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Tsuda, Shuichi; Sato, Tatsuhiko; Endo, Akira; Satoh, Daiki; Takahashi, Fumiaki; Sasaki, Shinichi*; Namito, Yoshihito*; Iwase, Hiroshi*; Ban, Shuichi*; Takada, Masashi*
no journal, ,
Energy deposition of secondary charged particles produced in tissue irradiated by heavy ion beams is important information in order to evaluate biological effects of cells. In this study a wall-less tissue equivalent proportional counter (wall-less TEPC) was designed and its performance tests have been carried out using checking sources such as a Cm-244 
source. It is found that the wall-less TEPC can be used in measurements of energy deposition in tissue irradiated by heavy ion beams, based on measurements of gas gain in tissue equivalent gas and lineal energy distributions.
Imazono, Takashi; Suzuki, Yoji; Sano, Kazuo*; Koike, Masato
no journal, ,
In magnetic science such as magnetic circular dichroism measurement, core electrons are excited by polarized soft X-ray. Experimenters using polarized soft X-rays as the incident light need the information on its polarization state, so that it is useful for them to evaluate it in advance. In the energy range from 0.7 to 0.9 keV, which is in the vicinity of the absorption edges of 3
transition metals, it makes impossible to perform the polarization measurement. It is because existing polarizing elements are unusable in this energy region. In order to develop new polarizing elements and evaluate the polarization state, an apparatus for soft X-ray ellipsometry based on the rotating-analyzer method has been designed and installed to the SR Center of Ritsumeikan University. We discuss the specification and the result of the preliminary performance test of this apparatus.
-FeSi
and SiAkutsu, Keiichi*; Hara, Yoshiaki*; Nakaoka, Kanichiro*; Yamamoto, Hiroyuki
no journal, ,
Near-infrared photoluminescence of eutectic mixture of -FeSi and Si has been investigated.
-FeSiMao, W.; Wakaya, Ippei*; Yamada, Yoichi; Esaka, Fumitaka; Yamamoto, Hiroyuki; Shamoto, Shinichi; Yamaguchi, Kenji; Udono, Haruhiko*
no journal, ,
Thin films of semiconducting -FeSi keep attracting considerable attentions for their promising applicability to the Si-based optoelectronics devices. Recently, large single-crystalline -FeSi has successfully been synthesized, providing a substrate for a well-defined homoepitaxy film. As a first step toward good homoepitaxy of -FeSi, we prepare and characterize low-index surfaces of -FeSi single crystal. Both LEED and STM reveal the absence of the long-ranged surface reconstruction for each face, which is favorable for the homoepitaxy on this substrate. On the other hand, STM suggests a presence of a significant amount of surface defects for each face, which should be improved in the next step. In addition to structural analysis, the stoichiometry of clean surfaces will be discussed on the basis of XPS and SIMS measurements.
Sagisaka, Akito; Daido, Hiroyuki
no journal, ,
no abstracts in English
-FeSi homoepitaxial growthWakaya, Ippei*; Ochiai, Kunihito*; Udono, Haruhiko*; Nagano, Takatoshi*; Yamada, Yoichi; Yamamoto, Hiroyuki; Esaka, Fumitaka
no journal, ,
Deposit condition in the first stage of -FeSi homoepitaxial growth has been investigated.
-rays and application to material studyToyokawa, Hiroyuki*; Hirade, Tetsuya; Tomota, Yo*; Ishibashi, Toshihiro*; Sugaya, Satoshi*; Suzuki, Ryoichi*
no journal, ,
The brittleness of materials might be affected by defects, dislocations and impurities. However it is not well understood. Clarifying these problems is very important to make reliable models for estimating the degradation of materials for atomic energy. Injecting high energy photons with more than 1.02 MeV to materials can produce electron/positron pairs. Collimated MeV-energy--rays with several mm diameters can produce needle shaped positron distribution. By use of the produced positrons, it is possible to make 3D views of defect distribution or cross section of electro/positron pair production at deeper region of materials. This method is expected to be applied for measurements in atmosphere or high-temperature/high-pressure environments. We succeeded to obtain CT images of the transmission view and electron/positron pair production cross section of reinforcing bars in concrete by use of 5 mm diameter 9.1 MeV -rays. We also measured S-parameters for defects in metal samples.
Toyota, Yuji; Nishi, Takaki; Murakami, Hiroshi; Nashima, Shigeki*; Hosoda, Makoto*
no journal, ,
no abstracts in English
Onoda, Shinobu; Oshima, Takeshi; Iwamoto, Naoya; Hirao, Toshio; Kojima, Kazutoshi*; Kawano, Katsuyasu*
no journal, ,
no abstracts in English
Mori, Michiaki; Mizuta, Yoshio*; Kondo, Kiminori; Nishiuchi, Mamiko; Kado, Masataka; Kando, Masaki; Pirozhkov, A. S.; Kotaki, Hideyuki; Ogura, Koichi; Sugiyama, Hironori*; et al.
no journal, ,
The collimatability of quasi-monoenergetic electron beam production in the self-injected laser-plasma acceleration regime is studied. The collimation of electron beam drived by terawatt femtosecond laser (4.1 TW, 40 fs) is measured at two species of gas material (Helium gasjet and Argon gasjet). We measured 3.2 mrad pointing stability and beam divergence of 11 mrad (r.m.s.) at Argon gasjet for 50 sequencial shots. At such condition, the peak electron energy is 9.1
1.0 MeV with 80% reproducebility. For Helium, the pointing stability is three times larger than that of Argon. It is considered that the laser channel formation is important role for stable electron beam generation.
