Unlike some other Monte Carlo particle transport codes, FLUKA gets its input
mainly from a simple file. It offers a rich choice of options for scoring most
quantities of possible interest and for applying different variance reduction
techniques, without requiring the user to write a single line of code.
However, although normally there is no need for any "user code", there are
special cases where this is unavoidable, either because of the complexity of
the problem, or because the desired information is too unusual or too
problem-specific to be offered as a standard option.
And on the other hand, even when this is not strictly necessary, experienced
programmers may like to create customised input/output interfaces.
A number of user routines (available on LINUX and UNIX platforms in directory
usermvax) allow to define non-standard input and output, and in some cases
even to modify to a limited extent the normal particle transport. Most of them
are already present in the FLUKA library as dummy or template routines, and
require a special command in the standard input file to be activated. Users
can modify any one of these routines, and even insert into them further calls
to their own private ones, or to external packages (at their own risk!). This
increased flexibility must be balanced against the advantage of using as far as
possible the FLUKA standard facilities, which are known to be reliable and well
tested.
To implement their own code, users must perform the following steps:
1) make a modified copy of one or more of these routines. It is recommended
that each modified routine should always print an informative message when
called for the first time, to confirm that it has been successfully
activated, for future documentation, and to avoid misinterpretations of the
standard output. It is important to remember that when calling modified
user routines, the units, titles etc. reported in the normal FLUKA output
become often meaningless.
A typical way to do this is:
..............
LOGICAL LFIRST
SAVE LFIRST
DATA LFIRST /.TRUE./
* return message from first call
IF (LFIRST) THEN
WRITE(LUNOUT,*) 'Version xxx of Routine yyy called'
LFIRST = .FALSE.
ENDIF
..............
IMPORTANT: The user should not modify the value of any argument in a routine
calling list, except when marked as "returned" in the description of the
routine here below.
Similarly, no variable contained in COMMON blocks should be overwritten
unless explicitly indicated.
2) compile the modified routines (with the fff script on LINUX/UNIX):
fff yyy.f (produces a new file yyy.o)
3) link them (with the lfluka script on LINUX/UNIX) to the FLUKA
library and any additional library of interest (for instance
CERNLIB):
lfluka -o myfluka -m fluka yyy.o
This will produce a new executable (indicated here as myfluka).
To run the new executable, launch the usual rfluka script with the option
-e myfluka.
INCLUDE files
-------------
It is recommended that at least the following lines be present at the beginning
of each routine:
INCLUDE '(DBLPRC)'
INCLUDE '(DIMPAR)'
INCLUDE '(IOUNIT)'
Each INCLUDE contains a COMMON block, plus related constants.
Additional INCLUDEs may be useful, in particular BEAMCM, CASLIM, EMFSTK, SOURCM,
EVTFLG, FHEAVY, GENSTK, LTCLCM, FLKMAT, RESNUC, SCOHLP, SOUEVT, FLKSTK, SUMCOU,
TRACKR, USRBIN, USRBDX, USRTRC, USRYLD.
Files flukaadd,add and emfadd.add contain a full documentation about the
meaning of the variables of these INCLUDE files.
Here is a summary of their content:
DBLPRC: included in ALL routines of FLUKA, contains the declaration
IMPLICIT DOUBLE PRECISION (A-H,O-Z)
and sets many mathematical and physical constants. Users are strongly
encouraged to adhere to "FLUKA style" by using systematically double
precision (except for very good reasons such as calling external single
precision scoring packages), and to use constants defined in this file
for maximum accuracy.
DIMPAR: dimensions of the most important arrays
IOUNIT: logical input and output unit numbers
BEAMCM: properties of primary particles as defined by options BEAM
and BEAMPOS
CASLIM: number of primary particles followed (needed for normalisation)
EMFSTK: particle stack for electrons and photons
SOURCM: user variables and information for a user-written source
EVTFLG: event flags (still undocumented)
FHEAVY: stack of heavy secondaries created in nuclear evaporation
GENSTK: properties of each secondary created in a hadronic event
LTCLCM: LaTtice CeLl CoMmon (needed when writing symmetry transformations for
Lattice Geometry)
FLKMAT: material properties
RESNUC: properties of the current residual nucleus
SCOHLP: SCOring HeLP (information on current estimator type). It contains a
flag ISCRNG, indicating the quantity being scored by the current
binning or estimator, and one JSCRNG corresponding to the
binning/estimator number. Binnings and estimators are sequentially
numbered according to their order of appearance in standard input.
Note that several estimators can have the same JSCRNG number (for
instance Binning N. 3 and Tracklength estimator N. 3). They can be
distinguished based on the value of ISCRNG. However, note that the
same value of ISCRNG may have different meanings in functions FLUSCW and
COMSCW.
SOUEVT: SOUrce EVenT (useful when source particles are obtained from an
external event generator)
FLKSTK: main FLUKA particle stack
SUMCOU: total numbers and total weights relative to many physical and Monte
Carlo events (needed for normalisation, energy balance etc.)
TRACKR: TRACKs Recording (properties of the currently transported particle and
its path)
USRBIN, USRBDX, USRSNC, USRTRC, USRYLD: parameters of the requested estimators
and binnings
User routines
-------------
===============================================================================
--------
abscff.f: user defined ABSorption CoeFFicient
--------
Argument list (all variables are input only):
WVLNGT : photon wavelength (in cm)
OMGPHO : angular frequency (omega = 2pi nu) of the photon (in s-1)
MMAT : material index
Function ABSCFF returns a user-defined absorption coefficient for optical
photons.
It is activated by setting WHAT(2) < -99 in command OPT-PROP, with SDUM = blank.
See option OPT-PROP and Chap. 12} for more information.
===============================================================================
--------
comscw.f: weighting deposited energy, stars or residual nuclei
--------
Argument list (all variables are input only):
IJ : particle type (1 = proton, 8 = neutron, etc.: see code in 5})
XA,YA,ZA : current particle position
MREG : current geometry region
RULL : amount to be deposited (unweighted)
LLO : particle generation
ICALL : internal code calling flag (not for general use)
This routine is activated by option USERWEIG, with WHAT(6) > 0.0.
Energy and star densities obtained via SCORE and USRBIN, and energy
and stars obtained via EVENTBIN and production of residual nuclei
obtained via RESNUCLEi are multiplied by the value returned
by this function. The user can implement any desired logic to
differentiate the returned value according to any information
contained in the argument list (particle type, position, region,
amount deposited, particle generation), or information available in
the SCOHLP COMMON block (binning number, type of scored quantity).
