A compact neutron source driven by a thyratron switched, pulsed current transformer

Pulsed neutron accelerators have been considered for active interrogation of special nuclear materials and also for location and imaging of explosives using PFNA. Alameda Applied Sciences Corporation is developing a <40 ns pulsed neutron source for these applications, based on the dense plasma focus (DPF). The Dense Plasma Focus (DPF) produces a 10-40 ns (FWHM) neutron pulse, with output scaling as I⁴ over a wide range¹ (~10 kA-l MA) of peak current (I). Typical outputs² are 10⁶ n/p at ~100 kA, scaling to ~10⁸ n/p at ~300 kA. The fast pulse enables time-gated detection of neutron induced emissions (prompt gamma or neutron) from targets as close as ~2 m from the source. The strong scaling of neutron output with discharge current and the fact that the voltage required is relatively low (~10 kV for a small source), allows the use of a pulsed current transformer architecture to efficiently drive the DPF. This paper describes the performance of a unit module of such a transformer driven neutron source. A single Thyratron switch is used to transform a 30 kV/13 kA pulse on the primary side of a metglas transformer into a 10 kV/40 kA pulse on the secondary. This secondary pulse drives a DPF at rep-rates from 10-lOO Hz, to produce ~20 ns neutron pulses. Optimization of the DPF head and its electrical coupling efficiency to the transformer driver are discussed. Conceptual designs for lOO kA and 300 kA versions of the pulsed transformer are presented, that are capable of driving DPF sources to 10¹² n/s (14.1 MeV DT neutrons) with <40 ns pulse widths.