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.
Hotchi, Hideaki; Harada, Hiroyuki; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Yoshimoto, Masahiro
Kasokuki, 16(2), p.109 - 118, 2019/07
no abstracts in English
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
JAEA-Evaluation 2019-003, 52 Pages, 2019/06
Evaluation Committee of Research Activities for J-PARC for interim assessment of Japan Proton Accelerator Research Complex evaluated the management and research activities of J-PARC center on the explanatory documents and oral presentations during the period from April 2015 to December 2018. This report summarizes the results of the assessment by the Committee with the Committee report attached.
Shinto, Katsuhiro; Okoshi, Kiyonori; Shibata, Takanori*; Nammo, Kesao*; Ikegami, Kiyoshi*; Takagi, Akira*; Namekawa, Yuya*; Ueno, Akira; Oguri, Hidetomo
AIP Conference Proceedings 2052, p.050002_1 - 050002_7, 2018/12
In the 2017/2018 campaign, the J-PARC cesiated rf-driven negative hydrogen (H) ion source producing H beam with the beam current of 47 mA accomplished three long-term operations more than 2,000 hours without any serious issues. On the final day of this campaign, the ion source produced an H beam current of 72 mA so that the linac commissioning group could demonstrate the beam current of 60 mA at the linac exit. We are also conducting an endurance test of a J-PARC-made antenna at a test bench. The antenna achieved the operation time approximately 1,400 hours.
Shobuda, Yoshihiro; Irie, Yoshiro*; Takayanagi, Tomohiro; Togashi, Tomohito; Yamamoto, Masanobu; Yamamoto, Kazami
Journal of Physics; Conference Series, 1067, p.062007_1 - 062007_8, 2018/10
The present four-terminal kicker at the Rapid Cycling Synchrotron (RCS) at the Japan Proton Accelerator Research Complex (J-PARC) has the power-saving benefit due to the doubled excitation currents by shorting two-terminals. On the other hand, beam instabilities are excited by the kicker impedances. In this report, we describe a scheme to reduce the kicker impedances using diodes (nonlinear devices) with resistors, while retaining the benefit of the doubled kicker excitation currents.
Takayanagi, Tomohiro; Ueno, Tomoaki*; Horino, Koki*
Journal of Physics; Conference Series, 1067, p.082019_1 - 082019_6, 2018/10
Yamamoto, Masanobu; Nomura, Masahiro; Shimada, Taihei; Tamura, Fumihiko; Furusawa, Masashi*; Hara, Keigo*; Hasegawa, Katsushi*; Omori, Chihiro*; Sugiyama, Yasuyuki*; Yoshii, Masahito*
Journal of Physics; Conference Series, 1067, p.052014_1 - 052014_6, 2018/10
The J-PARC RCS employs Magnetic Alloy (MA) loaded cavities. The RF power is fed by vacuum tubes in push-pull operation. We realize multi-harmonic RF driving and beam loading compensation thanks to the broadband characteristics of the MA. However, the push-pull operation has disadvantages in multi-harmonics. An unbalance of the anode voltage swing remarkably appears at very high intensity beam acceleration. We propose a single-ended MA cavity for the RCS beam power upgrade, where no unbalance arises intrinsically.
Shinto, Katsuhiro; Okoshi, Kiyonori; Ikegami, Kiyoshi*; Takagi, Akira*; Shibata, Takanori*; Nammo, Kesao*; Namekawa, Yuya*; Ueno, Akira; Oguri, Hidetomo
AIP Conference Proceedings 2011, p.050018_1 - 050018_3, 2018/09
Shinto, Katsuhiro; Shibata, Takanori*; Miura, Akihiko; Miyao, Tomoaki*; Wada, Motoi*
AIP Conference Proceedings 2011, p.080016_1 - 080016_3, 2018/09
Shibata, Takanori*; Shinto, Katsuhiro; Takagi, Akira*; Oguri, Hidetomo; Ikegami, Kiyoshi*; Okoshi, Kiyonori; Nammo, Kesao*; Naito, Fujio*
AIP Conference Proceedings 2011, p.020008_1 - 020008_3, 2018/09
Moriya, Katsuhiro; Kawane, Yusuke*; Miura, Akihiko; Futatsukawa, Kenta*; Miyao, Tomoaki*
Journal of Physics; Conference Series, 1067, p.072009_1 - 072009_3, 2018/09
no abstracts in English
Kamiya, Junichiro; Ogiwara, Norio*; Miura, Akihiko; Kinsho, Michikazu; Hikichi, Yusuke*
Journal of Physics; Conference Series, 1067, p.072006_1 - 072006_6, 2018/09
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.
Shibata, Takanori*; Ikegami, Kiyoshi*; Liu, Y.*; Miura, Akihiko; Naito, Fujio*; Nammo, Kesao*; Oguri, Hidetomo; Okoshi, Kiyonori; Otani, Masashi*; Shinto, Katsuhiro; et al.
Proceedings of 29th International Linear Accelerator Conference (LINAC 2018) (Internet), p.519 - 521, 2018/09
Transport process of negative hydrogen ion (H) in LEBT (Low Energy Beam Transport) is investigated by comparison of experimental and numerical results. A three dimensional Particle-In-Cell (PIC) particle transport model has been developed in order to take into account (i) axial magnetic field by two solenoids in J-PARC LEBT and (ii) radial electric field by space charge (SC) effect. Ratio of H beam particles inside the RFQ (Radio Frequency Quadrupole) acceptance to the total particles at the RFQ entrance is calculated for different current conditions in LEBT solenoid 1 and 2. The results are compared with RFQ transmission rate measured in the J-PARC linac commissioning. The double peak of RFQ transmission rate to the solenoid applied current seen in the measurement is explained by the calculation results. The results indicate that presence of the LEBT orifice for differential pumping plays a role as a collimator to reduce emittance at RFQ entrance.
