Material selection to reduce neutron activation in a petawatt laser target chamber

Abstract

Various types of ionizing radiation can be produced by petawatt lasers including high energy x-rays, neutrons, and gamma radiation. The radiation production depends greatly on the target materials being used. The ionizing radiation production was estimated by calculation based on the information available during the facility design. The petawatt laser system has an output energy of 640 joules and pulse duration of 400 femtosecond. Prompt radiation, such as x-ray and neutrons, are instantaneous and cease when the laser beam is terminated; however, some materials will become radioactive through neutron activation and will emit radiation after termination of the laser beam. The amount of induced radioactivity by neutron activation depends on many factors which will be discussed. Ionizing radiation exposure to researchers, workers, or the general public depends on a number of factors, such as: emitted radiation types, radioactive half-lives, presence of shielding material, general working environment and occupancy factors, etc. The potential radiation hazards may be minimized by evaluating the induced radioactivity in materials and avoiding materials that produce long-lived radioisotopes and radiation that are difficult to shield.Instrument component materials for this laser facility are considered based on evaluation of then neutron activation potential. Radioisotope production in an aluminum alloy 6061 and steel alloy 1040 target chamber were determined. A deuterium (D) and tritium (T) mixture for the target is assumed and associated with 14.1 MeV neutrons produced from the D-T fusion reaction. The atom populations, induced radioactivity from neutron activation, and gamma radiation exposures were calculated. The results of this evaluation are considered in the selection of target chamber structural material. In this case, steel alloy 1040 presented the least radiological hazard to workers.Various types of ionizing radiation can be produced by petawatt lasers including high energy x-rays, neutrons, and gamma radiation. The radiation production depends greatly on the target materials being used. The ionizing radiation production was estimated by calculation based on the information available during the facility design. The petawatt laser system has an output energy of 640 joules and pulse duration of 400 femtosecond. Prompt radiation, such as x-ray and neutrons, are instantaneous and cease when the laser beam is terminated; however, some materials will become radioactive through neutron activation and will emit radiation after termination of the laser beam. The amount of induced radioactivity by neutron activation depends on many factors which will be discussed. Ionizing radiation exposure to researchers, workers, or the general public depends on a number of factors, such as: emitted radiation types, radioactive half-lives, presence of shielding material, general working environment and occu...