SINGR (PhD Research)

I am currently working with Dr. Craig Hardgrove on development and 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. Image from Julia Bodnarik’s thesis.
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.
The six different top layer high-density polyethylene (HDPE) tile configurations used for the basalt and granite monuments, and the buried configuration used in the basalt monument. The small, white squares represent HDPE while the large, gray squares represent the underlying monument material. The full tile layer of HDPE in the buried configuration can be buried under layers of basalt plates to achieve a variety of burial depths.
Neutron die-away curves showing experimental results and simulated results side-by-side, focused on the neutron die-away region (200 – 2250 us). (A & D) The basalt monument experiment using the HDPE configurations. (B & E) MCNP 6.1 simulations of the HDPE configurations on the basalt monument with 0.25 wt % H throughout the basalt. (C & F) MCNP 6.1 simulations of the bare (no HDPE tiles modeled) monument with change in H from 0 – 50 wt % throughout the basalt. Note that curves (A) – (C) are normalized to the PNG output pulse region (0 – 200 us), and curves (D) – (F) are normalized to the thermal neutron return region (330 – 900 us). The magnitude of the die-away curve in the thermal region is expected to increase as wt % H increases (gray arrows), as shown in the pulse normalized plots (A – C). The shape of the die-away curve is expected to change from 0 – 2.5 wt % H, shifting slightly from right to left time bins. The change in shape is shown in plots D & E between bare and single HDPE tile curves, the change in shape for plot F is seen in light blue curves from 0 – 2.5 wt % H.

Abstracts/Presentations:

LPSC 2020 E-Poster

Accepted, 2021:

  • Active neutron interrogation experiments and simulation verification using the SIngle-scintillator Neutron and Gamma-Ray spectrometer (SINGR) for geosciences

Abstract:
We present a new SIngle-scintillator Neutron and Gamma Ray spectrometer (SINGR) instrument for use with both passive and active measurement techniques. Here we discuss the application of SINGR for planetary exploration missions, however, hydrology, nuclear non-proliferation, and resource prospecting are all potential areas where the instrument could be applied. SINGR uses an elpasolite scintillator, Cs2YLiCl6:Ce (CLYC), that has been shown to have high neutron efficiency even at small volumes, with a gamma-ray energy resolution of approximately 4% full-width-at-half-maximum at 662 keV. Active gamma-ray and neutron (GRNS) measurements were performed with SINGR at the NASA Goddard Space Flight Center (GSFC) Goddard Geophysical and Astronomical Observatory (GGAO) outdoor test site using a pulsed neutron generator (PNG) to interrogate geologically relevant materials (basalt and granite monuments). These experimental results, combined with simulations, demonstrate that SINGR is capable of generating neutron die-away curves that can be used to reconstruct the bulk hydrogen abundance and the depth distribution of hydrogen within the monuments. We compare our experimental results with Monte Carlo N-Particle (MCNP) 6.1 transport simulations to constrain the uncertainties in depth and hydrogen abundance from the neutron die-away data generated by SINGR. For future planetary exploration missions, SINGR provides a single detector system for interrogating the shallow subsurface to characterize the presence and abundance of hydrated phases and to provide bulk elemental analysis.

Publications in prep:

  • 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.