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Taira, Yoshitaka*; Endo, Shunsuke; Kawamura, Shiori*; Nambu, Taro*; Okuizumi, Mao*; Shizuma, Toshiyuki*; Omer, M.; Zen, H.*; Okano, Yasuaki*; Kitaguchi, Masaaki*
Physical Review A, 107(6), p.063503_1 - 063503_10, 2023/06
Times Cited Count：6 Percentile：62.78(Optics)no abstracts in English
Al
GaO
scintillators by gamma-ray-induced positron annihilation lifetime spectroscopyFujimori, Kosuke*; Kitaura, Mamoru*; Taira, Yoshitaka*; Fujimoto, Masaki*; Zen, H.*; Watanabe, Shinta*; Kamada, Kei*; Okano, Yasuaki*; Kato, Masahiro*; Hosaka, Masahito*; et al.
Applied Physics Express, 13(8), p.085505_1 - 085505_4, 2020/08
Times Cited Count：6 Percentile：27.95(Physics, Applied)To clarify the existence of cation vacancies in Ce-doped GdAlGaO (Ce:GAGG) scintillators, we performed gamma-ray-induced positron annihilation lifetime spectroscopy (GiPALS). GiPAL spectra of GAGG and Ce:GAGG comprised two exponential decay components, which were assigned to positron annihilation at bulk and defect states. By an analogy with Ce:YAl
O, the defect-related component was attributed to Al/Ga-O divacancy complexes. This component was weaker for Ce, Mg:GAGG, which correlated with the suppression of shallow electron traps responsible for phosphorescence. Oxygen vacancies were charge compensators for Al/Ga vacancies. The lifetime of the defect-related component was significantly changed by Mg co-doping. This was understood by considering aggregates of Mg
ions at Al/Ga sites with oxygen vacancies, which resulted in the formation of vacancy clusters.
Zhang, Z.*; Nishimura, Hiroaki*; Namimoto, Takura*; Fujioka, Shinsuke*; Arikawa, Yasunobu*; Nishikino, Masaharu; Kawachi, Tetsuya; Sagisaka, Akito; Hosoda, Hirokazu*; Orimo, Satoshi; et al.
Review of Scientific Instruments, 83(5), p.053502_1 - 053502_5, 2012/05
Times Cited Count：18 Percentile：59.64(Instruments & Instrumentation)X-ray line spectra ranging from 17 to 77 keV were quantitatively measured with a Laue spectrometer, composed of a cylindrically curved crystal and a detector. Either a visible CCD detector coupled with a CsI phosphor screen or an imaging plate can be chosen, depending on the signal intensities and exposure times. The absolute sensitivity of the spectrometer system was calibrated using pre-characterized laser-produced X-ray sources and radioisotopes. The integrated reflectivity for the crystal is in good agreement with predictions by an open code for X-ray diffraction. The energy transfer efficiency from incident laser beams to hot electrons, as the energy transfer agency for specific X-ray line emissions, is derived as a consequence of this work.
Zhang, Z.*; Nishikino, Masaharu; Nishimura, Hiroaki*; Kawachi, Tetsuya; Pirozhkov, A. S.; Sagisaka, Akito; Orimo, Satoshi; Ogura, Koichi; Yogo, Akifumi; Okano, Yasuaki*; et al.
Optics Express (Internet), 19(5), p.4560 - 4565, 2011/02
Times Cited Count：19 Percentile：64.77(Optics)
line emission from Mo and Ag plate were experimentally studied by using ultra-high intensity, clean femtosecond laser pulses. Absolutely yield of X-rays at 17 keV from Mo and 22 keV from Ag were measured as a function of the laser pulse contrast ratio and irradiation intensity. Significant enhancement of yields were obtained for both Mo and Ag with higher contrast ratios and high irradiance. The conversion efficiencies of 4.28 
10
/sr for Mo and 4.84 10/sr for Ag, the highest values ever obtained, have been demonstarted with the contrast ratio of 10
to 10
.
