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Journal Articles

Beam commissioning of the linac for iBNCT

Naito, Fujio*; Anami, Shozo*; Ikegami, Kiyoshi*; Uota, Masahiko*; Ouchi, Toshikatsu*; Onishi, Takahiro*; Oba, Toshiyuki*; Obina, Takashi*; Kawamura, Masato*; Kumada, Hiroaki*; et al.

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1244 - 1246, 2016/11

The proton linac installed in the Ibaraki Neutron Medical Research Center is used for production of the intense neutron flux for the Boron Neutron Capture Therapy (BNCT). The linac consists of the 3-MeV RFQ and the 8-MeV DTL. Design average beam current is 10mA. Target is made of Beryllium. First neutron production from the Beryllium target was observed at the end of 2015 with the low intensity beam as a demonstration. After the observation of neutron production, a lot of improvement s was carried out in order to increase the proton beam intensity for the real beam commissioning. The beam commissioning has been started on May 2016. The status of the commissioning is summarized in this report.

Journal Articles

Interaction of soft X-ray laser pulse radiation with aluminum surface; Nano-meter size surface modification

Ishino, Masahiko; Faenov, A.*; Tanaka, Momoko; Hasegawa, Noboru; Nishikino, Masaharu; Tamotsu, Satoshi*; Pikuz, S.*; Inogamov, N. A.*; Zhakhovsky, V. V.*; Skobelev, I.*; et al.

AIP Conference Proceedings 1465, p.236 - 240, 2012/07

 Times Cited Count:2 Percentile:30.79

We irradiated the focusing soft X-ray laser pulses having a wavelength of 13.9 nm and the duration of 7 ps to aluminum surface. After the irradiation process, the irradiated surface was observed with a scanning electron microscope. The surface modifications caused by soft X-ray laser single pulse exposure were clearly seen. In addition, it was found that the conical structures having around 100 nm in diameters were formed in the shallow features. The nano-meter size modified surface structures on aluminum induced by the soft X-ray laser pulse is interesting as the newly surface structure. Hence, the soft X-ray laser beam would be a candidate for a tool of micromachining. We also provide a thermomechanical modeling of the soft X-ray laser interaction with aluminum briefly to explain the surface modification.

Journal Articles

Nanomodification of gold surface by picosecond soft X-ray laser pulse

Norman, G.*; Starikov, S.*; Stegailov, V.*; Fortov, V.*; Skobelev, I.*; Pikuz, T.; Faenov, A.*; Tamotsu, Satoshi*; Kato, Yoshiaki*; Ishino, Masahiko; et al.

Journal of Applied Physics, 112(1), p.013104_1 - 013104_8, 2012/07

 Times Cited Count:35 Percentile:15.91(Physics, Applied)

Journal Articles

Surface modifications of metals induced by soft X-ray laser pulse irradiations

Ishino, Masahiko; Faenov, A. Y.*; Tanaka, Momoko; Hasegawa, Noboru; Nishikino, Masaharu; Tamotsu, Satoshi*; Pikuz, T.; Oba, Toshiyuki*; Kaihori, Takeshi; Kawachi, Tetsuya

Journal of Laser Micro/Nanoengineering, 7(2), p.147 - 151, 2012/05

 Times Cited Count:5 Percentile:67.34(Nanoscience & Nanotechnology)

We irradiated the soft X-ray laser (SXRL) pulses having a wavelength of 13.9 nm, the duration time of 7 ps to aluminum (Al), copper (Cu) and gold (Au) surfaces. After the irradiation processes of SXRL beam with laser flux of $$sim$$14 mJ/cm$$^{2}$$ for Al case and of $$sim$$21 mJ/cm$$^{2}$$ for Cu and Au cases, the modified surfaces were observed with the visible microscope, the scanning electron microscope, and the atomic force microscope. The surface modifications caused by the SXRL irradiations were clearly seen on the surfaces, and it was found that the conical structures having around 100 nm in diameters were formed on the Al surface under a single pulse shot. The conical structures were formed in the features with the average depth of about 40 nm, and this value was in accordance with the attenuation length of the SXRL beam for Al. The modified structure on Al surface induced by SXRL pulse irradiations is different from those of Cu and Au surfaces. The modified structure formed on Al surface induced by the SXRL pulse exposure is interesting as the newly structure. Hence, the SXRL beam would be a candidate for a tool of micromachining, which enable to fabricate of three dimensional structures with nano-meter size on Al surface.

