Microfabrication of a gadolinium-derived solid-state sensor for thermal neutrons

Area of Science:

• Materials Science
• Nuclear Instrumentation
• Semiconductor Physics

Background:

• Conventional neutron sensors face limitations in size, weight, cost, portability, and reliance on helium.
• There is a need for advanced neutron detection technologies for both civilian and military applications.

Purpose of the Study:

• To describe the microfabrication of gadolinium (Gd) conversion material-based heterojunction diodes for thermal neutron detection.
• To utilize electrical signals from internal conversion electrons (ICEs) for neutron sensing.

Main Methods:

• Microfabrication of Gd-based heterojunction diodes using radiofrequency sputtering.
• Development of stress-free Gd coatings with a neodymium-doped aluminum cap layer for stability.
• Integration of Gd directly onto the diode surface to maximize electron capture efficiency.

Main Results:

• Achieved stable Gd coatings with excellent shelf-life (≥6 years).
• Demonstrated a 200-fold increase in electron capture efficiency by eliminating the air gap.
• Reported fast detection (within 10 min) with optimal Gd thickness (10.4 μm) and diode configuration.
• Modeled ICE energies and correlated experimental results with theoretical predictions.

Conclusions:

• Semiconductor thermal neutron detectors offer significant advantages for field-sensing of radioactive neutron sources.
• The developed microfabricated diodes provide a compact, stable, and efficient solution for thermal neutron detection.
• This technology enhances sensitivity and specificity through optimized material deposition and detector design.