Polarimetry of Laser Plasma Accelerated Electron Beams

Laser Plasma Acceleration (LPA) with its extremely high gradients promises compact accelerators and great progress has been made in that direction. However, many applications in nuclear and high energy physics require polarised electron beams. The motivation of the LEAP project at DESY is the first time demonstration of LPA with polarisation. This thesis focuses on the design and commissioning of a Compton transmission polarimeter to verify electron polarisation in future LEAP experiments. The polarimeter makes use of the production of circularly polarised bremsstrahlung during the passage of the electrons through a suitable target. The photon polarisation is then measured with the aid of the transmission asymmetry related to the magnetisation direction of an iron absorber. A Monte Carlo design study revealed that a dedicated bremsstrahlung converter target had little impact on the asymmetry and was therefore omitted from the final design. Furthermore, resolving the small anticipated asymmetries ( ∼ 1.5‰) within a feasible number of shots requires an energy resolutionbetter than 2 % for the calorimeter detecting the transmitted photons. Consequently, a homogeneous lead-glass calorimeter was constructed.The LEAP polarimeter was commissioned using an unpolarised electron beam. It was found to perform as designed; however, the measurements were dominated by systematic uncertainties due to false asymmetries arising from fluctuations in beam charge and energy. The analysing power of the polarimeter was determined to be 11.74 ± 0.18 %.