Calculation of radiation yield

The number of photons per MeV per incident electron per $g/cm^2$ of radiator (Z,A) is given by [1]:

$\frac{d^2n}{d\kappa dt} = \frac{3.495 \times 10^{-4}}{A\kappa}[Z^2\Phi_n(Z,E_0,k)+Z\Phi_e(Z,E_0,k)](MeV^{-1}g^{-1}cm^2)$,

where $\kappa$ - photon kinetic energy in MeV $\Phi_e(Z,E_0,k) = C_B\{2[1-\frac{2E}{3E_0}+(\frac{E}{E})^2][L-\sqrt[2]{\eta}]\}$