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Ogiwara, Norio; Kanazawa, Kenichiro; Inohara, Takashi*; Wada, Kaoru*
Vacuum, 84(5), p.718 - 722, 2009/12
Times Cited Count：7 Percentile：30.11(Materials Science, Multidisciplinary)Recently turbo-molecular pumps (TMPs) have been widely used in nuclear fusion devices and sometimes in particle accelerators. Therefore, in order to use them in a quasi-static magnetic field the influence of the fields on TMPs has been exactly investigated. First of all, the influence for the two special magnetic fields has been examined: one is due to the vertical magnetic field, and the other due to the parallel component. The parallel magnetic field has no influence of the operation of the TMP. On the contrary, the driving power and the rotor temperature were largely affected by the vertical magnetic field. The eddy current loss in the vertical field increases rapidly with the field strength. It is proportional to the square of the field strength. The eddy current loss also increases as the revolution frequency, however, it has quite different dependence from the magnetic field strength. These dependences are well explained by the skin depth, which referred to the region where a localized magnetic field and current flow exists. Then we have successfully evaluated the influence of the magnetic field with an arbitrary direction by means of adding the contributions from the two magnetic components. Furthermore, from the demonstration experiment, it is generally found that the magnetic field with the symmetry around the rotor axis does not affect the operation of the TMP.
Ogiwara, Norio; Kinsho, Michikazu; Kamiya, Junichiro; Yamamoto, Kazami; Yoshimoto, Masahiro; Hikichi, Yusuke; Kanazawa, Kenichiro; Mio, Keigo; Takiyama, Yoichi; Suganuma, Kazuaki; et al.
Vacuum, 84(5), p.723 - 728, 2009/12
Times Cited Count：7 Percentile：30.11(Materials Science, Multidisciplinary)To minimize the radiation exposure during maintenance, it is necessary to compose the 3-GeV RCS vacuum system with reliable components which have long life time in such a high level of radiation. In addition, it is necessary to keep the operating pressure with beam in ultra high vacuum for suppressing the pressure instability. Thus we should think of not only the outgassing mainly due to ion desorption but also the pumping efficiency. From the above, the vacuum system was designed. The ring is divided by the isolation valves into 6 sections, which can be pumped down independently. For avoiding any eddy current loss ceramic ducts are used in the bending and focusing magnets. These ducts are connected to the Ti ducts, putting the Ti bellows between. Here, we adopt pure Ti as a material for the ducts and bellows because of its small residual radioactivity. The ring is evacuated with 20 ion pumps (0.7 m
/s) and 24 turbomolecular pumps (TMPs) (1.3 m/s), which are attached to the Ti ducts. The TMPs are used for not only rough pumping but also evacuation during the beam operation. Especially a collimator system for localizing beam losses in a restricted area is evacuated with the TMPs, because the outgassing from this region will be probably the largest. On the other hand, each arc section is pumped by 4 ion pumps and 2 TMPs. To realize the above system, we have developed some components such as large aperture ceramic ducts and TMPs with high radioactive-resistance, as well as several kinds of heat treatment to reduce the outgassing. Finally, we have realized the UHV without baking in the RCS and the beam operation has been succeeded until now.
Yamamoto, Kazami; Kamiya, Junichiro; Ogiwara, Norio; Kinsho, Michikazu; Hayashi, Naoki; Saeki, Riuji; Sato, Kenichiro*; Toyama, Takeshi*
Applied Surface Science, 256(4), p.958 - 961, 2009/11
Times Cited Count：2 Percentile：11.71(Chemistry, Physical)The Japan Proton Accelerator Research Complex (J-PARC) project is a joint project of Japan Atomic Energy Agency (JAEA) and High Energy Accelerator Research Organization (KEK). The accelerator complex of J-PARC consists of a 181 MeV Linac, a 3 GeV Rapid-Cycling Synchrotron (RCS) and a 50 GeV Main Ring (MR). The RCS ring is designed to support 1 MW of beam and to deliver a 3 GeV pulsed proton beam to the spallation neutron target and the MR at a repetition rate of 25 Hz. Since the RCS finally accelerates very high intensity beam, the secondary electron cloud may affect the accelerator performance. The electron cloud effect in RCS was evaluated by simulations, but the secondary electron emission yield (SEY) of the chamber surface and beam loss point, lost proton number were assumed. In this Study we measured the SEY from the samples which was dealt with similar process of an actual chamber surface. We estimate the practical influence of the secondary electron cloud during beam operation.
