Development of portable long counter with two different moderator materials

Area of Science:

• Nuclear instrumentation
• Neutron detection physics

Background:

• Traditional neutron detectors can be bulky and lack a flat energy response.
• Accurate neutron energy spectrum measurement is crucial for applications like nuclear safeguards and radiation protection.

Purpose of the Study:

• To develop a portable, lightweight long counter (LC) with a broad and flat neutron energy response.
• To improve sensitivity to low-energy neutrons using advanced moderator materials.

Main Methods:

• Design and construction of a compact LC incorporating a Helium-3 (He-3) thermal neutron detector, moderator, and shielding.
• Utilized polystyrene instead of polyethylene in the moderator to enhance low-energy neutron sensitivity.
• Employed the MCNP (Monte Carlo N-Particle) code for response function calculations.
• Validated simulation results through experiments using monoenergetic neutron calibration fields.

Main Results:

• Successfully developed a portable LC with dimensions of 11 cm radius and 39 cm length, weighing 15 kg.
• Achieved an almost flat response function for neutrons in the energy range of 0.4 eV to 5 MeV.
• MCNP simulations showed good agreement with experimental data, confirming the detector's performance.

Conclusions:

• The developed portable long counter meets design specifications for weight, size, and energy response.
• The use of polystyrene effectively increased sensitivity to low-energy neutrons.
• The validated design provides a reliable tool for neutron detection across a wide energy spectrum.