Journal Articles

Development of silver tape target system for high repetition X-ray laser

Nishikino, Masaharu; Ochi, Yoshihiro; Hasegawa, Noboru; Kawachi, Tetsuya; Oba, Toshiyuki; Kaihori, Takeshi; Nagashima, Keisuke

X-Ray Lasers 2010; Springer Proceedings in Physics, Vol.136, p.93 - 98, 2011/12

The improvement of X-ray laser generation so as to have a high repetition rate will open up the possibility of new applications. In the last decade, progress in reducing the required pump energy for the X-ray lasing and raising the repetition rate has been achieved by new technologies, such as the Transient Collisional Excitation (TCE) scheme and Grazing Incidence Pumping (GRIP). Under this circumstance, the development of continuous pumping to the target system is an important issue for realizing an XRL with the high repetition rate. We have developed a 13.9 nm XRL using a silver tape target4 and demonstrated a highly coherent XRL with an oscillator-amplifier configuration5 using two tape target systems and the TOPAZ laser system6 with a 10-J and a 0.1-Hz repetition rate. The output energy is comparable to the X-ray laser generated with a silver-deposited slab target, and the pointing stability using the new tape target system is better than conventional slab target.

Journal Articles

Source development and novel applications of laser-driven plasma X-ray lasers in JAEA

Kawachi, Tetsuya; Hasegawa, Noboru; Nishikino, Masaharu; Ishino, Masahiko; Imazono, Takashi; Oba, Toshiyuki; Kaihori, Takeshi; Kishimoto, Maki; Ochi, Yoshihiro; Tanaka, Momoko; et al.

X-Ray Lasers 2010; Springer Proceedings in Physics, Vol.136, p.15 - 24, 2011/12

This paper reviews recent improvement in the source development of laser-driven X-ray lasers and the applications in the research fields of material science, laser processing, X-ray imaging, and radiation damage in biological cells. In the application for material science, we have firstly observed temporal correlation between the domain structures of ferro-electric substance under the Curie temperature. In the laser processing, new X-ray laser interferometer reveals us the nano-scale surface distortion of substance pumped by a femto-second optical pulse. In the X-ray diffraction image, we have taken several static images of micro-structure of samples: now we are trying to extend the objective to nano-scale dynamics using pump and probe method. In the radiation damage of biological cells, we observed double strand break in DNA using X-ray laser exposure; this results are compared with the case using incoherent several KeV X-ray exposure.

Journal Articles

Development of the X-ray interferometer and the method of spatial and temporal synchronization of XRL and optical pulse

Hasegawa, Noboru; Ochi, Yoshihiro; Kawachi, Tetsuya; Terakawa, Kota*; Tomita, Takuro*; Yamamoto, Minoru; Nishikino, Masaharu; Oba, Toshiyuki; Kaihori, Takeshi; Imazono, Takashi; et al.

X-Ray Lasers 2010; Springer Proceedings in Physics, Vol.136, p.353 - 358, 2011/12

The understanding of the dynamics of the initial process is important for the micro processing and welding by the ultra-short laser pulse. The X-ray laser is suitable for probing this initial process because it has short wavelength (Ni-like Ag, 13.9 nm) and short duration (7 ps). For this investigation, the origin of time of the pumping pulse is quite important. In this study, we used the scintillation plate and the plasma gate technique to realize the spatial and temporal synchronization of the pump and probe pulses. For the spatial alignment, a CsI scintillation plate that was set at the sample position was illuminated by both the X-ray laser pulse, and the fluorescence light were detected by the CCD camera. For the temporal synchronization, we set a thin foil at the sample position. We measured the transmission of the X-ray laser while changing a temporal delay of the pumping laser with respect to the time of X-ray laser pulse to obtain the origin of the irradiation time.

Journal Articles

Laser ablation of gold; Experiment and atomistic simulation

Starikov, S. V.*; Stegailov, V. V.*; Norman, G. E.*; Fortov, V. E.*; Ishino, Masahiko; Tanaka, Momoko; Hasegawa, Noboru; Nishikino, Masaharu; Oba, Toshiyuki*; Kaihori, Takeshi; et al.

JETP Letters, 93(11), p.642 - 647, 2011/04

 Times Cited Count:23 Percentile:22.34(Physics, Multidisciplinary)

Journal Articles

Evaluation of ZnO fast scintillator spatial resolution using the FZP-focused X-ray laser

Tanaka, Momoko; Nakazato, Tomoharu*; Shimizu, Toshihiko*; Yamanoi, Kohei*; Sakai, Kohei*; Sarukura, Nobuhiko*; Nishikino, Masaharu; Oba, Toshiyuki; Kaihori, Takeshi; Ochi, Yoshihiro; et al.

JAEA-Conf 2011-001, p.126 - 128, 2011/03

The spatial resolution of hydrothermal method grown zinc oxide (ZnO) scintillator was evaluated using X-ray laser focused with Fresnel zone plate. The fluorescence image of the ZnO scintillator was measured to be less than 10um using CCD camera coupled with a Schbartzchild expander mirror. The availability of large size ZnO crystal up to 3-inch is quite attractive for future lithography and imaging applications.