The scored quantity is given by the flag ISCRNG (in SCOHLP):
ISCRNG = 1 --> Energy density binning
ISCRNG = 2 --> Star density binning
ISCRNG = 3 --> Residual nuclei scoring
The binning/estimator number is given by JSCRNG (in SCOHLP) and is
printed in output:
Res. nuclei n. 3 "any-name" , "high" energy products, region n. 4
R-Phi-Z binning n. 5 "other-name" , generalised particle n. 1
. Note that an estimator of residual nuclei can have the same JSCRNG
number as a binning (use the value of ISCRNG to discriminate).
Further information can be obtained including COMMON TRACKR (for
instance particle's total energy, direction cosines, age). TRACKR
contains also special user variables (both integer and in double
precision) which can be used to save information about particles which
have undergone some particular event. If data concerning the current
material are needed, it can be accessed as MEDIUM(MREG) if file (FLKMAT)
is included. Indeed, a common simple application of COMSCW is to score
dose according to the local density (especially useful to get the
correct average dose in bins straddling a boundary between two
different media):
..................
INCLUDE '(FLKMAT)'
INCLUDE '(SCOHLP)'
..................
* ========== In order to compute doses ========= *
* Medium(n) is the material number of region n
* Rho(m) is the density of material m (in g/cm3)
* Iscrng = 1 means we are depositing energy (not stars)
IF ( ISCRNG .EQ. 1 ) THEN
* to get dose in Gy (elcmks is the electron charge in C)
COMSCW = ELCMKS * 1.D12 / RHO (MEDIUM(MREG))
ELSE
* oneone is defined as 1.D0 in include DBLPRC
COMSCW = ONEONE
ENDIF
..................
Note: setting the variable LSCZER = .TRUE. before RETURN (LSCZER is in
COMMON SCOHLP), will cause zero scoring whatever the value returned
by COMSCW. This is more efficient than returning a zero value.
===============================================================================
--------
dffcff.f: user defined DiFFusion CoeFFicient
--------
Argument list (all variables are input only):
WVLNGT : photon wavelength (in cm)
OMGPHO : angular frequency (omega = 2pi nu) of the photon (in s-1)
MMAT : material index
Function DFFCFF returns a user-defined diffusion coefficient for optical photons.
It is activated by setting WHAT(3) < -99 in command OPT-PROP, with SDUM = blank.
See option OPT-PROP and Chap. 12} for more information.
===============================================================================
--------
endscp.f: ENergy density DiStributed - Change of Positions
--------
Argument list (all variables are input only):
IJ : particle type (input only)
NTRUCK : number of step points (input only)
XTRUCK,YTRUCK,ZTRUCK : particle step points, can be modified by user
MREG : region number (input only)
LLO : particle generation (input only)
ICALL : internal code calling flag (not for general use)
Subroutine ENDSCP allows to shift by a user-defined distance the energy which
is being deposited along a step or several step binning portions, by providing
new segment endpoints. A typical application is to simulate an instrument drift.
===============================================================================
--------
fldscp.f: FLuence DiStributed - Change of Positions
--------
Argument list (all variables are input only):
IJ : particle type
PLA : particle momentum (if > 0), or kinetic energy (if < 0)
(input only)
TXX,TYY,TZZ : particle direction cosines, can be modified by user
NTRUCK : number of step points
XTRUCK,YTRUCK,ZTRUCK : particle step points, can be modified by user
NREG : new region number (input only)
IOLREG : old region number (input only)
LLO : particle generation (input only)
ICALL : internal code calling flag (not for general use)
Subroutine FLDSCP allows to shift by a user-defined distance the track whose
length is being scored as fluence along a step or several step binning portions,
by providing new segment endpoints. A typical application is to simulate an
instrument drift.
===============================================================================
--------
fluscw.f: weighting fluence, current and yield
--------
Argument list (all variables are input only):
IJ : particle type
PLA: particle momentum (if > 0), or -PLA = kinetic energy
(if <0)
TXX,TYY,TZZ: particle current direction cosines
WEE: particle weight
XX,YY,ZZ: particle position
NREG: current region (after boundary crossing)
IOLREG: previous region (before boundary crossing). Useful only
whith boundary crossing estimators; for other estimators it
has no meaming.
LLO: particle generation
ICALL: internal code calling flag (not for general use)
Function FLUSCW is activated by option USERWEIG, with WHAT(3) > 0.0.
Yields obtained via USRYIELD, fluences calculated with USRBDX,
USRTRACK, USRCOLL, USRBIN, and currents calculated with USRBDX are
multiplied by the value returned by this function. The user can
implement any desired logic to differentiate the returned value
according to any information contained in the argument list (particle
type, energy, direction, weight, position, region, boundary, particle
generation), or information available in the SCOHLP COMMON block
(binning or estimator number, estimator type).
The scored quantity is given by the flag ISCRNG (in SCOHLP):
ISCRNG = 1 --> Boundary crossing estimator
ISCRNG = 2 --> Track length binning
ISCRNG = 3 --> Track length estimator
ISCRNG = 4 --> Collision density estimator
ISCRNG = 5 --> Yield estimator
The binning/estimator number is given by JSCRNG (in SCOHLP) and is
printed in output:
Bdrx n. 2 "bdxname" , generalised particle n. 8,
from region n. 22 to region n. 78
Track n. 6 "trkname" , generalised particle n. 14, region n. 9
. Note that a track-length estimator can have the same JSCRNG number as
a boundary crossing one or a binning etc. (use the value of ISCRNG to
discriminate).
Further information can be obtained including COMMON TRACKR (for
instance particle age). TRACKR contains also special user variables
(both integer and in double precision) which can be used to save
information about particles which have undergone some particular
event.
Function FLUSCW has many applications. A common one in shielding
calculations is to multiply selected scored fluences by
particle/energy-dependent fluence-to-dose equivalent conversion
coefficients, or by some instrument response, radiation damage curve,
etc. Another application is conditional scoring (score only if
within a certain distance from a point, etc.): for instance it is
possible to implement a sort of 2-dimensional fluence binning on
a plane boundary.
FLUSCW can be used also when scoring "fluxes" (i.e. fluences or
currents or yields) of heavy ions, to discriminate between different
types of ions.
All ions in FLUKA carry the same id-number IJ = -2: therefore ion
fluxes obtained by the various estimators will refer to all ions
unless an additional discrimination is introduced by the user at
scoring time. This can be done in FLUSCW as follows:
CALL USRDCI(IJ,IONA,IONZ,IONM)
The three integer values returned are the following ion properties:
IONA = mass number of the ion
IONZ = atomic number
IONM = flag for isomeric state
Based on their values, the user can decide or not to accept the
scoring.
Other interesting applications are based on the fact that
FLUSCW is called at every boundary crossing, provided that at least
one USRBDX estimator has been requested. Although the function has
been designed mainly to weight scored quantities, it can be "cheated"
to do all sorts of side things, even not directly connected with
scoring.
