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Kusano, Kanya*; Ichimoto, Kiyoshi*; Ishii, Mamoru*; Miyoshi, Yoshizumi*; Yoden, Shigeo*; Akiyoshi, Hideharu*; Asai, Ayumi*; Ebihara, Yusuke*; Fujiwara, Hitoshi*; Goto, Tadanori*; et al.
Earth, Planets and Space (Internet), 73(1), p.159_1 - 159_29, 2021/12
Times Cited Count：6 Percentile：49.29(Geosciences, Multidisciplinary)The PSTEP is a nationwide research collaboration in Japan and was conducted from April 2015 to March 2020, supported by a Grant-in-Aid for Scientific Research on Innovative Areas from the Ministry of Education, Culture, Sports, Science and Technology of Japan. It has made a significant progress in space weather research and operational forecasts, publishing over 500 refereed journal papers and organizing four international symposiums, various workshops and seminars, and summer school for graduate students at Rikubetsu in 2017. This paper is a summary report of the PSTEP and describes the major research achievements it produced.
Arita, Ren*; Nakazato, Tomoharu*; Shimizu, Toshihiko*; Yamanoi, Kohei*; Empizo, M.*; Hori, Tatsuhiro*; Fukuda, Kazuhito*; Minami, Yuki*; Sarukura, Nobuhiko*; Maruyama, Momoko; et al.
Optical Materials, 36(12), p.2012 - 2015, 2014/10
Times Cited Count：9 Percentile：45.56(Materials Science, Multidisciplinary)A single shot image of a ZnO crystal excited by the EUV laser of Kansai Photon Science Institute was captured. The evaluated EUV beam waist radii from the ZnO emission pattern along the horizontal and vertical axes are 5.0 and 4.7
m, respectively. The expected focal spot size of EUV laser and the spatial resolution of the magnifier (including the Schwarzschild objectives and lenses) are however 1 and 4m, respectively. The discrepancy on the spatial resolutions is attributed to exciton diffusion. We estimated the ZnO exciton diffusion length from the effective decay time which is shortened by exciton-exciton collision quenching and which is dependence on excitation energy density. Our results indicate that the short lifetime of ZnO is required to improve the spatial resolution.
imaging device of high spatial resolution ZnO scintillatorNakazato, Tomoharu*; Shimizu, Toshihiko*; Yamanoi, Kohei*; Sakai, Kohei*; Takeda, Kohei*; Nishi, Ryosuke*; Minami, Yuki*; Cadatal-Raduban, M.*; Sarukura, Nobuhiko*; Nishimura, Hiroaki*; et al.
Japanese Journal of Applied Physics, 50(12), p.122202_1 - 122202_4, 2011/12
Times Cited Count：10 Percentile：37.91(Physics, Applied)We demonstrate the potential of a hydrothermal method-grown ZnO as a high-spatial resolution imaging device for in-situ soft X-ray laser diagnostics by characterizing the exciton emission patterns. By plotting the emission pattern radii at each position, we estimated the evolution of the beam radius around the focal point. The beam profile of the Ni-like Ag ion plasma laser was estimated from the waist radii as 29 and 21m, the divergence angle as 7.2 and 11 mrad and the M2 factor as 47 and 50 in the horizontal- and vertical-axis, respectively. Spatial resolution of the magnifier was estimated to be 6m and is expected to improve by optimizing the optics of the magnifier and using a telescope. Our results would enhance the use of ZnO as an imaging device that would play a crucial role in the development and application of soft X-ray light sources.
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.
Sarukura, Nobuhiko*; Nakazato, Tomoharu*; Shimizu, Toshihiko*; Yamanoi, Kohei*; Sakai, Kohei*; Ehrentraut, D.*; Fukuda, Tsuguo*; Tanaka, Momoko; Nishikino, Masaharu; Kawachi, Tetsuya
Reza Kenkyu, 39(3), p.193 - 196, 2011/03
Development of light sources in the soft X-ray/X-ray region, such as laser induced plasma emission and XFEL, is in demand for applications in various fields of science, medicine, and industry, among others. To promote this endeavor, development of imaging devices as diagnostic tools in this wavelength region is required. ZnO is a prominent candidate material for high spatial and temporal resolution imaging devices because of its emission at 380 nm, lifetime of less than 1 ns, and availability of large and cheap but high quality crystals. We obtained a single shot image of ZnO emission pattern excited by an X-ray laser at the Advanced Photon Research Center, Japan Atomic Energy Agency. The spatial resolution was estimated to be around 10 m. This result shows that ZnO can be used as a powerful imaging device for applications such as EUV lithography.
Nakazato, Tomoharu*; Furukawa, Yusuke*; Tanaka, Momoko; Tatsumi, Toshihiro*; Nishikino, Masaharu; Yamatani, Hiroshi*; Nagashima, Keisuke; Kimura, Toyoaki*; Murakami, Hidetoshi*; Saito, Shigeki*; et al.
