KEK ATF Linac, Damping Ring accelerating field and RF-Gun laser system phase&amplitude stability study

Abstract KEK Accelerator Test Facility (ATF) conducts beam instrumentation R&D for International Linear Collider (ILC) project. There are several sections at ATF. Some of these sections are laser-driven RF-Gun, 1.3 GeV S-band Linac, Damping Ring (DR) and Final Focus test beamline. There are 11 S-band pulsed klystrons at Linac, which supply High-Power RF to accelerate electron beam, 1 Continuous Wave (CW) klystron at DR and RF-Gun laser system oscillator synchronization unit. These Linac, DR High-Power RF fields and laser pulse arrival time jitter and/or drift define the stability of the electron beam parameters, such as average energy, energy spread, emittance, bunch charge etc. This study demonstrates KEK ATF Linac and Damping Ring High-Power RF field phase and amplitude stability measurement results. Furthermore, the laser system oscillator laser pulse arrival stability is investigated. Moreover, a digital Low-level RF feedback system is introduced at ATF Linac RF system to stabilize accelerating field phase&amplitude long-term drift. A Field-Programmable Gate Array (FPGA) board based digital Low-Level RF phase&amplitude inter-pulse feedback system firmware and its performance results are described in this study.