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Abstract:

Two low-latency, sub-micron, beam position monitoring (BPM) systems have been developed and tested with beam at the KEK Accelerator Test Facility (ATF2). One system (upstream), based on stripline BPMs, uses fast analogue front-end signal processing and has demonstrated a position resolution as low as 400 nm for beam intensities of 1 nC, with single-pass beam. The other (IP) system, based on low-Q cavity BPMs and utilising custom signal processing electronics designed for low latency, provides a single pass resolution of approximately 100 nm. The BPM position data are digitised by fast ADCs on a custom FPGA-based feedback controller and used in three modes: 1) the upstream BPM data are used to drive a pair of local kickers nominally orthogonal in phase in closed-loop feedback mode; 2) the upstream BPM data are used to drive a downstream kicker in the ATF2 final focus region in feedforward mode; 3) the IP cavity BPM data are used to drive a local downstream kicker in the ATF2 final focus region in closed-loop feedback mode. In each case the beam jitter is measured downstream of the final focus system with the IP cavity BPMs. The relative performance of these systems is compared.

Abstract:

Ultra-high position resolution cavity beam position monitors (BPMs) have been developed to measure the beam position and to be linked to control the beam position stability within a few nanometres in the vertical direction at the focus, Interaction Point (IP), of the Accelerator Test Facility 2 (ATF2). In addition, for feedback applications a lower-Q and hence faster decay time system is desirable. Specialised cavities which is called Interaction Point BPM (IPBPM) has been tested in the ATF2 extraction beam line. Using IPBPMs, a position resolution of less than 5 nm has been measured in single bunch operation. Multibunch operation is also planned at ATF2 for the beam stabilisation. The nominal operation bunch spacing for the International Linear Collider (ILC) is 308 ns so the multibunch operation bunch spacing is ILC like. The IPBPM should be able to measure beam position to nanometre precision in multi-bunch modes. Therefore the position resolution in multi-bunch operation was also measured at ATF2 extraction line. The analysis method of cavity signals, calibration and results of multibunch operation are discussed in this proceeding.

Abstract:

An FPGA-based monitoring system has been developed to study multi-bunch beam instabilities in the damping ring (DR) of the KEK Accelerator Test Facility (ATF). The system utilises a stripline beam position monitor (BPM) and single-stage down-mixing BPM processor. The system is designed to record the horizontal and/or vertical positions of up to three bunches in the DR with c. 150ns bunch spacing, or the head bunch of up to three trains in a multi-bunch mode with a bunch spacing of 5.6 ns. The FPGA firmware and data acquisition software allow the recording of turnby- turn data. An overview of the system and performance results will be presented. Copyright © 2012 by IEEE.

Abstract:

For future linear colliders the precise control and mitigation of pulse-to-pulse orbit jitter will be very important to achieve the required luminosity. Diagnostic techniques for the orbit jitter measurement and correction for multibunch operation are being addressed at the KEK Accelerator Test Facility 2 (ATF2). In this paper we present recent studies on the vertical jitter propagation through the ATF2 extraction line and final focus system. For these studies the vertical pulse-to-pulse position and angle jitter have been measured using the available stripline beam position monitors in the beamline. The cases with and without intra-train orbit feedback correction in the ATF2 extraction line are compared. Copyright © 2012 by IEEE.