Note: setting the variable LSCZER (in SCOHLP) = .TRUE. before
RETURN, will cause zero scoring whatever the value returned
by FLUSCW. This is more efficient than returning a zero value.
===============================================================================
--------
formfu.f nuclear form factor
--------
Argument list (all variables are input only):
IJ : particle code, except that it is set to 3 for both e+ and e-
QU2 : squared momentum transfer (GeV/c)^2
ZMEDIU : atomic number of target nucleus
AMEDIU : atomic mass of target nucleus
Function FORMFU can be used to override the standard value of the
nuclear charge form factor. It must return the squared value of the
nuclear charge form factor for particle IJ.
The default version computes the form factor in Born approximation for
a medium of given composition, using the simple expression given by
Tsai [Tsa74], and accounts also for the contribution of incoherent
scattering.
The function is called by the multiple and single scattering routines if
option MULSOPT has been issued with WHAT(3) 8}). It is expected to transform coordinates and
direction cosines from any lattice cell (defined by card LATTICE) to
the reference system in which the basic structure has been described.
The user is expected to provide a transformation of coordinates and
vector direction cosines from each lattice cell to the corresponding
basic structure (in ENTRY LATTIC) and of direction cosines from the
basic structure to each corresponding lattice cell (in ENTRY LATNOR).
Entries:
LATTIC (position and direction symmetry transformation from lattice
cell to prototype structure)
Argument list:
XB(1), XB(2), XB(3) : actual physical position coordinates in IRLTGG
lattice cell
WB(1), WB(2), WB(3) : actual physical direction cosines in IRLTGG
lattice cell
DIST : reserved variable???
SB(1), SB(2), SB(3) : transformed coordinates in prototype cell
UB(1), UB(2), UB(3) : transformed cosines in prototype cell
IR : region number in prototype cell
IRLTGG : lattice cell number
IRLT : array containing region indices corresponding to
lattice cells
IFLAG : reserved variable
LATTIC returns the tracking point coordinates (SB) and direction
cosines(UB) in the reference prototype geometrical structure,
corresponding to real position/direction XB, WB in the actual cell
IRLTGG (defined as input region IR by a LATTICE card).
When the lattice option is activated, the tracking proceeds in two
different systems: the "real" one, and that of the basic symmetry unit.
Particle positions and directions are swapped from their real values
to their symmetric ones in the basic cell, to perform the physical
transport in the regions and materials that form the prototype
geometrical structure and back again to the real world. The
correspondence between "real" and "basic" position/direction depends
on the symmetry transformation and on the lattice cell number.
LATNOR (LATtice cell NORmal transformation from prototype structure to
lattice cell)
Argument list:
UN(1), UN(2), UN(3) : direction cosines of the vector normal to the
surface, in the prototype cell (entry values)
and in the lattice cell (returned values)
IRLTNO : present lattice cell number
Entry LATNOR transforms the direction cosines stored in the vector
UN(3) from the system of the basic prototype unit to that of the real
world in lattice cell number IRLTNO. Therefore, this cosine
transformation must be the inverse of that performed on the cosines by
the LATTIC entry: but while LATTIC maps vector UB to a different
vector WB, LATNOR maps the UN vector to itself.
Note that if the transformation implies a rotation, it is necessary to
save first the incoming UN cosines to local variables, to avoid
overwriting the vector before all transformation statements are
executed.
NOTES:
Different symmetry transformations can of course be implemented
in the same LATTIC routine (each being activated by a different cell
number or range of cell numbers).
The advantage of the lattice geometry is to avoid describing in detail
the geometry of repetitive multi-modular structures. It must be
realised, however, that a penalty is generally paid in computer
efficiency.
Also, a region contained in the prototype cell and all those "mirrored"
to it inside lattice cells are treated by the program as if they
were connected with "non-overlapping ORs" into a single region.
Therefore, any region-based scoring (options SCORE, USRTRACK, etc.)
can only provide quantities averaged over the whole structure. More
detailed information must be obtained by region-independent options
such as USRBIN or by user-written routines (MGDRAW).
===============================================================================
--------
magfld.f definition of a magnetic field
--------
Argument list:
X,Y,Z: current position (input only)
BTX,BTY,BTZ: direction cosines of the magnetic field vector
(returned).
B: magnetic field intensity in Tesla (returned)
NREG: current region (input only)
IDISC: if returned = 1, the particle will be discarded
MAGFLD is activated by option MGNFIELD with WHAT(4-6) = 0.0 and is
used to return intensity and direction of a magnetic field
based on the current position and region. It is called only
if the current region has been flagged as having a non-zero
magnetic field by option ASSIGNMAt, with WHAT(5) = 1.0.
The magnetic field spatial distribution is often read and
interpolated from an external field map. Note that in any
case the direction cosines MUST be properly normalised in
double precision (e.g. BTX = SQRT(ONEONE - BTY**2 - BTZ**2)),
even if B = 0.0.
Please read carefully the notes on option MGNFIELD.
===============================================================================
--------
mdstck.f management of the stack of secondaries
--------
Argument list:
IFLAG: type of nuclear interaction which has produced secondaries:
1: inelastic
2: elastic
3: low-energy neutron
NUMSEC: number of secondary particles produced in the interaction
MDSTCK is called after a nuclear interaction in which at least one
secondary particle has been produced, before any biasing
is applied to decide which secondary will be loaded in
the main stack for further transport. The properties of
the secondaries are stored in the secondary stack (COMMON
GENSTK). With MDSTCK, the user can analyse those secondaries,
write them to a file, or even modify the content of GENSTK
(for instance applying his own biasing). In the latter case,
however, it is his responsibility to make sure that energy is
conserved, the various physical quantities are still
consistent, etc.
===============================================================================
--------
mgdraw.f general event interface
--------
Subroutine MGDRAW, activated by option USERDUMP with WHAT(1) >= 100.,
usually writes a "collision tape", i.e. a file where all or selected
transport events are recorded. The default version (unmodified by the
user) offers several possibilities, selected by WHAT(3) in USERDUMP.
Details are given in 11}.
Additional flexibility is offered by a user entry USDRAW, interfaced
with the most important physical events happening during particle
transport.
The user can modify of course also any other entry of this
subroutine (MGDRAW for trajectory drawing, ENDRAW for recording of
energy deposition events, and SODRAW for recording of source events):
for instance the format of the output file can be changed, and
different combinations of events can be written to file.
But the most interesting aspect of the routine is that the four
entries (all of which, if desired, can be activated at the same time
by setting USERDUMP with WHAT(3) = 0.0 and WHAT(4) >= 1.0) constitute
a complete interface to the whole FLUKA transport. Therefore, MGDRAW
can be used not only to write a collision tape, but to do any kind
of complex analysis (for instance studying correlations between
events).
