A CLIC Injector Complex for the Main Beams

The feasibility study for an e+e- linear collider based on two beams accelerator and working at 30 GHz is investigated with the CLIC (Compact Linear Collider). A new set of beam parameters has been presented at the LC 97 Workshop. Compared to the previous reference scheme for the injector complex, several major changes occurred. The two options, 0.5 TeV and 1 TeV (centre of mass), are discussed. Several issues concerning the RF gun and the associated laser, the beam loading compensation, the positron source, the damping rings and the bunch compressors are presented. This note presents the study of the new CLIC injector complex

The CLIC positron production scheme

The CLIC (Compact Linear Collider) positron source is based on the conventional scheme, using a metal converter target and an Adiabatic Matching Device (AMD) composed of a Flux Concentrator (FC) and a constant magnetic field along the positron Pre-Injector linac. The positrons are accelerated with L-band RF structures. Beam dynamics simulations are described for the positron production in the target and capture section in the AMD. The distribution of the energy deposition in the target is studied with the EGS4 code. The dependence of the positron yield on several parameters is studied and optimised using both EGS4 and analytical calculations. Following this optimisation, a new set of design parameters is proposed and particle tracking simulations are performed to estimate the overall performance

The LEP Pre-Injector as a Multipurpose Facility

The LEP Pre-Injector (LPI) provides electron and positron beams at 500 MeV. In 1988, it was used for the first time to produce single electrons at 180 MeV in order to calibrate the L3 detector. Since this first experiment a dedicated irradiation area has been built downstream of the linac. This facility uses electron beams with an energy range adjustable from 180 MeV to 700 MeV with intensity, pul se duration and repetition rate, which can be varied within wide limits. Some LEP detectors, and almost all future LHC (Large Hadron Collider) detectors, have already used this facility intensively. W hen the LPI accumulator works at 308 MeV, the critical energy of the synchrotron light radiated in the bending magnets is 45 eV. It corresponds to the synchrotron radiation which will be produced by 7 TeV protons in the LHC. To study the crucial issue of desorption in the LHC vacuum chamber a first synchrotron light line, at room temperature, has been installed followed by a second one for cryogeni c temperatures. This paper reviews the experiments that have been done, the beam characteristics for these facilities and the possible evolutions in the near future

Beam Dynamics Studies in the CLIC Injector Linac

The CLIC Injector Linac has to accelerate both electron and positron main beams from 200 MeV up to 2.42 GeV prior to their injection into the pre-damping rings. Its 26 accelerating structures operate at 1.5 GHz, with a loaded gradient of 17 MV/m. A FODO lattice that wraps the accelerating structures at the beginning of the linac, followed by a succession of triplet lattices between the accelerating structures, is proposed. The large normalized transverse emittance (9200 mm.mrad rms), bunch length (5mmrms) and energy spread (7 MeV rms) of the e+ beam set constraints on the linac, in order to reach acceptable characteristics at 2.42 GeV for the injection into the predamping ring. The use of a bunch compressor at the linac entrance is an option in order to achieve good performance in both the longitudinal and transverse phase spaces. Tracking studies of both electron and positron beams in the linac have been performed and are presented

Isochronous Optics and Related Measurements in EPA

The time structure of the CLIC (Compact Linear Collider) drive beam is obtained by the combination of electron bunch trains in rings using RF deflectors [1]. The rings must be isochronous, in order to preserve the bunch length and separation during the combination process (4-5 turns). A first isochronicity test has been performed in the CERN EPA (Electron Positron Accumulator) ring. The calculated isochronous lattice can be obtained by changing the strength of existing quadrupole families without hardware modifications. Measurements of the synchrotron frequency and of the beam's time structure have been made for both the normal and the isochronous lattices. Streak camera measurements of the bunch length have been used to tune the lattice around the isochronous point. The bunch length increases rapidly over a few turns in the normal case, while no appreciable bunch lengthening is observed over 50 turns in the isochronous case. A quantitative evaluation of the momentum compaction is obtained by measuring the bunch separation in a train when close to, and far from, the isochronous condition. Plans for future tests in the EPA ring are also outline