-H2AX and phosphorylated ATM focus formation in cancer cells after laser plasma X irradiationSato, Katsutoshi; Nishikino, Masaharu; Okano, Yasuaki*; Oshima, Shinsuke*; Hasegawa, Noboru; Ishino, Masahiko; Kawachi, Tetsuya; Numasaki, Hodaka*; Teshima, Teruki*; Nishimura, Hiroaki*
Radiation Research, 174(4), p.436 - 445, 2010/10
Times Cited Count：16 Percentile：47.12(Biology)Usefulness of laser-plasma X-ray pulse for medical and radiation biological studies was investigated and compared with that of conventional sources such as those obtained from a linear accelerator. A cell irradiation system was developed which uses Copper-K
(8 keV) lines from an ultra-short high intensity laser to produce plasma. The absorbed dose of the 8 keV laser-plasma X-ray pulse was accurately estimated with Gafchromic EBT film. When the cells were irradiated with approximately 2 Gy of laser plasma X-ray, the circular regions on -H2AX positive cells could be clearly identified. Moreover, the number of -H2AX and phosphorylated ataxia telangiectasia mutated (ATM) foci induced by 8 keV laser plasma X-ray were comparable to those induced by 4MV X-ray. These results indicate that the laser plasma X-ray source can be useful for radiation biological studies.
Zhang, Z.*; Nishikino, Masaharu; Nishimura, Hiroaki*; Kawachi, Tetsuya; Sagisaka, Akito; Orimo, Satoshi; Ogura, Koichi; Pirozhkov, A. S.; Yogo, Akifumi; Okano, Yasuaki*; et al.
Reza Kenkyu, 38(9), p.698 - 701, 2010/09
Monochromatic X-ray generation from Cu plates was experimentally studied by using a high contrast femtosecond laser pulse. Absolute yield of Ka line at 8 keV was measured as a function of laser pulse contrast ration and irradiation intensity. The conversion efficiency of 8 10/sr, the highest value ever obtained, has been demonstrated at 5.5 10
W/cm
with a contrast ratio of 10.
X-ray probe in radiation biologyNishikino, Masaharu; Sato, Katsutoshi; Hasegawa, Noboru; Ishino, Masahiko; Oshima, Shinsuke*; Okano, Yasuaki*; Kawachi, Tetsuya; Numasaki, Hodaka*; Teshima, Teruki*; Nishimura, Hiroaki*
Review of Scientific Instruments, 81(2), p.026107_1 - 026107_3, 2010/02
Times Cited Count：23 Percentile：66.00(Instruments & Instrumentation)An X-ray generation and exposure system dedicated for radiation biology is developed. An X-ray pulse of 8.0 keV in energy as short as 1 ps is generated with a fs-laser pulse, and sample cells are irradiated through a specially designed cell dish with a silicon nitride membrane. DNA double-strand breaks in a nucleus of a human caner cell are caused by X-ray irradiation, and similar DNA breaks are obtained to those with the conventional X-ray source. This result demonstrates feasibility of radiobiological study with a single burst of X-rays shining on a single cell specimen.
Takamura, Shuichi*; Kado, Shinichiro*; Fujii, Takashi*; Fujiyama, Hiroshi*; Takabe, Hideaki*; Adachi, Kazuo*; Morimiya, Osamu*; Fujimori, Naoji*; Watanabe, Takayuki*; Hayashi, Yasuaki*; et al.
Kara Zukai, Purazuma Enerugi No Subete, P. 164, 2007/03
no abstracts in English
Kikuchi, Mitsuru; Tamai, Hiroshi; Matsukawa, Makoto; Fujita, Takaaki; Takase, Yuichi*; Sakurai, Shinji; Kizu, Kaname; Tsuchiya, Katsuhiko; Kurita, Genichi; Morioka, Atsuhiko; et al.
Nuclear Fusion, 46(3), p.S29 - S38, 2006/03
Times Cited Count：13 Percentile：40.18(Physics, Fluids & Plasmas)The National Centralized Tokamak (NCT) facility program is a domestic research program for advanced tokamak research to succeed JT-60U incorporating Japanese university accomplishments. The mission of NCT is to establish high beta steady-state operation for DEMO and to contribute to ITER. The machine flexibility and mobility is pursued in aspect ratio and shape controllability, feedback control of resistive wall modes, wide current and pressure profile control capability for the demonstration of the high-b steady state.
Nishikino, Masaharu; Zhang, Z.*; Nishimura, Hiroaki*; Kawachi, Tetsuya; Pirozhkov, A. S.; Sagisaka, Akito; Ogura, Koichi; Orimo, Satoshi; Okano, Yasuaki*; Oshima, Shinsuke*; et al.
no journal, ,
no abstracts in English
Nishikino, Masaharu; Sato, Katsutoshi*; Oshima, Shinsuke*; Hasegawa, Noboru; Ishino, Masahiko; Kawachi, Tetsuya; Okano, Yasuaki*; Numasaki, Hodaka*; Teshima, Teruki*; Nishimura, Hiroaki*
no journal, ,
We have started to develop a laser plasma X-ray microbeam irradiation system, and demonstrated a preliminary study of the cell survival and 
-H2AX focus formation in the culture cells irradiated with laser-produced plasma X-ray.
