Improving a high-power laser based relativistic electron source: the role of laser pulse contrast and gas jet density profile

Abstract A relativistic electron source based on high power laser interaction with gas jet targets has been developed at the Institute of Plasma Physics & Lasers of the Hellenic Mediterranean University. Initial measurements were conducted using the “Zeus” 45 TW laser with peak intensities in the range of 10 18 -10 19 W/cm 2 interacting with a He pulsed gas jet having a 0.8 mm diameter nozzle. A significant improvement of the electron signal was measured after using an absorber to improve the laser pulse contrast from 10 -10 to 10 -11 . A high stability quasi-monoenergetic electron beam of about 50 MeV was achieved and measured using a magnetic spectrometer for pulsed gas jet backing pressure of 12 bar. Supplementary studies using a 3 mm diameter nozzle for backing pressures in the range of 35 to 40 bar showed electron beam production with energies spread in the range from 50 to 150 MeV. The pulsed jet density profile was determined using interferometric techniques. Particle-in-cell (PIC) simulations, at the above experimentally determined conditions, support our experimental findings.