Calculation of radiation yield

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

[math]\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)[/math],

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