9.2.3 Dielectric electric fields and voltages

a. Unless it is demonstrated that the material, in the situation in which it is used, is capable to sustain a higher bulk field without ESD, electric fields within dielectric materials shall be kept to below a maximum electric field, E_max= 10⁷ V/m.

NOTE 1 The objective is to minimize the occurrence of discharges due to internal dielectric charging.

NOTE 2 The default value does not contain a safety margin. It is usual for a project specification to define an additional margin, depending on the mission and the approach to risk.

b. The electric field within dielectric materials shall be computed by simulation, or measured by test.

NOTE Particle transport simulation or ray-tracing can form part of the computer simulation.

c. Voltages on internal surfaces shall be kept below the maximum voltage limits described in 6.2.1.

NOTE The objective is to minimize the occurrence of internal surface discharges on surfaces not exposed to the ambient plasma but accessible by penetrating electrons.

d. The voltages on internal surfaces shall be computed by simulation, or measured by test.

NOTE Particle transport simulation or ray-tracing could form part of the computer simulation.

e. For analysis and testing, a customer-agreed worst-case environment shall be used, in the form of either:

1. a worst-case model of radiation belt electron fluxes in conjunction with an orbit generator, or

2. a worst-case spectrum for the orbit in question

NOTE 1 A worst case spectrum for internal charging is a time-average where the time period reflects the time-scale of internal charging (usually 1 day).

NOTE 2 The FLUMIC electron environment model (see Annex D.3) has been created specifically for internal charging assessments for all terrestrial orbits.

NOTE 3 Electron environment models which are averages of periods much longer than a day are used in assessments of other processes, e.g. dose analysis, but are inappropriate for internal charging analysis.

f. For systems sensitive to absolute levels of internal electric fields and comprising insulators or isolated conductors, electric fields induced by internal charging shall be assessed in the design phase (project Phase C).

NOTE Examples are MEMS and triaxial accelerometers.

g. The electric fields in systems sensitive to absolute levels of internal electric fields shall stay within the levels agreed with the customer.

NOTE 1 The acceptability of field levels depends on the application.

NOTE 2 The electric field can be controlled through radiation shielding of sensitive areas, grounding or controlled discharge strategies.