Refine your search:     
Report No.
 - 
Search Results: Records 1-20 displayed on this page of 95

Presentation/Publication Type

Initialising ...

Refine

Journal/Book Title

Initialising ...

Meeting title

Initialising ...

First Author

Initialising ...

Keyword

Initialising ...

Language

Initialising ...

Publication Year

Initialising ...

Held year of conference

Initialising ...

Save select records

Journal Articles

Ortho-para conversion of molecularly chemisorbed H$$_{2}$$ on Pd(210)

Ueta, Hirokazu; Fukutani, Katsuyuki

Vacuum and Surface Science, 64(9), p.430 - 434, 2021/09

Journal Articles

Two-step model for reduction reaction of ultrathin nickel oxide by hydrogen

Ogawa, Shuichi*; Taga, Ryo*; Yoshigoe, Akitaka; Takakuwa, Yuji*

Journal of Vacuum Science and Technology A, 39(4), p.043207_1 - 043207_9, 2021/07

 Times Cited Count:0 Percentile:0.01(Materials Science, Coatings & Films)

Nickel (Ni) is used as a catalyst for nitric oxide decomposition and ammonia production but it is easily oxidized and deactivated. Clarification of the reduction process of oxidized Ni is essential to promote more efficient use of Ni catalysts. In this study, the reduction processes were investigated by in situ time-resolved photoelectron spectroscopy. We propose a two-step reduction reaction model. The rate-limiting process for the first step is surface precipitation of O atoms and that of the second step is dissociation of H$$_{2}$$ molecules.

Journal Articles

Oxidation reaction kinetics on transition metal surfaces observed by real-time photoelectron spectroscopy

Ogawa, Shuichi*; Zhang, B.*; Yoshigoe, Akitaka; Takakuwa, Yuji*

Vacuum and Surface Science, 64(5), p.218 - 223, 2021/05

The oxidation reaction kinetics on Ti(0001) and Ni(111) surfaces were observed by real-time photoelectron spectroscopy using synchrotron radiation to measure the oxidation state and oxide thickness. After the Ti(0001) surface was wholly covered by TiO with a thickness of 1.2 nm, the rapid growth of n-type TiO$$_{2}$$ proceeded through the diffusion of Ti$$^{4+}$$ ions to the TiO$$_{2}$$ surface at 400$$^{circ}$$C. A saturation of oxygen uptake on the TiO surface indicates that the O$$_{2}$$ sticking coefficient on the TiO surface is negligibly small and the segregation of Ti to the TiO surface is a trigger to initiate the TiO$$_{2}$$ growth. On the Ni(111) surface at 350$$^{circ}$$C, a thermally stable NiO$$_{x}$$ proceeded preferentially and then the growth of p-type NiO was initiated. The time evolution of NiO thickness was represented by a logarithmic growth model, where the NiO growth is governed by the electron tunneling to the NiO surface.

Journal Articles

Development of ${it spatiotemporal}$ measurement and analysis techniques in X-ray photoelectron spectroscopy; From NAP-HARPES to 4D-XPS

Toyoda, Satoshi*; Yamamoto, Tomoki*; Yoshimura, Masashi*; Sumida, Hirosuke*; Mineoi, Susumu*; Machida, Masatake*; Yoshigoe, Akitaka; Suzuki, Satoru*; Yokoyama, Kazushi*; Ohashi, Yuji*; et al.

Vacuum and Surface Science, 64(2), p.86 - 91, 2021/02

We have developed ${it spatiotemporal}$ measurement and analysis techniques in X-ray photoelectron spectroscopy. To begin with, time-division depth profiles of gate stacked film interfaces have been achieved by NAP-HARPES (Near Ambient Pressure Hard X-ray Angle-Resolved Photo Emission Spectroscopy) data. We then have promoted our methods to quickly perform peak fittings and depth profiling from time-division ARPES data, which enables us to realize 4D-XPS analysis. It is found that the traditional maximum entropy method (MEM) combined with Jackknife averaging of sparse modeling in NAP-HARPES data is effective to perform dynamic measurement of depth profiles with high precision.

Journal Articles

${it In situ}$ optical microscopy of crystal growth of graphene using thermal radiation

Terasawa, Tomoo; Taira, Takanobu*; Obata, Seiji*; Saiki, Koichiro*; Yasuda, Satoshi; Asaoka, Hidehito

Vacuum and Surface Science, 62(10), p.629 - 634, 2019/10

Graphene, an atomically thin sheet composed of sp$$^{2}$$ carbon atoms, has been the most attractive material in this decade. The fascinating properties of graphene are exhibited when it is monolayer. Chemical vapor deposition (CVD) is widely used to produce monolayer graphene selectively in large-area. Here we introduce "radiation-mode optical microscopy" which we have developed in order to realize the ${it in situ}$ observation of the CVD growth of graphene. We show the method to observe graphene as bright contrast on Cu substrates in thermal radiation images. The growth mechanism, the nucleation site and rate limiting process, revealed by the ${it in situ}$ observation is presented. Finally, we show the CVD growth of graphene on Au substrates, resulting in the tuning of the emissivity of graphene by the pre-treatment procedures. Our method is not only a way to observe the graphene growth but also shed light on the thermal radiation property of graphene.

