Sets the tracking conditions for multiple Coulomb scattering (MCS), for both
FLUKA and EMF particles. Can also be used to activate single scattering.
(see also EMFFIX, FLUKAFIX, MCSTHRES, STEPSIZE)
For SDUM = anything except GLOBAL/GLOBEMF/GLOBHAD:
WHAT(1) : controls the step optimisation for multiple Coulomb scattering,
and the number of (possible) single scatterings on a material
by material basis
<= -1.0 : a possible previous request of optimisation is cancelled
and the number of single scatterings in the materials
indicated by WHAT(4)-WHAT(6) is reset to the default value
(i.e. 0, or the global default possibly set previously by
this option with SDUM = GLOBAL/GLOBHAD/GLOBEMF)
= 0.0 : ignored
= I0 + I1*10 + I2*100000
(with 0=< I0 =<1, 0=< I1 <10000, 0 =< I2 < 10000):
I0 >= 1 : the optimisation is activated
I1 - 1 = number of single scattering steps for hadrons and muons
in the materials indicated by WHAT(4)-WHAT(6)
I1 = 0 : ignored
I2 - 1 = number of single scattering steps for electrons and
positrons in the materials indicated by WHAT(4)-WHAT(6)
I2 = 0 : ignored
Default: -1.0 (no multiple scattering optimisation and no single
scattering)
WHAT(2) :
|WHAT(2)| = 1.0: spin-relativistic corrections are activated for
hadrons and muons at the 1st Born approximation
level
|WHAT(2)| = 2.0: spin-relativistic corrections are activated for
hadrons and muons at the 2nd Born approximation
level
WHAT(2) < 0.0: nuclear finite size effects are activated.
= -3.0: nuclear finite size effects (form factors) are
considered but not the spin-relativistic effects
WHAT(2) >= 3.0: multiple scattering for hadrons and muons is
completely suppressed
Default: 0.0 (no corrections)
WHAT(3) :
|WHAT(3)| = 1.0: spin-relativistic corrections are activated for
e+ and e- at the 1st Born approximation level
|WHAT(3)| = 2.0: spin-relativistic corrections are activated for
e+ and e- at the 2nd Born approximation level
WHAT(3) < 0.0: nuclear finite size effects are activated
WHAT(3) >= 3.0: multiple scattering for e+ and e- is completely
suppressed
Default: 0.0 (no corrections)
WHAT(4) = lower bound of the indices of the materials in which the
corrections are activated ("From material WHAT(4)...")
Default = 3.0
WHAT(5) = upper bound of the indices of the materials in which the
corrections are activated ("... to material WHAT(5)...")
Default = WHAT(4)WHAT(6) = step length in assigning indices
("...in steps of WHAT(6)")
Default: 1.0
SDUM = FANO-ON : Fano correction for inelastic interactions
on atomic electrons switched on (for the moment
only for charged hadrons and muons)
FANO-OFF: Fano correction for inelastic interactions on
atomic electrons is switched off
MLSH-ON : Moliere screening angle on for hadrons and muons
MLSH-OFF: Moliere screening angle for hadrons and muons as
modified by Berger & Seltzer for electrons
Default: Fano correction on, original Moliere screening
angle for hadrons on
Default (option MULSOPT not given): no MCS optimisation
For SDUM=GLOBAL/GLOBEMF/GLOBHAD: (GLOBEMF restricts
the input value use to the EM part, GLOBHAD to the hadron and muon
part)
WHAT(1) : controls the minimum MCS step size used by the boundary approach
algorithm for electron/positrons and charged heavy
particles (in the multiple scattering routine)
0.2 > WHAT(1) >= 0.0 : ignored
WHAT(1) >= 0.2 : the minimum step size is set equal to the size
corresponding to B=5 in Moliere theory,
multiplied by WHAT(1)
< 0.0 : the minimum step is reset to default
Default: WHAT(1) = 1 (maximum accuracy)
WHAT(2) : index of step stretching factor tabulation to be used
by the electron/positron transport algorithm when
approaching a boundary.
