• 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. Pfingstner, D. Schulte
  CERN, Geneva
• M. Hofbaur
  UMIT, Hall in Tirol

One of the major challenges of the CLIC main linac is the preservation of the ultra-low beam emittance. The dynamic effect of ground motion would lead to a rapid emittance increase. Orbit feedback systems (FB) have to be optimized to efficiently attenuate ground motion (disturbance), in spite of drifts of accelerator parameters (imperfect system knowledge). This paper presents a new FB strategy for the main linac of CLIC. It addresses the above mentioned issues, with the help of an adaptive control scheme. The first part of this system is a system identification unit. It delivers an estimate of the time-varying system behavior. The second part is a control algorithm, which uses the most recent system estimate of the identification unit. It uses H2 control theory to deliver an optimal prediction of the ground motion. This approach takes into account the frequency and spacial properties of the ground motion, as well as their impact on the emittance growth.

• 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.

• F. Stulle, D. Schulte, J. Snuverink
  CERN, Geneva
• A. Latina
  Fermilab, Batavia
• S. Molloy
  Royal Holloway, University of London, Surrey

Over the last months the general layout of the CLIC main beam RTML has stabilized and most important lattices are existing. This allowed us to perform detailed studies of tolerances on magnetic stray fields and on magnet misalignment. Additionally, beam lines could be improved in terms of performance and flexibility. We discuss the overall layout as will be described in the CLIC conceptual design report, highlight the improvements which have been made and show results of tolerance studies.

• F. Zimmermann, S. Bettoni, O.S. Brüning, B.J. Holzer, S. Russenschuck, D. Schulte, R. Tomás
  CERN, Geneva
• H. Aksakal
  N.U, Nigde
• R. Appleby
  UMAN, Manchester
• S. Chattopadhyay, M. Korostelev
  Cockcroft Institute, Warrington, Cheshire
• A.K. Çiftçi, R. Çiftçi, K. Zengin
  Ankara University, Faculty of Sciences, Tandogan/Ankara
• J.B. Dainton, M. Klein
  The University of Liverpool, Liverpool
• E. Eroglu, I. Tapan
  UU, Bursa
• P. Kostka
  DESY Zeuthen, Zeuthen
• V. Litvinenko
  BNL, Upton, Long Island, New York
• E. Paoloni
  University of Pisa and INFN, Pisa
• A. Polini
  INFN-Bologna, Bologna
• U. Schneekloth
  DESY, Hamburg
• M.K. Sullivan
  SLAC, Menlo Park, California

In a linac-ring electron-proton collider based on the LHC ("LR-LHeC"), the final focusing quadrupoles for the electron beam can be installed far from the collision point, as far away as the proton final triplet (e.g. 23 m) if not further, thanks to the small electron-beam emittance. The inner free space could either be fully donated to the particle-physics detector, or accommodate "slim" dipole magnets providing head-on collisions of electron and proton bunches. We present example layouts for either scenario considering electron beam energies of 60 and 140 GeV, and we discuss the optics for both proton and electron beams, the implied minimum beam-pipe dimensions, possible design parameters of the innermost proton and electron magnets, the corresponding detector acceptance, the synchrotron radiation power and its possible shielding or deflection, constraints from long-range beam-beam interactions as well as from the LHC proton-proton collision points and from the rest of the LHC ring, the passage of the second proton beam, and the minimum beta* for the colliding protons.

• F. Zimmermann, O.S. Brüning, E. Ciapala, F. Haug, J.A. Osborne, D. Schulte, Y. Sun, R. Tomás
  CERN, Geneva
• C. Adolphsen
  SLAC, Menlo Park, California
• R. Calaga, V. Litvinenko
  BNL, Upton, Long Island, New York
• S. Chattopadhyay
  Cockcroft Institute, Warrington, Cheshire
• J.B. Dainton, M. Klein
  The University of Liverpool, Liverpool
• A.L. Eide
  LPNHE, Paris

We consider three different scenarios for the recirculating electron linear accelerator (RLA) of a linac-ring type electron-proton collider based on the LHC (LHeC): i) a basic version consisting of a 60 GeV pulsed, 1.5 km long linac, ii) a higher luminosity configuration with a 60 GeV 4 km long cw energy-recovery linac (ERL), and iii) a high energy option using a 140 GeV pulsed linac of 4 km active length. This paper describes the footprint, optics of linac and return arcs, emittance growth from chromaticity and synchrotron radiation, a set of parameters, and the performance reach for the three scenarios.

• D. Schulte, R. Corsini, B. Dalena, J.-P. Delahaye, S. Döbert, G. Geschonke, A. Grudiev, J.B. Jeanneret, E. Jensen, P. Lebrun, Y. Papaphilippou, L. Rinolfi, G. Rumolo, H. Schmickler, F. Stulle, I. Syratchev, R. Tomás, W. Wuensch
  CERN, Geneva
• E. Adli
  University of Oslo, Oslo

The physics experiments at CLIC will require that the machine scans lower than nominal centre-of-mass energy. We present different options to achieve this and discuss the implications for luminosity and the machine design.

