Measurements of Ionizing Radiation Doses Induced by High Irradiance Laser on Targets in LCLS MEC Instrument

Comprehensive measurements for photon and neutron radiation doses generated from laserplasma interaction at SLAC’s MEC laser facility have been conducted. The goals of the measurements were to: 1. determine the radiation dose per laser shot as a function of laser, optic and target parameters that are relevant to the MEC laser operations, 2. validate the RPD-developed analytic model for photon dose calculations, and 3. evaluate the performance of various types of passive and active detectors in the laserinduced radiation fields. The MEC radiation measurements had laser irradiance between 3x10 16 and 6x10 17 W/cm 2 (about 30 to 150 mJ per pulse and 40 fs) hitting mainly thin gold and copper target plates. Radiation measurements with 10 Hz of laser pulses rastering over the target surface were conducted at various distances and angles relative to laser beam and target using a comprehensive set of passive and active detectors placed inside and outside the MEC aluminum target chamber, as well as outside the MEC hutch 6. Both passive and active detectors measured photon doses that agree with the RPD dose model calculations in this irradiance range. Active detectors were not affected by the electromagnetic pulses associated with the laser operation. Work supported in part by US Department of Energy under contract DE-AC02-76SF00515.