Taira, Yoshitaka*; Fujimoto, Masaki*; Fujimori, Kosuke*; Kitaura, Mamoru*; Zen, H.*; Okano, Yasuaki*; Hosaka, Masahito*; Yamazaki, Junichiro*; Kato, Masahiro*; Hirade, Tetsuya; et al.
no journal, ,
For general positron sources, radioisotopes such as 
Na are often used. However, there is a problem that positrons cannot probe the deep region of metal materials with a thickness of 1 mm or more. Gamma-ray induced positron annihilation lifetime measurement (GiPALS) is a method for generating positrons in bulk samples with a thickness of several centimeters and samples placed in vessels such as high temperature and/or pressure furnaces. The annihilation lifetime of positrons is about 200 ps for metal materials, so it is important to use gamma rays with a shorter pulse width for GiPALS in order to accurately measure the positron lifetime. We have succeeded in the proof-of-principle experiment for GiPALS of ultra-short pulse gamma rays with a pulse width of 2 ps, which was originally developed using 90
collision laser Compton scattering at UVSOR.
Taira, Yoshitaka*; Sugita, Kento*; Okano, Yasuaki*; Hirade, Tetsuya; Endo, Shunsuke; Zen, H.*; Shizuma, Toshiyuki*
no journal, ,
At UVSOR, a synchrotron radiation facility at the Institute for Molecular Science, gamma rays are generated by inverse Thomson scattering. Compared to gamma rays generated from radioisotopes and bremsstrahlung gamma rays, it has excellent features such as variable energy, quasi-monochromatic, low background, and high directivity. It is also possible to generate polarized gamma rays by using a polarized laser. Using this gamma ray, nuclear physics experiments such as isotope imaging by nuclear resonance fluorescence scattering, evaluation of gamma ray detectors, and research on material analysis by gamma ray-induced positron annihilation spectroscopy are being carried out. Positron annihilation spectroscopy is a powerful method that can analyze defects of sub-nm to several nm such as monatomic vacancies. Positrons can also be generated from gamma rays by pair production. By irradiating the sample with gamma rays, positrons are generated inside the sample, and it is possible to analyze defects in a bulk sample with a thickness of several cm. At this year's meeting, we will present the development of gamma ray sources in UVSOR, the magnetic Compton scattering experiment of circularly polarized gamma rays, the development of gamma ray-induced positron annihilation spectroscopy, and the development of measurement technology for spin-polarized positrons using circularly polarized gamma rays.
Taira, Yoshitaka*; Sugita, Kento*; Okano, Yasuaki*; Hirade, Tetsuya
no journal, ,
Positron annihilation spectroscopy is a powerful analytical method that can measure vacant defects in crystals and microvoids in insulating materials. UVSOR-III is developing gamma-ray-induced positron annihilation spectroscopy using ultrashort pulse gamma rays. Specifically, we have succeeded in positron annihilation lifetime (PAL) measurement and positron age-momentum correlation (AMOC) measurement. PAL has succeeded in directly measuring the spectrum of only the sample. In addition, AMOC also succeeded in observing the positron annihilation only in the samples, which shows the different momentum distribution for the different defect states. At present, coincidence Doppler broadening (COB) measurement is also available, and a CDB spectrum with only positron annihilation from the sample will be obtained by the newly developed analysis program.
Taira, Yoshitaka*; Sugita, Kento*; Okano, Yasuaki*; Hirade, Tetsuya
no journal, ,
We have developed the gamma-ray induced positron annihilation lifetime spectroscopy (GiPALS) with a time resolution of 140 ps. It has eight BaF detectors and two digital oscilloscopes currently available for users. In addition to GiPALS, we have developed gamma-ray induced age-momentum correlation (GiAMOC). We will present a generation method of the ultra-short pulsed gamma-rays, details of GiPALS and GiAMOC, and future plans, including the development of a spin-polarized positron source generated from circularly polarized gamma rays.
