Monte Carlo simulations and measurements of the radiation environment at a laser-plasma accelerator

Abstract: In current experiments at the high-power laser facility at the Lund Laser Centre, electrons accelerated to hundreds of MeV over short distances by means of laser wakefield acceleration in produced plasmas. To determine the amount of secondary radiation generated when accelerated electrons interact with surrounding materials is of interest to ensure a safe working environment. In this thesis, the radiation levels inside the laboratory are simulated using GEANT4, a C++ class library for particle physics and particle tracking using Monte Carlo methods. For persons directly outside the room of the vacuum chamber, conservative simulation results indicate that even for electrons accelerated to a relatively large average energy of 500 MeV, in bunches containing an average charge of 100 pC, in excess of 10 8 shots would need to be fired in a single year to reach doses of the order of the limits set by the Swedish Radiation Safety Authority. At a pulse rate of 0.1 shots per second, this corresponds to continuous operation for 27 700 hours. As a test of the simulations, experimental dose data were collected using dosimetric instruments – measuring doses from electron, gamma and neutron radiation – showing agreement with simulated doses to within reasonable error.