A technique for reducing the computational time of electron-photon cascade-shower simulation

The angular-lateral correlated Gaussian formula (Fermi's solution) of multiple Coloumb scattering of high-energy charged particles is extended to cases where the energy-loss rate of the particles is constant in homogeneous matter as well as in the atmosphere. Then, a method is shown how to apply the formulas to the electron-phonon cascade process where many generations of electrons and photons are involved. The technique speeds up the Monte Carlo simulation of the electron-photon cascade by 3 to 5 times as compared to a conventional method. Though the approximations used may seem rather rough, results for high-energy incident particles (>several hundred MeV) are even quantitatively comparable with experimental results. The technique may be implemented in many Monte Carlo simulation programs as an option to be used for specific applications. (orig.)