| Paper | Title | Page |
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| MOPS005 | Beam Dynamics Simulations of J-PARC Main Ring for Upgrade Plan of Fast Extraction Operation | 598 |
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| Beam loss simulations under space charge effects are necessary to seek higher intensity proton beams. This paper presents simulations for fast extraction operation of Japan Proton Accelerator Research Complex (J-PARC) Main Ring. For upgrade plan, increasing protons per bunch and making higher repetition pattern are considered. Their optimal balance is discussed to minimize beam losses for aimed beam power considering space charge effects. We found that to optimize RF voltage pattern is a strong key to reduce beam losses for higher repetition. As benchmark works, we compare our simulations with the measured beam loss in our past operation. | ||
| TUPC098 | Beam Profile Measurement using Flying Wire Monitors at the J-PARC Main Ring* | 1239 |
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| Transverse beam profiles have been measured using flying wire monitors at the main ring of the Japan Proton Accelerator Research Complex (J-PARC). The flying wire is a beam profile monitor using a thin carbon fiber as a target. The beam is scanned with the wire target at the maximum speed of 5 m/s. The secondary particles from the beam-wire scattering are detected using a scintillation counter as a function of the wire position. The measurement has revealed a characteristic temporal change of the beam profile during the injection period of 120 ms. A multiparticle tracking simulation program, SCTR, taking account of space charge effects has successfully reproduced the beam profiles. | ||
| TUPC099 | New Measurements of Proton Beam Extinction at J-PARC | 1242 |
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| Proton beam extinction, defined as a residual to primary ratio of beam intensity, is one of the most important parameters to realize the future muon electron conversion experiment (COMET) proposed at J-PARC. To achieve the required extinction level of 10-9, we started measuring extinction at main ring (MR) as its first step. According to the various measurements done at the different positions, empty RF buckets of RCS, which were considered to be swept away by the RF chopper, contained about 10-7 ~ 10-5 of the main beam pulse due to chopper inefficiency. We have developed a new beam monitor with improved performance for further studies at the abort line. In addition, we have started new measurements at the Hadron experimental hall by using slow-extracted beam. In this paper, we present recent results and future prospect of beam extinction measurements. | ||
| TUPS034 | Development and Construction of the Beam Dump for J-PARC Hadron Hall | 1608 |
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Funding: This work is supported by Grant-in-Aid (No.22740184) for Young Scientists (B) of the Japan Ministry of Education, Culture, Sports, Science and Technology [MEXT]. A facility of Hadron hall at Japan Proton Accelerator Research Complex (J-PARC) had been constructed in June 2007. Hadron hall is designed to handle intense slow-extraction proton beam from the main accelerator of J-PARC, i.e. 50-GeV-PS. The first transportation of the proton beam to the hall was successfully made in Jan. 2009. A beam dump constructed at the end of the primary proton beam line in Hadron hall is designed to safely absorb 15 μA (=750-kW) proton beam. Its central core of the dump is made of copper with water cooling and is surrounded by iron and concrete for radiation protection. We made thermal and mechanical FEM analysis for investigating heat generation and mechanical stress from energy deposition. We also made cooling experiments for measuring heat transfer coefficient of candidates for new cooling device. As a result, the adopted device has direct cooling paths which are prepared as long holes made by Gun Drill from the outer surface of the copper core. In addition, the beam dump is designed to safely move to 50-m downstream as one body for future expansion of Hadron hall. This paper reports development and construction of the beam dump in Hadron hall. |
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| THPC034 | Post-earthquake Recovery of PF Ring and PF-AR | 2984 |
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| When the unprecedented scale of earthquake occurred in Japan on the afternoon of March 11, 2011, PF ring and PF-AR, two synchrotron light sources in KEK, also suffered various damages. At PF ring, a formed bellows in a wall current monitor was broken, and atmospheric air rushed into the beam duct. At PF-AR, which is installed in the underground tunnel, the alignment of the ring magnets seemed to be disordered to an order of ten mm. At both rings, a lot of electronics racks and toolboxes in the control rooms or in the experimental halls were tilted or tipped over. It was extremely fortunate that the user operation had just been stopped on the morning of that day, and all the gate valves in the rings and to the beam lines had already been closed for the scheduled shutdown. A wide area blackout took place at the big earthquake, and the electric power for the accelerator was interrupted over the next two weeks because of temporal shortage of the electricity in the eastern part of Japan. In April, we could start detailed investigation of machine damages and repair works towards recommissioning of the rings before the summer and resumption of the user operations in the autumn. | ||