Philip Burrows

Abstract:

A low-latency, sub-micron resolution stripline beam position monitoring (BPM) system has been developed and tested with beam at the KEK Accelerator Test Facility (ATF2), where it has been used as part of a beam stabilisation system. The fast analogue front-end signal processor is based on a single-stage RF down-mixer and a position resolution below 400 nm has been demonstrated for beam intensities of 1 nC, with single-pass beam. The BPM position data are digitised by fast ADCs on an FPGA-based digital feedback controller, which is used to drive either a pair of kickers local to the BPMs and nominally orthogonal in phase, in closed-loop feedback mode, or a downstream kicker in the ATF2 final focus region, in feedforward mode. The beam jitter is measured downstream of the final focus system with high resolution, low-Q, cavity BPMs, and the relative performance of both systems in stabilising the beam is compared.

Abstract:

A low-latency, intra-train, beam feedback system utilising a cavity beam position monitor (BPM) has been developed and tested at the final focus of the Accelerator Test Facility (ATF2) at KEK. A low-Q cavity BPM was utilised with custom signal processing electronics, designed for low latency and optimal position resolution, to provide an input beam position signal to the feedback system. A custom stripline kicker and power amplifier, and an FPGA-based digital feedback board, were used to provide beam correction and feedback control, respectively. The system was deployed in single-pass, multi-bunch mode with the aim of demonstrating intratrain beam stabilisation on electron bunches of charge ∼1 nC separated in time by c. 280 ns. The system has been used to demonstrate beam stabilisation to below the 100 nm level. Results of the latest beam tests, aimed at even higher performance, will be presented.

Abstract:

Six UK institutes are engaged in a collaborative R&D programme with CERN aimed at demonstrating key aspects of technology feasibility for the Compact Linear Collider (CLIC). We give an overview and status of: 1) Drive-beam components: quadrupole magnets and the beam phase feed-forward prototype. 2) Beam instrumentation: stripline and cavity beam position monitors, an electro-optical longitudinal bunch profile monitor, and laserwire and diffraction and transition radiation monitors for transverse beam-size determination. 3) Beam delivery system and machinedetector interface design, including beam feedback/control systems and crab cavity design and control. 4) RF structure design. In each case we report on the status of prototype systems and performance tests with beam at the CTF3, ATF2 and CESRTA test facilities, including plans for future experiments.

Abstract:

A novel scheme for the focusing of high-energy leptons in future linear colliders was proposed in 2001 [P. Raimondi and A. Seryi, Phys. Rev. Lett. 86, 3779 (2001)]. This scheme has many advantageous properties over previously studied focusing schemes, including being significantly shorter for a given energy and having a significantly better energy bandwidth. Experimental results from the ATF2 accelerator at KEK are presented that validate the operating principle of such a scheme by demonstrating the demagnification of a 1.3 GeV electron beam down to below 65 nm in height using an energy-scaled version of the compact focusing optics designed for the ILC collider.

Abstract:

Nanometre 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, or 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. Two cavity so-called IP BPMs have been installed inside the IP chamber at the ATF2 focus area. To measure the resolution of IPBPMs two additional C-band cavity BPMs have been installed one upstream and one downstream of the IP. One cavity BPM has been installed at an upstream vertical image point of the IP. The performance of the BPMs is discussed and the correlation between the IP and image point positions is presented along with a discussion of using these BPMs for position stabilisation at the IP. Copyright © 2013 by JACoW.