The values of the index implemented for the moment are 1,2,3,4.
Values 11,12,13,14 cause the sensing algorithm to multiply
the range/mcs step rather than the current step.
Values 101,111,102,112,103,113,104,114 have the additional
effect of making the algorithm resample as unphysical any
step cut at a boundary and "reflected" from the boundary.
= 0.0 : ignored
< 0.0 : the tabulation index is reset to default
Default: WHAT(2) = 1 (maximum accuracy)
WHAT(3) : controls the optimal step to be used by the optimisation
option (and to some extent by the hadron/muon boundary approach
algorithm).
0.2 > WHAT(3) >= 0.0 : ignored
WHAT(3) >= 0.2 : the minimum step size is set equal to the size corresponding
to B = 5 in Molière theory [Mol47,Mol48,Mol55,Bet53],
multiplied by WHAT(3)
< 0.0 : the minimum step is reset to its default value
Default: minimum step equal to that corresponding to B=5,
multiplied by 20
WHAT(4) > 0: single scattering option activated at boundaries or
for too short steps
< 0: resets to default
= 0: ignored
Default: single scattering not activated
WHAT(5): (meaningful only if single scattering is activated at
boundaries and when step is too short: see WHAT(4) above)
> 0: single scattering option activated for energies too small
for Molière theory to apply
< 0: not activated
= 0: ignored
Default: not activated
WHAT(6): (meaningful only if single scattering is activated at
boundaries and when step is too short: see WHAT(4) above)
> 0: number of single scatterings to be performed when
crossing a boundary
= 0: ignored
< 0: resets the default
Default: 1
Note: When optimisation is requested, the program always makes the
minimum step for which the Molière theory of multiple
scattering is applicable. Optimisation via MULSOPT is
available only for charged hadrons and muons. For
electrons and positrons, option EMFFIX is recommended.
The correction for the nuclear finite size has been
implemented using simple Thomas-Fermi form factors
according to Tsai [Tsa74]. The user can provide more
sophisticated values by supplying a function FORMFU
which must return the square of the nuclear form factor.
(See details in 13}).
Complete suppression of multiple scattering can be useful in
some particular cases, for instance when replacing a gas of
extremely low density by a gas of the same composition but of
much larger density in order to increase the frequency of
inelastic interactions or bremsstrahlung reactions (of course,
the results must then be scaled by the density ratio). In such
a case, one should also select the biased density so that
no re-interaction of secondaries can take place.
Runs for which the nuclear form factor is taken into account
and/or the 2nd Born approximation is requested are very
CPU-time consuming at low energy (but not at high energy).
Setting WHAT(6) > 1000.0 with SDUM = GLOBAL, GLOBHAD or GLOBEMF,
replaces systematically multiple scattering with single scattering
everywhere. This choice is generally extremely demanding in CPU
time, except for particles of very low energy (a few keV), which
have a very short history anyway. In such cases, the single
scattering option is even recommended ([Fas01]).
Example 1:
* Activate spin-relativistic corrections and nuclear finite size effects
* for heavy charged particles in the first Born approximation.
* Activate spin-relativistic corrections but not nuclear size effects
* for electrons and positrons in materials 5, 10 and 15
*...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+...
MULSOPT 1.0 -1.0 2.0 5.0 15.0 5.0
Example 2:
* Maximum accuracy requested for the electron step size used in the boundary
* approach and in the optimisation algorithm. Single scattering activated for
* electrons at boundary crossing and when the step is too short for Moliere
* (but not when the energy is too low for Moliere). Boundaries will be
* crossed with 2 single scatterings.
*...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+...
MULSOPT 1.0 1.0 1.0 1.0 0.0 2. GLOBEMF
Example 3:
* Single scattering activated everywhere for all charged particles
*...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+...
MULSOPT 0.0 0.0 0.0 1.0 1.0 99999999.GLOBAL
