https://doi.org/10.1351/goldbook.09251
\(\mathit{\Phi} = \rm{d}N/\rm{d}t\), where \(N\) is number of particles of a specified type and \(t\) is time.
Notes:
- For a parallel beam, fluence rate and flux density are equivalent measures.
- SI unit: \(\pu{s^{-1}}\). For a beam of charged particles (ions) the flux is expressed in ampere, i.e. \(F \times ze\), where \(z\) is the charge on a particle and \(e\) the elementary charge (\(\pu{1.602176634E-19 C}\)).