Experimental time resolved electron beam temperature measurements using Bremsstrahlung diagnostics

Electron beam temperature, /spl beta//sub /spl perp//(=v/sub /spl perp///v), is important to control for the development of high dose flash radiographic Bremsstrahlung sources. At high voltage (>5 MV) increasing electron beam temperature has a serious deleterious effect on dose production. The average and time resolved behavior of beam temperature was measured during radiographic experiments on the HERMES III accelerator (10 MV, 50 kA, 70 ns). A linear array of thermoluminescent dosimeters (TLDs) were used to estimate the time integrated average of beam temperature. On and off-axis photoconducting diamond (PCD) detectors were used to measure the time resolved Bremsstrahlung dose rate, which is dependent on beam energy and temperature. The beam temperature can be determined by correlating PCD response with accelerator voltage and current and also by analyzing the ratio of PCD amplitudes on and off axis. This ratio is insensitive to voltage and current and thus, is more reliable than utilizing absolute dose rate. The data is unfolded using comparisons with Monte Carlo simulations to obtain absolute beam temperatures. The data taken on HERMES III show abrupt increases in /spl beta//sub /spl perp// midway through the pulse indicating rapid onset of beam instability.