Photoneutron Production Using Bremsstrahlung from the 14-TW Pulsed-Power HERMES III Electron Accelerator

An intense reusable source of pulsed photoneutrons is developed that produces ≈0.5 or 1.0 × 10¹⁴ neutrons in an ∼15-ns pulse from natural lead or depleted uranium, respectively, on the HERMES III electron accelerator. Corresponding to this source, a numerical model is developed that is applicable to other pulsed-power systems. If V_p represents the peak voltage of HERMES III measured in megavolts, then model predictions show that over the range 12 MV < V_p< 20 MV, the number of neutrons produced per incident electron is 7.2 × 10^-6(V_P — 11)^2.0 and 1.2 × 10^-6(V_P — 7.4)^{2 8} in lead and uranium, respectively. Measurements using a set of nuclear activation foils confirm these predictions as well as predictions of the spatial and spectral distribution of the neutrons at V_p = 19 MV.