Journal Articles

Turbomolecular pump as main pump in a high-power proton accelerator vacuum system

Kamiya, Junichiro; Kinsho, Michikazu; Ogiwara, Norio*; Sakurai, Mitsuru*; Mabuchi, Takuya*; Wada, Kaoru*

Vacuum and Surface Science, 62(8), p.476 - 485, 2019/08

J-PARC 3GeV rapid cycling synchrotron (RCS) is one of the highest beam power proton accelerators. Challenges for achieving low pressure region in ultra-high vacuum (UHV) in the beam line are the large outgassing source. We focused turbo molecular pumps (TMP) as maing pump because it can evacuate the continuous and additional outgassing with large pumping speed in wide pressure range. It is also possible to evacuate from low vacuum to UHV with only a few hours by using TMP, which ensures users' experimental time after vacuum device maintenance. During more than 10 years operation of the vacuum system, many experiences have been accumulated about the usage of TMP in RCS. In this presentation, we discussed about validity of TMP as main pump in high power proton beam accelerator by showing the performance of the beam line pressure during the beam operation. Further, in anticipation of upgrade higher beam power more than 1 MW, validity of a combination of TMP and NEG pump will be mentioned.

Journal Articles

Development of a gas distribution measuring system for 2-D beam profile monitor

Yamada, Ippei; Ogiwara, Norio*; Hikichi, Yusuke*; Kamiya, Junichiro; Kinsho, Michikazu

Vacuum and Surface Science, 62(7), p.400 - 405, 2019/07

no abstracts in English

Journal Articles

Simultaneous observation of Si oxidation rate and oxidation-induced strain using XPS

Ogawa, Shuichi*; Yoshigoe, Akitaka; Takakuwa, Yuji*

Vacuum and Surface Science, 62(6), p.350 - 355, 2019/06

Thermal oxidation of Si substrate is an indispensable process for the Si device fabrication. However, the influence of oxidation induced strain cannot be ignored for thin films. Synchrotron radiation real-time photoelectron spectroscopy was used as a method to measure simultaneously oxidation induced strain and oxidation rate. It was found that the acceleration of interfacial oxidation induced by thermal strain was observed for the rapid thermal oxidation. The results can be explained by the model in which point defects caused by strain become reaction sites at the SiO$$_{2}$$/Si interface.

Journal Articles

Large-aperture alumina ceramics beam pipes with titanium bellows for the rapid cycling synchrotron at Japan Proton Accelerator Research Complex

Kamiya, Junichiro; Kinsho, Michikazu; Abe, Kazuhiko*; Higa, Kyusaku*; Koizumi, Oji*

Journal of Vacuum Science and Technology A, 36(3), p.03E106_1 - 03E106_10, 2018/05

 Times Cited Count:0 Percentile:0.01(Materials Science, Coatings & Films)

The 3 GeV Rapid Cycling Synchrotron (RCS) in J-PARC aims to generate one of the highest power protons in the world, whose design extraction beam power is 1 MW. Beam pipes of alumina ceramics are used to prevent the induced current, which is caused by the rapid change of the magnetic field. In the beam injection section, ceramics beam pipes for a quadrupole magnet and a horizontal shift bump magnet are connected without bellows due to the very limited space. To improve maintainability, the ceramics beam pipes for the quadrupole magnet were newly designed to insert the bellows. We will report the design concept of the new alumina ceramics beam pipes with low spring constant bellows and the several results of the verification tests.

Journal Articles

Thermal desorption characteristics of several charge stripper carbon films for J-PARC RCS

Kamiya, Junichiro; Kinsho, Michikazu; Yamazaki, Yoshio; Yoshimoto, Masahiro; Yanagibashi, Toru*

Journal of the Vacuum Society of Japan, 60(12), p.484 - 489, 2017/12

Multi-turn H$$^{-}$$ charge exchange injection is employed as a beam injection method in the 3-GeV RCS (Rapid cycling synchrotron) at J-PARC (Japan Proton Accelerator Research Complex). In this method, injection H$$^{-}$$ beam is put on the same orbit as already circulating proton (H$$^{+}$$) beam in a dipole magnetic field due to the opposite curvature of the injected and circulating beams. In the straight section, where the two beams coincide with each other, both beams are passed through a thin foil, which strips two weakly bound electrons off each H$$^{-}$$ ion, forming an intense beam of protons. The thin foil, which is mostly made of carbon, would be the source of the outgassing, especially when its temperature rises due to the beam hitting. Therefore it is important to estimate the amount and components of the outgassing from the charge stripping foil. In this paper, we will report the thermal desorption measurement results for the several foil, which is used as the charge stripping foil in the RCS.

