Abstracts Brochure - CERN

TUPCH — Poster Session 27-Jun-06 16:00 - 18:00
Precision Beam Timing Measurement System for CLIC Synchronization
Very precise synchronization between main
and drive beams is required in CLIC to avoid J.P.H. Sladen, A. Andersson (CERN)
excessive luminosity loss due to energy variations.
One possibility to accomplish this would be to measure and correct the drive beam phase. The timing reference
for the correction could be the beam in the outgoing transfer line of the main linac. The timing of both main and drive
beams will have to be measured to a precision in the region of 10 fs. The aim is to achieve this by means of a beam
measurement at 30 GHz with the signal mixed down to an intermediate frequency (IF) for precise phase detection.
The RF and IF electronics are being developed, and tests will be carried out in CTF3.
High Dynamic Range Beam Profile Measurements
In future high intensity, high energy accelerators,
beam loss has to be minimized to maximize
performance and minimize activation
of accelerator components. It is imperative
C.P. Welsch, E. Bravin, B. Burel, T. Lefevre (CERN) T. Chapman,
M.J. Michael (Thermo)
to have a clear understanding of the mechanisms that can lead to halo formation and to have the possibility to test
available theoretical models with an adequate experimental setup. Measurements based on optical transition radiation
(OTR) provide an interesting opportunity for high resolution measurements of the transverse beam profile. In
order to be applicable for measurements within the beam halo region, it is of utmost importance that a high dynamic
range is covered by the image acquisition system. The existing camera system as it is installed in the CLIC Test Facility
(CTF3) is compared to a step-by-step measurement with a photo multiplier tube (PMT) and measurements with a
cooled charge injection device (CID) camera. The latter acquisition technique provides an innovative and highly
flexible approach to high dynamic range measurements and is presented in some detail.
Investigations of OTR Screen Surfaces and Shapes
Optical transition radiation (OTR) has
proven to be a flexible and effective tool for C.P. Welsch, E. Bravin, T. Lefevre (CERN)
measuring a wide range of beam parameters,
in particular the beam divergence and the transverse beam profile. It is today an established and widely used diagnostic
method providing linear real-time measurements. Measurements in the CLIC Test Facility (CTF3) showed that the
performance of the present profile monitors is limited by the optical acceptance of the imaging system. In this paper,
two methods to improve the systems’ performance are presented and results from measurements are shown. First,
the influence of the surface quality of the OTR screen itself is addressed. Several possible screen materials have been
tested to which different surface treatment techniques were applied. Results from the measured optical characteristics
are given. Second, a parabolic-shaped screen support was investigated with the aim of providing an initial focusing
of the emitted radiation and thus to reduce the problem of aperture limitation. Measured and calculated emission
distributions are presented.
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