• Cross-section versus linear energy transfer curve;
  • Dirichlet process prior;
  • Markov chain Monte Carlo methods;
  • On-orbit upset rate

Summary.  This work is concerned with the vulnerability of spaceborne microelectronics to single-event upset, which is a change of state caused by high-energy charged particles in the solar wind or the cosmic ray environment striking a sensitive node. To measure the susceptibility of a semiconductor device to single-event upsets, testing is conducted by exposing it to high-energy heavy ions or protons produced in a particle accelerator. The number of upsets is characterized by the interaction cross-section, which is an increasing function of linear energy transfer. The prediction of the on-orbit upset rate is made by combining the device geometry and cross-section versus linear energy transfer curve with a model for the orbit-specific radiation environment. We develop a semiparametric isotonic regression method for the upset count responses, based on a Dirichlet process prior for the cross-section curve. The methodology proposed allows the data to drive the shape of the cross-section versus linear energy transfer relationship, resulting in more robust predictive inference for the on-orbit upset rate than conventional models based on Weibull or log-normal parametric forms for the cross-section curve. We illustrate the modelling approach with data from two particle accelerator experiments.