Experimental Time Resolved Electron Beam Temperature Measurements Using211 Bremsstrahlung Diagnostics

摘要

Electron beam temperature, (beta)(perpendicular) (= v(perpendicular)/v), is211u001eimportant to control for the development of high dose flash radiographic 211u001ebremsstrahlung sources. At high voltage (> 5 MV) increasing electron beam 211u001etemperature has a serious deleterious effect on dose production. The average and 211u001etime resolved behavior of beam temperature was measured during radiographic 211u001eexperiments on the HERMES III accelerator (10 MV, 50 kA, 70 ns). A linear array 211u001eof thermoluminescent dosimeters (TLDs) were used to estimate the time integrated 211u001eaverage of beam temperature. On and off-axis photoconducting diamond (PCD) 211u001edetectors were used to measure the time resolved bremsstrahlung dose rate, which 211u001eis dependent on beam energy and temperature. The beam temperature can be 211u001edetermined by correlating PCD response with accelerator voltage and current and 211u001ealso by analyzing the ratio of PCD amplitudes on and off axis. This ratio is 211u001einsensitive to voltage and current and thus, is more reliable than utilizing 211u001eabsolute dose rate. The data is unfolded using comparisons with Monte Carlo 211u001esimulations to obtain absolute beam temperatures. The data taken on HERMES III 211u001eshow abrupt increases in (beta)(perpendicular) midway through the pulse 211u001eindicating rapid onset of beam instability.