Entries:
MGDRAW (trajectory dumping for drawing)
Argument list (all variables are input only):
ICODE: FLUKA physical compartment originating the call
= 1: call from Kaskad (hadrons and muons)
= 2: call from Emfsco (electrons, positrons and photons)
= 3: call from Kasneu (low-energy neutrons)
= 4: call from Kashea (heavy ions)
= 5: call from Kasoph (optical photons)
MREG: current region
MGDRAW writes by default, for each trajectory, the following
variables (contained in COMMON TRACKR):
NTRACK: number of track segments
MTRACK: number of energy deposition events along the track
JTRACK: type of particle
ETRACK: total energy of the particle
WTRACK: weight of the particle
Ntrack values of XTRACK, YTRACK, ZTRACK: end of each track
segment
Mtrack values of DTRACK: energy deposited at each deposition
event
CTRACK: total length of the curved path
Other variables are available in TRACKR (but not written by
MGDRAW unless the latter is modified by the user: particle
momentum, direction cosines, cosines of the polarisation
vector, age, generation, etc. (see a full list in the comment
in the INCLUDE file).
BXDRAW (boundary crossing dumping)
Argument list (all variables are input only):
ICODE: FLUKA physical compartment originating the call
= 19: call from Kaskad (hadrons and muons)
= 29: call from Emfsco (electrons, positrons and photons)
= 39: call from Kasneu (low-energy neutrons)
= 49: call from Kashea (heavy ions)
= 59: call from Kasoph (optical photons)
MREG: number of region before boundary crossing
NEWREG: number of region after boundary crossing
XSCO, YSCO, ZSCO: coordinates of crossing point
BXDRAW is called at each boundary crossing (if requested by the user
with USERDUMP, WHAT(3) =< 0.0). There is no default output: any
output must be supplied by the user.
EEDRAW (event end)
Argument list:
ICODE = -1: event not completed
= 0: normal event termination
= 4: stack overflow
EEDRAW is called at the end of each event, or primary history,
(if requested by the user with USERDUMP, WHAT(3) =< 0.0). There is no
default output: any output must be supplied by the user.
ENDRAW (energy deposition dumping)
Argument list (all variables are input only):
ICODE: type of event originating energy deposition
1x: call from Kaskad (hadrons and muons)
10: elastic interaction recoil
11: inelastic interaction recoil
12: stopping particle
13: pseudo-neutron deposition
14: particle escaping (energy deposited in blackhole)
2x: call from Emfsco (electrons, positrons and photons)
20: local energy deposition (i.e. photoelectric)
21 or 22: particle below threshold
23: particle escaping (energy deposited in blackhole)
3x: call from Kasneu (low-energy neutrons)
30: target recoil
31: neutron below threshold
32: neutron escaping (energy deposited in blackhole)
4x: call from Kashea (heavy ions)
40: ion escaping (energy deposited in blackhole)
5x: call from Kasoph (optical photons)
50: optical photon absorption
51: optical photon escaping (energy deposited in
blackhole)
MREG: current region
RULL: energy amount deposited
XSCO, YSCO, ZSCO: point where energy is deposited
ENDRAW writes by default, for each energy deposition point:
0: flag identifying ENDRAW output from that of other entries
ICODE: see argument list
JTRACK, ETRACK, WTRACK: see MGDRAW above
XSCO, YSCO, ZSCO, RULL: see argument list
SODRAW (source particle dumping)
No arguments
SODRAW writes by default, for each source or beam particle:
-NCASE (in COMMON CASLIM, with a minus sign to identify
Sodraw output): number of primaries followed so far
NPFLKA (in COMMON FLKSTK): stack pointer
NSTMAX (in COMMON FLKSTK): highest value of the stack pointer
encountered so far
TKESUM (in COMMON SOURCM): total kinetic energy of the
primaries of a user written source (see source.f
here below), if applicable. Otherwise = 0.0
WEIPRI (in COMMON SUMCOU): total weight of the primaries
handled so far
Npflka times: ILOFLK: type of source particle
TKEFLK+AM: total particle energy (kinetic+mass)
WTFLK: source particle weight
XFLK, YFLK, ZFLK: source particle position
TXFLK, TYFLK, TZFLK: source particle direction cosines
USDRAW
Argument list (all variables are input only):
ICODE: 10x: call from Kaskad (hadron and muon interactions)
100: elastic interaction secondaries
101: inelastic interaction secondaries
102: particle decay secondaries
103: delta ray generation secondaries
104: pair production secondaries
105: bremsstrahlung secondaries
20x: call from Emfsco (electron, positron and photon
interactions)
208: bremsstrahlung secondaries
210: Moller secondaries
212: Bhabha secondaries
214: in-flight annihilation secondaries
215: annihilation at rest secondaries
217: pair production secondaries
219: Compton scattering secondaries
221: photoelectric secondaries
225: Rayleigh scattering secondaries
30x: call from Kasneu (low-energy neutron interactions)
300: interaction secondaries
40x: call from Kashea (heavy ion interactions)
400: delta ray generation secondaries
MREG: current region
XSCO, YSCO, ZSCO: interaction point
USDRAW is called after each particle interaction (if requested by
the user with USERDUMP, WHAT(4) >= 1.0). There is no default output:
any output must be supplied by the user.
Information about the secondary particles produced is available
in COMMON GENSTK, except that concerning delta rays produced by heavy
ions (in which case the properties of the single electron produced
are available in COMMON EMFSTK, with index NP).
Information about the interacting particle and its trajectory can be
found in COMMON TRACKR (see description under the MGDRAW entry
above). In TRACKR there are also some spare variables at the user's
disposal: LLOUSE (integer), ISPUSR (integer array) and SPAUSR
(double precision array). Like many other TRACKR variables, each of
them has a correspondent in the particle stacks, i.e. the COMMONs
from which the particles are unloaded at the beginning of their
transport: FLKSTK, EMFSTK and OPPHST (respectively, the stack of
hadrons/muons, electrons/photons, and optical photons). The
correspondence with TRACKR is shown below under STUPRF/STUPRE.
When a particle is generated, its properties (weight, momentum,
energy, coordinates etc., as well as the values of the user flags)
are loaded into one of the stacks. The user can write a STUPRF or
STUPRE subroutine (see description below) to change anyone of such
flags just before it is saved in stack.
When a particle starts to be transported, its stack variables are
copied to the corresponding TRACKR ones. Unlike the other TRACKR
variables, which in general become modified during transport due to
energy loss, scattering etc., the user flags keep their original
value copied from stack until they are changed by the user himself
(generally in USDRAW).
