Abstract
Summary form only given. The research and development of compact repetitive miniature plasma focus devices, with stored energy from few tens to few hundred joules, is becoming increasingly important because of their potential applications as portable neutron source for explosive and contraband material detection. In this paper, we report the neutron emission results from our most updated version of Fast Miniature Plasma Focus device, namely FMPF-3. The FMPF-3 (2.4 μF, 34 nH, 103 kA @ 14.0 kV, T/4 ~460 ns) is an advanced prototype of previous versions of FMPF series which achieves higher performance through the use of four parallel pseudo-spark gap switches for each module instead of single switch used in FMPF-2. This lead to the lower system impedance and hence higher discharge current with further enhancement in neutron to record time average yield of (1.2±0.2)×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> neutrons/sec at 10Hz operation. The analysis of experimental data for plasma focus devices with stored bank energies of 400 J to 1 MJ showed the neutron yield scaling with peak discharge current as Yn~I <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3.9</sup> . The scaling law at the lower energy limits of 120 - 235 J for FMPF-3 was found to scale on higher side as Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> ~I <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6.9</sup> . The shot to shot stability of neutron emission was tested at different repetition rates from 1 to 10 Hz for shot sequence of 50 shots. It was realized that if the device is operated at the pressure optimized for single shot operation then the neutron yield decreases monotonously after about 30 shots. The increase in operating deuterium pressure lead to the stabilization of neutron yield for 50 shot sequence for repetitive operations. In addition to above results, the paper will also discuss briefly the conceptualization and development of FMPF-3, along with key technical and physical issues and challenges encountered.
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