Journal Articles

Nanoscale surface modifications and formation of conical structures at aluminum surface induced by single shot exposure of soft X-ray laser pulse

Ishino, Masahiko; Faenov, A. Ya.*; Tanaka, Momoko; Hasegawa, Noboru; Nishikino, Masaharu; Tamotsu, Satoshi*; Pikuz, T. A.*; Inogamov, N. A.*; Zhakhovskii, V. V.*; Skobelev, I. Yu.*; et al.

Journal of Applied Physics, 109(1), p.013504_1 - 013504_6, 2011/01

 Times Cited Count:32 Percentile:19.02(Physics, Applied)

no abstracts in English

Journal Articles

Observations of the intense soft X-ray emissions from ultra thin Au films irradiated with high contrast laser pulses

Ishino, Masahiko; Kado, Masataka; Nishikino, Masaharu; Shinohara, Kunio*; Tamotsu, Satoshi*; Yasuda, Keiko*; Hasegawa, Noboru; Kishimoto, Maki; Oba, Toshiyuki; Kawachi, Tetsuya

Proceedings of SPIE, Vol.7589, p.75891B_1 - 75891B_8, 2010/02

 Times Cited Count:2 Percentile:22.8

Soft X-ray microscopes operating in the water window are capable of imaging living hydrated biological specimens. Laser produced plasmas are attractive soft X-ray sources, because of their short duration time. Based on the minimum dose calculation, soft X-ray photons more than 10$$^{5}$$ photons/$$mu$$m$$^{2}$$ at the sample surface are needed to acquire an image of the biological specimens with spatial resolution up to 100 nm. The observations of soft X-ray emissions from laser produced plasmas using ultra thin film targets have been carried out. Au thin films were irradiated by a high contrast Nd:glass laser pulses. The spectral properties of emitted soft X-rays were monitored by an X-ray spectrograph from the rear side with respect to the surface of laser irradiation. The observed emission intensities had an obvious dependence on the film thickness, and the most intense emissions were obtained at the thickness of 28 nm. The experimental results have suggested that the most of the laser energy irradiated is absorbed by the film target, and it is resulted an efficient energy deposition from laser to X-rays.

Journal Articles

Demonstration of submicroJoule, spatially coherent soft-X-ray laser pumped by 0.1 Hertz, 10 Joule, picosecond laser

Ochi, Yoshihiro; Kawachi, Tetsuya; Hasegawa, Noboru; Nishikino, Masaharu; Oba, Toshiyuki; Tanaka, Momoko; Kishimoto, Maki; Kaihori, Takeshi; Nagashima, Keisuke; Sugiyama, Akira

Japanese Journal of Applied Physics, 48(12), p.120212_1 - 120212_3, 2009/12

 Times Cited Count:31 Percentile:22.43(Physics, Applied)

We have demonstrated the fully spatial coherent 13.9-nm laser with output energy of submicroJoule by means of the double target geometry by using new driver system. The power amplifiers providing tow beams with 10-J energy and picoseconds duration at the repetition rate of 0.1 Hz. The obtained 13.9-nm laser pulse with 10$$^{10}$$ coherent photons will enable us to make single-shot pump-probe observation of non-periodic ultrafast phenomena.

Journal Articles

Demonstration of a highly coherent 13.9 nm X-ray laser from a silver tape target

Nishikino, Masaharu; Ochi, Yoshihiro; Hasegawa, Noboru; Kawachi, Tetsuya; Yamatani, Hiroshi*; Oba, Toshiyuki; Kaihori, Takeshi; Nagashima, Keisuke

Review of Scientific Instruments, 80(1), p.116102_1 - 116102_3, 2009/11

 Times Cited Count:12 Percentile:46.94(Instruments & Instrumentation)

A highly coherent 13.9 nm X-ray laser is generated under an oscillator-amplifier configuration using a new tape target system and a driver laser system with a 0.1 Hz repetition rate. The output energy is comparable to the X-ray laser generated with a silver-deposited slab target, and the pointing stability using the new tape target system is better than conventional slab targets.

Journal Articles

Present status of operation and maintenance of JRR-3

Ichimura, Toshiyuki; Suwa, Masayuki; Fukushima, Manabu; Oba, Toshinobu; Nemoto, Yoshinori; Terakado, Yoshibumi

Proceedings of 12th International Group on Research Reactors (12th IGORR) (USB Flash Drive), 8 Pages, 2009/10

Journal Articles

New driver laser system for double target X-ray lasers at JAEA

Ochi, Yoshihiro; Hasegawa, Noboru; Kawachi, Tetsuya; Nishikino, Masaharu; Tanaka, Momoko; Kishimoto, Maki; Oba, Toshiyuki

X-Ray Lasers 2008; Springer Proceedings in Physics Series, Vol.130, p.161 - 166, 2009/00

