FLUKA: ELCFIELD Previous Index Next

# ELCFIELD

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defines an homogenous electric field

WHAT(1) = largest angle (in degrees) that a particle is allowed to travel
in a single step
Default: 20 degrees

WHAT(2) = error of the boundary iteration (minimum accuracy accepted in
determining a boundary intersection)
Default: 0.01 cm

WHAT(3) = minimum step if the step is forced to be smaller due to a too
large angle
Default: 0.1 cm
WHAT(4) = Ex (x-component of the electric field, in MV/m)

WHAT(5) = Ey (y-component of the electric field, in MV/m)

WHAT(6) = Ez (z-component of the electric field, in MV/m)

Default (Ex = Ey = Ez = 0.0): user-supplied subroutine
ELEFLD is assumed to provide the actual values
(see Notes 2 and 3 below)

SDUM :    not used
Notes:
1) If Ex = Ey = Ez = 0, the user-written subroutine ELEFLD is
called at each step to get the direction cosines and the
module (in MV/m) of the electric field as a function of
region or of coordinates or time. A sample subroutine is
provided with the FLUKA code; instructions on how to write
user-supplied routines can be found in 13}.

2) Note that the argument list of subroutine ELEFLD is
( X, Y, Z, T, ETX, ETY, ETZ, E, NREG, IDISC )
where ETX, ETY, ETZ are the DIRECTION COSINES of the electric
field at point X, Y, Z, at time T (NOT the components of the
field! The field magnitude is given by E). For this reason, it
is imperative that ELEFLD returns normalised values of ETX,
ETY and ETZ such that the sum of their squares is = 1.0
IN DOUBLE PRECISION.
Three zero values are not accepted: if the field is zero
at the point in question, you must return for instance 0, 0, 1
and E = 0. On the contrary, note that Ex, Ey, Ez in the
ELCFIELD option, given by WHAT(4)...WHAT(6) as described
above, are the field components and not the cosines.

3) Electric field tracking is performed only in regions defined
as electric field regions by command ASSIGNMAt. It is
strongly recommended to define as such only regions where an
electric field effectively exists, due to the complexity
of the tracking algorithm used in electric/magnetic fields.
To define a region as having an electric field and to return
systematically E = 0 in that region via subroutine ELEFLD, is
not allowed.

4) Tracking in electric fields is possible at present only in
vacuum regions. Arbitrary combinations of electric and magnetic
fields are supported. Whenever an electric field is present
the tracking is performed with a Runge-Kutta-Gill 4th order
algorithm for the combined electric and magnetic (if any) fields.
The same approach can be requested also for dis-homogeneous
magnetic fields (in vacuum) even if no electric field is
present, using SDUM=RUNGKUTT in the MGNFIELD card

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