Dosimetry of Thermal Neutron Beamlines at a Pulsed Spallation Source for Application to the Irradiation of Microelectronics

Gas electron multiplier (GEM) detectors and activation foils have been used for dosimetry of thermal beamlines of a pulsed neutron source. The first is an active detector that performs measurements using the time-of-flight technique, taking advantage of the pulsed nature of the source. The same detector has been used successfully to measure the profiles of the beams. The second is a passive irradiation method that independently confirms the measured fluxes of equipment materials and mechanics analyzer (EMMA) and rotating analyzer crystal (X) spectrometer (ROTAX) beamlines of the ISIS neutron source. They feature different thermal spectra, the first being moderated with water (300 K) and the second with liquid methane (100 K). These two characterized beamlines have been used for the irradiation of microelectronics for single-event effect testing using a reference static random access memory (SRAM) module. It is shown that results are consistent and that a correction factor must be applied to scale the results on the cold beamline to the one at room temperature.