A background-free direction-sensitive neutron detector

Abstract

We show data from a new type of detector that can be used to determine the neutron flux, the energy distribution, and the direction of motion neutron for both fast and thermal neutrons. Many neutron detectors are plagued by large backgrounds from X-rays and gamma rays, and most current neutron detectors lack single-event energy sensitivity or any information on neutron directionality. Even the best detectors are limited by cosmic ray neutron backgrounds. All applications (neutron scattering and radiography, measurements of solar and cosmic ray neutron flux, measurements of neutron interaction cross-sections, monitoring of neutrons at nuclear facilities, oil exploration, and searches for fissile weapons of mass destruction) will benefit from the improved neutron detection sensitivity and improved measurements of neutron properties made possible by this detector. The detector is free of backgrounds from X-rays, gamma rays, beta particles, relativistic singely charged particles, and cosmic ray neutrons. It is sensitive to thermal neutrons, fission neutrons, and high energy neutrons with detection features distinctive for each energy range. It is capable of determining the location of a source of fission neutrons based on the characteristics of elastic scattering of neutrons by helium nuclei. The detector we have constructed could identify 1 g of reactor grade plutonium, 1 m away, with less than 1 min of observation time.