Cosmogenic radionuclide production modeling with Geant4: Experimental benchmarking and application to nuclear spectroscopy of asteroid (16) Psyche

NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS

卷:446

Article

Peplowski, Patrick N.¹  Wilson, Jack T.¹  Burks, Morgan²  Beck, Andrew W.¹  Jun, Insoo³  Lawrence, David J.¹  Yokley, Zachary W.¹ 

[1] Johns Hopkins Appl Phys Lab, 11100 Johns Hopkins Rd, Laurel, MD 20723 USA

[2] Lawrence Livermore Natl Lab, 7000 East Ave, Livermore, CA 94550 USA

[3] CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA

关键词: Gamma-ray spectroscopy;    Geant4;    Cosmogenic radionuclides;    Activation;    Asteroid;    Planetary gamma-ray spectroscopy;   

DOI  :  10.1016/j.nimb.2019.03.023

来源: Elsevier

【 摘 要 】

Measurements of gamma-ray emissions from the decay of cosmogenic radionuclides provide an opportunity to characterize the elemental composition of a terrestrial planet or asteroid surface. We report on the development of a Geant4 application which models cosmogenic radionuclide production on metal-rich surfaces. The model was benchmarked using measurements of radionuclides produced during 1 GeV proton irradiation of a target made from the Campo del Cielo iron meteorite. The gamma-ray emitting radionuclides Co-58, Co-57, Co-56, Mn-54, Mn-52, Cr-51, V-48, Sc-46 and Na-22 were observed following the irradiation. Our model reproduced the measured radionuclide production rates to within a factor of 2.5 or better. All but two of the elements (Mn-54, Sc-46) have a perfect model-to-data match within their measurement uncertainties. The benchmarked model was used to predict cosmogenic radionuclide production on a large (similar to 100-km radius) metal-rich asteroid. The results are relevant for planned gamma-ray measurements of the metallic asteroid (16) Psyche, which will be visited by the Psyche spacecraft in 2026. We found that galactic-proton-induced radionuclide decay is unlikely to be observed by the Psyche Gamma-Ray Spectrometer (GRS), however an intense solar proton event ( > 2 x 10(6) protons cm(-2) over < 5 days) will produce measurable quantities of radioisotopes. Measurements of these radioisotopes could provide an independent method of determining the Ni-to-Fe ratio of materials at Psyche's surface. Such an analysis will require the use of radionuclide production cross sections to convert GRS-measured cosmogenic radionuclide decay rates to elemental composition information with the similar to 10% precision required for planetary geochemical studies.

【 授权许可】

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