tokens: Under the conditions specified in requirement 10.4.2a.1 , the energy deposition spectrum from direct ionization shall be calculated by using one of the following formulas : 1 . From direct ionization , by one of the following formulas : ( a ) Detailed calculation : ( b ) Approximated calculation : where dY / de(e ) = energy deposition rate spectrum ; A = total surface area of the SV or detector ; dF / dE(E ) = differential incident particle flux spectrum expressed as a function of energy , E ; dPCL / dD(D ) = differential chord length distribution through the sensitive volume for an isotropic distribution ; dE / dx(E ) = stopping power for particles of energy E ; Emin = minimum energy for the incident particle spectrum ; Emax = maximum energy of the incident particle spectrum . NOTE This expression assumes the incident particle spectrum on the detector is or can be approximated to a isotropic angular distribution . Furthermore , it is assumed that the change in the stopping power of the particle through the sensitive volume and any multiple scattering can be neglected .