The Lawrence Berkeley National Laboratory and Adelphi Technology Inc. have developed a series of high-yield neutron generators using the D-D reaction with an axial geometry. They operate with a single ion beam and can have a small origin size useful for immediate moderation and a high concentration of thermal neutrons. The generator uses RF induction discharge to efficiently ionize the deuterium gas. This discharge method provides high plasma density for high output current, high atomic species from molecular gases, long life operation and versatility for various discharge chamber geometries. These generators are open systems that can be actively pumped for a continuous supply of deuterium gas further increasing the generator's expected lifetime. Since the system is open, many of the components, including the target, can be easily replaced. Pulsed and continuous operation has been demonstrated. In either mode of operation these generators have been used for Prompt Gamma Neutron Activation Analysis (PGNAA) and neutron activation analysis (NAA). Carleton University and Heliocentric Technologies are developing an Elemental Analyzer based on this neutron source.
High-intensity fast white neutron pulses are needed for pulsed fast neutron transmission spectroscopy ͑PFNTS͒. A compact tritium-tritium fusion reaction neutron generator with an integrated ion beam chopping system has been designed, simulated, and tested for PFNTS. The design consists of a toroidal plasma chamber with 20 extraction slits, concentric cylindrical electrodes, chopper plates, and a central titanium-coated beam target. The total ion beam current is 1 A. The beam chopping is done at 30 keV energy with a parallel-plate deflector integrated with an Einzel lens. Beam pulses with 5 ns width can be achieved with a 15 ns rise/fall time ±1500 V sweep on the chopper plates. The neutrons are produced at 120 keV energy. A three-dimensional simulation code based on Vlasov iteration was developed for simulating the ion optics of this system. The results with this code were found to be consistent with other simulation codes. So far we have measured 50 ns ion beam pulses from the system.
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