Novel beryllium-scintillator, neutron-fluence detector for magnetized liner inertial fusion experiments

Progress in the development of a neutron detector employing the Be-9(n, alpha)He-6(beta(-),tau(1/2) = 807 ms) reaction is reported. This detector's intended use is to estimate 2.45-MeV, deuterium-deuterium (DD) neutron yields from magnetized liner fusion (MagLIF) targets and proposed future gas-puff experiments at Sandia National Laboratory's Z facility, Albuquerque, NM. This unique detector employs a simple stackedcomponent construction: 23 flat beryllium plates (99% pure, 0.318 cm thick) sandwiched between 22 plastic scintillator sheets (BC-404, 1-mm-thick). Each Be plate and scintillator sheet is a planar square (10 cm on a side) and the assembly is enclosed in a cubical, sealed, 1.5-mm-thick, Al-walled box. Scintillation light due to deposited energy from the He-6 betas is emitted and transmitted edgewise to ultraviolet-transmitting Lucite light guides optically coupled to two, independent, high-gain photomultiplier tubes. Reported here are details of the characterization of the neutron detection sensitivity (beta decay counts per incident neutron) of each photomultiplier tube side. These measurements were conducted at the Sandia National Laboratories ion beam facility, which provided beams of pulsed 175-keV deuterons focused onto a 2.6-micron thick deuterated erbium target (ErD2). Neutrons were produced via the D(d, n)(3) He reaction. The neutron flux (incident neutrons/cm(2)/sec) on the Be detector was inferred by the measurement of the protons from the equally branched D(d, p)T reaction. Steady-state neutron pulses incident on the Be detector induced the He-6 beta decay activity necessary to determine the detector's neutron sensitivity referred to as the F-factor. The rational, methodology, and experimental details behind this approach and the results with uncertainties of the subsequently determined F-factor of the Be detector are detailed. Additional comments regarding improvements to the calibration methodology plus future studies and the use of this detector in Z experiments will be discussed briefly.