SINGR (PhD Research)

I am currently working with Dr. Craig Hardgrove on development and/or characterization of a variety of nuclear spectroscopy instruments including SINGR, LunaH-Maps’ Mini-NS, MiniPNG, and various CLYC scintillator detectors. My responsibilities consist of developing techniques using active neutron sample analysis with DT generators and dual scintillator detectors such as CLYC. Our testing is done in collaboration with both NASA Goddard Space Flight Center (GSFC) and Los Alamos National Labs (LANL). I have been debugging and characterizing electronic systems for use with CLYC pulse-shape discrimination algorithms, in collaboration with RMD Inc. and ASU’s EEE dept.

The SIngle-scintillator Neutron and Gamma Ray spectrometer (SINGR) can be used on future rovers or landers where the mission science goals include characterization of the hydrogen content, the depth distribution of hydrogen, and the bulk geochemistry of a planetary surface.

A neutron generator is used to create the source term in place of GCRs. The neutrons then interact with the nuclei of the material in the surface of a body (up to ~ 1 meter in depth), resulting again in the emission of thermal neutrons and/or gamma-rays. Neutron die-away experiments count neutrons by their arrival time (time resolved data) after the PNG pulse and are used to determine the hydrogen abundance, the hydrogen distribution with depth, and the macroscopic absorption cross section of planetary surfaces.
Photograph of the basalt monument at the GSFC GGAO test site. The SINGR detector and PNG are fastened to the aluminum scaffolding above the monument in order to keep a constant, measured distance (80 cm in our studies) from the surface, and to mimic the use of the system onboard a rover.
We used six different polyethylene geometry set-ups to simulate an increase in wt% H abundance, including one buried polyethylene set-up to demonstrate H distribution with depth.
The shape of the neutron die-away curve changes significantly for low amounts of H (~0 to 6 wt.% WEH in top 2” layer), as shown in A for the bare and poly1 set-ups. However, for high amounts of H (⪆10 wt.% WEH in top 2” layer) the normalized curves are no longer distinguishable between measurements (poly1 through 3 and polytope, B).

Abstracts/Presentations:

LPSC 2020 E-Poster

Publications in prep:

  • Working Title: Pulsed Neutron Investigations of Planetary Surfaces using a Single Detector System: Field Experiments and Data

Working Abstract:
Gamma-ray and neutron spectrometers (GRNS) can be used to determine the hydrogen content and elemental abundances within the top ~tens of cms of planetary surfaces. Through the added use of a D-T (Deuterium-Tritium) pulsed neutron generator (PNG) GRNS can more rapidly characterize a planet’s surface material; this makes active GRNS useful for roving and landed missions. The SIngle-scintillator Neutron and Gamma Ray spectrometer (SINGR) instrument was characterized for use with both passive and active techniques on a rover/lander scale. Active GRNS measurements were performed with SINGR at the NASA Goddard Space Flight Center (GSFC) Goddard Geophysical and Astronomical Observatory (GGAO) outdoor test site to interrogate geologically relevant materials (Mars, the Moon, Titan) and to demonstrate the capability of a dual-use scintillator to provide neutron and gamma-ray spectroscopy using a PNG. By running the neutron generator in a pulsed mode (250 – 1000 Hz), GRNS responses can be studied both during and between pulses. We successfully constructed neutron die-away curves (i.e. bulk hydrogen abundance with depth distribution) as well as gamma-ray spectra (i.e. Fe, Si, Al, O, K, Th abundances). We investigated planetary analog materials such as basalt (volcanic, extrusive), granite (crustal, intrusive, high Th & K), polyethylene (ice, water, hydrated material simulant), and organic (milorganite fertilizer) for our measurements; we also acquired neutron die-away data for low to high amounts of H. These experiments contribute to a better understanding of instruments that will be useful for landed missions to Mars, the Moon, Titan, and other planetary bodies.

  • Working Title: Pulsed Neutron Investigations of Planetary Surfaces: Simulations and Sensitivity

Working Abstract:
Information about the elemental composition of a planetary surface can be determined through the use of nuclear instrumentation, such as neutron spectrometers (NS) and gamma-ray spectrometers (GRS). The overall goal of this research is to develop and characterize dual instrument gamma-ray and neutron spectrometers (GRNS) for detecting neutrons and gamma-rays to measure planetary surface composition. This paper explores the possible uses of a variety of gamma-ray and neutron spectrometers, via simulations using MCNP 6.1, for a variety of different landed planetary scenarios on Mars, Titan, and the Moon.