Journal Articles

Conductance of a long rectangular channel; Pressure dependence

Ogiwara, Norio; Hikichi, Yusuke*; Kamiya, Junichiro; Kinsho, Michikazu; Yoshida, Hajime*; Arai, Kenta*

Journal of the Vacuum Society of Japan, 60(12), p.475 - 480, 2017/12

Journal Articles

Vacuum technologies in high-power proton accelerators

Kamiya, Junichiro

Journal of the Vacuum Society of Japan, 59(8), p.213 - 221, 2016/08

Basic role of the vacuum systems in conventional particle accelerators is to maintain enough low pressure in the beam lines to guarantee the beam lifetime. In high power proton beam accelerators, the requirement for the vacuum system is much tougher due to the large size vacuum devices and high radioactivation. In addition, it is essential to pre-treat the vacuum materials in order to suppress pressure instability due to gas desorption from the vacuum wall originating from the large amount of the charged particles. Further, the rapid evacuation from the atmospheric pressure to the UHV after maintenance is also required to ensure the beam operation time. We aim to present the typical vacuum technologies in high power proton beam accelerator by introducing the vacuum system of J-PARC, especially of 3GeV rapid cycling synchrotron (RCS).

Journal Articles

Detection of electron beam with a gas sheet

Ogiwara, Norio; Hikichi, Yusuke; Kamiya, Junichiro; Kinsho, Michikazu

Journal of the Vacuum Society of Japan, 59(4), p.79 - 82, 2016/04

Journal Articles

${{it In situ}}$ baking method for degassing of a kicker magnet in accelerator beam line

Kamiya, Junichiro; Ogiwara, Norio; Yanagibashi, Toru*; Kinsho, Michikazu; Yasuda, Yuichi*

Journal of Vacuum Science and Technology A, 34(2), p.021604_1 - 021604_10, 2016/03

 Times Cited Count:3 Percentile:17.7(Materials Science, Coatings & Films)

In this study, we propose a new ${{it in situ}}$ degassing method by which only kicker magnets in the accelerator beam line are baked out without raising the temperature of the vacuum chamber to prevent unwanted heat expansion of the chamber. The bake-out system comprises the heater and thermal radiation shield plates, which are installed between the kicker magnet and the chamber wall. The result of the verification test showed that each part of the kicker magnet was heated to above the target temperature with a small rise in the vacuum chamber temperature. A graphite heater was selected in this application to bake-out the kicker magnet in the beam line to ensure reliability and easy maintainability of the heater. The vacuum characteristics of graphite were suitable for heater operation in the beam line. A preliminary heat-up test conducted in the accelerator beam line also showed that each part of the kicker magnet was successfully heated and that heat expansion of the chamber was negligibly small.

Journal Articles

Topmost surface structure analysis by Total-Reflection High-Energy Positron Diffraction (TRHEPD)

Fukaya, Yuki

Journal of the Vacuum Society of Japan, 59(2), p.35 - 39, 2016/02

no abstracts in English

Journal Articles

Titanium alloy as a potential low radioactivation vacuum material

Kamiya, Junichiro; Hikichi, Yusuke; Kinsho, Michikazu; Ogiwara, Norio; Fukuda, Mitsuhiro*; Hamatani, Noriaki*; Hatanaka, Kichiji*; Kamakura, Keita*; Takahisa, Keiji*

Journal of Vacuum Science and Technology A, 33(3), p.031605_1 - 031605_8, 2015/05

 Times Cited Count:4 Percentile:15.85(Materials Science, Coatings & Films)

For the vacuum systems of high-intensity beam accelerators, low radioactivation materials with good vacuum characteristics and high mechanical strength are required. The titanium alloy Ti-6Al-4V was investigated as a potential low activation vacuum material with high mechanical strength for the fabrication of vacuum components, particularly the flanges of beam pipes, in the J-PARC 3 GeV synchrotron. The dose rate of Ti-6Al-4V when irradiated by a 400 MeV proton was observed to decrease more rapidly than that of stainless steel. Furthermore, the generated radioactive isotopes were nuclides with relatively short half-lives. The outgassing rate of Ti-6Al-4V was the same as the typical value for stainless steel. Additionally, the hydrogen concentration in bulk Ti-6Al-4V was reduced to approximately 1 ppm by vacuum firing. These results indicate that Ti-6Al-4V is a good candidate for use as a low activation vacuum material with high mechanical strength.

