Speaker
Description
Magnetic alloy (MA) cavities have wideband frequency responses, which allow multiharmonic rf voltage excitation in a single cavity. In the low level rf (LLRF) control system for the Japan Proton Accelerator Research Complex (J-PARC) Rapid Cycling Synchrotron (RCS) the multiharmonic vector rf voltage control feedback is implemented to realize the dual harmonic rf operation for bunch shaping and to compensate of the multiharmonic beam loading. The multiharmonic feedback consists of several classical IQ feedback blocks, and the RCS system has eight feedback blocks. Similar feedback systems are employed for the other proton synchrotrons, such as CERN PSB and CSNS. The possible application of multiharmonic feedback is not limited to bunch shaping using dual harmonic. Using triple harmonic operation, we can generate more flat rf buckets for realization of flatter bunches. Ultimately, barrier buckets can be generated using many harmonics. Other interesting application is generating a non-integer harmonic rf with several harmonics, which can be used for butch compression. In the presentation, we will explore these possible applications. We will also discuss important considerations when using multiharmonic feedback. One must be careful about the frequency response of the cavity voltage monitor to adjust the precise harmonic voltages. Another point is that unwanted cavity voltage jump may happen after fast extraction of a high intensity beam.
| Abstract Category | System and Operation |
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