Design and Testing of a High Pressure Gas Target for Fast Neutron Resonance Radiography

Abstract

A high pressure deuterium gas target has been designed to provide high-flux fast neutrons using the D(d,n)3He reaction for use as a neutron source. The deuterium gas cell holds 4 atm D2 gas at 298 K and is projected to tolerate a beam current of ~50 muA of 3.0 MeV deuterons for 8 hours of continuous use. The high-pressure gas cell is designed to provide a fast neutron flux on the order of 105 n/cm2-s at one meter. Measurements of gamma ray production from deuterium impingement have shown tungsten to generate the fewest gamma rays; the primary components of the gas target have been constructed out of tungsten to decrease the number of gamma rays. To accommodate the high gas pressure, thin foil tungsten windows have been structurally reinforced with a tungsten support allowing for more than 60% beam transmission while greatly increasing the structural reliability of the thin windows. Extensive simulation and experimental testing have demonstrated the heating tolerances of the gas target thin windows and have shown that the peak temperature of the thin foils does not exceed 600degC, while the edges of the foil do not exceed 100degC, well within the limits of the foil windows and the gas sealing structures