; Tanoue, Manabu; Kondo, Shuji; Kanazawa, Shuhei; Pirozhkov, A. S.; Esirkepov, T. Z.; Hayashi, Yukio; et al.
Applied Sciences (Internet), 3(1), p.214 - 250, 2013/03
Times Cited Count：15 Percentile：50(Chemistry, Multidisciplinary)This paper reviews techniques for improving the temporal contrast and spatial beam quality in an ultra-intense laser system that is based on chirped-pulse amplification (CPA). We describe the design, performance, and characterization of our laser system, which has the potential for achieving a peak power of 600 TW. We also describe applications of the laser system in the relativistically dominant regime of laser-matter interactions and discuss a compact, high efficiency diode-pumped laser system.
/SiO multilayerTateno, Ryo*; Okada, Hajime; Otobe, Tomohito; Kawase, Keigo*; Koga, J. K.; Kosuge, Atsushi; Nagashima, Keisuke; Sugiyama, Akira; Kashiwagi, Kunihiro*
Journal of Applied Physics, 112(12), p.123103_1 - 123103_3, 2012/12
Times Cited Count：3 Percentile：13.53(Physics, Applied)Elucidation of the mechanisms of laser damage is indispensable in realizing high resistance mirrors for the next generation of ultra-short pulse high intensity lasers. In this study, the surface and a section of the laser-damaged area of a laser mirror were observed with a laser microscope and a transmission electron microscope (cross-sectional TEM), respectively. A grain boundary of HfO microcrystal was observed in the damaged area. This observation, and an evaluation of the mirror's damage resistance showed that the formation of crystals in the multilayer mirror is one of the major determinants of damage resistance.
for high-power terahertz-wave generation [Jpn. J. Appl. Phys. 49 (2010) 122504]Nagashima, Keisuke; Kosuge, Atsushi
Japanese Journal of Applied Physics, 51(11), P. 119201_1, 2012/11
Times Cited Count：4 Percentile：88.56(Physics, Applied)Erratum; Design of rectangular transmission gratings fabricated in LiNbO for high-power terahertz-wave generation [Jpn. J. Appl. Phys. 49 (2010) 122504]
Sugiyama, Akira; Kiriyama, Hiromitsu; Ochi, Yoshihiro; Mori, Michiaki; Tanaka, Momoko; Sasao, Fumitaka; Kosuge, Atsushi; Okada, Hajime
JAEA-Conf 2011-001, p.15 - 18, 2011/03
Main theme of our group in this middle term JAEA program is a development of high-averaged power short pulse laser system pumped by LDs (laser diodes). To realize this next term laser system, we have just started considering a Yb doped ceramics laser with a several members of KPSI. We have also developed a laser system named QUADRA (high-Quality Ultra ADvanced RAdiation Sources) in C-Phost program. In the first term up to FYH22, essential studies for QUADRA have been investigated. In the second term, QUADRA development will be merged with the next term laser system in JAEA to produce high powered THz radiation. In addition to these developments, we support to improve the performances of conventional high-power laser system, J-KAREN, for the requirement of advanced application studies in this middle term JAEA program.
for high-power terahertz-wave generationNagashima, Keisuke; Kosuge, Atsushi
Japanese Journal of Applied Physics, 49(12), p.122504_1 - 122504_4, 2010/12
Times Cited Count：24 Percentile：67.15(Physics, Applied)Precise parameters are investigated for rectangular transmission gratings fabricated in LiNbO substrate for the purpose of high-power terahertz-wave generation. Here, a simple setup is considered, where the pumping laser is injected to the grating surface from air or fused silica. The maximum diffraction efficiencies are 0.4 for air and 0.9 for fused silica. The designed gratings have deep grooves with the depth of about 0.5 
m and the width of 0.12-0.14 m. It was found that the diffraction efficiency is much less sensitive to the groove depth, than to the groove width.
Kiriyama, Hiromitsu; Mori, Michiaki; Nakai, Yoshiki*; Shimomura, Takuya; Sasao, Hajime*; Tanaka, Momoko; Ochi, Yoshihiro; Tanoue, Manabu*; Kondo, Shuji; Kanazawa, Shuhei; et al.
Reza Kenkyu, 38(9), p.669 - 675, 2010/09
This paper reviews the temporal contrast and spatial beam quality improvement techniques in a high intensity Ti:sapphire laser system that is based on chirped-pulse amplification (CPA). We describe a low gain optical parametric chirped-pulse amplification (OPCPA) preamplifier that uses high energy, clean pulse seeding and is shown to significantly improve the contrast to better than 10
-10
relative to the peak of the main femtosecond pulse. We also report the use of a diffractive optical element for beam homogenization of a 100 J level Nd:glass green pump laser, achieving a flat-topped spatial profile with a filling factor near 80 %.
Kosuge, Atsushi; Kiriyama, Hiromitsu; Shimomura, Takuya*; Tanoue, Manabu*; Kanazawa, Shuhei; Ochi, Yoshihiro; Mori, Michiaki; Tanaka, Momoko; Okada, Hajime; Sasao, Hajime*; et al.
Reza Kenkyu, 38(9), p.706 - 710, 2010/09
High conversion efficiency of optical parametric chirped-pulse amplification (OPCPA) is demonstrated with the use of a commercial frequency-doubled Q-Switched Nd:YAG laser. In the high energy seeded OPCPA, we have achieved a pump-to-signal conversion efficiency of 28%. Our result represents, to our knowledge, the most efficient OPCPA to date pumped by a commercial frequency-doubled Q-switched Nd:YAG laser.
Kondo, Kiminori; Kosuge, Atsushi; Sugiyama, Akira
no journal, ,
In Kerr lens mode lock optical cavity, if the intense region with a short pulsewitdth, where the optical Kerr effect drives mode locking actio, with inserting pulse compressor and stretcher there, the short pulse part is separated from the comparatively long pulse part in that optical resonator. So called "Chirped Pulse Amplification (CPA)" can be taken in the mode lock optical cavity resonator. In this study, by confirming the possibility of CPA action in the optical cavity, the optical ring resonator with negative and positive dispersion components for controlling a chirp. The experimental results suggest that the successful control of a chirp in Kerr lens mode lock optical cavity.
Sugiyama, Akira; Kiriyama, Hiromitsu; Ochi, Yoshihiro; Tanaka, Momoko; Nakai, Yoshiki; Sasao, Hajime; Tateno, Ryo; Okada, Hajime; Kosuge, Atsushi; Tsubouchi, Masaaki
no journal, ,
The main subject of our group is upgrade of J-KAREN and TOPAZ laser systems. The J-KAREN achieves the potential for generating a peak power of 500 TW, and exceeds a contrast ratio of 10E10. The TOPAZ achieves pulse power of 15 J at a repetition rate of 0.1 Hz. We also started a development of another laser system named QUADRA (Quality Ultra ADvanced RAdiation Source) in C-Phost. The QUADRA system is a high averaged short pulse laser pumped by high power LD at kHz repetition rate. This development is essential for the developments of other new laser systems in the next 5-year program of JAEA.
-ray beam, 1; Facility design and R&D statusHajima, Ryoichi; Hayakawa, Takehito; Kikuzawa, Nobuhiro; Shizuma, Toshiyuki; Nishimori, Nobuyuki; Nagai, Ryoji; Sawamura, Masaru; Kawase, Keigo; Kosuge, Atsushi; Tateno, Ryo; et al.
no journal, ,
no abstracts in English