JAEA Reports

Gas Migration Phnomena in Potential Components of Near-Field Barrier System II

Yamamoto, Mikihiko*; Ito, Takao*; Oba, Toshiyuki*

JNC-TJ8400 2003-061, 25 Pages, 2003/02

JNC-TJ8400-2003-061.pdf:2.05MB

Gas production resulting from some mechanisms, including metal corrosion and microbial degradation in a geological repository, enables to lead overpressurization of pore pressure and enhanced release of pore water with dissolved radionuclides. In this study, gas injection experiments under three-dimensional confinement pressure, a gas-water capillary pressure test using high speed centrifuge method and high pressure mercury injection test were performed on tuff core samples to clarify flow parameters of gas and water. Results of the gas injection tests under the condition of constant injection pressure and axial flow were described. The water permeability of saturated samples were existing between 8.4 $$times$$ 10$$^{-19}$$ and 8.9 $$times$$ 10$$^{-19}$$m$$^{2}$$ although the gas permeability of dried sample were varied between 2.3 $$times$$ 10$$^{-16}$$ and 2.5 $$times$$ 10$$^{-15}$$ m$$^{2}$$ depending on gas injection pressure. Gas breakthrough phenomenon after rapid rise in outflow rate of water was indicated rather slow increase of gas outflow than that observed on clay materials. Obtained excess pressure when the breakthrough phenomena occurred were 700 and 1,700 kPa. Grater the gas injection pressure, higher the excess pressure at breakthrough. Threshold pressure obtained from the capillary pressure test was order of 10$$^{1}$$ kPa which was two order of magnitude lower than the value of clay materials. Based on these experimental results, the gas migration process and the retention curve of the tuff sample indicated typical properties observed on porous media. Thus it is expected that the conventional continuum two-phase flow model will be applied reasonably for the tuff sample.

JAEA Reports

Gas Migration Phnomena in Potential Components of Near-Field Barrier System II

; Yamamoto, Mikihiko*; Ito, Takao*; Oba, Toshiyuki*

JNC-TJ8400 2003-060, 81 Pages, 2003/02

JNC-TJ8400-2003-060.pdf:5.1MB

Gas migration phnomena in potential components of near-field barrier system was investigated.

Oral presentation

Recent progress in X-ray laser research in JAEA

Kawachi, Tetsuya; Kishimoto, Maki; Kado, Masataka; Tanaka, Momoko; Hasegawa, Noboru; Ochi, Yoshihiro; Nishikino, Masaharu; Ishino, Masahiko; Imazono, Takashi; Kunieda, Yuichi; et al.

no journal, , 

Recent progress in X-ray laser research in Japan Atomic Energy Agency is reviewed. Using the nickel-like silver soft X-ray laser at the wavelength of 13.9 nm, the application experiments have been conducted in the research fields such as material science, high-density plasma diagnostics, XRL ablation, XRL imaging using single-shot holography and atomic physics. The repetition rate of the XRL beam has been improved from each 10-20 minutes to 0.1 Hz by using new driver laser system with Nd: glass zigzag slab amplifier, and we are now constructing new beam line for the pump-probe measurement of the surface phase-transition by the method of X-ray laser interferometer. In the research activity on the extension of the wavelength region of the X-ray lasers, firstly, the demonstration of novel coherent X-ray generation by "flying mirror" technique is reported. The second is theoretical investigation of the resonance photo-pumping scheme toward water-window region.

Oral presentation

10 J, picosecond, 0.1-Hz Nd:glass laser system dedicated to X-ray lasers

Ochi, Yoshihiro; Hasegawa, Noboru; Kawachi, Tetsuya; Tanaka, Momoko; Nishikino, Masaharu; Kishimoto, Maki; Oba, Toshiyuki; Sugiyama, Akira

no journal, , 

Oral presentation

Single-shot focal spot image of EUV laser using a ZnO scintillator

Nakazato, Tomoharu*; Shimizu, Toshihiko*; Yamanoi, Kohei*; Takatori, Satoru*; Estacio, E.*; Cadatal, M.*; Sarukura, Nobuhiko*; Nishimura, Hiroaki*; Mima, Kunioki*; Tanaka, Momoko; et al.

no journal, , 

We have observed the single shot, focused image of a EUV laser through the emission of a ZnO scintillator. An estimated EUV laser focal spot size of 50$$times$$88 micrometer is reasonable considering the long focal length of the spherical mirror. This work reports a feasible method to perform single-shot beam diagnostics for EUV laser sources using a ZnO crystal scintillator. Furthermore, since the ZnO fluorescence is at 380 nm wavelength, the imaging optics for the diagnostics can all be placed outside the vacuum chamber; thereby making experiments less cumbersome. Having a capability in fast and efficient beam profiling of EUV laser sources with acceptable resolving power is very important in future lithography applications.

41 (Records 1-20 displayed on this page)