Abstract
In the 3 GeV rapid cycling synchrotron of the Japan Proton Accelerator Research Complex, significant losses were observed at the branching of the ${\mathrm{H}}^{0}$ dump line and the beam position monitor that was inserted downstream of the ${\mathrm{H}}^{0}$ dump branch duct. These losses were caused by the large-angle scattering of the injection and circulating beams at the charge-exchange foil. To realize high-power operation, these losses must be mitigated. Therefore, a new collimation system was developed and installed in October 2011. To efficiently optimize this system, the behavior of particles scattered by the foil and produced by the absorber were simulated, and the optimal position and angle of the absorber were investigated. During this process, an angle regulation method for the absorber was devised. An outline of this system, the angle regulation method for the absorber, and the performance of this new collimation system are described.
Highlights
For the proton synchrotron, the high beam intensity can be achieved by dividing the injection into a number of turns and adding the injection beam to the circulating beam
Ten plastic scintillators were placed horizontally as a beam loss monitor (BLM) between the H0 collimator and the QFM, and a BLM signal was obtained for 2 ms after the initiation of multiturn injection
The value of the integration of the BLM signal from the initiation of injection to 700 s is defined as the loss caused by foil scattering, because the fixed orbit bump made by the SB1-4 begins to decay after the completion of multiturn injection, and the circulating beams hit the foil during approximately the first 700 s, the multiturn injection time is 500 s
Summary
The high beam intensity can be achieved by dividing the injection into a number of turns and adding the injection beam to the circulating beam. It is impossible to lead the injection beam to the same phase space which the circulating beam fills at the injection point if the injection beam and the circulating beam have the same charge. This principle is known as Liouville’s theorem. The charge-exchange foil is placed at the injection point in order to convert HÀ ions to protons. This scheme is known as multiturn chargeexchange injection
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