Esaka, Fumitaka; Yamamoto, Hiroyuki; Sasase, Masato*; Magara, Masaaki; Shinohara, Nobuo
no journal, ,
In the present study, synchrotron radiation excited XPS (SR-XPS) is used to the analysis of surface oxides of stainless steels for obtaining information on surface composition in detail. Here, non-destructive depth profiling was performed by obtaining XPS spectra with different excitation X-ray energies. By oxidation at 200 
C, significant change of the ratio was observed, indicating the enrichment of iron oxide on the surface at an initial stage of oxidation. With increasing oxidation temperature, enrichment of chromium oxide on the surface proceeded. No significant change with photon energy was observed for the sample oxidized at 400-800 C. These results imply that SR-XPS becomes a powerful tool for chemical state analysis of materials owing to the ability of non-destructive depth profiling.
Kamiya, Junichiro; Yamamoto, Kazami; Ogiwara, Norio; Kinsho, Michikazu
no journal, ,
The rapid-cycling synchrotron (RCS) in J-PARC has succeeded to accelerate proton beam up to 3 GeV. The buildup of the beam power is performed over the next several years. The quality of the vacuum of the RCS is the key element for the beam power augmentation. The extraction kicker magnets have been installed in the vacuum chambers to prevent the electrical discharge. Therefore, the vacuum characteristic of the kicker magnet will become very important for the buildup of the beam. We have focused our effort to reduce the outgassing from the kickers. In addition, we have to care for the phenomenon which is caused by the interaction between the beam and the residual gass or vacuum surface. Especially, the secondary electron emission (SEE) coefficient is very important factor because SEE is the source of the electron cloud which caused the beam instability. In this report, the SSE coefficients of the components of the kicker magnet are systematically shown.
Honda, Mitsunori; Sekiguchi, Tetsuhiro; Baba, Yuji; Shimoyama, Iwao; Hirao, Norie; Narita, Ayumi
no journal, ,
no abstracts in English
interface by PEEM using synchrotron radiationHirao, Norie; Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Honda, Mitsunori; Narita, Ayumi
no journal, ,
The electrical properties of Si-based semiconductor devices such as SOI depend on the valence state of silicon at the Si-SiO interface. In order to observe valence states of a solid surface at nanometer scale, we have developed a photoelectron emission microscopy (PEEM) system combined with synchrotron soft X-ray. The samples investigated were micropattern of Si and SiO prepared by ion implantation. We have observed the chemical state at the Si-SiO interface and the lateral diffusion of the valence states, during the annealing. Compared to the previously reported longitudinal diffusion, two differences are found in the present lateral diffusion, i.e., (1) the diffusion temperature is lower than that of longitudinal diffusion by 300C, and (2) the intermediate valence states are absent at the Si-SiO interface. These differences are interpreted by the volatile property of SiO molecules, i.e., SiO released from surface during the diffusion.
