• P. Burrows, R. Apsimon, D.R. Bett, G.B. Christian, B. Constance, H. Dabiri Khah, C. Perry, J. Resta-López, C. Swinson
  JAI, Oxford

We present the design of a stripline beam position monitor (BPM) signal processor with low latency (c. 10ns) and micron-level spatial resolution in single-pass mode. Such a BPM processor has applications in single-pass beamlines such as those at linear colliders and FELs. The processor was deployed and tested at the Accelerator Test Facility (ATF2) extraction line at KEK, Japan. We report the beam test results and processor performance, including response, linearity, spatial resolution and latency.

• J. Resta-López, J. Dale
  JAI, Oxford
• B. Dalena, D. Schulte, J. Snuverink, F. Stulle, R. Tomás
  CERN, Geneva
• A. Latina
  Fermilab, Batavia

We present the current status of the beam tracking simulations of the Compact Linear Collider (CLIC) from the exit of the damping ring to the interaction point, including the ring to main linac (RTML) section, main linac, beam delivery system (BDS) and beam-beam interactions. This model introduces realistic alignment survey errors, dynamic imperfections and also the possibility to study collective effects in the main linac and the BDS. Special emphasis is put on low emittance transport and beam stabilization studies, applying beam based alignment methods and feedback systems. The aim is to perform realistic integrated simulations to obtain reliable luminosity predictions.

• J. Resta-López, R. Apsimon, P. Burrows, G.B. Christian, B. Constance
  JAI, Oxford
• J. Alabau-Gonzalvo
  IFIC, Valencia

The commissioning of the ATF2 final focus test beam line facility is currently progressing towards the achievement of its first goal: to demonstrate a transverse beam size of about 40 nm at the focal point. In parallel, studies and R&D activities have already started towards the second goal of ATF2, which is the demonstration of nanometer level beam orbit stabilization. These two goals are important to achieve the luminosity required at future linear colliders. Beam-based intra-train feedback systems will play a crucial role in the stabilization of multi-bunch trains at such facilities. In this paper we present the design and simulation results of beam-based intra-train feedback systems at the ATF2: one system located in the extraction line at the entrance to the final focus, and another at the interaction point. The requirements and limitations of these systems are also discussed.

• P. Burrows, R. Apsimon, D.R. Bett, G.B. Christian, B. Constance, H. Dabiri Khah, C. Perry, J. Resta-López, C. Swinson
  JAI, Oxford

We present the design and beam test results of a prototype beam-based digital feedback system for the Interaction Point of the International Linear Collider. A custom analogue front-end signal processor, FPGA-based digital signal processing boards, and kicker drive amplifier have been designed, built, deployed and tested with beam in the extraction line of the KEK Accelerator Test Facility (ATF2). The system was used to provide orbit correction to the train of bunches extracted from the ATF damping ring. The latency was measured to be approximately 140 ns.

• J. Resta-López, P. Burrows
  JAI, Oxford

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 design and simulation of an intra-train feedback system for CLIC. Results of luminosity performance simulation are presented and discussed.

• J. Resta-López
  JAI, Oxford
• D. Angal-Kalinin, J.-L. Fernandez-Hernando, F. Jackson
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• B. Dalena, D. Schulte, R. Tomás
  CERN, Geneva
• A. Seryi
  SLAC, Menlo Park, California

Important efforts have recently been dedicated to the improvement of the design of the baseline collimation system of the Compact Linear Collider (CLIC). Different aspects of the design have been optimized: the transverse collimation depths have been recalculated in order to reduce the collimator wakefield effects while maintaining a good efficiency in cleaning the undesired beam halo; the geometric design of the spoilers have also been reviewed to minimize wakefields; in addition, the optics design have been polished to improve the collimation efficiency. This paper describes the current status of the CLIC collimation system after this optimization.

• R. Tomás, B. Dalena, J. Pfingstner, D. Schulte, J. Snuverink
  CERN, Geneva
• J.K. Jones
  Cockcroft Institute, Warrington, Cheshire
• A. Latina
  Fermilab, Batavia
• J. Resta-López
  JAI, Oxford

The CLIC BDS tuning, alignment and feedbacks studies have been typically performed independently and only over particular sections of the BDS. An effort is being put to integrate all these procedures to realistically evaluate the luminosity performance.

• R. Tomás, B. Dalena, E. Marin, D. Schulte, G. Zamudio
  CERN, Geneva
• D. Angal-Kalinin, J.-L. Fernandez-Hernando, F. Jackson
  Cockcroft Institute, Warrington, Cheshire
• J. Resta-López
  JAI, Oxford
• A. Seryi
  SLAC, Menlo Park, California

The CLIC Conceptual Design Report must be ready by 2010. This paper aims at addressing all the critical points of the CLIC BDS to be later implemented in the CDR. This includes risk evaluation and possible solutions to a number of selected points. The smooth and practical transition between the 500 GeV CLIC and the design energy of 3 TeV is also studied.

• J.-L. Fernandez-Hernando
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• J. Resta-López
  JAI, Oxford

Beryllium is being considered as an option material for the CLIC energy collimators in the Beam Delivery System. Its high electrical and thermal conductivity together with a large radiation length compared to other metals makes Beryllium an optimal candidate for a long tapered design collimator that will not generate high wakefields, which might degrade the orbit stability and dilute the beam emittance, and in case of the beam impacting the collimator temperature rises will not be sufficient enough to melt the metal. This paper shows results and conclusions from simulations of the impact of a CLIC bunch train hitting the collimator.