Kazuo Hasegawa

Commissioning of the J-PARC linac

The J-PARC (Japan Proton Accelerator Research Complex) is a multi purpose facility with 1 MW class proton beam power. The J-PARC comprises a linac, a 3 GeV rapid-cycling synchrotron (RCS), a 50 GeV main ring synchrotron (MR) and experimental facilities. The energy of the linac is reduced to 181 MeV for the time being, and it will be increased to 400 MeV in the near future. The 3 MeV RFQ, which is a front end of the linac, has been beam commissioned since November 2006, and we continue to work on the rest of the linac such as a 50 MeV DTL and a 181 MeV Separated-type DTL. The results and status of the J-PARC linac beam commissioning are presented.

Development of superconducting cavities for high intensity proton accelerator at JAERI

The Japan Atomic Energy Research Institute (JAERI) is proposing a high intensity proton accelerator for the Neutron Science Project. A superconducting (SC) RF structure is the main option for the high energy part of the linac. Design and development work of the SC proton linac is in progress in JAERI. Three single-cell SC prototype cavities were fabricated and their performances were tested. The test results were good enough to apply to the SC linac. This paper describes the present status of the design and development work for the SC proton linac.

Beam dynamics design of the muon linac high-beta section

A muon linac development for a new muon g-2 experiment is now going on at J-PARC. Muons from the muon beam line (H line) at the J-PARC muon science facility are once stopped in a silica-aerogel target, and room temperature muoniums are evaporated from the aerogel. They are dissociated with lasers, then accelerated up to 212 MeV using a linear accelerator. For the accelerating structure from 40 MeV, disk-loaded traveling-wave structure is applicable because the particle beta is more than 0.7. The structure itself is similar to that for electron linacs, however, the cell length should be harmonic to the increase of the particle velocity. In this paper, the beam dynamics design of this muon linac using the disk-loaded structure (DLS) is described.

Path to 1-MW at J-PARC Rapid Cycling Synchrotron

The accelerator system at Japan Proton Accelerator Research Complex (J-PARC) has been operational since May 2008 and has mainly been used to perform physics experiments. The accelerator system consists of a Linac, a Rapid Cycling Synchrotron (RCS), and a Main Ring Synchrotron. The originally designed RCS injection energy is 400MeV, but the first operation started at 181MeV. New acceleration cavities were installed in J-PARC Linac during the summer shutdown of 2013, and user operation by the Material and Life science Facility (MLF) at the injection energy of 400MeV was started from February 2014. Post beam commissioning of 400MeV injection energy, beam loss was small enough, and we established 300kW continuous operation. Subsequently, the peak current of the Linac was increased from 30mA to 50mA. This upgrade enabled us to try 1-MW beam acceleration. Finally, after some additional improvements, we successfully accelerated 1-MW equivalent protons.

Vacuum properties and operation stability of the radio-frequency quadrupole accelerator in Japan Proton Accelerator Research Complex linac

The Japan Proton Accelerator Research Complex accelerator comprises an injector linac, a 3-GeV rapid-cycling synchrotron (RCS), and a 30-GeV main ring. The linac provides a 400-MeV negative hydrogen ion beam to the RCS. For beam power upgrade, a new radio-frequency quadrupole (RFQ) was designed to increase the peak beam current from 30 to 50u2009mA. This RFQ was fabricated and installed in the front end of the linac beam line in the summer of 2014. Since then, the RFQ has been operated without serious problems for more than two years. However, operational stability of the RFQ can be improved further. The RFQ operation trips occasionally owing to sparking between vane tips. An increase in residual gas components is observed during beam operation. A part of the beam lost in the RFQ hits the inner surface of the cavity, which induces outgassing from the surface. Moreover, the trip rate depends on the beam operating condition. Under a higher trip rate, a larger increase in the carbon-related residual gas componen...

Upgrade and Operation of J-PARC Linac

Kazuo HASEGAWA*, Hidetomo OGURI, Takashi ITO, Etsuji CHISHIRO, Koichiro HIRANO, Takatoshi MORISHITA, Shinichi SHINOZAKI, Hiroyuki AO, Kiyonori OHKOSHI, Yasuhiro KONDO, Jun TAMURA, Saishun YAMAZAKI, Toshihiko HORI, Fumiaki SATO, Yasuo NEMOTO, Isao KOIZUMI, Nobuo OUCHI, Nobuhiro KIKUZAWA, Akira UENO, Akihiko MIURA, Shinpei FUKUTA, Akinobu YOSHII, Koichi SATO, Akira OZONE, Yuki SAWABE, Yusuke KAWANE, Hiroshi IKEDA, Yuichi ITO, Yuko KATO, Kazuo KIKUCHI, Fumio HIROKI, Toshio TAKAYASU, Tsutomu USAMI, Munetoshi YANAI, Kazuhiko TADOKORO, Kenji OHSAWA, Fujio NAITO, Yong LIU, Zhigao FANG, Takashi SUGIMURA, Kenta FUTATSUKAWA, Kiyoshi IKEGAMI, Masato KAWAMURA, Kesao NANMO, Yuji FUKUI, Tomoaki MIYAO, Tomofumi MARUTA and Akira TAKAGI