Sasaki, Akira; Nishihara, Katsunobu*; Sunahara, Atsushi*; Nishikawa, Takeshi*; Koike, Fumihiro*; Furukawa, Hiroyuki*
no journal, ,
no abstracts in English
Yamauchi, Toshihiko; Takemoto, Ryo*; Kanno, Yoshinori*; Kobayashi, Seiji*; Nakagaki, Keita*; Kato, Hatsuhiro*
no journal, ,
no abstracts in English
Takahashi, Masamitsu
no journal, ,
Stranski-Krastanow growth of InAs/GaAs(001) has attracted much attention for controlling the size and shape of InAs quantum dots. In this work, we have investigated the evolution of the internal lattice constant distribution, height and diameter of quantum dots by in situ synchrotron X-ray diffraction during molecular beam epitaxy (MBE) at varying temperatures. Experiments were performed at BL11XU at SPring-8 using an MBE chamber coupled with an X-ray difractometer. Three samples grown at substrate temperatures of 478
C, 469C and 454C were subjected to measurements. A combination of in situ X-ray diffraction and postgrowth atomic force microscopy revealed that the total volume of the quantum dots increased at a rate 1.5 times as large as the supplying rate of In. This suggests that a mass transfer from the wetting layer of the substate contributes to the growth of quantum dots.
Zhao, M.; Inoue, Aichi; Yamamoto, Shunya; Yoshikawa, Masahito
no journal, ,
This study reports an unusual response of ultra thin Pd films upon exposure to H. Palladium was deposited to form the films with thickness less than 10 nm by RF sputtering on a Si substrate at room temperature. The resistance of Pd film with thickness of 6.8 nm that decreases during exposure to H has been reported previously. When the film thickness is less than 2 nm, however, the resistance increases with a consequently reduction was observed during exposure to H. This phenomenon could be only observed in discontinuously films composed of nano-metered particles. Such behavior is considered to be results of the formation of the hydride and the closure of the conduction path due to expansion of the lattice. The result indicates that the discontinuously thin Pd film (
2 nm) could be considered as a very competitive candidate for hydrogen sensing.
Sato, Shinichiro; Miyamoto, Haruki*; Imaizumi, Mitsuru*; Shimazaki, Kazunori*; Morioka, Chiharu*; Kawano, Katsuyasu*; Oshima, Takeshi
no journal, ,
no abstracts in English
Imaizumi, Mitsuru*; Oshima, Takeshi; Harris, R. D.*; Walters, R. J.*
no journal, ,
no abstracts in English
Asaoka, Hidehito; Yamazaki, Tatsuya; Shamoto, Shinichi; Filimonov, S.*; Suemitsu, Maki*
no journal, ,
no abstracts in English
adsorption on Si(111)-7
7 via trapping-mediated mechanism by real-time synchrotron radiation photoelectron spectroscopyYoshigoe, Akitaka; Teraoka, Yuden
no journal, ,
Since initial sticking probability decreses with translational kinetic energy of O from 0.03eV to 0.07eV, the trapping-mediated adsorption mechanism is dominant at this energy region. Using real-time O1s and Si2p photoelectron spectroscopy, we observe the time evolution of adsorption states and those correlation as a finction of Ek. When Ek becomes 0.07eV, the increase rate of each component becomes loose and the time correlation however is unchanged. This result indicates that the mobile precursor states which is physisorption state exists and the trapping probability dominates the initial adsorption process.
adsorption on Si(111)-77 in direct adsorption mechanismYoshigoe, Akitaka; Teraoka, Yuden
no journal, ,
When the translational kinetic energy of O (Ek) becomes over 0.07eV, initial sticking probability (S0) changes from decreasing feature to increasing one and thus the direct adsorption mechanism becomes dominant. Since the correlation between adsorption states and those time evolution depending on the Ek is not clear, the real time O1s and Si2p photoelectron spectroscopy is carried out. Comparing Ek=0.07eV and 0.15eV condition, the growth rate increases with increasing Ek as seen for ins oxygen. Furthermore, Si
and Si
species have been observed simultaneously. This result indicates that oxygen molecule adsorbs via molecularly chemisorbed states or directly dissociative chemisorbs without trapping states.
-ray analysis utilizing high resolution Ge spectrometersOshima, Masumi
no journal, ,
no abstracts in English