MegaJOuLe Neutron Imaging Radiography (MJOLNIR) Dense Plasma Focus Rebuild and High Current Experiments

A dense plasma focus (DPF) is a co-axial plasma railgun, whose discharge ends in a z-pinch phase. The MegaJOuLe neutron imaging radiography (MJOLNIR) DPF is a Lawrence Livermore National Laboratory (LLNL) experiment to demonstrate feasibility of flash neutron radiography using the DPF as a neutron source and a neutron camera to record an image. The MJOLNIR team is in the process of commissioning the DPF to full stored energy and current, 2 MJ/4.5 MA, with 1.3-MJ stored energy and 3.8-MA peak currents achieved as of October 2023. A recent redesign/rebuild of the MJOLNIR DPF has enabled robust operations, supporting >900 high voltage/plasma shots, 570+ on a single hardware setup, over the course of 11 months. Neutron yields in excess of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\times 10^{{12}}$ </tex-math></inline-formula> have been achieved on the highest current shots with deuterium gas fill. Successful high current operation requires interleaving of high current shots with lower current (~2.8-MA peak) shots. Neutron spot sizes have been measured as a function of voltage, pressure, anode implosion radius, and gas dopant levels. We document an overview of the MJOLNIR redesign and high-current experimental results.