Abstract
Following the discovery of the Higgs-like boson at the Large Hadron Collider, there is demand for precision measurements on recent findings. The Compact Linear Collider, CLIC, is a candidate for a future linear electron-positron collider for such precision measurements. In CLIC, the beams will be brought to collisions in the multi-TeV regime through high gradient acceleration with high frequency RF power. A high intensity electron beam, the so-called drive beam, will serve as the power source for the main beam, as the drive beam is decelerated in special structures, from which power is extracted and transfered to the main beam. When the drive beam is decelerated the beam quality deteriorates and the momentum spread increases, which makes the beam transport challenging. Dedicated diagnostics to monitor the momentum profile along each bunch train and transverse profile diagnostics will be needed to guarantee the reliability of the decelerator and consequently the power source of the main beam acceleration.A test facility, CTF3, has been constructed at CERN to validate key technical aspects of the CLIC concept. The beam quality in the decelerator will be investigated in the test beam line, TBL, where several power extraction structures reduce the drive beam energy by up to 55%. At the same time, the single-bunch rms energy spread grows from the initial value of 1% to almost 6%. To monitor the parameters of such a beam is challenging but crucial for the optimization of the beamline. In this thesis we report on progress made on adapting generally used methods for beam profile measurements to the demanding conditions of a wide momentum profile. Two detector technologies are used for measuring transverse profile and momentum profile and we discuss the performance of these instruments, in the view of the large momentum spread and with the outlook towards equivalent beam profile monitors in the CLIC decelerator.
Highlights
A promising candidate for performing precision measurements in the multi-TeV regime is the compact linear collider Compact Linear Collider (CLIC) [1]
To the accelerating structures, that will operate at a gradient of 100 MeV=m in order to increase the energy of the main beam to the TeV range in the 21 km linac, the power is extracted from the in parallel running drive beam by so-called power extraction and transfer structures (PETS) [2]
The power extraction from the drive beam deteriorates the beam quality and increases the energy spread significantly, which calls for careful monitoring of the beam properties
Summary
A promising candidate for performing precision measurements in the multi-TeV regime is the compact linear collider CLIC [1]. The beam current in TBL is about 4 times lower than in CLIC, and in order to compensate for this and to reach the required power level of 140 MW the PETS are 4 times longer than those designed for CLIC. This causes a deceleration of the beam by 5.2 MeV in each PETS. The deceleration process leads to an asymmetric energy distribution shown in Fig. 3 with a significant high-energy tail all the way up to the initial energy in TBL of 150 MeV. We conclude by discussing the extrapolation of the TBL diagnostics to the CLIC regime
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