Development of a portable pulsed fast ⩾10⁶ neutron generator based on a flexible miniature plasma focus tube

Abstract

Plasma focus is a laboratory fusion device that is used to produce pulsed neutrons for a few tens of ns duration. A compact plasma focus tube (volume ≈ 130 cm3) has been developed and this was connected to a newly developed capacitor bank using twenty four coaxial cables, each 10 m long. The capacitor bank was of compact size and this was consisted of four energy storage capacitors (each 6 µF, 20 kV, size:20 cm × 20 cm × 30 cm). The peak discharge current of the capacitor bank was estimated to be 176 kA with rise time of around 3.6 µs at maximum 4.8 kJ operation energy. The average neutron yield was observed to be maximum (3.1±1.0)×106 neutrons/pulse with pulse duration of 15 to 25 ns at an operation energy of 2.7 kJ (15 kV) and deuterium gas filling pressure of 4 mbar. Long coaxial cables allow only the plasma focus head (neutron source) to be moved as per needs, making this a portable pulsed neutron source useful in many applications including in extreme conditions such as in borehole logging applications for oils and minerals mapping. This report describes the details about various components of this portable neutron generator along with its neutron emission characteristics.