%0 Thesis
%A Reuter, Maria
%T Characterisation of a laser wakefield accelerator with ultra-short probe pulses
%I Friedrich-Schiller-Universität Jena 
%V Dissertation
%C Jena
%M GSI-2019-00396
%P 137 S.
%D 2019
%Z Dissertation, Friedrich-Schiller-Universität Jena , 2018
%X Within the frame of this thesis, aspects of the acceleration of electrons with high-intensitylaser pulses inside an underdense plasma were investigated. The basic acceleration mecha-nism, which is referred to as laser wakefield acceleration relies on the generation of a plasmawave by an intense laser pulse. Since the plasma wave co-propagates with the laser pulse,its longitudinally alternating electric field moves with a velocity close to the speed of lightand electrons trapped in the accelerating phase of the wave can be accelerated to relativisticenergies. While basic principles such as the generation of a plasma wave, the injection ofelectrons into the accelerating phase of the wave and limitsto the acceleration process areknown, the exact processes occurring during the nonlinear interaction of laser pulse andplasma wave still need to be explored in more detail. The consequence of those nonlinearprocesses is a drastic change of the electron parameters – e.g. final electron energy, band-width and pointing – through slight changes in the initial conditions. In this context, theposition in the plasma at which electrons are injected into the plasma wave plays a key rolefor the maximum achievable electron energy. Therefore, theinjection of electrons at a de-fined position is a possibility to reduce shot-to-shot fluctuations and might make the electronpulses applicable, e.g. as a stable source of secondary radiation for temporally and spatiallyhighly resolving imaging techniques. The investigation ofcontrolled injection of electrons atan electron density transition demonstrated a correlationof electron pulse parameters suchas electron energy gain and accelerated charge to the properties of the transition, and thus,might be a promising method to generate custom designed electron pulses. Nevertheless,shot-to-shot fluctuations in the electron parameters were still observed and are most likelycaused by the nonlinear evolution of the laser pulse inside the plasma. To further reduceinstabilities, deeper insight into these nonlinear processes is required and hence, a methodto observe the plasma wave and the laser pulse. Combining an ultra short probe pulse witha highly resolving imaging system as successfully implemented at the institute of Optics andQuantumelectronics in Jena, more light can be shed on these processes, which take placeon femtosecond and micrometer scales. With that system, characteristics of the magneticfields inextricably connected to the acceleration process could be studied in unprecedenteddetail. This deeper insight allowed to observe signatures of the magnetic field of the drivinglaser pulse for the first time, which paves the way for the indirect observation of the mainlaser pulse during the interaction.
%F PUB:(DE-HGF)11
%9 Dissertation / PhD Thesis
%U https://repository.gsi.de/record/218418