Rotating Aperture Deuterium Gas Cell Development for High Brightness Neutron Production

Work is underway at LLNL to design and build a high-brightness mono-energetic source for fast neutron imaging. The approach being pursued will use a 7-MeV deuterium linac for producing high-energy neutrons via a D(d,n)³He reaction. To achieve a high-brightness neutron source, a windowless rotating aperture gas cell approach is being employed. Using a series of close-tolerance rotor and stator plates, a differential pumping assembly was designed and built that contains up to 3 atmospheres of deuterium gas in a 40-mm-long gas cell. Rarefaction of the gas due to beam-induced heating will be addressed by rapidly moving the gas across the beam channel in a cross flow tube. The design and fabrication process was guided by extensive 3D modeling of the hydrodynamic gas flow and structural dynamics of the assembly. Summaries of the modeling results, the fabrication of the rotating aperture system, and initial measurements of gas leakage are presented.