Philip Burrows

Abstract:

Future lepton colliders such as the International Linear Collider (ILC), and the Compact Linear Collider (CLIC) require nanometer-sized beams at the interaction point (IP). We report on the design, protoyping and testing of beam-based feedback systems for steering the beams into collision at the IP so as to maximise the luminosity performance of the colliders. Both all-analogue and digital feedback prototypes have been built and tested for CLIC and ILC, respectively. The latency of such systems needs to be very low so as to match the bunch spacing and bunch-train length. We report on the achievement of systems with 130ns and 23ns latency that meet the beam position resolution and beam kick requirements of both ILC and CLIC, respectively; the prototypes were tested with ILC- and CLIC-like beams at the Accelerator Test Facility at KEK. We have simulated the measured performance and demonstrated the potential of the feedbacks to compensate for ground-motion disruption and recover almost all of the design luminosity.

Abstract:

Instabilities associated with beam-size blow-up have previously been observed with multi-bunch beam in the damping ring (DR) of the KEK Accelerator Test Facility (ATF). A system has been developed to monitor such instabilities, utilising an ATF stripline beam position monitor (BPM) in the DR, and BPM processor hardware designed for the FONT upstream feedback system in the ATF extraction line. The system is designed to record the horizontal and/or vertical positions of up to three bunches in the DR in single-bunch multi-train mode or the head bunch of up to three trains in multi-bunch mode, with a bunch spacing of 5.6 ns. The FPGA firmware and data acquisition software were modified to record turn-by-turn data for up to six channels and 1-3 bunches in the DR. The maximum memory configuration on the FPGA allows 131071 bunch-turn-channels of data to be recorded from a particular machine pulse, and the system has the capability to select only certain turns at a regular interval in which to record data, in order to zoom out and cover the entire period of the damping cycle at the ATF. An overview of the system and initial results will be presented.