CLIC and CTF3

The CLIC study has been exploring the scheme for an electron-positron Collider (CLIC) with high luminosity (10$^{34}$ - 10$^{35}$ cm2/s) and a nominal centre-of-mass energy of 3 TeV in order to make the multi-TeV range accessible for physics. The CLIC Test Facility CTF3, built at CERN by an international collaboration, aims at demonstrating the feasibility of the CLIC scheme by 2010. CTF3 consists of a 150 MeV electron linac followed by a 42 m long delay loop and an 84 m combiner ring, followed by a two-beam test stand and a test decelerator. The linac and delay loop have been previously commissioned, while the combiner ring has been recently completed. After a presentation of the recent CLIC parameters, the status of the test facility, the experimental results achieved and the future plans will be presented

New Methods of Improving the Orbit Determination and Stability at LEP

The orbit quality is of particular importance for a good performance of an accelerator. Beam parameters like the interaction rate of a collider or the level of spin polarization strongly depend on the orbit. Two new methods to improve the orbit measurement and stability are demonstrated. The beam position monitors in an accelerator are carefully aligned to the centres of the quadrupole magnets. A residual mechanical but also electronical offset can persist. This offset is measured by a beam based alignment method developed at LEP. The method and its installation are described. Measurement procedures as well as results for different magnet types and BPM electronics are shown. The impact of the BPM offsets on the achievable spin polarization level is outlined. The vertical orbit has shown large variations during LEP operation. Frequent orbit corrections were required to avoid a decrease of the interaction rate. Low-beta insertion quadrupoles were suspected to be the origin of the drifts. The positions of these magnets have been monitored by different systems. The movements are compared to the orbit variations and the correlation is shown. An orbit feedback based on the mechanical measurements has been put into operation to keep the LEP orbit stable

Low-β\beta Quadrupole Movements as Source of Vertical Orbit drifts at LEP

In LEP, the superconducting low-beta quadrupole magnets (QS0) are a major source of vertical orbit drifts. During the 1995 LEP operation, measurements of the vertical movements of these quadrupoles were taken systematically for the first time. The analysis described in this note gives clear evidence for the correlation between the mechanical movements of the magnets and the drifts of the vertical orbit. This opens the possibility for a feedback system to prevent large vertical orbit drifts

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

Closed orbit feed-back from low-β\beta quadrupole movements at LEP

Left and right of each of the four LEP interaction points superconducting low-beta quadrupole magnets are installed to squeeze the vertical beam size at the interaction points. These magnets are the dominant source of vertical closed orbit drifts at LEP because of their strength, the large vertical beta function and their support. Hydrostatic Levelling Systems and resistor-based position sensors were installed to measure the vertical movements of these magnets continuously. The correlation between the mechanical movements and closed orbit variations has been studied. The analysis has shown that the orbit can be kept stable by acting on one correction dipole per low-beta quadrupole pair. This has led to a feed-back system which uses the mechanical measurements to correct the closed orbit and to prevent large orbit variations

Beam Dynamics for the Preliminary Phase of the New CLIC Test Facility (CTF3)

In the framework of the CLIC (Compact Linear Collider) RF power source studies, the scheme of electron pulse compression and bunch frequency mulitiplication, using injection by RF deflectors into an isochronous ring, will be tested, at low charge, during the preliminary phase of the new CLIC Test Facility (CTF3) at CERN. In this paper, we describe the beam dynamics studies made in order to assess the feasibility of the bunch combination experiment, as well as the related beam measurements performed on the LEP Pre-Injector complex (LPI) before its transformation into CTF

Beam Dynamics for the CTF3 Preliminary Phase

In the framework of the CLIC RF power source studies, the new scheme of electron pulse compression and bunch frequency multiplication, using injection by RF deflectors into an isochronous ring, will be tested at CERN during the CTF3 preliminary phase. The present LPI complex will be modified in order to allow a test of this scheme at low charge. The design of the new front-end, of the modified linac, of the matched transfer line, and of the isochronous ring lattice is presented here.The results of the related beam dynamics studies are also discussed

Status of the CTF3 commissioning

The Preliminary Phase of the new CLIC Test Facility CTF3 consists of a low-charge demonstration of the electron bunch train combination process on which the CLIC drive beam generation scheme is based. The principle of the combination relies on the injection of short electron bunches into an isochronous ring using RF deflecting cavities. The commissioning of this facility started in September 2001, with alternating periods of installation work and beam studies. In this paper, we present the status of the facility, the first beam measurements and the next steps towards the completion of the experiment