Evaluation of 2-D transverse beam profile monitor using gas sheet at J-PARC LINAC

Kamiya, Junichiro; Okabe, Kota; Kinsho, Michikazu; Moriya, Katsuhiro; Yamada, Ippei; Ogiwara, Norio*; Hikichi, Yusuke*; Wada, K.*

Journal of Physics; Conference Series, 1350, p.012149_1 - 012149_6, 2019/12

https://doi.org/10.1088/1742-6596/1350/1/012149

To obtain a getter effect to titanium vacuum duct surface, the method to remove the oxide on the surface by sputtering with ionized molecules has been developed. In the method, a sheet-shaped gas distribution with a uniform and high density is generated through a narrow slit by a small amount of gas. In this report, the gas density distribution was calculated by the Monte Carlo simulation code. As a result, it was found that a gas injection from both directions was effective to generate uniform density distribution. Furthermore, the gas injection method was applied to a non-destructive beam profile monitor, that detects ions generated by the interaction between gas molecules and beam. In this monitor, dependence of the beam profile on the injected gas amount was measured. A small amount of injected gas was found to be ideal for the beam profile measurements in the unsaturated and a high S/N ratio region.

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

https://doi.org/10.1380/vss.62.400

no abstracts in English

Non-destructive 2-D beam profile monitor using gas sheet in J-PARC LINAC

Kamiya, Junichiro; Ogiwara, Norio*; Miura, Akihiko; Kinsho, Michikazu; Hikichi, Yusuke*

Journal of Physics; Conference Series, 1067, p.072006_1 - 072006_6, 2018/09

https://doi.org/10.1088/1742-6596/1067/7/072006

A beam profile monitor using interaction between the beam and the gas molecules distributed in sheet shape has been developed. Ions or luminescence generated by passing the beam through the gas sheet has the information of cross-section shape of the beam. The gas sheet beam monitor will become a useful tool to measure the profile of high power beams because it has no breakable element such as wires. Furthermore, 2-D beam profile can be obtaine at a certain position of beam line. We applied the gas-sheet based beam profile monitor to J-PARC LINAC, where the negative hydrogen atoms are accelerated to the energy of 400 MeV. The vacuum system was carefully designed not to make an unacceptable pressure rise in nearby cavities when the gas was injected. The clear image of the beam profile was successfully obtained by detecting the ionized N gas.

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

https://doi.org/10.3131/jvsj2.60.475

Vacuum improvement of kicker magnet area in J-PARC 3 GeV synchrotron

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

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1193 - 1196, 2016/11

In this study, we propose a new 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 thermal expansion of the chamber. By simply installing the heater and thermal radiation shield plates between the kicker magnet and the chamber wall, most of the heat flux from the heater directs towards the kicker magnet. 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. The outgassing rage was reduced to one tenth comparing to the case without bake out.

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

https://doi.org/10.3131/jvsj2.59.79

Degassing of kicker magnet by in-situ bake-out method

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

Proceedings of 6th International Particle Accelerator Conference (IPAC '15) (Internet), p.2911 - 2913, 2015/06

New method of in-situ degassing of the kicker magnet in the beam line has been developed. The heater and heat shielding panels are installed in the vacuum chamber in this method. The heater was designed considering the maintainability. The graphite was selected as the heater and the high melting point metals were used as the reflectors just near the heater. The thermal analysis and the temperature measurement with the designed heater was performed. The ideal temperature distribution for the kicker degassing was obtained. The outgassing of the graphite during rising the temperature was measured. The result showed that the outgassing was extremely suppressed by the first heating. This means the outgassing of the graphite heater was negligible as long as it is used in the beam line without exposure to the air.

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

https://doi.org/10.3131/jvsj2.58.168

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 (: distance from the rotating axis and : 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 / (: radius of the disk and : 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 less than 2, where the rotating vector is specified to be oriented to zenith.

Beam loss reduction by magnetic shielding using beam pipes and bellows of soft magnetic materials

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

Nuclear Instruments and Methods in Physics Research A, 763, p.329 - 339, 2014/11

https://doi.org/10.1016/j.nima.2014.06.062

One of the main sources of beam loss in high power accelerators is unwanted stray magnetic fields from magnets near the beam line, which can distort the beam orbit. The most effective way to shield such magnetic fields is to perfectly surround the beam region without any gaps with a soft magnetic high permeability material. This leads to the manufacture of vacuum chambers (beam pipes and bellows) with soft magnetic materials. Using this heat treatment, the ratio of the integrated magnetic flux density along the beam orbit between the inside and outside of the beam pipe and bellows became small enough to suppress beam orbit distortion. The outgassing rate of the materials with this heat treatment was reduced by one order magnitude compared to that without heat treatment. By installing the beam pipes and bellows of soft magnetic materials as part of the Japan Proton Accelerator Research Complex 3 GeV rapid cycling synchrotron beam line, the closed orbit distortion was reduced by more than 80%. In addition, a 95.5% beam survival ratio was achieved by this COD improvement.

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

https://doi.org/10.3131/jvsj2.57.131

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 350C) 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.