Journal Articles

Monte Carlo simulations of the beam effect for the emitted molecules from the rotating disks

Ogiwara, Norio

Journal of the Vacuum Society of Japan, 58(5), p.168 - 172, 2015/05

The angular distribution of molecules emitted from rotating disks with a small gap was simulated using the Monte Carlo method. As the molecules have a circumferential velocity $$r$$$$omega$$ ($$r$$: distance from the rotating axis and $$omega$$: angular velocity), when they leave the surfaces of the rotating disks, they tend to be emitted toward the tangent lines of the rims of the disks. When the disks rotate with a velocity ratio $$eta$$ $$equiv$$ $$r$$ $$_{1}$$$$omega$$/ $$<$$$$nu$$$$>$$ ($$r$$$$_{1}$$: radius of the disk and $$<$$$$nu$$$$>$$: mean velocity of the molecules) of 3.8, three quarters of the outgoing molecules gather within an angle of 0.4 radians from the tangent line. The angular distribution is related to the altitude almost independent of the revolution frequency with a value of $$eta$$ less than 2, where the rotating vector is specified to be oriented to zenith.

Journal Articles

In situ degassing of the kicker magnet in J-PARC RCS

Kamiya, Junichiro; Ogiwara, Norio; Hikichi, Yusuke; Yanagibashi, Toru; Kinsho, Michikazu

Journal of the Vacuum Society of Japan, 58(4), p.134 - 139, 2015/04

This report aims to propose a new in situ degassing method by which only the kicker magnets were baked out without raising the temperature of the vacuum chamber by installing heat source and heat shield between the kicker magnet and the chamber wall. The target temperature of the ferrites in the kicker magnet is above 100$$^{circ}$$C, while keeping the temperature rise of the vacuum chamber less than 30$$^{circ}$$C in order to prevent the heat expansion of the vacuum chamber. After checking the operability of this method by thermal analysis with simple model, the experimental measurement was performed by using a RCS kicker magnet. The results showed that the target temperature was able to be achieved by this degassing method.

Journal Articles

Study of oxide film with the hard X-ray photoelectron spectroscopy

Kobata, Masaaki; Kobayashi, Keisuke*

Journal of the Vacuum Society of Japan, 58(2), p.43 - 49, 2015/02

We report the applications of a hard X-ray photoelectron spectroscopy to the characterization of SiO$$_{2}$$/Si(001)systems. Large escape depth of high-energy photoelectron enables us to probe buried layers and their interfaces in multilayer structures. Estimation of SiO$$_{2}$$ overlayer thicknesses up to 25 nm by angle resolved XPS was possible in SiO$$_{2}$$/Si(001) samples. Determination of the thickness profile of a wedged shape SiO$$_{2}$$ buried layer was successfully done in Ir (8 nm)/HfO$$_{2}$$ (2.2 nm)/thickness graded-SiO$$_{2}$$ (0-10 nm) / Si (100). The Si 1s core level showed a SiO$$_{2}$$ thickness dependent shift, which was ascribed to fixed charge at the SiO$$_{2}$$-Si interface. Energy distribution of interface states at ultrathin thermal oxide/Si(100) interfaces were determined by Si 1${it s}$ core level shift by applying gate bias in metal-oxide-semiconductor (MOS) structure with 5 nm Au gate electrodes.

Journal Articles

Design consideration of beam duct for quadrupole correctors in J-PARC RCS

Kamiya, Junichiro; Kinsho, Michikazu; Hayashi, Naoki; Hotchi, Hideaki; Ogiwara, Norio; Tani, Norio; Watanabe, Yasuhiro

Journal of the Vacuum Society of Japan, 57(4), p.131 - 135, 2014/04

In J-PARC 3GeV synchrotron (RCS), new quadrupole magnets (quadrupole correctors) are planned to be installed in order to correct the edge focusing effect and tune. In this report, we describe a deliberation flow about the design of the beam ducts, which are installed in the quadrupole corrector. The effects of eddy current were examined in the case of the titanium duct. The calculated results showed that the temperature rise was too much (up to over 350$$^{circ}$$C) and the magnetic field in the beam duct is largely distorted. Therefore we decided to employ alumina ceramics beam ducts. The stress and displacement, which are caused by the atmospheric pressure, were estimated by simulating the realistic equipments in the beam line. It was found that there was no large stress and displacement by installing the alumina ceramics duct.

95 (Records 1-20 displayed on this page)