Optimization of the testing volumes with respect to neutron flux levels in the two-target high flux D-Li neutron source for the international fusion materials irradiation facility

A design using two 250-mA beams on two lithium targets has been proposed to maximize the test volume while minimizing the flux gradients. A spatial, energy-, and angle-dependent neutron source model the D-Li reaction was used to provide a 3-D map of uncollided flux within the test volume. An optimization of the uncollided flux showed that ~8 l of test volume with uncollided fluxes of 10¹⁴ n/cm ²/s is available with flux gradients <10%/cm. The collided flux within the test volume was then determined by coupling the source model with a Monte Carlo computation. The spectral effect of the high-energy tail was evaluated as to possible impact on materials response. Calculations comparing the radiation damage to materials from the D-Li source to that caused by a standard DT-fusion first-wall neutron flux spectrum show that the He and dpa production, as well as the ratio He/dpa and dpa/MW/m² are within 30% for the two sources