M.Y. Huang, S. Wang, S.Y. Xu
IHEP, Beijing, People’s Republic of China
Funding:Work supported by National Natural Science Foundation of China (Project Nos. 12075134 and U1832210 ) In this paper, firstly, the beam commissioning of the injection system for CSNS/RCS will be studied, including: timing adjustment of the injection pulse powers, injection beam parameter matching, calibration of the injection painting bumps, measurement of the painting distribution, injection method adjustment, application of the main stripping foil, optimization of the injection beam loss and radiation dose, etc. Secondly, the painting methods for the CSNS/RCS will be studied, including: the fixed-point injection method, anti-correlated painting method and correlated painting method. The results of the beam commissioning will be compared with the simulation results. Combining with other precise optimizations, the beam power on the target has successfully reached the design value of 100kW and the stable operation of the accelerator has been achieved.
T. Toyama, A. Kobayashi, T. Nakamura, M. Okada, M. Tobiyama
KEK, Tokai, Ibaraki, Japan
Y. Shobuda
JAEA/J-PARC, Tokai-mura, Japan
In the J-PARC MR, according to the beam power upgrade over 100 kW, beam losses due to transverse collective beam instabilities had started to appear. We had introduced "bunch-by-bunch feedback" system in 2010. Continuing beam power upgrade over 250 kW again caused the transverse instabilities. We introduced "intra-bunch feedback" system in 2014. This has been suppressing those instabilities very effectively. But further beam power upgrade over 500 kW (2.6·10+14 ppp, 8 bunches) needs upgrade of "intra-bunch feedback" system. The current understanding of the transverse instabilities in the MR and the effect of the feedback system are presented from the view points of simplified simulation without the space charge effect and measurements. We are upgrading the system in two steps. The first step is "time-interleaved sampling and kicking" with two feedback systems. The second step is getting the sampling rate twice as much as the current rate, ~110 MHz. Details are explained using simulation.
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M. Tomizawa, Y. Arakaki, T. Kimura, S. Murasugi, R. Muto, H. Nishiguchi, K. Okamura, Y. Shirakabe, Y. Sugiyama, E. Yanaoka, M. Yoshii
KEK, Ibaraki, Japan
K. Noguchi
Kyushu University, Fukuoka, Japan
F. Tamura
JAEA/J-PARC, Tokai-mura, Japan
A high-intensity proton beam accelerated in the J-PARC main ring (MR) is slowly extracted by using the third integer resonance and delivered to the experimental hall. A critical issue in slow extraction (SX) is a beam loss caused during the extraction. A dynamic bump scheme under an achromatic condition provides extremely high extraction efficiency. We have encountered a beam instability in the debunch formation process, which is estimated to be triggered by a longitudinal microstructure of the beam. To suppress this instability, the beam to the MR has been injected into the RF bucket with a phase offset. A newly developed RF manipulation, 2-step voltage debunch, has successfully pushed up the beam power up to 64.6 kW keeping a high extraction efficiency of 99.5%. A drastic beam loss reduction has been demonstrated in the beam test using a diffuser installed upstream of the first electrostatic septum (ESS1). 8 GeV bunched slow extraction tests for the neutrino-less muon to electron conversion search experiment (COMET Phase-I) have been successfully conducted.
