Michikazu Kinsho

2.5 MeV electron irradiation effect of alumina ceramics

In order to choose an alumina ceramic material for use as a vacuum beam duct in a rapid cycling synchrotron, several kinds of alumina ceramics, having different microstructures, were examined under radiation fields of 2.5 MeV electrons. Since a long ceramic duct can only be manufactured by glazing duct segments, the mechanical strength and deterioration not only of the ceramics but also in the glazing joint were measured after irradiation. These ceramics have a sufficiently high flexural strength of more than 300 MPa before electron beam irradiation, and the experimental results showed no deterioration of the flexural strength after 1000 MGy electron beam irradiation. Also no noticeable changes could be seen in the measured tensile strength of Ti-ceramic brazed samples after 1000 MGy electron beam irradiation.

Lattice and Collimation System for J‐PARC

In order to localize beam loss, several kinds of beam collimation systems are prepared for the J‐PARC accelerators. The calculation results showed that almost all halo beams could be collimated by each collimation system.

Conceptual Design of Beam Dividing System for J-PARC Transmutation Experimental Facility

The Japan Proton Accelerator Research Complex (J-PARC) consists of three accelerators and three experimental facilities. In addition, new experimental facility for the Accelerator-driven system (ADS), the Transmutation Experimental Facility (TEF), is planned [1, 2]. The TEF is composed of two experimental facilities, Transmutation Physics Experimental Facility (TEF-P) and ADS Target Test Facility (TEF-T), and both facilities use the 400MeV proton beam from the LINAC [3, 4]. The LINAC is now operating in repetition of 25Hz for the 3GeV rapid-cycling synchrotron (RCS) and downstream facilities. Therefore in order to keep beam power for existing experimental facilities and furthermore to deliver the beam to the TEF, the LINAC should be operating in 50Hz and new beam dividing system will be installed at the upstream of the L3BT (LINAC to 3GeV RCS Beam Transport) straight section. The L3BT straight section of a doublet structure is adopted as the fundamental lattice, keeping the continuity of the transverse focusing scheme [5, 6]. The pulsed bending magnet, which is a main component of the beam dividing system, repeats between the unexcited and excited state in 25Hz, and divides the beam into the RCS and the TEF respectively. However, as a result of our early feasibility study, it is difficult to obtain the enough beam orbit separation at the doublet with the only pulsed bending magnet. Thus, the beam for the TEF is extracted with both the pulsed bending magnet and a static septum magnet. In this scheme, the doublet quadrupole magnets should be improved. In this presentation, we will report a conceptual design of the beam dividing system for the TEF.

Measur ements and PHITS Monte Carlo Estimations of Residual Activities Induced by the 181 MeV Proton Beam in the Injection Area at J-PARC RCS Ring

At the injection area of the RCS ring in the J-PARC, residual gamma dose at the rectangular ceramic ducts, especially immediately downstream of the charge-exchanged foil, has increased with the output beam power. In order to investigate the cause of high residual activities, residual gamma dose and radioactive sources produced at the exterior surface of the ducts have been measured by a GM survey meter and a handy type of Germanium (Ge) semiconductor detector in the case of 181 MeV injected proton beam energy. With these measurements, it is revealed that the radioactive sources produced by nuclear reactions cause the high activities at the injection area. For a better understanding of phenomena in the injection area, various simulations have been done with the PHITS Monte Carlo code. The distribution of radioactive sources and residual gamma dose rate obtained by the calculations are consistent with the measurement results. With this consistency, secondary neutrons and protons derived from nuclear reactions at the charge-exchanged foil are the dominant cause to high residual gamma dose at the ceramic ducts in the injection area. These measurements and calculations are unique approaches to reveal the cause of high residual dose around the foil. This study is essential for the future of high-intensity proton accelerators using a stripping foil.

