Neutron Time-of-Flight Measurements on the Verus Research 750KJ Dense Plasma Focus

Two sets of neutron time-of-flight (nTOF) detectors with different neutron sensitivities have been developed to measure the neutron emission history and energy spectrum from fusion neutrons produced by the D(D,n)3He reaction on the Verus Research dense plasma focus (DPF). The two sets of detectors are designed to have scintillators with thickness less than the mean free path of a 2.45 MeV fusion neutron to decrease the broadening of the signal from the neutron transit time in the scintillator and provide different sensitivities to the neutrons, with the detector sets having 5.5cm and 1.27cm thick scintillators respectively. Both nTOF designs utilize Ej -232Q scintillators that have been quenched with 0.5% Benzophenone to decrease the light output and provide shorter scintillator decay times. The detectors utilize fast photomultiplier tubes (PMTs) operated in their linear current mode at -2700V and -3400V. The instrument response function (IRF) to a single neutron for each detector was measured using a PuBe and Cf-252 neutron source providing the effects of the scintillator, PMT, and cable and the measured signal. This IRF is then removed from the measured signal using a Fourier-Deconvolution method1 to yield the true temporal neutron signal. The detectors have been placed radially with respect to the z-axis of the pinch with each set of detectors containing a near and far detector located at two different distances from the pinch. By measuring the difference in the time of arrival of the neutrons from the near to the far detector the signal is brought from the time to the energy domain to measure the shape of the neutron energy spectrum. Design of the diagnostics and IRF measurements will be presented, along with the measurements of the pinch dynamics from these detectors.