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Hayashi, Naoki
Proceedings of 4th International Beam Instrumentation Conference (IBIC 2015) (Internet), p.381 - 385, 2016/02
The J-PARC RCS (Rapid-Cycling proton Synchrotron) runs with repetition rate of 25 Hz. The beam intensity of current monitors and beam loss monitors (BLM) data are archived for all pulses and they are analyzed to study the machine stability. It was found that after replacing ion source, the beam intensity seems to be more stable than before. In addition BPM data are also recorded regularly, it was investigated what was recorded by the BLM or BPM, when a magnet power supply feedback or a vacuum pump get into troubles. In case of the bending magnet problem, not all BLMs show increasing signal, some BLMs' signal were decreasing. In case of the pump trouble, within a few seconds, the beam losses were quickly increasing. It is described these incidents with various data.
Yamamoto, Kazami
Proceedings of 4th International Beam Instrumentation Conference (IBIC 2015) (Internet), p.80 - 84, 2016/02
The 3 GeV rapid cycling synchrotron of the J-PARC accelerates a proton beam up to 3 GeV and delivers it to the main ring and the material and life science facility. The main magnets (dipole and quadrupole magnets) of the synchrotron have large aperture, and thickness of yoke is larger than 200 mm. Considering the stopping power of a proton, a shielding effect of the magnets for beam loss monitor strongly depends on the lost beam energy. When the beam loss occurs during injection, the lost proton cannot penetrate the magnet yoke. But when the beam loss occurs after acceleration, lost beam easily pass the magnet. Therefore the signal response of the beam loss monitor is changed by the lost energy. We estimated the signal dependence on the lost energy by the simulation. The results indicated that the response strongly depends on the location of the lost point and lost energy. It is proportional to the lost power except the condition that the magnets become the radiation shielding.
Miura, Akihiko; Hayashi, Naoki; Maruta, Tomofumi*; Liu, Y.*; Miyao, Tomoaki*; Fukuoka, Shota*
Proceedings of 4th International Beam Instrumentation Conference (IBIC 2015) (Internet), p.386 - 389, 2016/02
We have used bunch shape monitors (BSMs) to measure the longitudinal bunch length of negative hydrogen ion beam in the J-PARC linac. In order to evaluate the measurement errors with peak beam current increasing, we observed waveforms with various beam current. As the result, an RMS bunch length depends on the peak beam current and the bending at the pulse head grows with the peak beam current. We also compared the data taken at an off-center beam to avoid the thermal stress with the ones at an on-center beam, because a target wire will be exposed to a higher peak beam current. In this paper, we introduced the peak beam current dependence of the bunch length waveforms, and an effect of on- /off-centering of the wire position. Finally the new buncher tuning method using one BSM have been discussed.
Yoshimoto, Masahiro; Harada, Hiroyuki; Okabe, Kota; Kinsho, Michikazu
Proceedings of 4th International Beam Instrumentation Conference (IBIC 2015) (Internet), p.575 - 579, 2016/01
In the J-PARC RCS, transverse beam profiles including both the beam core and halo at extraction beam transport line (3NBT) were measured by using a combination with a wire scanner type beam scraper and some beam loss monitors (BLMs). Our final goal of this halo monitor is to measure the intra-bunch beam halo of extracted two bunches from the RCS. Thus the plastic scintillator and photomultiplier (PMT) assemblages were adopted as the BLMs with quick time response. However, we found that the BLMs detected not only the radiation from the wire but also reflected one from other devices and wall. Therefore we tried to develop new-type BLMs, which are scintillation-type BLM of lead glass and Cherenkov-type BLM of quartz or UV acrylic. In this presentation, we will report on the overview and experimental results of the new-type BLMs together with the outline of halo monitor system.
