Title: Development of a lithium-glass based composite neutron detector for He replacement

Radiation portal monitors used for interdiction of illicit materials at borders include highly sensitive neutron detection systems. The main reason for having neutron detection capability is to detect fission neutrons from plutonium. The currently deployed radiation portal monitors (RPMs) from Ludlum and Science Applications International Corporation (SAIC) use neutron detectors based upon 3He-filled gas proportional counters, which are the most common large neutron detector. There is a declining supply of 3He in the world and, thus, methods to reduce the use of this gas in RPMs with minimal changes to the current system designs and sensitivity to cargo-borne neutrons aremore » being investigated. Four technologies have been identified as being currently commercially available, potential alternative neutron detectors to replace the use of 3He in RPMs. Reported here are the results of tests of the lithium-loaded glass fibers option. This testing measured the neutron detection efficiency and gamma ray rejection capabilities of a small system manufactured by Nucsafe (Oak Ridge, TN).« less

A gamma-free neutron-sensitive scintillator is needed to enhance radiaition sensing and detection for nonproliferation applications. Such a scintillator would allow very large detectors to be placed at the perimeter of spent-fuel storage facilities at commercial nuclear power plants, so that any movement of spontaneously emitted neutrons from spent nuclear fuel or weapons grade plutonium would be noted in real-time. This task is to demonstrate that the technology for manufacturing large panels of fluor-doped plastic containing lithium-6 phosphate nanoparticles can be achieved. In order to detect neutrons, the nanoparticles must be sufficiently small so that the plastic remains transparent. In thismore » way, the triton and alpha particles generated by the capture of the neutron will result in a photon burst that can be coupled to a wavelength shifting fiber (WLS) producing an optical signal of about ten nanoseconds duration signaling the presence of a neutron emitting source.« less

A proposed high-flux high energy fusion materials irradiation facility uses a deuteron beam impinging on a lithium target to produce neutrons with a spectrum that peaks around 14 MeV. The lithium target consists of a jet of liquid lithium of appropriate thickness. The lithium target development activity is examining the possibility of creating a stable planar free jet of desirable thermal hydraulic characteristics through magnetohydrodynamic body forces created by a DC magnetic field.

This report covers the period of work from December 1, 1986 through November 30, 1987. The work on mercuric iodide has now entered a new and more developmental phase with support now being obtained from other agencies (NIH, NASA, JPL, the CalTech President's Fund etc.) for specific, directed applications. These include development of arrays of HgI/sub 2/ x-ray spectrometers for synchrotron radiation application supported by NIH and for long term space mission use supported by NASA. It has been undertaken during the past year (with some work done in the previous year) to re-examine the technology of high field ''avalanche''more » radiation detector structures which use the ''controlled surface'' principle as developed previously under DOE sponsorship. This was undertaken because of the advent of a fundamental advance in silicon single crystal technology -''neutron transmutation doped'' or ''NTD'' single crystal. This new material conceptually solves a basic problem that previously halted the development of these potentially useful radiation detection structures. That problem was the non-uniform, (or ''striated'') distribution of donor impurities which adversely affected electric field distribution and thus attainable avalanche gain in these structures. A new effort started late in the year springs from the development of high critical temperature superconducting ceramic compounds. In essence, the phenomenon of superconductivity can now be achieved at temperatures reached by liquid nitrogen rather than expensive and more complicated cryogenic helium. This, in essence, then brings superconductivity into the same temperature range where lithium drifted silicon and intrinsic germanium already operate. The usefulness of superconductivity in detection and spectroscopy of ionizing radiations based on the narrow superconductive band gap is very appealing and we have begun theoretical (presented herein) and experimental studies investigating these new materials.« less