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flair-2.3-0e 06-May-2024


-- New Fluka Major Release
( 06.05.2024 )

FLUKA 2024.1.0 is available.
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defines a detector for a collision fluence estimator


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)  > 0: region defining the detector
             = -1: all regions (see Note 7)
             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 lowest energy limit of the last neutron group
               is 1.E-14 GeV (1.E-5 eV) for the 260 data set.
               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 detector



  • 1) IMPORTANT! The results of a USRCOLL collision estimator are always given as DIFFERENTIAL distributions of fluence in energy, in units of 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).

  • 2) If the generalised particle is 208.0 (ENERGY) or 211.0 (EM-ENRGY), 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.

  • 3) 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.

  • 4) 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, USRGLO 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.

  • 5) 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 lowest energy limit of the last neutron group is 1.E-14 GeV (1.E-5 eV) for the 260 data set. All group energy boundaries are listed in two Tables in (10).

  • 6) A program USTSUW is available with the normal FLUKA code distribution in directory $FLUPRO/flutil. USTSUW reads USRCOLL results in binary form from several runs and allows to compute standard deviations. It returns differential and cumulative fluence, with the corresponding percent errors, in a file, and differential fluence in another file formatted for easy plotting. It also returns a binary file that can be read out in turn by USTSUW. The content of this file is statistically equivalent to that of the sum of the files used to obtain it, and it can replace them to be combined with further output files if desired (the USTSUW program takes care of giving it the appropriate weight).

  • 7) Setting WHAT(4) = -1 will provide the sum of the collisions in all regions, divided by the value set by the user for WHAT(5).


 USRCOLL         -1.0   NEUTRON      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.

© FLUKA Team 2000–2024

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