Studies for Upgrading and Optimising the CLEAR Beamline, and Generating Uniform Electron-Beam Profiles for Irradiation Experiments

Irradiation facilities around the world are used to investigate the effect of high-energy particle beams on electronics, to study the makeup of historical objects and art, and for medical applications, notably radiotherapy. The CERN Linear Electron Accelerator for Research (CLEAR) is an irradiation facility that produces 200 MeV beams of electrons with parameters tuned to the needs of users. One of the most commonly requested beam parameters is for bunch lengths of less than 1 ps, which was not previously possible for high-charge bunches. In this thesis, the ability to compress high-charge bunches to sub-ps bunch lengths, using the velocity bunching technique, is shown in simulation. The simulations are then verified with experimental measurements taken at CLEAR. The ability to reduce the emittance of the beam during compression is also presented. Potential upgrades to the CLEAR facility are proposed, namely a new laser system and the installation of an additional klystron. The benefits of these upgrades are explored in simulation, demonstrating that they would allow the production of shorter bunches, with lower energy spread, and lower emittance. It is shown that by using a modified version of the CLEAR photoinjector it is possible to produce bunches with a uniform transverse profile using a simple Gaussian laser with a 1 ps pulse length. A compact irradiation facility was proposed consisting of the CLEAR photoinjector, an X-band linac using cavities similar to those developed for the Compact Linear Collider, and a quadrupole matching section. It was shown that such a facility could produce beams of different sizes with uniform beam profiles. The stability of such a facility was investigated, demonstrating that beam jitters do not significantly reduce beam uniformity.