• T. Morishita, K. Hasegawa, Y. Kondo
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
• H. Baba, Y. Hori, H. Kawamata, H. Matsumoto, F. Naito, Y. Saito, M. Yoshioka
  KEK, Ibaraki

The J-PARC RFQ (length 3.1m, 4-vane type, 324 MHz) accelerates a negative hydrogen beam from 0.05MeV to 3MeV toward the following DTL. We started the preparation of a new RFQ as a backup machine. The new cavity is divided by three unit tanks in the longitudinal direction. The unit tank consists of two major vanes and two minor vanes. A numerical controlled machining with a conventional ball-end-mill has been chosen for the vane modulation cutting instead of the wheel shape cutter. In this presentation we will report the machining procedure, the results of the vane machining, RF properties, and some topics during the fabrication.

• T. Morishita, K. Hasegawa, Y. Kondo
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
• H. Baba, Y. Hori, H. Kawamata, H. Matsumoto, F. Naito, Y. Saito, M. Yoshioka
  KEK, Ibaraki

The J-PARC RFQ (length 3.1m, 4-vane type, 324 MHz) accelerates a negative hydrogen beam from 0.05MeV to 3MeV toward the following DTL. We started the preparation of a new RFQ as a backup machine. The new cavity is divided by three unit tanks in the longitudinal direction. The unit tank consists of two major vanes and two minor vanes. A one-step vacuum brazing of a unit tank has been chosen to unite these four vanes together with the flanges and ports. In this presentation we will report the results of the vacuum brazing with the dimension accuracy and an RF property.

• T. Ito
  JAEA/LINAC, Ibaraki-ken
• C. Kubota, F. Naito, K. Nanmo
  KEK, Ibaraki

The operation of the DTL and the Separated type DTL (SDTL) of the J-PARC started in November 2006. The DTL and SDTL are currently running stable and accelerating the beam. For stable operation of the DTL/SDTL, We have done maintenance of the equipments, like an RF coupler, and improved the troubles. In this paper, we will present the operation experiences of the DTL and the SDTL.

• F. Naito, K. Nanmo, H. Tanaka
  KEK, Ibaraki
• H. Asano, T. Ito
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken

X-ray radiation from the SDTL of J-PARC linac has been observed with the beam loss monitor by the cavity. The results show that the X-ray intensity depends not only on the RF power level of the tank but also on the RF structure of the tank. In the paper we will show the results of the investigation for the origin of the X-ray radiation from the tank.

• M. Kawamura, Y. Fukui, F. Naito
  KEK, Ibaraki
• E. Chishiro, H. Suzuki, M. Yamazaki
  JAEA, Ibaraki-ken
• K. Hasegawa, S. Shinozaki
  JAEA/J-PARC, Tokai-mura

This report will describe the present status of the power supply systems (PS systems) for the klystrons in the J-PARC (Japan Proton Accelerator Research Complex) linac. The technical specification, the operating experience, and the upgrade plan, of the PS systems will be presented in this report. Now the energy of the J-PARC linac is 181MeV, and the linac includes twenty 324MHz klystrons. In 2012, the energy will be upgraded to 400MeV, and the linac will include twenty 324MHz klystrons and twenty-five 972MHz klystrons. The klystrons are the modulating-anode types. The PS systems include the High voltage DC power supplies (DCPSs) and the anode-modulators. One DCPS drives one or four klystrons, and one anode-modulator drives one klystron.

• Y. Kondo
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
• M. Ikegami, F. Naito
  KEK, Ibaraki
• J. Qiang
  LBNL, Berkeley, California

For the beam current upgrade of the J-PARC linac, a new RFQ (RFQ III)is developing. The peak beam current of RFQ III is 50mA. To increase the peak current from the existing RFQ (RFQ I), the longitudinal and/or transverse emittances are expected to be increased. However, the increase of the longitudinal emittance will affect the performance of the RF chopper system. In this paper, detailed simulations of the RF chopper system are described and the requirement for the longitudinal emittance of the RFQ is clarified.