Evidence for a Radiation Induced Electromotive Force (RIEMF) in Dielectrics Exposed to Very High 14 MeV Neutron Flux by Means of Neutron Induced Recoils

摘要

To assess phenomena occurring in coaxial cables under high flux of 14 MeV neutrons in D-T fusion experiments, a Polyethylene, Teflon™ or vacuum sandwiched between two electrodes Mock-Up is proposed. This Mock-Up was exposed to the subnanosecond flux at the LLE OMEGA facility in Rochester (above 10$^{18}$ n/cm$^{2}$-s) normally to the electrodes or with a tilt angle. A radiation induced current probing a Radiation Induced Electromotive Force (RIEMF) is measured and a model is proposed based on the range of the neutron-induced recoils. The GEANT4 simulation toolkit has been used to take advantage of the implementation of both nuclear and electromagnetic processes in order to compute the tracks and the strong angle dependence. Good agreements between simulations and experimental results are found for Polyethylene in contrast with Teflon™ where the 3-$alpha$ break-up of $^{12}$C not considered in GEANT4 seems to make a major contribution to the measured induced current. Comparison with the photon flux is made.