Teraoka, Yuden; Yoshigoe, Akitaka; Harries, J.
no journal, ,
Correlation between thermal desorption of hydrogen and chemical bonding states in the over-layer has been investigated via photoemission spectroscopy with synchrotron radiation for poly-crystalline Vanadium surface. An O1s photoemission spectrum for the native over-layer consisted of at least two components. The lower binding energy component was bulk sensitive and the other was surface sensitive. V2p photoemission peaks contributed from bulk could be observed with photon energy larger than 795 eV so that the thickness of native over-layer might be at least 3 nm. By flash heating at 873 K, the O1s and the Vanadium oxide peaks disappeared. The clean surface was irradiated by the oxygen beams with translational energy of 0.48 eV and 2.3 eV. In both cases, similar oxide was formed. But, the thickness was smaller than that of native oxide. The artificial oxide could be removed by the same heating procedure as the native oxide.
Abe, Hiroshi; Morimoto, Ryo*; Uchida, Hirohisa*; Oshima, Takeshi
no journal, ,
Regarding the hydrogen storage in metals, it was reported that the absorption concentration of hydrogen atoms and the hydrogen absorption rate depend strongly on the surface state of metals. For the surface modification of materials, ion implantaton/irradiation with both lon and high energy are known to be a quite useful method. These facts give the possibility that the hydrogen absorptivity in Pd is improved by surface modification using ion irradiation.
Onuki, Shun*; Abe, Hiroshi; Matsumura, Yoshihito*; Uchida, Hirohisa*
no journal, ,
Hydrogen storage alloys are applied to the negative electrodes of the Ni-MH batteries. In such metal alloys high hydrogen absorption rate is required for the practical use. The electron/ion beam modifications are of effective methods to improve the hydrogen absorption rate in metal. In the present study, we have carried out the irradiation of electron beam and charged ion to La-Ni based hydrogen storage alloy. We measured the hydrogen absorption rates in irradiated/un-irradiated La-Ni based alloys. The samples used in this study were LaNi
Al
alloys. An electron beam or several ion irradiations used the 2 MV Cockcroft-Walton electron accelerator or the TIARA(Takasaki Ion Accelerators for Advanced Radiation Application) 400 kV ion implanter in JAEA. The hydrogen absorption rate measurements were also performed for the irradiated and un-irradiated La-Ni based alloy samples using the Severs equipment. The chemical compositions in the surface of the irradiated La-Ni bossed alloys were analyzed by scanning electron microscopy equipped with energy dispersive spectroscopy. The crystal structure and phase of the bulk into the irradiated La-Ni based alloys were determined by X-ray diffraction.
carbon in a diamond-like carbon film by hyperthermal atomic oxygen exposuresTagawa, Masahito*; Yokota, Kumiko*; Kitamura, Akira*; Matsumoto, Koji*; Yoshigoe, Akitaka; Teraoka, Yuden; Kanda, Kazuhiro*; Niibe, Masahito*
no journal, ,
In this study, the change of sp/sp ratio in a hydrogenated diamond-like carbon irradiated by hyperthermal atomic oxygen beams has been investigated by a near edge X-ray absorption fine structure method. The near edge X-ray absorption fine structure measurements, Rutherford back scattering measurements, and photoemission spectroscopic measurements were performed at the BL9 of NewSUBARU synchrotron facility, Kobe University, and BL23SU of SPring-8 facilities, respectively. It was found that the sp component, which was characteristic to a grafite structure, was selectively etched off by hyperthermal atomic oxygen beams with 2 eV. This result is consistent with previously obtained information of a larger erosion rate of grafite in the space environment than diamond.
Yokota, Kumiko*; Tagawa, Masahito*; Kitamura, Akira*; Matsumoto, Koji*; Yoshigoe, Akitaka; Teraoka, Yuden
no journal, ,
In this study, in order to investigate basic properties of hydrogen in a diamond-like carbon film, effects on hyperthermal atomic oxygen beam irradiation has been observed. The irradiation of hyperthermal atomic oxygen beams, the elastic recoil detection analysis, and the Rutherford back scattering analysis were performed at Kobe University. It was found that the region of hydrogen decrease became deeper with increasing collision energies. The hydrogen atoms in the diamond-like carbon film was easier to be released comparing with carbon atoms.
