Philip Burrows

Abstract:

The CLIC two beam acceleration technology requires a drive beam phase stability better than 0.3 deg rms at 12 GHz, corresponding to a timing stability below 50 fs rms. For this reason the CLIC design includes a phase stabilization feed-forward system. It relies on precise beam phase measurements and their subsequent correction in a chicane with the help of fast kickers. A prototype of such a system is being installed in the CLIC Test Facility CTF3. In this paper its design and implementation is described in detail. Additionally, the performance of the precision phase monitor prototypes installed at the end of the CTF3 linac, as measured with the drive beam, is presented. Copyright © 2013 by JACoW.

Abstract:

A low-latency, sub-micron resolution stripline beam position monitoring system has been developed and tested with beam at the KEK Accelerator Test Facility, where it has been used as part of a feedback system for beam stabilisation. The fast analogue front-end signal processor is based on a single-stage down-mixer and is combined with an FPGA-based system for digitisation and feedback control. A resolution as low as 400 nm has been demonstrated for beam intensities of ∼1 nC, with singlepass beam. The latest results of recent modifications to balance the input path lengths to the processor will be discussed. These modifications compensate for the inherent phase sensitivity of the processors, and hence improve the intrinsic resolution, without the need for offline correction. Modifications to the FPGA firmware will also be described, to allow for flexible operation with variable system-synchronous data acquisition at up to 400 MHz, with up to nine data channels of 13-bit width, and a nominal record length of 1 kS/channel/pulse (extensible to a total record length of 120 kS per pulse, for example, for use with long bunch trains or wide-band multi-turn measurements in storage rings). Copyright © 2013 by JACoW.

Abstract:

A prototype ultra-fast beam-based feedback system for deployment in single-pass beamlines, such as a future lepton collider (ILC or CLIC) or a free-electron laser, has been fabricated and is being tested in the extraction and final focus lines of the Accelerator Test Facility (ATF) at KEK. FONT5 is an intra-train feedback system for stabilising the beam orbit via different methods: A position and angle feedback correction in the extraction line or a vertical feedforward correction applied at the interaction point (IP). Two systems comprise three stripline beam position monitors (BPMs) and two stripline kickers in the extraction line, two cavity BPMs and a stripline kicker at the IP, a custom FPGA-based digital processing board, custom kicker-drive amplifiers and low-latency analogue front-end BPM processors. Latest results from the experiment are presented. These include beam position correction in the extraction line, as well as preliminary results of beam correction at the IP. Copyright © 2013 by JACoW- cc Creative Commons Attribution 3.0 (CC-BY-3.0).

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.