Measurements of materials shielding properties with 1GeV/nuc 56Fe

Abstract

Abstract. The design of future spacecraft such as the Crew Exploration Vehicle must take into account the radiation shielding properties of both the structural components as well as dedicated shielding materials. Since modest depths of shielding stop the vast majority of Solar Energetic Particles (SEP), the greater challenge is posed by the need to shield crew from the Galactic Cosmic Rays (GCR), which include highly-charged and highly-energetic particles. Here, we report on results from tests performed with beams of 1 GeV/nuc 56 Fe at the Brookhaven National Laboratory. A wide variety of targets, both elemental and composite, were placed in the particle beams, and the spectra of particles emerging from the targets were measured using a stack of silicon detectors. Results are presented primarily in terms of dose reduction per g cm -2 of target material, and support the conclusions of an earlier calculation by Wilson et al. showing that performance improves as the shield's mass number decreases, with hydrogen being by far the most effective. The data also show that, as depth increases, the incremental benefit of adding shielding decreases, particularly for aluminum and other elements with higher atomic mass numbers.

Shielding experiments with high-energy heavy ions for spaceflight applications

“…Some of these modifications, in particular the increased complexity of the experimental trigger, complicate the data analysis. Nonetheless, we are able to present results that are directly comparable with our previous work in this area [6,7].…”

“…In [6], we showed that, as expected from the calculations in [8], hydrogen produces the greatest dose reduction per unit areal density of any shielding material for 1 GeV nucleon −1 56 Fe ions. As the mass number of the target nucleus increases, shielding effectiveness per unit mass decreases, also as predicted.…”

“…In our previous studies [6,7], we defined δ D n , the change in dose per incident beam ion, normalized (hence the subscript 'n') to the depth of the target in units of grams per square centimetre. For the planar geometry of our experiments, in which we always detect at least one charged particle emerging from the target for every incident primary ion, it is straightforward to show that the dose delivered by the mix of fragments and surviving primary ions (i.e.…”

“…Ideally, the hull of a spacecraft would also provide good shielding against GCR, but to date all spacecraft hulls have been made of aluminium alloys, and-as previous work shows-aluminium is far from optimal for radiation protection purposes. Also, as shown in [6], the shielding effectiveness of any material depends on the depth and composition of shielding that precedes it, as we will explain in more detail below.…”

Solid State Microdosimetry With Heavy Ions for Space Applications

“…Different accelerator facilities have in place different beam monitoring/modifying devices which can contribute to a different spectrum of secondary particles. The spectra of secondary particles in such heavy ion experiments can be significant (as evidenced in [30]) and can influence microdosimetry measurements.…”