One common application is the following: after an interaction which
has produced sencondaries, let USDRAW copy some properties of the
interacting particle into the TRACKR user variables. When STUPRF is
called next to load the secondaries into stack, by default it copies
the TRACKR user variables to the stack ones. In this way,
information about the parent can be still carried by its daughters
(and possibly by further descendants). This technique is sometimes
referred to as "latching".
===============================================================================
--------
ophbdx.f user defined Optical PHoton BounDary-(X)crossing properties
--------
Argument list (all variables are input only):
OMGPHO : angular frequency (omega = 2 pi nu) of the photon (in s-1)
WVLNGT : photon wavelength (in cm)
MREG : old region number
NEWREG : new region number
SIGANW : absorption coefficient in the new region (cm-1)
SIGDNW : diffusion coefficient in the new region (cm-1)
RFNDPR : refractive index in the new region
VGRPNW : group velocity in the new region (cm s-1)
LPHKLL : if .TRUE., the photon will be absorbed on the boundary
Subroutine OPHBDX sets the optical properties of a boundary surface.
The call is activated by command OPT-PROP, with SDUM = SPEC-BDX.
See option OPT-PROP and Chap. 12} for more information.
===============================================================================
--------
queffc.f: user defined QUantum EFFiCiency
--------
Argument list (all variables are input only):
WVLNGT : photon wavelength (in cm)
OMGPHO : angular frequency (omega = 2pi nu) of the photon (in s-1)
Function QUEFFC returns a user-defined quantum efficiency for an optical
photon of the given wavelength or frequency.
It is activated by OPT-PROP, with SDUM = SENSITIV, by setting
the 0th photon sensitivity parameter to a value < -99.
See option OPT-PROP and Chap. 12} for more information.
===============================================================================
--------
rflctv.f: user defined ReFLeCTiVity
--------
Argument list (all variables are input only):
WVLNGT : photon wavelength (in cm)
OMGPHO : angular frequency (omega = 2pi nu) of the photon (in s-1)
MMAT : material index
Function RFLCTV returns a user-defined value equal to 1-R, where R is the
reflectivity of the current material for an optical photon of the given wavelength or
frequency.
It is activated by OPT-PROP, with SDUM = METAL, and WHAT(3) < -99.
See option OPT-PROP and Chap. 12} for more information.
===============================================================================
--------
rfrndx.f: user defined ReFRaction iNDeX
--------
Argument list (all variables are input only):
WVLNGT : photon wavelength (in cm)
OMGPHO : angular frequency (omega = 2pi nu) of the photon (in s-1)
MMAT : material index
Function RFRNDX returns a user-defined refraction index of the current material for
an optical photon of the given wavelength or frequency.
It is activated by OPT-PROP, with SDUM = blank, and WHAT(1) < -99.
See option OPT-PROP and Chap. 12} for more information.
===============================================================================
--------
soevsv.f SOurce EVent SaVing
--------
No arguments
Subroutine SOEVSV is always called after a beam particle is loaded
into FLKSTK, but a call to SOEVSV can be inserted by the user anywhere
in a user routine.
SOEVSV copies the whole FLKSTK to another COMMON, SOUEVT, which can
be included in other user routines. In other words, this routine is
used to "take a snapshot" of the particle bank at a particular time
for further use (interfacing to independent generators, etc.)
===============================================================================
--------
source.f user-written source
--------
Argument list:
NOMORE: if set = 1, no more calls will occur (the run will be
terminated after exhausting the primary particles loaded
into FLKSTK stack in the present call). The history number limit
set with option START will be overridden.
Subroutine SOURCE is probably the most frequently used user routine.
It is activated by option SOURCE and is used to sample primary
particle properties from distributions (in space, energy, time,
direction, polarisation or mixture of particles) too complicated to be
described with the BEAM, BEAMPOS and POLARIZAti cards alone. For each
phase-space variable, a value must be loaded into COMMON FLKSTK (particle
bank) before returning control. These values can be read from a file,
generated by some sampling algorithm, or just assigned.
Reading from a file:
--------------------
Reading from a file is needed, for instance, when the particle data
are taken from a collision file, written by FLUKA or by another
program. The user must open the file with a unit number > 20 (unit
numbers lower than 20 are reserved), in one of the following ways:
1) Using option OPEN, with SDUM = OLD
2) In a user subroutine USRINI (see below), with a Fortran OPEN
statement. Option USRICALL is needed to activate the call to
the routine.
3) With an OPEN statement in the initialisation part of subroutine
SOURCE itself.
Then, a READ statement in SOURCE can be used to get the data to load
in stack, for instance:
READ(21,*) IPART, X, Y, Z, COSX, COSY, COSZ, ENERGY, WEIGHT
ILOFLK (NPFLKA) = IPART
XFLK (NPFLKA) = X
YFLK (NPFLKA) = Y
ZFLK (NPFLKA) = Z
TXFLK (NPFLKA) = COSX
...etc...
(NPFLKA is the current stack index).
Direct assignment:
------------------
Direct assignment can be done explicitly, for instance:
PMOFLK (NPFLKA) = 305.2D0
or implicitly, leaving unmodified values input with BEAM or BEAMPOS:
PMOFLK (NPFLKA) = PBEAM
(PBEAM is the momentum value input as WHAT(1) in option BEAM).
A set of direct assignments, one for each of several different stack
entries, can be useful, for example, to define a series of RAYs through
the geometry (see 14}):
DO 10 I = 1, 20
NPFLKA = NPFLKA + 1
ILOFLK (NPFLKA) = 0 (0 is the RAY particle id number)
XFLK (NPFLKA) = 500.D0 + DBLE(I) * 40.D0
YFLK (NPFLKA) = 200.D0
...etc...
10 CONTINUE
Sampling from a uniform distribution:
-------------------------------------
To sample from a uniform distribution, the user must use the
function FLRNDM(DUMMY), which returns a double precision
pseudo-random number uniformly distributed between 0 (included)
and 1 (not included). Actually, DUMMY can be any variable name.
A simple example of sampling from a uniform distribution is that of
a linear source along the Z axis, between Z = 10 and Z = 80:
Z1 = 10.D0
Z2 = 80.D0
ZFLK (NPFLKA) = 10.D0 + (Z2 - Z1) * FLRNDM(XXX)
Sampling from a generic distribution:
-------------------------------------
One way to sample a value XX from a generic distribution f(x) is
the following.
First integrate the distribution function, analytically or
numerically, and normalise to 1 to obtain the normalised
cumulative distribution:
/x /xmax
F(x) = | f(x)dx / | f(x)dx
/xmin /xmin
Then, sample a uniform pseudo-random number t using FLRNDM and
-1
get the desired result by finding the inverse value XX = F (t)
(analytically or most often by interpolation).
