LLRF controls in SuperKEKB Phase-1 commissioning
First beam commissioning of SuperKEKB (Phase-1), which is an asymmetry double ring collider of 7-GeV electron and 4-GeV positron beams, which had started from February, has been successfully accomplished at the end of June 2016, and the desired beam current for Phase-1 was achieved in both rings. This paper summarize the operation results related to low level RF (LLRF) control issues during the Phase-1 commissioning, including the system tuning, the coupled bunch instability and the bunch gap transient effect. RF system of SuperKEKB consists of about thirty klystron stations in both rings. Newly developed LLRF control systems were applied to the nine stations among the thirty for Phase-1. The RF reference signal distribution system has been also upgraded for SuperKEKB. These new systems worked well without serious problem and they contributed to smooth progress of the commissioning. The old existing systems, which had been used in the KEKB operation, were still reused for the most stations, and they also worked as soundly as performed in the KEKB operation.
RF Issues for High Intensity Factories
This paper presents a brief report on the RF issues concerning high-luminosity electron-positron colliders, referred to as “factories”, such as phi, tau-charm, and B factories. In order to realize the high luminosity required for such factories, heavy demands are placed on the RF system. This paper discusses the requirements for the RF system, approaches to the challenging tasks, and the R&D status at each factory.
DIGITAL LOW-LEVEL RF CONTROL SYSTEM WITH FOUR INTERMEDIATE FREQUENCIES AT STF
A field programmable gate array (FPGA)-based digital low-level RF (LLRF) control system is used with a feedback control system to achieve amplitude and phase stabilities of the accelerating field in superconducting accelerators. A new digital LLRF control system that uses different intermediate frequencies (IFs) has been developed to decrease the number of analog-to-digital converters (ADCs) required during the feedback operation of the RF sources. Operation of a digital LLRF control system using four different IFs at the Superconducting RF Test Facility (STF) in KEK was commenced in December 2008, and feedback operation was performed using four superconducting cavities. The performance of this digital LLRF control system has been reported in this paper.