Accelerator conceptual design of the international fusion materials irradiation facility

The accelerator system of the International Fusion Materials Irradiation Facility (IFMIF) provides the 250-mA, 40-MeV continuous-wave deuteron beam at one of the two lithium target stations. It consists of two identical linear accelerator modules, each of which independently delivers a 125-mA beam to the common footprint of 20 cm × 5 cm at the target surface. The accelerator module consists of an ion injector, a 175 MHz RFQ and eight DTL tanks, and rf power supply system. The requirements for the accelerator system and the design concept are described. The interface issues and operational considerations to attain the proposed availability are also discussed.

Recent Progress of 1-MW Beam Tuning in the J-PARC 3-GeV RCS

This paper presents the recent progress of 1-MW beam tuning in the J-PARC 3-GeV RCS, especially focusing on our approaches to beam loss issues.

The Path to 1 MW: Beam Loss Control in the J-PARC 3-GeV RCS

The J-PARC 3-GeV RCS started a 1-MW beam test in October 2014, and successfully achieved a 1-MW beam acceleration in January 2015. Since then, a large fraction of our effort has been concentrated on reducing and managing beam losses. In this paper, recent progresses of 1-MW beam tuning are presented with particular emphasis on our approaches to beam loss issues.

First Simulation Results of Heavy-Ion Acceleration in the RCS of J-PARC

We present first space charge simulation results of heavyion (HI) acceleration in the 3-GeV Rapid Cycling Synchrotron (RCS) of Japan Proton Accelerator Research Complex (J-PARC). RCS is 1 MW proton beam power source for the Material and Life Science Experimental Facility (MLF) as well as an injector for the Main Ring (MR). Recently, importance of heavy-ion (HI) physics program in J-PARC are being intensively discussed for studying so-called QCD phase structures at high baryon density by using slowly extracted HI beam of 1-20 AGeV in the MR. Although detail accelerator scheme to adapt HI has not yet been fixed, in this work we studied possibilities of U86+ acceleration in the RCS by using ORBIT 3-D simulation code. The simulation results show that a more than 1×1011 of U86+ ions per pulse can be accelerated in the RCS without any significant beam losses. That gives a total of 4×1011 ions for each MR cycle and sufficiently meets experimental requirements concerning primary beam intensity.

The Evaluation of the Residual Dose Caused by the Large-Angle Foil Scattering Beam Loss for the High Intensity Beam Operation in the J-PARC RCS

The Japan Proton Accelerator Research Complex 3-GeV rapid cycling synchrotron (RCS) has adopted the multi-turn charge-exchange injection scheme that uses H beams. During injection, both the injected and circulating beams scatter from the charge-exchange foil. Therefore, the beam loss caused by the large-angle scattering from the foil occurs downstream of the injection point. For countermeasure against the uncontrolled beam loss, a new collimation system was developed and installed in the summer shutdown period in 2011. During beam commissioning, this uncontrolled beam loss was successfully localized for a 300 kW beam. Since the present target power of the RCS is 1 MW, the accurate simulation model to reproduce experimental results has been constructed in order to evaluate residual dose at higher power operation.

The Realignment of the Beamline for J-PARC 3 GeV RCS

J-PARC 3GeV RCS suffered from the misalignments of several millimeters of the magnets in both horizontal and vertical directions caused by the Tohoku Region Pacific Coast Earthquake on March 11, 2011. As the result of the orbit calculation showed that the beam loss was acceptable for beam operation at 300kW, beam operation with the current placement was implemented until May, 2013. However according to the simulation of beam loss at 1MW operation, it was found out that the beam loss increased and the horizontal emittance expanded. Therefore it was understood that 1MW operation was difficult without the realignment of the beamline [1]. The realignment of the beamline was carried out from July to November, 2013 in conjunction with the upgrade of Linac. During the realignment, the adjustment of the magnets and the ceramics chambers was mainly performed. The magnets were adjusted to within ±0.2mm. The ceramics chambers were aimed to be adjusted within ±0.5mm. Beam commissioning started on January 30, 2014. RCS succeeded in injection of 400MeV beam from the upgraded Linac and extraction of 3GeV beam to MLF. In this paper, the alignment result of the magnets and the ceramics chambers that constitute the beamline of 3GeV RCS is reported.