New Neutron Detectors with Pulse Shape Discrimination

Proliferation of the weapons of mass destruction such as nuclear weapons is a serious threat in the world today. Preventing the spread of nuclear weapons has reached a state of heightened urgency in recent years, especially since the events on September 11, 2001 and its aftermath. One way to passively determine the presence of nuclear weapons is to detect and identify characteristic signatures of highly enriched uranium and weapons grade plutonium. Neutrons and gamma rays are two signatures of these materials. Gamma ray detection techniques are useful because the presence of gamma rays of specific energies can confirm the presence of a particular isotope. This technique however, has one significant drawback: In the presence of dense surrounding material such as lead, gamma ray attenuation can be significant. This can mask the gamma signatures of these special nuclear materials(SNM). Neutrons, on the other hand, easily penetrate dense, high atomic number materials compared to gamma-rays. Under these circumstances, passive assay techniques based on neutron detection can provide valuable information. When detected, neutrons are direct indicator of presence of spontaneously fissioning isotopes (plutonium and californium) and induced fissions (uranium). At present, there is a real need for a compact, efficient detection system that would allow neutron detection with an ability to discriminate gamma events from neutron events. The goal of the proposed effort is to address this need.