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Proceedings Paper

Strontium iodide gamma ray spectrometers for planetary science (Conference Presentation)
Author(s): Thomas H. Prettyman; Emmanuel Rowe; Jarrhett Butler; Michael Groza; Arnold Burger; Naoyuki Yamashita; James L. Lambert; Keivan G. Stassun; Patrick R. Beck; Nerine J. Cherepy; Stephen A. Payne; Julie C. Castillo-Rogez; Sabrina M. Feldman; Carol A. Raymond

Paper Abstract

Gamma rays produced passively by cosmic ray interactions and by the decay of radioelements convey information about the elemental makeup of planetary surfaces and atmospheres. Orbital missions mapped the composition of the Moon, Mars, Mercury, Vesta, and now Ceres. Active neutron interrogation will enable and/or enhance in situ measurements (rovers, landers, and sondes). Elemental measurements support planetary science objectives as well as resource utilization and planetary defense initiatives. Strontium iodide, an ultra-bright scintillator with low nonproportionality, offers significantly better energy resolution than most previously flown scintillators, enabling improved accuracy for identification and quantification of key elements. Lanthanum bromide achieves similar resolution; however, radiolanthanum emissions obscure planetary gamma rays from radioelements K, Th, and U. The response of silicon-based optical sensors optimally overlaps the emission spectrum of strontium iodide, enabling the development of compact, low-power sensors required for space applications, including burgeoning microsatellite programs. While crystals of the size needed for planetary measurements (>100 cm3) are on the way, pulse-shape corrections to account for variations in absorption/re-emission of light are needed to achieve maximum resolution. Additional challenges for implementation of large-volume detectors include optimization of light collection using silicon-based sensors and assessment of radiation damage effects and energetic-particle induced backgrounds. Using laboratory experiments, archived planetary data, and modeling, we evaluate the performance of strontium iodide for future missions to small bodies (asteroids and comets) and surfaces of the Moon and Venus. We report progress on instrument design and preliminary assessment of radiation damage effects in comparison to technology with flight heritage.

Paper Details

Date Published: 2 November 2016
PDF: 1 pages
Proc. SPIE 9968, Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XVIII, 99680H (2 November 2016); doi: 10.1117/12.2237919
Show Author Affiliations
Thomas H. Prettyman, Planetary Science Institute (United States)
Emmanuel Rowe, Fisk Univ. (United States)
Jarrhett Butler, Fisk Univ. (United States)
Vanderbilt Univ. (United States)
Michael Groza, Fisk Univ. (United States)
Arnold Burger, Fisk Univ. (United States)
Naoyuki Yamashita, Planetary Science Institute (United States)
James L. Lambert, Jet Propulsion Lab. (United States)
Keivan G. Stassun, Vanderbilt Univ. (United States)
Patrick R. Beck, Lawrence Livermore National Lab. (United States)
Nerine J. Cherepy, Lawrence Livermore National Lab. (United States)
Stephen A. Payne, Lawrence Livermore National Lab. (United States)
Julie C. Castillo-Rogez, Jet Propulsion Lab. (United States)
Sabrina M. Feldman, Jet Propulsion Lab. (United States)
Carol A. Raymond, Jet Propulsion Lab. (United States)

Published in SPIE Proceedings Vol. 9968:
Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XVIII
Ralph B. James; Michael Fiederle; Arnold Burger; Larry Franks, Editor(s)

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