Improvement of calibration assessment for gold fast-neutron activation analysis using Plasma Focus devices

By exploiting the gamma detector-shielding configuration in a plasma focus (PF) device dedicated to fast-neutron activation analysis of gold, a reliable neutron counter may be established. The decay of 207 Pbm induced by neutrons in the lead shielding surrounding the photon detector produces gamma photons of 569.7 and 1063.6 ke V, which peaks are registered in the same spectrum containing the 279 ke V peak of the photons following the 197 Aum decay from fast-neutron activation. These decay peaks are found to be linearly correlated to the neutron flux and represent a stable and robust internal standard for monitoring the intrinsic variability in neutron flux production by PF devices. A comparison with the usual external neutron counter techniques shows a great improvement both for the calibration assessment and for the in-field measurements when this internal counter is considered.