Double differential neutron yields from thick targets used in space applications

Natalie A Mcgirl,Ashwin P Srikrishna,Adam Rusek,Steve Blattnig,Cary Zeitlin,Tony Slaba,Martha Clowdsley,Luis A Castellanos,Michael Sivertz,Chiara La Tessa,Lawrence H Heilbronn

doi:10.1051/epjconf/201715304002

Abstract

In March 2016, secondary neutron production from thick-target shielding experiments were conducted at the National Aeronautics and Space Administration’s (NASA) Space Radiation Laboratory at Brookhaven National Laboratory. Ion beams of proton, helium, and iron projectiles were aimed at aluminum targets with areal densities of 20, 40, and 60 g/cm2 . The ion beams were extracted at energies of 400 and 800 AMeV and neutron yields were measured with liquid scintillators at 10°, 30°, 45°, 60°, 80°, and 135° off the beam axis. A second 60 g/cm2 aluminum target was placed 3.5 m downstream from the middle of front target to study backscattered neutrons. Double differential thick-target neutron yields for various combinations of projectile, projectile energy, target material, target thickness, and detector location were produced using the time-of-flight technique. These measurements will help NASA perform uncertainty analyses on their transport codes and contribute to shielding design studies for future space applications.

Highlights

The future of manned, deep-space missions includes the need to sufficiently protect astronauts from the ionizing radiation effects caused by Solar Energetic Particles (SEP) and Galactic Cosmic Rays (GCR) for an extended length of time
The purpose of this study is to determine the double differential thick-target yields for neutrons produced directly from GCR-like heavy ion interactions with aluminum or high density polyethylene (HDPE) shielding. These results will be compared with transport model calculations and incorporated into the uncertainty analysis for transport codes developed by the National Aeronautics and Space Administration (NASA)
Neutrons and light charged ions were measured at six angular locations off beam axis using EJ301 and EJ-309 liquid scintillators

Summary

Introduction

The future of manned, deep-space missions includes the need to sufficiently protect astronauts from the ionizing radiation effects caused by Solar Energetic Particles (SEP) and Galactic Cosmic Rays (GCR) for an extended length of time. Habitats and other transit vehicles often contain areas of thick (30-40 g/cm or greater) shielding materials such as aluminum or high density polyethylene (HDPE) [1]. Thickly-shielded environment may decrease an astronaut’s exposure to the primary radiation field, the creation of a secondary radiation field, which includes neutrons and light charged ions, still poses a risk [2]. The purpose of this study is to determine the double differential thick-target yields for neutrons produced directly from GCR-like heavy ion interactions with aluminum or HDPE shielding. These results will be compared with transport model calculations and incorporated into the uncertainty analysis for transport codes developed by the National Aeronautics and Space Administration (NASA). This paper presents a selection of results from an experiment conducted in March 2016

Experiment Overview

Neutron Time of Flight Analysis

Selection of Experimental Results

Future Work

Findings

Summary