API PNG Laboratory

We are establishing an Associated Particle Imaging Pulsed Neutron Generator (API PNG) laboratory in the School of Earth and Space Exploration at ASU. The facility is currently in the design and safety engineering phase: radiation shielding is being modeled with MCNP, and we are working with ASU Radiation Safety on the licensing and approvals needed to operate a neutron generator on campus.

How It Works

A pulsed neutron generator is a compact sealed-tube particle accelerator. Deuterium ions are accelerated into a tritium-loaded target, and each D-T fusion reaction emits a 14 MeV neutron together with an alpha particle in nearly the opposite direction (a deuterium-deuterium mode producing 2.45 MeV neutrons is also possible). In associated particle imaging, an embedded detector tags the alpha particle from each reaction. That coincidence gives the emission time and direction of the paired neutron, enabling time-of-flight measurements and depth-resolved, directional interrogation of a target rather than a simple integrated count. When the generator is powered off, no radiation is produced.

Planned Capabilities

• Active neutron imaging, scattering, and die-away experiments on planetary regolith simulants
• Capture gamma-ray spectroscopy for elemental analysis
• Characterization and calibration of flight-heritage detector technologies, including CLYC and LaBr₃ scintillators, building on our LunaH-Map, Lunar-VISE, and SINGR instrument lineage
• Validation targets for our GEANT4 and MCNP radiation transport models
• Applied measurements for environmental and materials applications, including radiation effects testing

Collaborations

The laboratory design builds on our associated particle imaging experiments with collaborators at Lawrence Berkeley National Laboratory, where D-T generator measurements with CLYC and LaBr₃ detectors on regolith simulant targets demonstrated depth-resolved sensing of buried hydrogen-bearing layers.

Related Publications

• Ölçek, D., Ayllon Unzueta, M., Hardgrove, C., Persaud, A. (2026). Concept development of an active fast neutron backscatter imaging technique for planetary subsurface studies. Nucl. Instrum. Methods Phys. Res. A.
• Heffern, L.E., Hardgrove, C.J., et al. (2021). Active neutron interrogation experiments and simulation verification using the SINGR spectrometer for geosciences. Nucl. Instrum. Methods Phys. Res. A.
• Prettyman, T.H., Hardgrove, C., et al. (2025). Gamma-ray and neutron spectrometers for lunar science and exploration. Proc. SPIE 13621.