Neutron diagnostics and timing on the MJOLNIR dense plasma focus

The MJOLNIR dense plasma focus (DPF) prototypes configurations to optimize flash neutron radiography.  In order to properly time the neutron camera to the unscattered neutrons, the “prompt” neutron pulse is measured using a series of shadowbarred detectors at the location of the neutron camera scintillator.  The pulse is transformed back into the DPF pinch location and time within a few ns and is correlated with other diagnostics.

These include:

PMT-coupled scintillators 4 m and 6 m away and SIPM-coupled scintillators 0.4 m away provide information about the neutron flux envelope.  Beryllium, Bromine, and Yttrium activation detectors monitor the yield, the scattering contribution, and the dose to the neutron camera.  A 16-frame, 3 ns exposure framing camera monitors pinch stagnation, breakup time, and location.  Frequency-calibrated electromagnetic probes monitor the current and electric field in the DPF circuit at the time of neutron production.

Diagnostics are analyzed to quantify timing jitter from small differences in fill pressure and bank voltage (1 part in 1000).  The data are analyzed to assess what happens in a high yield vs low yield pinch.