Philip Burrows

Abstract:

The drive beam phase stability is one of the critical issues of the Compact Linear Collider (CLIC). In this paper the generation and propagation of drive beam phase errors is studied for effects that vary during the drive beam pulse. This includes the influence of drive beam current and phase errors as well as of drive beam accelerator RF phase and amplitude errors on the drive beam phase after the compressor chicanes and the analysis of the propagation of these errors through the drive beam combination scheme. The impact of the imperfections on the main beam is studied including the possible correction with help of a feedforward system.

Abstract:

Pulse-to-pulse orbit jitter, if not controlled, can drastically degrade the luminosity in future linear colliders. The second goal of the ATF2 project at the KEK accelerator test facility is to stabilise the vertical beam position down to approximately 5% of the nominal rms vertical beam size at the virtual Interaction Point (IP). This will require control of the orbit to better than 1 micrometre at the entrance of the ATF2 nal focus system. In this paper, by means of computer simulations, we study the vertical jitter propagation along the ATF2 from the start of the extraction line to the IP. For this study pulse-to-pulse vertical jitter measurements using three stripline beam position monitors are used as initial inputs. This study is performed for the case of a bunch-train with three bunches, but could easily be extended for a larger number of bunches. The cases with and without intra-train orbit feedback correction in the extraction line of ATF2 are compared.

Abstract:

The design luminosity of the future linear colliders requires transverse beam size at the nanometre level at the interaction point (IP), as well as stabilisation of the beams at the sub-nanometre level. Different imperfections, for example ground motion, can generate relative vertical offsets of the two colliding beams at the IP which significantly degrade the luminosity. In principle, a beam-based intra-train feedback system in the interaction region can correct the relative beam-beam offset and steer the beams back into collision. In addition, this feedback system might considerably help to relax the required tight stability tolerances of the final doublet magnets. For CLIC, with bunch separations of 0.5 ns and train length of 156 ns intra-train feedback corrections are specially challenging. In this paper we describe the conceptual design and simulation of an intratrain feedback system for CLIC. Results of luminosity performance simulation are presented and discussed.

Abstract:

To achieve the design luminosity at future linear colliders, control of beam stability at the sub-nanometre level at the interaction point will be necessary. Any source of beam motion which results in relative vertical offsets of the two beams at the interaction point may significantly reduce the luminosity from the nominal value. Beam-based intra-train feedback systems located in the interaction region are foreseen to correct the relative beam-beam offset and thus to steer the two beams into collision. These feedback systems must be capable of acting within the bunch train. In addition, these feedback systems might considerably help to relax the tight stability tolerances required for the final doublet magnets. For the Compact Linear Collider (CLIC), the extremely short nominal bunch spacing (0.5 ns) and very short nominal pulse duration (156 ns) make the intratrain feedback implementation technically very challenging. In this paper the conceptual design of an intra-train feedback system for the CLIC interaction point is described. Results of luminosity performance simulations are presented and discussed for different scenarios of ground motion. We also show how the intra-train feedback system can help to relax the very tight tolerances of the vertical vibration on the CLIC final doublet quadrupoles. © 2010 IOP Publishing Ltd and SISSA.