This chapter explains the displacement damage (DD) effect, identifies technologies and components susceptible to DD, and specifies the requirements for calculating the DD threat to spacecraft systems, and standard methods of calculation.
Displacement damage (also referred to as non-ionising dose damage) is a cumulative damage process induced by energetic particles and which affect components such as opto-electronics, bipolar devices, and solar cells. The damage mechanism is as a result of collisions with atoms to displace them from lattice positions creating interstitials and vacancies. These interstitials and vacancies are mobile and can cluster together or react with impurities in the lattice structure creating stable defect centres. The overall effect of displacement damage (DD) is a change in the minority carrier lifetimes of semiconductors, and increased light absorption and colouration in crystalline optical materials.
Displacement damage is sometimes quantified in terms of component degradation as a function of particle fluence for a specific particle spectrum (with units, for example, or protons/cm2 or electrons/cm2). However, since the level of degradation varies with spectrum shape as well as intensity, such a definition has limited applications, and for general applications, in this Standard DD is expressed as specified in clause 8.2.
Total non-ionising dose is included in the overall radiation assessment.