A fast pulsed neutron source driven by a 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 DPF benefits from well established scaling laws that cover a wide range of outputs from 104 up to 1012 n/pulse. The strong scaling of neutron output with discharge current (as the fourth power of the 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 - 100 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 100 kA and 300 kA versions of the pulsed transformer are presented, that are capable of driving DPF sources to 1012 n/s (D-T) output with 14.1 MeV neutrons in < 40 ns pulse widths. (author)