Journal of Crystal Growth, 311(3), p.875 - 877, 2009/01
Times Cited Count：24 Percentile：86.11(Crystallography)The temperature dependence of scintillation properties of a hydrothermal-method-grown zinc oxide (ZnO) emission is investigated using a nickel-like silver laser emitting at 13.9 nm. A broad peak at 386 nm with a full-width at half-maximum (FWHM) of 15 nm at room temperature (298 K) is obtained. The peak position tends to be blue shifted while the FWHM becomes narrower when the crystal temperature is decreased to 25 K. Streak images fitted by a double exponential decay reveal that the measured emission decay at 105 K was 
= 0.88 ns and 
= 2.7 ns. This decay time of a few nanoseconds is suitable for lithographic applications and is sufficiently short for the characterization of laser plasma extreme ultraviolet (EUV) sources with nanosecond durations.
Tanaka, Momoko; Furukawa, Yusuke*; Nakazato, Tomoharu*; Tatsumi, Toshihiro*; Murakami, Hidetoshi*; Shimizu, Toshihiko*; Sarukura, Nobuhiko*; Nishikino, Masaharu; Kawachi, Tetsuya; Kagamitani, Yuji*; et al.
X-Ray Lasers 2008; Springer Proceedings in Physics, Vol.130, p.501 - 505, 2009/00
We measured the time-resolved fluorescence spectra of ZnO and GaN single crystals excited by an X-ray laser operating at 13.9 nm and evaluated their scintillation properties for EUV excitation as compared with UV excitation case. For ZnO, a clear fluorescence peak of excitonic origin was observed at around 380 nm and the decay lifetime of less than 3 ns is found to be almost similar to the UV excitation case. The fluorescence at 380 nm is ideal for scintillator device design in the EUV and further applications. For GaN, the lifetimes are much longer than ZnO and the temporal profile of the EUV-excited fluorescence differs with the UV excitation case. As such, the EUV scintillation properties of ZnO is said to be more favorable than GaN. Finally, it is also demonstrated that an X-ray laser is an excellent tool for spectroscopic characterization of materials intended for next-generation lithography applications.
Hamamoto, Shimpei; Iigaki, Kazuhiko; Shimizu, Atsushi; Sawahata, Hiroaki; Kondo, Makoto; Oyama, Sunao; Kawano, Shuichi; Kobayashi, Shoichi; Kawamoto, Taiki; Suzuki, Hisashi; et al.
JAEA-Technology 2006-030, 58 Pages, 2006/03
JAEA-Technology-2006-030.pdf:10.69MB
During normal operation of High Temperature engineering Test Reactor (HTTR) in Japan Atomic Energy Agency (JAEA), the reactivity is controlled by the Control Rods (CRs) system which consists of 32 CRs (16 pairs) and 16 Control Rod Drive Mechanisms (CRDMs). The CR system is located in stand-pipes accompanied by the Reserved Shutdown System (RSS). In the unlikely event that the CRs fail to be inserted, the RSS is provided to insert B
C/C pellets into the core. The RSS shall be designed so that the reactor should be held subcriticality from any operation condition by dropping in the pellets. The RSS consists of BC/C pellets, hoppers which contain the pellets, electric plug, driving mechanisms, guide tubes and so on. In accidents when the CRs cannot be inserted, an electric plug is pulled out by a motor and the absorber pellets fall into the core by gravity. A trouble, malfunction of one RSS out of sixteen, occurred during a series of the pre-start up checks of HTTR on February 21, 2005. We investigated the cause of the RSS trouble and took countermeasures to prevent the issue. As the result of investigation, the cause of the trouble was attributed to the following reason: In the motor inside, The Oil of grease of the multiplying gear flowed down from a gap of the oil seal which has been deformed and was mixed with abrasion powder of brake disk. Therefore the adhesive mixture prevented a motor from rotating.
Shimizu, Atsushi; Hamamoto, Shimpei; Kobayashi, Shoichi; Ishii, Yoshiki; Iigaki, Kazuhiko; Inoi, Hiroyuki; Kawamoto, Taiki; Mizushima, Toshihiko; Nakazawa, Toshio
no journal, ,
no abstracts in English
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
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.
Nakazato, Tomoharu*; Shimizu, Toshihiko*; Yamanoi, Kohei*; Sakai, Kohei*; Sarukura, Nobuhiko*; Ehrentraut, D.*; Fukuda, Tsuguo*; Tanaka, Momoko; Nishikino, Masaharu; Yamatani, Hiroshi*; et al.
no journal, ,
no abstracts in English
excimer using EUV free electron laserNishi, Ryosuke*; Minami, Yuki*; Yamanoi, Kohei*; Nakazato, Tomoharu*; Shimizu, Toshihiko*; Sarukura, Nobuhiko*; Iwayama, Hiroshi*; Shigemasa, Eiji*; Harries, J.; Nagasono, Mitsuru*
no journal, ,
no abstracts in English
Yasue, Kenichi; Sugai, Toshihiko*; Tokuyasu, Kayoko; Komatsu, Tetsuya; Horiuchi, Yasuharu; Shimizu, Hitoshi*; Morita, Yasuhiko*
no journal, ,
no abstracts in English
