The production of low-energy neutrons for the RHMMS

Neutron interrogation is used in both the active neutron measurement cell for the identification of fissile materials and in the hazardous material cell for the capture gamma identification of the hazardous elements in waste. The use of radiological neutron sources and neutron generators, using the deuterium/tritium or deuterium/deuterium reactions for neutron production, results in the production of high energy neutrons. For most materials the high absorption cross sections are in the neutron thermal energy range. The moderation of the high energy neutrons to provide a high ratio thermal/epithermal spectrum is difficult. The effort herein reported seeks to find methods of producing neutrons at much lower energy levels, preferably below 200 KeV. 1 ref., 2 tabs

Programmable multi-timer for TRU waste analysis applications

A programmable, multiple-function timing module has been developed for use in transuranic (TRU) waste analysis applications at the Idaho National Engineering Laboratory. The Programmable Multi-Timer (PRMT) is an expanded version of a module originally built for accelerator-based active photon interrogation experiments. During the course of the experiments, it became obvious that a more versatile timer was needed to meet several unforeseen requirements. The PRMT was designed to meet the new requirements and to serve as a general-purpose timing module for other applications

Neutron ion temperature measurement

One important use of fusion product diagnostics is in the determination of the deuterium ion temperature from the magnitude of the 2.5 MeV d(d,n)/sup 3/He neutron emission. The detectors, calibration methods, and limitations of this technique are reviewed here with emphasis on procedures used at PPPL. In most tokamaks, the ion temperature deduced from neutrons is in reasonable agreement with the ion temperature deduced by other techniques

Fusion-neutron production in the TFTR with deuterium neutral beam injection

We report measurements of the fusion reaction rate in the Tokamak Fusion Test Reactor (TFTR) covering a wide range of plasma conditions and injected neutral beam powers up to 6.3 MW. The fusion-neutron production rate in beam-injected plasmas decreases slightly with increasing plasma density n/sub e/, even though the energy confinement parameter n/sub e/tau/sub E/ generally increases with density. The measurements indicate and Fokker-Planck simulations show that with increasing density the source of fusion neutrons evolves from mainly beam-beam and beam-target reactions at very low n/sub e/ to a combination of beam-target and thermonuclear reactions at high n/sub e/. At a given plasma current, the reduction in neutron source strength at higher n/sub e/ is due to both a decrease in electron temperature and in beam-beam reaction rate. The Fokker-Planck simulations also show that at low n/sub e/, plasma rotation can appreciably reduce the beam-target reaction rate for experiments with co-injection only. The variation of neutron source strength with plasma and beam parameters is as expected for beam-dominated regimes. However, the Fokker-Planck simulations systematically overestimate the measured source strength by a factor of 2 to 3; the source of this discrepancy has not yet been identified

Count rate performance of a microchannel plate photomultiplier

The count rate dependent gain change of a microchannel plate photomultiplier has been measured. Gain changes of 60% have been observed for count rates in excess of 2 x 10/sup 5/ s/sup -1/. The microchannel plate photomultiplier was used as a multiplying element of a scintillation detector system using NaI(Tl) as the scintillator. Data are compared to a simplified model of this form of photomultiplier

Electronics system for transuranic waste assays

A slagging pyrolysis incinerator has been proposed to reduce the volume of stored transuranic (TRU) waste material. This report describes the electronics developed for a fast TRU waste assay system using photon interrogation. The system uses a pulsed electron beam from a linear accelerator to produce a high-energy photon burst, termed the gamma flash, from a metallic converter. The photons induce fission in the TRU. A high-rate counting system is used to relate the production rate of photon induced neutrons to the amount of fissile material present in the waste