A FLUKA subroutine is available to sample directly from a Gaussian
distribution:
CALL FLNRRN (RGAUSS)
or, if two independent Gaussian distributed numbers are needed:
CALL FLNRR2 (RGAUS1, RGAUS2)
(faster than calling FLNRRN twice).
Sampling from a biased distribution:
------------------------------------
The technique for sampling from a generic distribution described
above can be extended to modify the probability of sampling in
different parts of the interval (importance sampling). We
replace f(x) by a weighted function g(x) = f(x) * h(x), where h(x)
is any appropriate function of x we like to choose. We normalise g(x)
in the same way as f(x) before:
/x /xmax /x
G(x) = | g(x)dx / | g(x)dx = | f(x)*h(x)dx / B
/xmin /xmin /xmin
and we need also the integral of f(x) over the whole interval:
/xmax
A = | f(x)dx
/xmin
All the sampling is done using the biased cumulative normalised
function G instead of the original unbiased F: we sample a uniform
pseudo-random number t as before, and we get the sampled value XX by
inverting G(x):
-1
XX = G (t)
The particle is assigned a weight B/(A * h(XX))
A special case of importance sampling is when the biasing function
chosen is the inverse of the unbiased distribution function:
h(x) = 1/f(x)
g(x) = f(x) * h(x) = 1
G(x) = (x - xmin) / (xmax - xmin)
In this case we sample a uniform pseudo-random number t using
FLRNDM as shown above. The sampled value XX is simply given by:
XX = xmin + (xmax - xmin)*t
and the particle is assigned a weight = f(XX)*(xmax - xmin).
Because XX is sampled with the same probability over all possible
values of x, independently of the value f(XX) of the function,
this technique is used to ensure that sampling is done uniformly
over the whole interval, even though f(x) might have very small
values somewhere. For instance it may be important to avoid
undersampling in the high-energy tail of a spectrum, steeply falling
with energy but more penetrating, such as that of cosmic rays or
synchrotron radiation.
Option SOURCE allows the user to input up to 12 numerical values
(WHASOU(1),(2)...(12)) and one 8-character string (SDUSOU) which can
be accessed by the subroutine by including the following line:
INCLUDE '(SOURCM)'
These values can be used as parameters or switches for a multi-source
routine capable to handle several cases, or to identify an external
file to be read, etc., without having to compile and link again the
routine.
In the SOURCE routine there are a number of mandatory statements,
(clearly marked as such in accompanying comments) which must not be
removed or modified. The following IF block initialises the total
kinetic energy of the primary particles and sets two flags: the
first to skip the IF block in all next calls, and the second to
remind the program, when writing the final output, that a user source
has been used:
* +-------------------------------------------------------------------*
* | First call initialisations:
IF ( LFIRST ) THEN
* | *** The following 3 cards are mandatory ***
TKESUM = ZERZER
LFIRST = .FALSE.
LUSSRC = .TRUE.
* | *** User initialisation ***
END IF
* |
* +-------------------------------------------------------------------*
The user can insert into the above IF block any other initialisation
needed, for instance the preparation of a cumulative spectrum
array from which to sample the energy of the source particles.
Note that user initialisation can take place also in routine USRINI
(activated at input time by input option USRICALL) and USREIN (called
before unloading from stack the first source particle of an event,
i.e., just after the call to SOURCE)
At the time SOURCE is called, the particle bank FLKSTK is always empty
and the stack pointer NPFLKA has value 0.
The user can load into the FLKSTK stack one or more source particles
at each call: for each particle loaded the pointer must be increased
by 1.
The template version of SOURCE loads only one particle: if several
are loaded the following sequence, until the statement CALL SOEVSV not
included, must be repeated once for each particle, possibly inside a
DO loop:
NPFLKA = NPFLKA + 1 increases the pointer
The following statements assign a value to each of the FLKSTK
variables concerning the particle being loaded.
WTFLK (NPFLKA) = ONEONE sets the weight of the particle = 1.
This must be changed if the sampling of one or more of the
particle properties are biased. In that case, generally the weight
must be set after the sampling, and its value depends on the
sampling outcome.
WEIPRI = WEIPRI + WTFLK (NPFLKA) updates the total weight of the
primaries (don't change)
ILOFLK (NPFLKA) = IJBEAM by default sets the type of particle
equal to the one defined by the BEAM card (if no BEAM card is
given in input, IJBEAM is = 1 (proton)).
The above statement is followed by several others that must not be
changed or removed. In the template routine, they are encompassed by
the comment lines:
From this point .... / ... to this point: don't change anything
These statements are:
* From this point ....
LOFLK (NPFLKA) = 1 Generation is 1 for source particles
LOUSE (NPFLKA) = 0 User variables: the user can set
DO 100 ISPR = 1, MKBMX1 different values in the STUPRF or
SPAREK (1,NPFLKA) = ZERZER STUPRE routine, but it is better
100 CONTINUE not to do it here
DO 200 ISPR = 1, MKBMX2
ISPARK (ISPR,NPFLKA) = 0 More user variables (integer)
200 CONTINUE
NPARMA = NPARMA + 1 Updating the maximum particle number
NUMPAR (NPFLKA) = NPARMA Setting the current particle number
NEVENT (NPFLKA) = 0 Resetting the current event number
DFNEAR (NPFLKA) = +ZERZER Resetting the distance to the
nearest boundary
* ... to this point: don't change anything
The following statements can be overridden or rewritten by the user,
assigning new values or sampling them from problem-dependent
distributions.
First three statements which are rarely modified:
AGESTK (NPFLKA) = +ZERZER Particle age is zero by default
AKNSHR (NPFLKA) = -TWOTWO Resets the Kshort component of
K0/K0bar. Usually not to be changed.
IGROUP (NPFLKA) = 0 Group number for low energy
neutrons: if set to 0, the program
derives it from the kinetic energy
Then the most frequently changed lines: both energy and momentum of
the particle must be loaded onto FLKSTK, but the two cannot be defined
independently. Appropriate kinematical (relativistic) relations must
be applied to derive one from the other.
In the template routine, the momentum is assumed to be assigned by
BEAM option (its value, PBEAM, is taken from COMMON BEAMCM, which
contains all values defined by options BEAM and BEAMPOS).
