Neutron dosimetry employing soft errors in dynamic random access memories

Abstract

A programme of work on soft errors of 64 K and 256 K DRAMs has begun in these laboratories, studying the error rates and modelling them. A feasibility study is being carried out of neutron dosimetry employing soft errors in 256 K DRAM. Thermal neutrons from a neutron howitzer and albedo neutrons from 252Cf neutrons scattered off a water phantom produced 'soft errors', through the action of alpha particles and tritons, generated by the (n, alpha ) reaction in 6LiF converters. The energy dependence of the soft error rate (SER) was studied by degrading 5.5. MeV alpha particles after passage through plastic absorbers. The dependence of SER on the operating bias of DRAM was also studied. For the study of thermal neutron sensitivity, the thickness of the 6LiF converter was optimised. A calibration curve of soft errors against dose equivalent was plotted, the dose equivalent having been calculated from thermal neutron flux measurements. A dose equivalent of 25 mu Sv corresponds to a soft error of about 1. There are potential advantages of a DRAM as a digital neutron dosemeter.