Williame Coosemans

A 3 TeV

A possible design of a multi-TeV e+e- linear collider is presented. The design is based on the CLIC (Compact Linear Collider) two-beam technology proposed and developed at CERN. Though the study has shown that this technology is applicable to a linear collider with centre-of-mass energies from 500 GeV or less up to 5 TeV, the present report focuses on the nominal energy of 3 Te V. First, a short overview is given of the physics that could possibly be done with such a collider. Then, the description of the main-beam complex covers the injection system, the 30 GHz main linac, and the beam delivery system. The presentation of the RF power source includes the beam-generation scheme, the drive-beam decelerator, which consists of several 625 m long units running parallel to the main linac, and the power-extraction system. Finally, brief outlines are given of all the CLIC test facilities. They cover in particular the new CLIC test facility CTF3 which will demonstrate the feasibility of the power production technique, albeit on a reduced scale, and a first full-scale single-drive-beam unit, CLICI, to establish the overall feasibility of the scheme.

e^+ e^-

The present parameters of the CLIC study require the collision of small emittance beams with a vertical spot size of 1 nm. The tolerances on vertical quadrupole vibration (above a few Hz) are as small as a few nm in the linac and most of the Final Focus. The final focusing quadrupole has a stability requirement of 4 nm in the horizontal and 0.2 nm in the vertical direction. Those tolerances can only be achieved with the use of damped support structures for CLIC. A study has been set-up at CERN to explore the application of stabilization devices from specialized industry and to predict the time-dependent luminosity performance for CLIC. The results will guide the specification of required technological improvements and will help to verify the feasibility of the present CLIC parameters.

Linear Collider Based on CLIC Technology

The Compact Linear Collider (CLIC) aims at colliding e/sup +/e/sup -/ beams at 1.5 TeV with effective transverse spot sizes of 60 nm (horizontal) times 0.7 nm (vertical). Strict stability tolerances must be respected in order to achieve a sufficient overlap of the two colliding beams. A stability test stand has been set up at CERN, bringing latest stabilization technology to the accelerator field. Using this technology, a CLIC prototype magnet was stabilized in a normal CERN working environment to less than 1-nm vertical RMS motion above 4 Hz. Detailed simulations of the time-dependent luminosity performance of CLIC are discussed. They include the beam-beam interaction, the beam-based feedbacks and the measured data on magnet stability.

The CLIC study of magnet stability and time-dependent luminosity performance

The pre-alignment and active control method for the Compact Linear Collider (CLIC) is described. Two new types of instruments are used in this system-a biaxial Wire Positioning System (WPS) which uses a stretched wire as the spatial reference, and a capacitive three axes Tilt Meter System (TMS). The instruments, and the way they are used with the well-known Hydrostatic Levelling System (HLS) are described.

Colliding nanobeams in CLIC with magnets stabilized to the sub-nm level

It is noted that the accelerating and focusing structure of the CERN high-energy linear collider must be aligned and maintained in the transverse plane to very tight tolerances (5 mu m for the accelerating sections and 1 mu m for the quadrupoles) to avoid excessive beam blow-up due to beam-induced transverse wake fields. Since normal ground motion produces displacements which exceed these tolerances, a dynamic alignment system using beam-derived signals from beam position monitors to drive precision micromovers under closed-loop control to maintain the components in position is foreseen. A remote computer-controlled micro-movement test facility has been constructed at CERN to study the various problems associated with such systems. The behavior of a string of 40 2.5-m-long girders using this prealignment system has been simulated using an existing CERN geodesic compensation program.<<ETX>>