9.1 Overview

This Clause provides an explanation of single event effects, identifies technologies and components susceptible to the SEEs, and specifies the methods to be used to calculate single event rates for spacecraft systems.

Single event effects are a collection of phenomena whereby microelectronics can be disrupted or permanently damaged by single incident particles (as opposed to effects like total ionising dose where cumulative damage occurs from many particles). Protons and heavier ions, and neutrons can induce such effects: in the case of heavy ions, this occurs by direct ionisation of sensitive regions of the semiconductor, and for protons and neutrons, their nuclear interactions within or very near to the active semiconductor can produce localised charge generation.

SEE phenomena can be divided into two sub-groups:

• destructive effects, where high-current conditions are induced which have the potential to destroy the device. SEE examples include single event latch-up (SEL), single event gate rupture (SEGR), single event burn-out (SEB), and single event snap-back (SESB) (see ECSS-E-HB-10-12 Section 8.6).

• non-destructive effects, in which data are corrupted or the device is placed in a different operational state (e.g. a diagnostic mode) or power cycling is employed to return the state of the device to its normal condition. Examples of such effects include single event upset (SEU), multiple-bit upset (MBU), multiple-cell upset (MCU), single-word multiple-bit upsets (SMU), single event functional interrupt (SEFI), single event hard error (SEHE), single event disturb (SED), and single event transient (SET) (see ECSS-E-HB-10-12 Section 8.7).

NOTE Here, the term multiple-cell upset (MCU) refer to events in which several memory cells are corrupted, whether they form part of the same word (as in SMU) or not.

Radiation susceptibility of a device is expressed as a cross-sectional area, usually in units of cm²/device or cm²/bit (the latter being used for single event upset analysis). The cross-section is a function of incident particle species and energy. However, for ions heavier than protons, the cross-section can be expressed as a function of linear energy transfer (LET), which is the energy deposition per unit pathlength of the ion, often expressed in units of MeV×cm²/g or MeV×cm²/mg.