Philip Burrows

Abstract:

A high-resolution, low-latency beam position monitor (BPM) system has been developed for use in particle accelerators and beamlines that operate with trains of particle bunches with bunch separations as low as several tens of nanoseconds, such as future linear electronpositron colliders and free-electron lasers. The system was tested with electron beams in the extraction line of the Accelerator Test Facility at the High Energy Accelerator Research Organization (KEK) in Japan. The fast analogue front-end signal processor is based on a single-stage RF down-mixer. The processor latency is 15.6 +-0.1 ns. A position resolution below 300 nm has been demonstrated for beam intensities of around 1 nC, with single-pass beam.

Abstract:

The two-beam acceleration scheme envisaged for CLIC will require a high degree of phase stability between two beams at the drive beam decelerator sections, to allow efficient acceleration of the main beam. There will be up to 48 such decelerator sections for the full 3 TeV design, and each decelerator section will be instrumented with a feed-forward system to correct the drive beam phase to a precision of 0.2 degrees at 12 GHz relative to the main beam, using a kicker system around a four-bend chicane. A prototype system has been developed and tested at the CLIC Test Facility (CTF3) complex, where the beam phase is measured upstream of the combiner ring and corrected with two kickers in a dog-leg chicane just upstream of the CLEX facility, where the resulting phase change is measured. This prototype is designed to demonstrate correction of a portion of the CTF3 bunch train to the level required for CLIC, with a bandwidth of greater than 30 MHz, and within a latency constraint of 380 ns as set by the beam time-of-flight through the combiner ring complex. A description of the hardware will be given and initial results from the first phase of the experiment will be presented.

Abstract:

In the CLIC two beam acceleration scheme 100 MV/m normal conducting cavities are fed with RF power extracted from a secondary high power but low energy drive beam. To ensure the efficiency and luminosity performance of CLIC the phase synchronisation between the high energy main beam and the drive beam must be maintained to within 0.2 degrees of 12 GHz. To reduce the drive beam phase jitter to this level a low-latency drive beam phase feedforward correction with bandwidth above 17.5 MHz is required. A prototype of this system has been installed at the CLIC test facility CTF3 to prove its feasibility, in particular the challenges of high bandwidth, high power and low latency hardware. The final commissioning and first results from operation of the complete phase feedforward system are presented here.

Abstract:

Ultra-low latency beam-based digital feedbacks have been developed by the Feedback On Nanosecond Timescales (FONT) Group and tested at the Accelerator Test Facility (ATF2) at KEK in a programme aimed at beam stabilisation at the nanometre level at the ATF2 final focus. Three prototypes were tested: 1) A feedback system based on high-resolution stripline BPMs was used to stabilise the beam orbit in the beamline region c. 50m upstream of the final focus. 2) Information from this system was used in a feed-forward mode to stabilise the beam locally at the final focus. 3) A final-focus local feedback system utilising cavity BPMs was deployed. In all three cases the degree of beam stabilisation was observed in high-precision cavity BPMs at the ATF2 interaction point. Latest results are reported on stabilising the beam position to approximately 50nm.