Investigation of electron acceleration and deceleration in plasmas

This work covers several aspects related to Laser WakeField Acceleration (LWFA). A strong and ultrashort laser pulse can generate plasma waves with accelerating gradients up to 100s GV/m, four orders of magnitude higher than a conventional radio frequency linear accelerator. The LWFA electrons have been characterized as an ultra-short and high brilliance source. These remarkable properties lead to a compact accelerator which is of great scientific interest for building a table-top coherent free electron laser as well as a single-shot electron diffraction device. On the other hand, a new application of LWFA is to utilize the high peak current LWFA electron bunch to drive a wakefield efficiently inside a high density underdense plasma. The resulting wakefield quickly decelerates the driver bunch or accelerates a properly designed witness bunch, and therefore the plasma is utilized as a compact beam dump or an afterburner staged after a regular LWFA.