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Journal Articles

Measurement of the spatial polarization distribution of circularly polarized gamma rays produced by inverse Compton scattering

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:0 Percentile:0.01(Optics)

no abstracts in English

Journal Articles

Visualizing cation vacancies in Ce:Gd$$_{3}$$Al$$_{2}$$Ga$$_{3}$$O$$_{12}$$ scintillators by gamma-ray-induced positron annihilation lifetime spectroscopy

Fujimori, 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:4 Percentile:27.19(Physics, Applied)

To clarify the existence of cation vacancies in Ce-doped Gd$$_{3}$$Al$$_{2}$$Ga$$_{3}$$O$$_{12}$$ (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:Y$$_{3}$$Al$$_{5}$$O$$_{12}$$, 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$$^{2+}$$ ions at Al/Ga sites with oxygen vacancies, which resulted in the formation of vacancy clusters.

Journal Articles

Quantitative measurement of hard X-ray spectra for high intensity laser produced plasma

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:62.46(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.

Journal Articles

Efficient multi-keV X-ray generation from a high-Z target irradiated with a clean ultra-short laser pulse

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:18 Percentile:65.23(Optics)

$$Kalpha$$ line emission from Mo and Ag plate were experimentally studied by using ultra-high intensity, clean femtosecond laser pulses. Absolutely yield of $$Kalpha$$ 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 $$Kalpha$$ yields were obtained for both Mo and Ag with higher contrast ratios and high irradiance. The conversion efficiencies of 4.28 $$times$$ 10$$^{-5}$$/sr for Mo and 4.84 $$times$$ 10$$^{-5}$$/sr for Ag, the highest values ever obtained, have been demonstarted with the contrast ratio of 10$$^{-10}$$ to 10$$^{-11}$$.

Journal Articles

$${gamma}$$-H2AX and phosphorylated ATM focus formation in cancer cells after laser plasma X irradiation

Sato, 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:49.45(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$${alpha}$$ (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 $${gamma}$$-H2AX positive cells could be clearly identified. Moreover, the number of $${gamma}$$-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.

Journal Articles

Monochromatic X-ray emission from laser produced plasma with a clean ultra-short laser pulse

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 $$times$$ 10$$^{-5}$$/sr, the highest value ever obtained, has been demonstrated at 5.5 $$times$$ 10$$^{16}$$ W/cm$$^{2}$$ with a contrast ratio of 10$$^{-11}$$.

Journal Articles

Application of laser produced plasma K$$alpha$$ X-ray probe in radiation biology

Nishikino, 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:22 Percentile:66.97(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.

Journal Articles

Introduction to plasma fusion energy

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

Journal Articles

Overview of the national centralized tokamak programme

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:41.84(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.

Oral presentation

Development of focused laser plasma X-ray beam for radiobiological applications

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.

Oral presentation

Monoenergetic hard X-ray emission from carbon-nanotube-array coated targets with femtosecond laser pulses

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.

Oral presentation

Development of focused laser plasma X-ray beam for radiobiological applications

Nishikino, Masaharu; Ishino, Masahiko; Hasegawa, Noboru; Kawachi, Tetsuya; Sato, Katsutoshi*; Numasaki, Hodaka*; Teshima, Teruki*; Oshima, Shinsuke*; Okano, Yasuaki*; 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 LPP and soft X-ray lasers (XRLs). The monochromaticity is particularly important when X-rays are handled with a narrowband optics or used to selectively excite a specific material involved in matters. In addition, timeduration of such sources is typically an order of picosecond, 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.

Oral presentation

Development of focused laser plasma X-ray beam for radiobiological applications

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 $$gamma$$-H2AX focus formation in the culture cells irradiated with laser-produced plasma X-ray.

Oral presentation

Development of microbeam system using laser-plasma X-ray and identification of DNA double strand breaks in the cancer cell

Sato, Katsutoshi*; Nishikino, Masaharu; Okano, Yasuaki*; Hasegawa, Noboru; Ishino, Masahiko; Oshima, Shinsuke*; Numasaki, Hodaka*; Kawachi, Tetsuya; Teshima, Teruki*; Nishimura, Hiroaki*

no journal, , 

no abstracts in English

Oral presentation

Application of laser produced plasma X-ray probe in radiation biology

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.

Oral presentation

Monoenergetic hard X-ray emission using ultra-short laser pulses with high contrast

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

Oral presentation

Development of gamma-ray induced positron annihilation lifetime spectroscopy

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 $$^{22}$$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$$^{circ}$$ collision laser Compton scattering at UVSOR.

Oral presentation

Development of gamma-ray induced positron annihilation lifetime spectroscopy at UVSOR

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 $$^{22}$$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$$^{circ}$$ collision laser Compton scattering at UVSOR.

Oral presentation

Development of gamma-ray induced positron annihilation spectroscopy

Taira, Yoshitaka*; Sugita, Kento*; Okano, Yasuaki*; Fujimoto, Masaki*; Hirade, Tetsuya

no journal, , 

Positron annihilation spectroscopy is a powerful analytical method that can observe single-atom vacant defects in crystals and micro voids in insulating materials. UVSOR-III installed at the Institute of Molecular Science is promoting the development and user use of Gamma-ray induced positron annihilation spectroscopy (GiPAS) by ultrashort pulse gamma rays. Since the ultrashort pulse gamma rays generate positrons inside the material by pair production, positron annihilation experiments of bulk materials with a thickness of several cm can be performed non-destructively. We have succeeded in the generation of ultrashort pulse gamma rays and positron annihilation experiments such as the lifetime measurement and the positron age-momentum correlation measurement.

Oral presentation

Positron annihilation spectroscopy using ultra-short pulsed laser Thomson scattered gamma-rays

Taira, Yoshitaka*; Fujimoto, Masaki*; Okano, Yasuaki*; Kitaura, Mamoru*; Hirade, Tetsuya

no journal, , 

Laser Thomson/Compton scattering is a unique technique to generate gamma-rays with features such as quasi-monochromatic and tunable energy, highly polarized, low divergence angle, and low background. We have developed GiPALS using an ultra-short pulsed gamma-ray generated at the synchrotron radiation facility UVSOR-III. The gamma-rays are generated via laser Thomson scattering with 90 degree collisions between a 750-MeV electron beam and a Ti:Sa laser. The pulse width of the gamma-rays is calculated to be 5 ps (FWHM). The gamma-ray induced positron annihilation lifetime spectroscopy (GiPALS) is currently available for users. In addition to GiPALS, we develop gamma-ray induced age-momentum correlation (GiAMOC), which measures the lifetime and Doppler broadening of annihilation gamma-rays simultaneously. In this conference, we will present a generation method of the ultra-short pulsed gamma-rays and details of GiPALS and GiAMOC.

30 (Records 1-20 displayed on this page)