Operational characterization of the radiation field of the high intensity operating mode of Hermes III

A high-intensity mode for Hermes III gamma simulator at Sandia National Laboratories, providing an average dose rate of 2.5 x 10l3 rads(Si)/s over a 2:1 uniformity area of 80 cm2, has been reported previously. This source provides an average dose of 370 krad(Si) over the useful area in a radiation pulse with a rise time of 8 ns and a pulse width of 11 ns. Use of this source permits photon testing of radiation effects in a regime previously accessible only underground or using e-beam simulation. This work characterizes both the spatial and temporal variations of the radiation field produced by the high-intensity source. This radiation source depends on the transport of a converging electron beam in a gas cell to the converter, where the forward-directed character of the bremsstrahlung results in the formation of a radiation focus slightly downstream of the faceplate. Because the electron trajectories vary during the radiation pulse, the time history of the radiation is a function of position