• J. Snuverink, W. Herr, C. Jach, J.B. Jeanneret, D. Schulte, F. Stulle
  CERN, Geneva

The Compact Linear Collider (CLIC) accelerator has strong precision requirements on the position of the beam. The beam position will be sensitive to external dynamic magnetic fields (stray fields) in the nanotesla regime. The impact of these fields on the CLIC main beam has been studied by performing simulations on the lattices and tolerances have been determined. Several mitigation techniques will be discussed.

• G. Rumolo, J.B. Jeanneret, D. Schulte
  CERN, Geneva

The maximum tolerable pressure value in the chamber of the CLIC electron Main Linac is determined by the threshold above which the fast ion instability sets in over a bunch train. Instability calculations must take into account that, since the accelerated beam becomes transversely very small, its macroscopic electric field can reach values above the field ionization threshold. In this paper we first discuss threshold values of the electric field for field ionization and the extent of the transverse region that gets fully ionized along the ML. Then, we show the results of the instability simulations from the FASTION code using the new model, and consequently review the pressure requirement in the ML.

• B. Dalena, D. Schulte
  CERN, Geneva

Beam-Beam background is one of the main issues of the CLIC MDI at 3 TeV CM. The background level have a significant impact on the interaction region design. This paper presents a study of the background expected rates versus luminosity according to different beam parameters and considering different machine conditions, using an integrated simulation of the Main LINAC and BDS sub-systems.

• 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.

• B. Dalena, D. Schulte, R. Tomás
  CERN, Geneva

The main detector solenoid and associated magnets can have an important impact on the CLIC luminosity. These effects are discussed for different solenoid designs. In particular, the luminosity loss due to incoherent synchrotron radiation in the experiment solenoid and QD0 overlap is evaluated. The impact of the AntiDiD (Anti Detector integrated Dipole) on luminosity and compensated techniques on beam optic distortion are also discussed.

• 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.

• E. Adli
  University of Oslo, Oslo
• A.E. Dabrowski, S. Döbert, M. Olvegård, D. Schulte, I. Syratchev
  CERN, Geneva
• R.L. Lillestol
  NTNU, Trondheim

The CLIC Test Facility 3 Test Beam Line is the first prototype for the CLIC drive beam decelerator. Stable transport of the drive beam under deceleration is a mandatory component in the CLIC two-beam scheme. In the Test Beam Line more than 50% of the total energy will be extracted from a 150 MeV, 28 A electron drive beam, by the use of 16 Power Extraction and Transfer structures. A number of experiments are foreseen to investigate the drive beam characteristics under deceleration in the Test Beam Line, including beam stability, beam blow up and the efficiency of the power extraction. General benchmarking of decelerator simulation and theory studies will also be performed. Specially designed instrumentation including precision BPMs, loss monitors and a time-resolved spectrometer dump will be used for the experiments. This paper describes the experimental program foreseen for the Test Beam Line, including the relevance of the results for the CLIC decelerator studies.

• A. Latina, N. Solyak
  Fermilab, Batavia
• D. Schulte
  CERN, Geneva

Polarized positron and electron beams are ideal for searching for new physics at the Compact Linear Collider (CLIC). In order to properly orient and preserve the polarization of the beam at the interaction point, the beam polarization must be manipulated by a spin rotator along the beam line. In this paper a spin rotator design for the CLIC is presented and its integration into the CLIC ring to main linac transport system is discussed.

• Y. Papaphilippou, F. Antoniou, M.J. Barnes, S. Bettoni, S. Calatroni, P. Chiggiato, R. Corsini, A. Grudiev, R. Maccaferri, M. Modena, L. Rinolfi, G. Rumolo, D. Schoerling, D. Schulte, M. Taborelli, A. Vivoli
  CERN, Geneva
• E.B. Levichev, S.V. Sinyatkin, P. Vobly, K. Zolotarev
  BINP SB RAS, Novosibirsk

The CLIC damping rings should produce the ultra-low emittance necessary for the high luminosity performance of the collider. This combined to the high bunch charge present a number of beam dynamics and technical challenges for the rings. Lattice studies have been focused on low emittance cells with optics that reduce the effect Intra-beam scattering. The final beam emittance is reached with the help of super-conducting damping wigglers. Results from recent simulations and prototype measurements are presented, including a detailed absorption scheme design. Collective effects such as electron cloud and fast ion instability can severely limit the performance and mitigation techniques have been identified and tested. Tolerances for alignment and technical system design such as kickers, RF cavities, magnets and vacuum have been finally established.