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The DEFAULTS card parameter EM-CASCAde is the obvious one needed for this problem, since no particles other than electrons and photons are concerned. This default implies that the most important effects from the point of view of dosimetry are taken into account: Rayleigh scattering and inelastic form factor corrections to Compton scattering, detailed photoelectric edge treatment, production of fluorescence photons, restricted ionisation fluctuations for electrons. Of course it can be convenient to overwrite some of the choices, for instance reducing the maximum energy loss per electron step from 20% to 10% by means of the EMFFIX directive. Also, difficulties in considering the low operating pressure of the machine, mentioned in the previous section, cannot be solved completely by the trick to work at atmospheric pressure and to scale the final results. This because the multiple scattering is practically negligible in the vacuum chamber of a storage ring, while it is responsible of large broadening of the beam at atmospheric pressure.

Therefore it must be suppressed in the FLUKA simulations and this is driven by means of the MULSOPT card. In a similar way, Moller scattering, which at amospheric pressure would cause electron angular deflections due to the production of δ rays, has been suppressed by means of an EMFCUT card with the ELPO-THR parameter.

The code energy cuts are set at 50 keV for charged particles and 1 keV for photons (see again the EMFCUT cards).

Giuseppe Battistoni; INFN, Milano
Alberto Fassò; SLAC, California

Last updated: 10th of October, 2008