defines a detector for a collision fluence estimator
(see also USRBDX, USRBIN, USRTRACK)
The full definition of the detector may require two successive cards
(the second card, identified by the character '&' in any column > 70,
must be given unless the corresponding defaults are accepted)
First card:
WHAT(1) = 1.0 : linear binning in energy
= -1.0 : logarithmic binning in energy
Default = 1.0 (linear binning)
WHAT(2) = (generalised) particle type to be scored
Default = 201.0 (all particles)
WHAT(3) = logical output unit:
> 0.0 : formatted data are written on WHAT(3) unit
< 0.0 : unformatted data are written on |WHAT(3)| unit
Values of |WHAT(1)| < 21 should be avoided (with the
exception of +11).
Default = standard output unit
WHAT(4) = region defining the detector
Default = 1.0
WHAT(5) = volume of the detector in cm**3
Default = 1.0
WHAT(6) = number of energy bins
Default = 10.0
SDUM = any character string (not containing '&') identifying the
collision detector (max. 10 characters)
Continuation card:
WHAT(1) = maximum energy for scoring
Default: Beam particle total energy as set by the BEAM
option (if no BEAM card is given, the energy corresponding
to 200 GeV/c momentum will be used)
WHAT(2) = minimum energy for scoring (note that the energy limits of
the thermal neutron group for the ENEA data sets are
1.E-14 GeV (1.E-5 eV) and 4.14E-10 GeV (0.414 eV))
Default = 0.0 if linear binning, 0.001 GeV otherwise
WHAT(3)..WHAT(6) : not used
SDUM = & in any position in column 71 to 78
Default (option not given): no collision estimator
IMPORTANT!
----------
Note: The results of USRCOLL are always given as DIFFERENTIAL
distributions of fluence in energy (cm-2 GeV-1 per incident
primary unit weight), Thus, for example, when requesting a
fluence energy spectrum, to obtain INTEGRAL BINNED results
(fluence in cm-2 PER ENERGY BIN per primary) one must multiply
the value of each energy bin by the width of the bin (even for
logarithmic binning).
If the generalised particle is 208.0 or 211.0, the quantity
scored is differential energy fluence, expressed in GeV per
cm2 per energy unit per primary. That can sometimes lead to confusion
since GeV cm-2 GeV-1 = cm-2, where energy does not appear.
Note that integrating over energy one gets GeV/cm2.
The maximum number of collision + tracklength detectors (see
option USRTRACK) that the user can define is 400. This value
can be changed by modifying the parameter MXUSTC in member
USRTRC of the flukaadd library or directory and then
re-compiling and linking FLUKA.
The logical output unit for the estimator results (WHAT(3) of
the first USRCOLL card) can be any one of the following:
- the standard output unit 11: estimator results will be
written on the same file as the standard FLUKA output
- a pre-connected unit (via a symbolic link on most UNIX systems,
ASSIGN under VMS, or equivalent commands on other systems)
- a file opened with the FLUKA command OPEN
- a file opened with a Fortran OPEN statement in a user-written
initialisation routine such as USRINI or SOURCE (see 13})
- a dynamically opened file, with a default name assigned by the
Fortran compiler (typically fort.xx or ftn.xx, with xx equal
to the chosen logical output unit number).
The results of several USRCOLL and USRTRACK detectors in a same FLUKA
run can be written on the same file, but of course only if they are
all in the same mode (all formatted, or all unformatted).
It is also possible in principle to write on the same file the
results of different kinds of estimators (USRBDX, USRBIN, etc.)
but this is not recommended, especially in the case of an
unformatted file, because it would make very difficult any reading
and analysis.
When scoring neutron fluence, and the requested
energy bin structure overlaps with that of the low energy
neutron groups, bin boundaries are forced to coincide with
group boundaries and no bin can be smaller than the
corresponding group.
Actually, the program uses the requested energy limits and
number of bins to estimate the desired bin width. The number
of bins above the upper limit of the first low-energy neutron
group is recalculated according to such width.
Note that the energy limits of the thermal neutron group
are 1.E-14 GeV (1.E-5 eV) and 4.14E-10 GeV (0.414 eV) for the
ENEA data sets. All group energy boundaries are listed in
a Table in 10}.
An example on how to read USRCOLL unformatted output
is given in a Note to option USRTRACK (the two options produce
output with identical format). An explanation of the meaning of the
different variables is given in the comments at the beginning
of the program.
A more complex program USTSUW, which allows to compute also
standard deviations over several runs and cumulative
distributions, is available with the normal FLUKA code
distribution in directory $FLUPRO/flutil.
Example:
*...+....1....+....2....+....3....+....4....+....5....+....6....+....7...+...8
USRCOLL -1.0 8.0 23.0 15.0 540.0 350. NeutFlu
USRCOLL 250.0 1.E-14 0.0 0.0 0.0 0. &
* Calculate neutron fluence spectrum in region 15 from thermal energies to
* 250 GeV, in 350 logarithmic energy intervals. Write formatted results on
* unit 23. The volume of region 15 is 540 cm3.
