Testing and Characterization of SrI2:Eu2+ for Implementation in the PNG-Grand Experiment

For future planetary exploration, improved observational capabilities are needed for better understanding of planetary formation and dynamics through measurements of the spatial distribution of elemental and mineral abundances. Such improved in situ measurements require the development of sensitive tools. We are currently working with The Planetary Geochemistry Flight Instrumentation Group in the Astrochemistry Laboratory located at the NASA/GSFC on an existing project for this purpose. The group at Goddard, directed by Dr. Ann Parsons, has developed instrumentation that will determine complete bulk soil elemental composition, density, water content and layering configuration down to within 50 cm beneath the planetary surface without the need for drilling [Parsons 2011]. The instrument combines a Pulsed Neutron Generator, Gamma-Ray spectrometer and Neutron detector technologies, previously used for oil well logging. Gamma ray spectrometer detectors tested so far include the semi-conductors: HPGe, and CZT [Bodnarik 2010] while the scintillators are LaBr₃:Ce³⁺ and LaCl₃:Ce³⁺ [Parsons 2011]. We will be working with the Goddard group to test another scintillator developed at Fisk University, strontium iodide doped with europium (SrI2:Eu²⁺) since it has the potential of superseding the performance of LaBr₃:Ce³⁺. The SrI2(Eu²⁺) scintillator will be evaluated for its energy resolution, rise and decay constants and detection efficiency (compared with LaBr₃(Ce³⁺)) prior to taking it to NASA/GSFC. At Goddard, we will demonstrate the merits of the use of the SrI₂(Eu²⁺) in detecting hydrogenous material. We expect the SrI₂:Eu²⁺ technology could be used for a wide variety of solar system exploration and hard X-ray and gamma ray astrophysics applications.