Abstract
The dual-harmonic operation, in which the accelerating cavities are driven by the superposition of the fundamental and the second harmonic rf voltage, is useful for acceleration of the ultrahigh intensity proton beam in the rapid cycling synchrotron (RCS) of Japan Proton Accelerator Research Complex (J-PARC). However, the precise and fast voltage control of the harmonics is necessary to realize the dual-harmonic acceleration. We developed the dual-harmonic auto voltage control system for the J-PARC RCS. We describe details of the design and the implementation. Various tests of the system are performed with the RCS rf system. Also, a preliminary beam test has been done. We report the test results.
Highlights
Japan Proton Accelerator Research Complex (J-PARC) [1,2] is a project of a high-intensity proton accelerator complex, which consists of 181 MeV linac, 3 GeV rapid cycling synchrotron (RCS), and 50 GeV synchrotron (MR)
The rf signal from the level rf (LLRF) system is led to the transistor driver amplifier, which is located in the power supply room on the ground floor
We summarize the article as follows: (i) Dual-harmonic rf is useful to accelerate the ultrahigh intensity proton beam in the J-PARC RCS
Summary
Japan Proton Accelerator Research Complex (J-PARC) [1,2] is a project of a high-intensity proton accelerator complex, which consists of 181 MeV linac (to be 400 MeV in the energy-recovery plan), 3 GeV rapid cycling synchrotron (RCS), and 50 GeV synchrotron (MR). Since the beam power of the RCS is to be very high, 1 MW with the full design energy of the linac, it is important to accelerate the beams with minimal losses, which cause activation of the accelerator components. In the RCS the proton beam is accelerated from 181 MeV to 3 GeV in 20 ms. The repetition rate is 25 Hz. The maximum rf voltage is 450 kV per turn. To generate the high accelerating voltage in the limited space of the ring, we employ magnetic-alloy (MA) loaded cavities. The MA-loaded cavity can achieve a very high accelerating field at the level of 25 kV=m, which is more than twice of the field achieved by ferrite-loaded cavities (10 kV=m)
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