L. Thorndahl

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^-

Abstract A survey of the theory of stochastic cooling is presented followed by a report on experiments in this field. It is shown that the results of these experiments agree with the theoretical predictions.

Linear Collider Based on CLIC Technology

Antiprotons have been stored in the ICE Storage Ring and held for 85h with the help of stochastic cooling. We set a limit of at least 32 h for the antiproton lifetime (in its rest frame).

Physics and technique of stochastic cooling

Recent experiments on stochastic cooling have resulted in cooling rates several orders of magnitude higher than obtained previously in the ISR. Two cooling systems reduce betatron oscillations. A third system reduces momentum spread, using the so-called filter method. The favourable signal-to-noise ratio of this method has led to cooling times (e-folding of peak density) of 15 s with 7.107 protons in ICE. Betatron cooling times are longer due to the lower signal-to-noise ratio. Simultaneous cooling in all three planes has yielded lifetimes of about 100 h, a value consistent with losses caused by single scattering on the residual gas. The existing stochastic cooling theory has been confirmed.

Measurement of antiproton lifetime using the ice storage ring

Improvement of transverse stochastic cooling in cases where the pick-up-to-kicker distance is not optimal may be obtained by using a transmission-line filter that causes opposite phase shift at alternating Schottky sidebands. Improvement of the horizontal stack-core cooling in the Antiproton Accumulator by using a pickup at a zero dispersion location is planned; the filter technique will make this possible. The improvement of the signal-to-noise ratio in the 250-500 MHz stack tail termination resistors is discussed, as well as some problems caused by undesired modes perturbing the pickup response.