Publications

Development of Fast-Pulse Neutron Generation Capability by Beam-Target Interaction on HERMES-III for Radiation Effects Testing (Final Report)

Renk, Timothy J.; Ottinger, Paul O.; Durrer, Russell E.

The goal of this project is to produce an intense neutron pulse on HERMES III using the beam-target method with an intense proton beam. The potential advantage of proton use is that the generated neutron spectrum contains significantly more high-energy neutrons than that produced by electron-beam generated photoneutrons using the same facility. And compared to (D,T) facilities such as NIF, no tritium (or deuterium) is required for this process. To achieve the mid ~10¹⁰ neutrons/cm² at a test object location listed as the goal in the Proposal, it was proposed that a radial ion diode previously developed and fielded at the 6 MeV - level be extended in performance to the full-power level on HERMES, with proton energies in the neighborhood of 15 MeV. This Report details the successful development of the radial ion diode at full power, which required more durable hardware which could be fielded at a one shot/day basis with minimal debris and activation (an important concern), and which could be substituted quickly into the normal negative-polarity bremsstrahlung source experiments without compromising the main HERMES validation mission. As direct measurement of proton beam characteristics proved challenging, the Project relied on an extensive series of simulations, LSP for beam dynamics and MCNP to characterize neutron output. Simulation results will be discussed, including the conclusion that neutron measurements made are consistent with an MCNP-predicted proton beam of 16 MeV peak energy, and 200 kA peak current. This Project also contributes to physics understanding of the use of inductive voltage adder (IVA) platforms to drive diode loads. Since such diodes operate independently of the physics of IVAs, the IVA-diode coupling requires matching of the MITL flow to the requirements of ion diode operation.