fluence (of particle radiation)

The number of radiant-energy particles emitted from or incident on a surface in a given period of time, divided by the area of the surface.

NOTE 1 The equation "fluence = N/A" applies, where N and A represent the quantities number of particles and area. Fluence can also be calculated by integrating the flux density over the given period of time, e.g., as in a run.

NOTE 2 The unit symbol (e.g., cm²) does not identify particle type. The particle name may be placed before the term, e.g., "neutron fluence", or in the spelled-out unit name, e.g., "neutrons per square centimeter".

NOTE 3 Fluence of particle radiation incident on a surface is maximized when the surface is perpendicular to the direction of the incident particle flow.

References: 

JESD57#, 12/96
JESD89A#, 10/06