Shigeru Murasugi

Kicker Magnet System of the RCS in J-PARC

Kicker magnets are installed in the extraction section of the RCS (Rapid Cycling Synchrotron) in J-PARC (Japan Proton Accelerator Research Complex) facility. They extract a 3 GeV proton beam and inject it into a downstream beam transport line at a repetition rate of 25 Hz. The power supply is mainly composed of the charging unit, the pulse forming network, and thyratrons as switching device. The maximum charging voltage is 80 kV. The kicker magnet is a distributed (transmission line) twin-C type. The circuit parameters are designed to have the 10 Omega characteristic impedance. The magnets are installed in vacuum chambers to prevent voltage breakdown. In order to accept 1 MW beam power, strict conditions are imposed on the kicker system. In the first part of this paper, we give an outline of the RCS extraction kicker system. Next, we report the specifications and performance of the power source and magnet. In addition, we report the measurements of the vacuum performance and magnetic field

Manufacturing and Operation of the Magnetic Septa for the Slow Beam Extraction From the J-PARC 50 GeV Proton Synchrotron

The magnetic septa have been developed for the slow beam extraction from the 50 GeV Proton Synchrotron to the Hadron Experimental Hall at J-PARC (Japan Proton Accelerator Research Complex). The magnetic septa consist of two thin magnetic septa, four medium thick magnetic septa and four thick magnetic septa. The typical operating current is 3000 A and the total kick angle is 77 mrad with the 30 GeV proton beam. All parts of the thin and of the medium thick septum magnets are made of inorganic materials to resist high radiation environment. The positions of the thin and medium thick septa can be aligned remotely in the horizontal range of ±5 mm, which enables us to minimize the beam loss at the magnetic septum section. The septa were installed in the synchrotron ring in December, 2008, after a test at KEK (High Energy Accelerator Research Organization), and were successfully operated in the beam time for the slow beam extraction in January and February, 2009, which resulted in the first 30 GeV slow extracted beam delivery to the Hadron Experimental Hall.

Hardware R&D of the KEK/JAERI 50 GeV synchrotron fast extraction kicker magnets

The fast extraction kicker magnets of the 50 GeV synchrotron are now in an intensive R&D stage. In the 50 GeV ring, the fast extraction system is designed to deliver the 50 GeV beam to the downstream neutrino oscillation experiment beam line with the Super-Kamiokande detector. At the same time, the fast extraction line is required to function as a beam abort, in case of hardware failure during acceleration of the beam from 3 GeV to 50 GeV. In order to fulfill both demands, the extraction system is designed to accommodate bipolar beam extraction. A new technology to make the bipolar kicker magnet system, using a symmetric Blumlein pulse forming network (SBPFN) system, has been introduced. Its validity is being investigated, both theoretically and experimentally. R&D programs aimed at establishing some of the important technical elements in the fast extraction kicker system are presently in progress. This R&D includes experimental studies of the bipolar kicker principle and the development of IGBT switching modules that satisfy full switching capability of the designed current and voltage.

Switching power supply for the PFL kicker magnet

SI-thyristor is expected as a solid-state high power switching semi-conducting device for the kicker magnet in the circular accelerator. Current rise has reached to 100 kA//spl mu/s. We noticed this characteristic and tried the use it for the pulse forming line (PFL). Preliminary results of the proto-type power supply of 20 kV-120 ns, with various impedance, although the intention is 75 kV-100 ns, are presented.