Taira, Yoshitaka*; Sugita, Kento*; Okano, Yasuaki*; Hirade, Tetsuya
no journal, ,
We have developed ultra-short, pulsed gamma rays at the synchrotron radiation facility UVSOR-III by a 90-degree collision between a 750-MeV electron beam and a Ti:Sa laser pulse. The maximum energy of the gamma rays is 6.6 MeV and the pulse width is calculated to be sub-ps to ps ranges. We applied this ultra-short, pulsed gamma rays to positron annihilation spectroscopy (PAS). A positron is an excellent probe of atomic-scale defects in solids such as vacancies, dislocations, and clusters and of free volumes in polymers. PAS using a high energy gamma-ray, which is called gamma induced PAS (GiPAS), has several advantages compared with PAS using Na-22. We will present a generation method of the ultra-short, pulsed gamma rays and details of GiPAS.
Nishikino, Masaharu; Okano, Yasuaki*; Sato, Katsutoshi*; Hasegawa, Noboru; Ishino, Masahiko; Oshima, Shinsuke*; Kawachi, Tetsuya; Numasaki, Hodaka*; Teshima, Teruki*; Nishimura, Hiroaki*
no journal, ,
Recently, high energy, monochromatic X-rays emanating from laser-produced plasma (LPP) are attracting much attention as a new radiation source indispensable for high energy density physics, bioscience, and material sciences. Aiming at these applications, we have been improving performances of Ka lines emitted from and soft X-ray lasers. The monochromaticity is particularly important when X-rays are handled with a narrow-band optics or used to selectively excite a specific material involved in matters. In addition, time-duration of such sources is typically an order of pico-second, and it could be comparable or even shorter than recovery time of radiatively-damaged biological cell, so that the LPP source can be a new source for investigating the mechanisms of irradiation survival and death of biological cells. We propose to develop an ultrashort, intense X-ray microbeam system to study the radiobiological effect and the bystander effect.
Taira, Yoshitaka*; Okano, Yasuaki*; Hirade, Tetsuya
no journal, ,
BL1U is a beamline that researches the development of new light sources and the exploration of usage methods. We are generating 6.6 MeV ultrashort pulse gamma rays using a Ti: Sa laser with a wavelength of 800 nm and are researching gamma ray-induced positron annihilation spectroscopy (GiPALS). GiPALS is a method that measures the lifetime of positrons by measuring the emission time distribution of annihilation gamma rays and can analyze the type and size of defects inside a sample. GiPALS is available to users for in-situ measurements of defect formation in metallic materials during stress loading and measurements of bulk samples such as ferrous materials, catalytic materials, and scintillators.
Okano, Yasuaki*; Nishikino, Masaharu; Nakahara, Shogo*; Tokita, Shigeki*; Masuno, Shinichiro*; Hashida, Masaki*; Sakabe, Shuji*; Nakano, Hidetoshi*; Kawachi, Tetsuya; Nishimura, Hiroaki*; et al.
no journal, ,
The generation of monoenergetic hard X-rays more than 10 keV has attracted much attention for X-ray imaging in the field of high density physics and biomedical applications. Our group is currently developing an X-ray microbeam system to study radiobiological effects of cells as fundamental study of radiation therapy. In such applications, improvement of conversion efficiency (CE) from the driving laser to X-rays is an important issue and some approaches for efficient X-ray generation up to several keV have been proposed so far using low density, surface-structured targets, such as porous metals, velvet targets, and carbon nanotubes (CNTs), with the concepts of improvement of the laser absorption efficiency. In this work, we investigated the yields of K-alpha emission from bare and aligned CNT-array coated metal targets to take baseline data aiming to improve the CE in hard X-ray region (multi-keV to tens of keV) by adapting such kind of method.
Nishikino, Masaharu; Sato, Katsutoshi; Ishino, Masahiko; Hasegawa, Noboru; Kado, Masataka; Kawachi, Tetsuya; Numasaki, Hodaka*; Teshima, Teruki*; Okano, Yasuaki*; Oshima, Shinsuke*; et al.
no journal, ,
A dedicated radiation biologyn X-ray generation and exposure system has been dedicated for radiation biology is developed. An X-ray pulse of 8.0 keV in energy X-ray pulses is generated with an fs-laser pulse were used to irradiate, and sample cells are irradiated through a custom-made culture dish with a silicon nitride membrane. The X-ray irradiation resulted in DNA double-strand breaks in thea nucleus of a culture cell are caused by X-ray irradiation that were, and similar DNA breaks are obtained to those obtained with athe conventional X-ray source, thus. This result demonstrating thees feasibility of radiobiological studiesy utilizing with a single burst of X-rays focused shining on a single cell specimens.
