------------------------ Accuracy and computer speed depend on several parameters that can be freely tuned by the user: but in general an increase of either one results in a decrease of the other. The proper balance must be based both on physical and on practical considerations. The present defaults have been designed to give satisfactory results in the most common cases: but other sets of defaults can be implemented using option DEFAULTS (to be placed at the beginning of the input file, just after the title). Even when one set of defaults is enforced, the user can still override some of them by modifying single parameters. The most used ones concern energy cutoffs (option EMFCUT for electrons and photons, LOW-BIAS for low-energy neutrons, PART-THR for all other particles), thresholds for delta-ray production (option DELTARAY), particles to be ignored (option DISCARD), switching on or off some physical effect (EMFCUT, IONFLUCT, MUPHOTON, PAIRBREM, PHOTONUC, PHYSICS, POLARIZAti), and (more rarely) the size of the step for transporting charged particles (FLUKAFIX, MCSTHRES, MULSOPT, STEPSIZE). Energy cutoffs for each particle are listed in a table on standard output ("Particle transport thresholds").
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