PMOFLK (NPFLKA) = PBEAM
Therefore, the kinetic energy (in GeV) must be derived:
TKEFLK (NPFLKA) = SQRT ( PBEAM**2 + AM (IJBEAM)**2 ) - AM (IJBEAM)
(where AM is the rest mass, in COMMON PAPROP, and IJBEAM is the
particle type, in COMMON BEAMCM)
If instead the energy had been sampled first from some spectrum, and
ENSAMP would be the sampled value, the two statements above would
become:
TKEFLK (NPFLKA) = ENSAMP
PMOFLK (NPFLKA) = SQRT(ENSAMP * (ENSAMP + TWOTWO * AM(IJBEAM)))
The direction cosines are loaded next:
TXFLK (NPFLKA) = UBEAM Assumed here to be the same as
TYFLK (NPFLKA) = VBEAM defined by option BEAMPOS. UBEAM,
TZFLK (NPFLKA) = WBEAM VBEAM, WBEAM are some among the beam
properties in COMMON BEAMCM.
(If BEAMPOS is not given, by default UBEAM = VBEAM = 0.0, WBEAM= 1.0)
Remember to make sure that the cosines are normalised! One could
replace the last statement by:
TZFLK (NPFLKA) = SQRT ( ONEONE - TXFLK(NPFLKA)**2 - TYFLK(NPFLKA)**2 )
The polarisation cosines are not set by default:
TXPOL (NPFLKA) = -TWOTWO -2 is a flag for "no polarisation"
TYPOL (NPFLKA) = +ZERZER
TZPOL (NPFLKA) = +ZERZER
but appropriate values need to be given in some cases, for instance
in synchrotron radiation shielding problems.
Finally the particle coordinates, set again by default equal to those
input with BEAMPOS:
XFLK (NPFLKA) = XBEAM Assumed here to be the same as
YFLK (NPFLKA) = YBEAM defined by option BEAMPOS. XBEAM,
ZFLK (NPFLKA) = ZBEAM YBEAM, ZBEAM are also in COMMON
BEAMCM.
(If BEAMPOS is not given, by default XBEAM = YBEAM = ZBEAM = 0.0)
If for example our problem required instead a linear source uniformly
distributed along Z between Z1 and Z2, we could replace the last
statement by:
ZFLK (NPFLKA) = Z1 + FLRNDM(UGH) * (Z2 - Z1)
The following lines in the template SOURCE routine should never be
changed. They calculate the total energy of the primary particles,
define the remaining properties of the particles (starting region and
lattice cell) and do some geometry initialisation.
The last line calls the SOEVSV user routine (see description above)
to save the stack for possible further use.
===============================================================================
--------
stupre.f SeT User PRoperties for EMF particles
stuprf.f SeT User PRoperties for FLUKA particles
--------
These two functions are used to assign a value to one or more stack
user variables when the corresponding particle is loaded into one of
the stacks (FLKSTK for hadrons/muons, EMFSTK for electrons/photons,
OPPHST for optical photons).
In each of these stacks the user has access to one integer variable,
one integer array and one double precision array. Each of them is
copied to a correspondent variable or array in COMMON TRACKR at the
beginning of transport:
Correspondence: FLKSTK EMFSTK OPPHST TRACKR
-------------- ----- ------ ------ ------
integer variable: LOUSE LOUEMF LOUOPP --> LLOUSE
integer array: ISPARK IESPAK ISPORK --> ISPUSR
double precision array: SPAREK ESPARK SPAROK --> SPAUSR
The user can access and modify the TRACKR variables via subroutine
MGDRAW and its entries ENDRAW, SODRAW and especially USDRAW (see
description above). STUPRF and STUPRE can be used to do the reverse,
namely to copy TRACKR user variables to those of the relevant stack
(see USDRAW above).
STUPRE is called before loading into stack electrons, positrons and
photons.
No arguments
The default version does nothing (the user variables of the parent
particle are already set equal to the original projectile by the
various electromagnetic interaction routines. Also the
region/position etc. are already set inside the stack arrays.
STUPRF is called before loading into stack hadrons, muons, neutrinos,
low-energy neutrons, heavy ions and optical photons
Argument list:
IJ : type of the parent particle
MREG : current region
XX, YY, ZZ: particle position
NUMSEC : index in the GENSTK COMMON of the secondary being loaded
onto stack
NPPRMR : if > 0, the secondary being loaded is actually still the
interacting particle (it can happen in some biasing
situations)
Note that heavy ions in FLUKA carry all the same id-number IJ = -2.
The characteristics of primary ions are characterised by option
HI-PROPE. To obtain the those of a secondary ion, call the routine
USRDCI as follows:
CALL USRDCI(IJ,IONA,IONZ,IONM)
The three integer values returned are the following ion properties:
IONA = mass number of the ion
IONZ = atomic number
IONM = flag for isomeric state
The default version of STUPRF copies to stack the user flags of the
parent.
===============================================================================
--------
ubsset.f User BiaSing SETting
--------
Argument list:
IR : region number
RRHADR : multiplicity biasing factor to be applied to the
secondaries from hadronic interactions in region IR
(WHAT(2) of card BIASING)
HMPHAD : Importance of region IR for hadrons and muons (WHAT(3) of
card BIASING, with WHAT(1) = 0 or 1).
Actually the routine argument is an integer, IMPHAD, equal
to importance multiplied by 10000, but the user should
consider only the double precision version HMPHAD
(a conversion from and to the integer version is provided
at the beginning and at the end of the routine, and should
not be changed).
HMPLOW : Importance of region IR for low energy neutrons (WHAT(3)
of card BIASING, with WHAT(1) = 0 or 3).
Actually the routine argument is an integer, IMPLOW, equal
to importance multiplied by 10000, but the user should
consider only the double precision version HMPLOW
(a conversion from and to the integer version is provided
at the beginning and at the end of the routine, and should
not be changed).
HMPEMF : Importance of region IR for electrons and photons (WHAT(3)
of card BIASING, with WHAT(1) = 0 or 2).
Actually the routine argument is an integer, IMPEMF, equal
to importance multiplied by 10000, but the user should
consider only the double precision version HMPEMF
(a conversion from and to the integer version is provided
at the beginning and at the end of the routine, and should
not be changed).
IGCUTO : Cut-off group index for low energy neutrons in region IR
(WHAT(1) in card LOW-BIAS)
IGNONA : Non-analogue absorption group limit for low energy neutrons
in region IR (WHAT(2) in card LOW-BIAS)
PNONAN : Non-analogue survival probability for low energy neutrons in
region IR (WHAT(3) in card LOW-BIAS)
IGDWSC : Group limit for biased downscattering for low energy
neutrons in region IR (WHAT(1) in card LOW-DOWN)
FDOWSC : Biased downscattering factor for low energy neutrons in
region IR (WHAT(2) in card LOW-DOWN)
JWSHPP : Weight-Window/importance profile index for low energy
neutrons in region IR (SDUM in WW-FACTO)
WWLOW : Weight-Window lower level in region IR (WHAT(1) in card
WW-FACTO, possibly modified by WHAT(4) in WW-THRES or
WHAT(2) in WW-PROFI)
WWHIG : Weight-Window upper level in region IR (WHAT(2) in card
WW-FACTO, possibly modified by WHAT(4) in WW-THRES or
WHAT(2) in WW-PROFI)
WWMUL : Weight-Window multiplicative factor applied to the two
energy thresholds defined with WW-THRES, for region IR
(WHAT(3) in card WW-FACTO)
EXPTR : Exponential transform parameter for region IR (WHAT(2) in
card EXPTRANS) (not implemented yet!!!!!!!!)
