• P. Burrows, R. Apsimon, C.I. Clarke, B. Constance, H. Dabiri Khah, A.F. Hartin, C. Perry, J. Resta-López, C. Swinson
  JAI, Oxford
• G.B. Christian
  ATOMKI, Debrecen
• A. Kalinin
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire

We present the results of beam tests of the FONT4 ILC prototype intra-train beam feedback system. The system comprises a stripline BPM, a fast analogue BPM signal processor, a custom FPGA-based digital feedback board, a high-power fast-response drive amplifier, and a stripline kicker. The hardware was deployed at the Accelerator Test Facility at KEK. Trains comprising three electron bunches were extracted from the ATF damping ring, with bunch spacing c. 150ns. The feedback loop was closed by measuring the position of bunch 1 and correcting bunches 2 and 3. We report the performance of the feedback, including gain studies, the correction dynamic range, latency measurement, and quality of the beam position correction. The system achieved micron-level bunch stabilisation with a latency of c. 140ns.

• P. Burrows, R. Apsimon, C.I. Clarke, B. Constance, H. Dabiri Khah, A.F. Hartin, C. Perry, J. Resta-López, C. Swinson
  JAI, Oxford
• G.B. Christian
  ATOMKI, Debrecen
• A. Kalinin
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire

We present the design of prototype fast beam position monitor (BPM) signal processors for use in inter-bunch beam-based feedbacks for linear colliders and electron linacs. We describe the FONT4 intra-train beam-based digital position feedback system prototype deployed at the Accelerator test facility (ATF) extraction line at KEK, Japan. The system incorporates a fast analogue beam position monitor front-end signal processor, a digital feedback board, and a fast kicker-driver amplifier. The total feedback system latency is less than 150ns, of which less than 10ns is used for the BPM processor. We report preliminary results of beam tests using electron bunches separated by c. 150ns. Position resolution of order 1 micron is obtained.