Interferometric Charecterization of Supersonic Gas-Jets for Laser Wakefield Acceleration

Abstract: The Multi-Terawatt laser at the LLC (Lund Laser Centre) is used to accelerate particles using laser wakefield acceleration. Laser wakefield acceleration is a particle acceleration method that utilizes intense electric fields in plasma created by high intensity laser pulses when passing through gas. A gas nozzle is used to introduce gas in the beamline to produce the plasma needed and the supersonic gas-jets produced by this nozzle were characterized in this project. Characteristics such as density profile and stability were the main focus. The method tested to characterize the jets was interferometry using a Mach-Zehnder interferometer and then treating recorded data using a MATLAB script. The main conclusion was that this method to characterize the gas works, as it can reproduce the density profile of the gas-jet, showing a density of 0.23 kg/m3 at maximum for a profile that is flat at the center of the jet and decreases beyond a certain radius using a gas pressure of 5 bar in the gas system and at 1.5ms after the nozzle was opened.