Designing and commissioning of a setup for timing-jitter measurements using electro-optic temporal decoding

Precise measurements of the arrival time jitter between the ionization laser, used to create the plasma, and the driver beam in the PWFA setup of the FLASHForward project are of high interest for the operation and optimization of the experiment. In this thesis, an electro-optic temporal decoding (EOTD) setup with near crossed polarizer detection scheme is presented, which can measure the timing-jitter to an accuracy of around 30 fs. This result was obtained during several measurements conducted at the coherent transition radiation beamline CTR141 at FLASH, using a 100 μm thick GaP crystal and coherent diffraction/transition radiation, generated from the FLASH1 electron bunches. Measurements were performed during long and short electron bunch operation at FLASH, showing that best results are obtained with CDR from long electron bunches. Utilizing CTR led to a higher EO signal and ''over-compensation'' of the SHG background level during the measurement, which resulted in a double-peak structure of the observed THz pulses. To resolve the single-cycle nature of these THz pulses, the SHG background had to be adjusted properly. Furthermore, EOTD measurements during a short bunch operation run at FLASH exhibited strong oscillations in the EO signal, which were suspected to come either from internal lattice resonances of the EO crystal or internal reflections, or excitation of water vapor in the humid air in the laboratory. The oscillations spoiled the observed EOTD trace leading to no sensible measurements of the arrival time jitter during this short bunch operation. To evaluate the capabilities of the setup for monitoring the timing jitter of short PWFA accelerated electron bunches or very short driver bunches at FLASHForward, further investigations on the observed oscillations in the EOTD traces have to be performed during short bunch operation at FLASH with different crystals and under vacuum conditions, to understand the oscillations of the EO signal better.