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EMFFIX


    Sets the size of electron steps corresponding to a fixed fraction of the
    total energy. The setting is done by material, giving as many EMFFIX
    definitions as needed. Only meaningful when the EMF option has been
    requested (explicitly or implicitly via option DEFAULTS).

    See also EMF, FLUKAFIX, MULSOPT, STEPSIZE

     
WHAT(1)
= index or name of the material concerned
WHAT(2)
= maximum fraction of the total energy to be lost in a step
Default
: 20% (it is strongly recommended not to set higher than this value!)
WHAT(3)
= same as
WHAT(1)
;
WHAT(4)
= same as
WHAT(2)
WHAT(5)
= same as
WHAT(1)
;
WHAT(6)
= same as
WHAT(2)
SDUM
= PRINT : electron and positron dE/dx and maximum allowed step tabulations for this material are printed = NOPRINT: tabulations are not printed (cancels any previous PRINT request for the given materials) = blank: ignored
Default
: NOPRINT
Default
(option EMFFIX not requested): the energy lost per step is 20% for all materials
Notes:
1) The default provided (step length such that 20% of the energy is lost) is acceptable for most routine problems. In dosimetry problems and in thin-slab geometries it is recommended not to exceed 5-10%. For a detailed discussion of the step length problem, see [Fer91a]. 2) Related options are STEPSIZE, MCSTHRES, FLUKAFIX and MULSOPT (see). MCSTHRES and FLUKAFIX concern only heavy charged particles (hadrons and muons), while STEPSIZE applies to ALL charged particles (hadrons, muons and electrons). However, STEPSIZE defines the steplength in cm and by region, while EMFFIX relates the step length to the maximum allowed energy loss and is based on materials. STEPSIZE works also in vacuum and is adapted to problems with magnetic fields; if both options are used, the smallest of the two steps is always chosen. Note however that if a step required by STEPSIZE is too small for the Molière algorithm, multiple scattering IS turned off (contrary to what happens with EMFFIX). MULSOPT is very CPU-time consuming; however, it gives the highest accuracy compatible with the Molière theory. It is used rarely, mostly in low-energy and in backscattering problems. Example (number based):
*...+....1....+....2....+....3....+....4....+....5....+....6....+....7...
MATERIAL 13. 0.0 2.6989 3. 0. 0. ALUMINUM MATERIAL 82. 0.0 11.35 4. 0. 0. LEAD MATERIAL 29. 0.0 8.96 12. 0. 0. COPPER MATERIAL 6. 0.0 2.00 26. 0. 0. CARBON MATERIAL 7. 0.0 0.0012 27. 0. 0. NITROGEN MATERIAL 8. 0.0 0.0014 28. 0. 0. OXYGEN MATERIAL 1. 0.0 0.0001 29. 0. 1. HYDROGEN MATERIAL 0. 0.0 1.0000 30. 0. 0. TISSUE COMPOUND 5.57E-3 26.0 1.118E-3 27. 2.868E-2 28. TISSUE COMPOUND 6.082E-2 29.0 0. 0. 0. 0. TISSUE EMFFIX 3. 0.15 4. 0.15 12. 0.15 EMFFIX 30. 0.05 0. 0. 0. 0. PRINT
* In this example, a maximum energy loss per step of 15% is requested
* for aluminium, copper and lead, while a more accurate 5% is requested
* for tissue
The same example, name based: MATERIAL 13. 0.0 2.6989 0.0 0. 0. ALUMINUM MATERIAL 82. 0.0 11.35 0.0 0. 0. LEAD MATERIAL 29. 0.0 8.96 0.0 0. 0. COPPER MATERIAL 6. 0.0 2.00 0.0 0. 0. CARBON MATERIAL 7. 0.0 0.0012 0.0 0. 0. NITROGEN MATERIAL 8. 0.0 0.0014 0.0 0. 0. OXYGEN MATERIAL 1. 0.0 0.0001 0.0 0. 1. HYDROGEN MATERIAL 0. 0.0 1.0000 0. 0. 0. TISSUE COMPOUND 5.57E-3 CARBON 1.118E-3 NITROGEN 2.868E-2 OXYGEN TISSUE COMPOUND 6.082E-2 HYDROGEN 0. 0. 0. 0. TISSUE EMFFIX ALUMINUM 0.15 LEAD 0.15 COPPER 0.15

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