Yamamoto, Kazami; Yamakawa, Emi*; Takayanagi, Tomohiro; Miki, Nobuharu*; Kamiya, Junichiro; Saha, P. K.; Yoshimoto, Masahiro; Yanagibashi, Toru*; Horino, Koki*; Nakanoya, Takamitsu; et al.
ANS RPSD 2018; 20th Topical Meeting of the Radiation Protection and Shielding Division of ANS (CD-ROM), 9 Pages, 2018/08
The existing beam power of the J-PARC Rapid Cycling Synchrotron is up to 500 kW, and higher radiation doses are concentrated in the injection area. These activations are caused by the interaction between the foil and the beam. To reduce dose exposure to workers near the injection point, we study a new design of the injection scheme. Experience has shown that eddy currents are generated in the metal flange near the magnet owing to the pulsed magnetic field, and the temperature exceeds 100 degrees C. The shield installed in the new injection system needs to have a layer structure, in which an insulator is inserted between iron shields to reduce the eddy current. From the results of the shielding calculation, even if 1 mm of polyethylene was inserted between two 9-mm-thick SUS 316 plates, which serve as shielding material, the shielding performance was reduced only about 5%, and we confirmed that it would function well.
Okoshi, Kiyonori; Shinto, Katsuhiro; Nammo, Kesao*; Shibata, Takanori*; Ikegami, Kiyoshi*; Takagi, Akira*; Ueno, Akira; Namekawa, Yuya*; Oguri, Hidetomo
Proceedings of 15th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.889 - 892, 2018/08
In 2017-2018 campaign, three times of long-time operation more than 2,000 hours of the J-PARC rf-driven negative hydrogen (H) ion source producing H beam with the beam current of 47 mA were successfully achieved without any serious problems. At the final day of this campaign, the ion source produced an H beam with the current of 72 mA in order to demonstrate the beam current of 60 mA at the linac exit. We are also conducting an endurance test of a J-PARC-made antenna at a test bench. Approximately 1,400-hour operation with the antenna was successfully performed.
Kamiya, Junichiro; Yamamoto, Kazami; Yanagibashi, Toru*; Sato, Atsushi*; Miki, Nobuharu*
Proceedings of 15th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.645 - 648, 2018/08
Surround of the beam injection point in the J-PARC 3 GeV Rapid Cycling Synchrotron is the area where the residual radioactive dose is higher than other areas due to the beam scattering by the charge stripping foil. However, there is very little space to install radiation shields around the vacuum chamber in the beam injection point. Furthermore, the vacuum leak has often occurred due to the heat expansion of the chamber flange due to the induced current by the nearby pulse magnet. To solve such problems for minimizing the radiation exposure of maintenance workers, the vacuum chamber rin the beam injection point was newly designed. The space for the radiation shields was created by lengthening and the changing the cross-sectional shape. The titanium alloy with high mechanical strength was used for the flange material so that the flange was able to be fastened with higher tightening torque.
Shobuda, Yoshihiro; Chin, Y. H.*
Scientific Reports (Internet), 8, p.12805_1 - 12805_19, 2018/08
In typical numerical simulations, the space-charge force is calculated by slicing a beam into manylongitudinal segments and by solving the two-dimensional Poisson equation in each segment. Thismethod neglects longitudinal leakage of the space-charge force to nearby segments owing to itslongitudinal spread over 1/Lorentz-. By contrast, the space-charge impedance, which is the Fourier transformof the wake function, is typically calculated directly in the frequency-domain. So long as we followthese approaches, the longitudinal leakage effect of the wake function will remain to be unclear. In thepresent report, the space-charge wake function is calculated directly in the time domain by solving thethree-dimensional Poisson equation for a longitudinally Gaussian beam. We find that the leakage effectis insignificant for a bunch that is considerably longer than the chamber radius so long as the segmentlength satisfies a certain condition. We present a criterion for how finely a bunch should be sliced so thatthe two-dimensional slicing approach can provide a good approximation of the three-dimensional exactsolution.
Yukuatsu Gijutsu, 57(7), p.44 - 50, 2018/07
For vacuum systems in high-power proton accelerators, there are many challenging requirements in addition to their basic role owing to the existence of a large number of high-energy protons, rapid cycling of the magnetic field, and high radioactivation. In addition, it is necessary to promptly evacuate from the atmospheric pressure to UHV and ensure sufficient pumping speed against an additional gas load. The vacuum system of the 3 GeV Rapid Cycling Synchrotron (RCS) at the Japan Proton Accelerator Research Complex fulfills such unique requirements. Many vacuum devices such as turbo molecular pumps with radiation toughness, beam pipes made of alumina ceramics, and titanium beam pipes and bellows were developed in accordance with the design concept of the system. Treatments to minimize both static and dynamic outgassing were also performed, e.g., surface polishing, coating, and vacuum firing. This paper aims to review the vacuum technologies in accelerators taking J-PARC as an example.
Meigo, Shinichiro; Iwamoto, Hiroki; Matsuda, Hiroki; Takei, Hayanori
Journal of Physics; Conference Series, 1021(1), p.012072_1 - 012072_4, 2018/06
no abstracts in English