Extreme Damage Events Produced by Single Particles

Recent measurements of permanent displacement damage produced in charge coupled devices by single neutron and proton interactions revealed that some of the events exceeded the mean value by more than a factor of ten. These extreme events cannot be readily explained in terms of calculated recoil spectra. In view of this finding it is of interest to estimate the probability of exceeding a given level of damage as the particle fluence is increased and multiple events occur. Analytical methods applicable to this problem are described and applied to the reported displacement damage data. The results indicate that the character of the damage distributions will change rapidly as the particle fluence is increased and a transition is made from single to multiple events. Although the damage distribution approaches a Gaussian form, the extreme events will persist up to exposure levels 100 times higher than that used in the reported experiments.