Thick-target yields of secondary ions and neutrons for validation of radiation transport codes

摘要

This paper presents the yields of secondary light ions and neutrons produced from bombardments of thick targets of aluminum by protons, helium, and iron ions. In March 2016, ion beams of 400- and 800-MeV protons, 400-AMeV helium, and 400- and 800-AMeV iron bombarded aluminum targets of 20, 40, and 60 g/cm thickness at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory (BNL) over the course of 100 hours. An additional aluminum target of thickness 60 g/cm was placed 3.5 meters downstream to model the increased secondary particle yields in an enclosed space. Surveys of neutrons and light ions were taken with organic liquid scintillators at six angles between 10° and 135° off beam axis, with further light ion measurements taken with pairs of sodium iodide (NaI) detector arrays at two positions between 10° and 30°. Utilizing the organic scintillators, neutron events were isolated with pulse shape discrimination, while charged particles were discerned by comparing energy deposited in the detector and time of flight. Energy spectra were then obtained by using time-of-flight analysis techniques. Light ion spectra were generated using NaI detector array data by comparison of energy deposition between the NaI detectors pairs. These results will be compared to simulations of the experiment calculated by MCNP6. This experiment is a part of a multi-year project to supplement the amount of measured data available for validation and verification of radiation transport computer codes used in quantifying radiation exposure and assessing cancer risk incurred during manned space flight missions.