Analytical and experimental dosimetry technique for calibrating a low energy x-ray radiation source

Evaluating the radiation tolerance of microelectronic parts and subsystems in the high-total-dose ionizing-radiation environments required for some military space and missile systems dictates the use of large, expensive simulators. This paper describes the method used to calibrate a large-volume continuous-wave x-ray radiation test chamber. The x-ray tube has a tungsten target and emits a bremsstrahlung x-ray spectrum with end point energies up to 160 keV. Analytical tools and experimental dosimetry techniques were developed to ma; the radiation field intensity and the resulting dose-deposition profiles in a variety of materials throughout the chamber. Three detector types (x-ray vacuum diodes, silicon PIN diodes, and PMOS FETs) were used to measure spectral intensity and dose deposition in silicon devices. CEPXS and PHOTCOEF electron-photon transport codes were used to calculate the incident spectral energy distribution and the energy deposition in the detector. Calculated and experimental diode detector responses agreed to within 10 percent over the full energy range. PMOS FETs were used to demonstrate the correlation between total-dose-deposited in the x-ray chamber and in the Cobalt-60 cell. The results of this effort provide dosimetry and analysis tools needed to perform ionizing radiation testing of large area (0.5m2) electronic subsystems