No abstract

The Compact Linear Collider (CLIC) is a study for a future linear electron-positron collider based on a two-beam acceleration scheme in which a high-intensity drive beam is decelerated in order to provide the power to accelerate the main beam for collision in the TeV range. The power extracted from the drive beam deteriorates the beam quality and increases the energy spread significantly. Monitoring of the beam properties is therefore challenging but essential. These challenges are being addressed experimentally at the CLIC test facility where up to 55% of the power is extracted from the beam in the test beam line, a small-scale version of the CLIC drive-beam decelerator, leaving the beam with a very wide energy profile. For monitoring of the transverse beam profile and Twiss parameters we use optical transition radiation screens and quadrupole scans. The intra-pulse-train energy spectrum before and after deceleration is measured with segmented beam dumps. In this paper we discuss the performance of these diagnostic devices with a particular emphasis on the large energy spread and its effect on the beam imaging techniques, and with a final outlook to the CLIC drive-beam diagnostics.

No abstract

We discuss beam deceleration through a series of 12 power extraction and transfer structures, at the CLIC test facility 3 at CERN, as a proof-of-principle of the CLIC deceleration scheme. Up to 36% of the kinetic energy of an electron drive beam is extracted and converted to 12 GHz rf power. We look at the average and maximum energy loss of the particles, and compare them with simulations performed with the PLACET tracking code. The measured final energy is also compared to predictions based on the measured beam current and rf power in the structures. In the analysis we make use of the charge distribution form factor, taking into account the bunch length and the bunch phase. Finally, we look at the evolution of the transverse emittance with deceleration and compare the measured emittance with simulations.