ELECUT : e+,e- cut-off in region IR (WHAT(1) in card EMFCUT)
GAMCUT : Photon cut-off in region IR (WHAT(2) in card EMFCUT)
LPEMF : Leading Particle Biasing flag in region IR (SDUM = LPBEMF
in card EMF-BIAS, or WHAT(3) in card EMFCUT)
ELPEMF : Maximum e+/e- energy for applying Leading Particle Biasing
(WHAT(2) in card EMF-BIAS with SDUM = LPBEMF)
PLPEMF : Maximum photon energy for applying leading particle
biasing (WHAT(3) in card EMF-BIAS with SDUM = LPBEMF)
Subroutine UBSSET does not require a special command to be activated:
it is always called several times for each region: (once for every
biasing option or suboption) after the end of input reading and
before starting the calculations. The default version is a dummy and
does nothing. The user can replace it to override any biasing
parameters specified in input.
The UBSSET subroutine is used especially in cases with a large number
of regions, because it allows to derive the biasing parameters from
simple algorithms instead of entering each input value by hand.
Choosing an appropriate numbering scheme for the geometry regions can
often facilitate the task.
For instance, assuming a simple slab geometry with an expected
exponential hadron attenuation from region 3 to region 20, each
region being one half-value-layer thick, one could write the
following in order to set importances that would keep the hadron
number about constant in all regions:
IF(IR .GE. 3 .AND. IR .LE. 20) HMPHAD = ONEONE * TWOTWO**(IR-3)
It is important, however, not to do recursive assignments of the type:
GAMCUT(5) = GAMCUT(5) * HLFHLF (HLFHLF is a FLUKA constant for 0.5D0)
because that would halve the value of the photon cut-off for
Region 5 AT EVERY CALL, and the number of calls is not known to the
user.
===============================================================================
--------
udcdrl.f User defined DeCay DiRection biasing and Lambda (for neutrinos only)
--------
Argument list:
IJ : type of decaying particle
KPB : outgoing neutrino (???)
NDCY : (???)
UDCDRB, VDCDRB, WDCDRB : cosines of the preferential outgoing
direction for the neutrino (???)
Function UDCDRL is used to bias the direction of a neutrino emitted
by a decaying particle of type IJ. The value returned by UDCDRL is
the Lambda for direction biasing (1-cos(theta)) (???)
===============================================================================
--------
usimbs.f User defined IMportance BiaSing
--------
Argument list:
input:
MREG : region at the beginning of the step
NEWREG : region at the end of the step
output:
FIMP : returns the user-defined importance ratio between the
The routine is called AT EVERY PARTICLE STEP. It can be used to
implement any importance biasing scheme based on region number and
on phase space coordinates and other information provided by
COMMON TRACKR.
WARNING: The user must balance the very effective biasing power offered
by the routine with the important demand on CPU time due to the
large number of calls.
===============================================================================
--------
usrein.f USeR Event INitialisation
--------
No arguments
Subroutine USREIN is called just before the first source particle of
an event is unloaded from stack and begins to be transported.
An event is the full history of a group of related particles and their
descendants. If primaries are loaded into stack by the input option
BEAM, there is only one source particle per event; but there can be
more if the user routine SOURCE is used to load particles into stack.
USREIN does not need any special command to be activated, but the
default version of USREIN does nothing: the user can write here any
kind of initialisation.
===============================================================================
--------
usreou.f USeR Event OUtput (called at the end of each event)
--------
No arguments
Subroutine USREOU is called at the end of each event, namely after all
event primary particles and their descendants have been transported.
(See USREIN above for a definition of an event).
USREOU does not need any special command to be activated, but the
default version of USREOU does nothing: the user can write here any
kind of event analysis, output, etc.
===============================================================================
--------
usrini.f USeR INItialisation
--------
Argument list:
WHAT(1), (2), (3), (4), (5), (6) : user-given numerical parameters
SDUM : user-given character string (8 characters)
Subroutine USRINI is called every time a USRICALL card is read in
input. It can be used to do any kind of initialisation: reading
and manipulating data from one or more files, calling other private
routines, etc.
The calling parameters can carry any kind of useful information or can
be used as flags to choose between different possible actions to be
performed before any particle transport takes place.
===============================================================================
--------
usrmed.f USeR MEDium dependent directives
--------
Argument list:
IJ : particle type
EKSCO : particle kinetic energy (GeV)
PLA : particle momentum (GeV/c)
WEE : particle weight
MREG : previous region number
NEWREG : current region number
XX, YY, ZZ : particle position
TXX, TYY, TZZ : particle direction
Subroutine USRMED is activated by option MAT-PROP with SDUM = USERDIRE,
for one or more materials indicated by the user.
It is called every time a particle is going to be transported in one of
the user-flagged materials.
Two cases are possible:
1) MREG = NEWREG: the particle is going to move from a point inside
the medium. The user is allowed to change only the particle weight.
Typical application: simulating attenuation of optical photons in an
absorbing medium by reducing the photon weight.
2) MREG not = NEWREG: the particle is going to move from a point on a
boundary between two different regions. The user may change any of
the following: particle weight, current region number, direction
cosines.
Typical applications:
- simulating refraction, by changing the direction cosines so that
the particle is still inside the same region. To do this, one
generally needs the direction cosines of the normal to the
surface: TXNOR(NPFLKA), TYNOR(NPFLKA), TZNOR(NPFLKA) (COMMON
FLKSTK must be included).
- simulating reflection (albedo) at a boundary. The direction
cosines must be modified according to some reflection law or
albedo angular distribution, and NEWREG must be set = MREG.
In both cases the weight can also be reduced to account for surface
reflectivity or similar (if the particle is an optical photon, the
FRGHNS user function can be called to establish a surface roughness)
===============================================================================
--------
usrout.f USeR OUTput
--------
Argument list:
WHAT(1), (2), (3), (4), (5), (6) : user-given numerical parameters
SDUM : user-given character string (8 characters)
Subroutine USROUT is called every time a USROCALL card is read in
input. It is used to print special user-written output in addition
to the standard one provided by default.
The calling parameters can carry any kind of useful information or can
be used as flags to choose between different possible actions to be
performed after all particle transport has taken place.
