The Fluence Rate Calculation node is used to compute the fluence rate within domains. Fluence rate is defined as the total radiant power that would hit a small sphere located within the domain, divided by the cross sectional area of the sphere. The sphere is assumed to be much smaller than any geometric details but much larger than the wavelength of the radiation, so that Mie scattering can be neglected.

This feature is available when the ray power is solved for. The variable for fluence rate is <phys>.<name>.E0, where <phys> is the name of the Geometrical Optics physics interface and <name> is the name of the physics feature, for example gop.frc1.E0.