13.2.24} 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 : Cutoff 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- cutoff in region IR (
WHAT(1)
 in card EMFCUT)
          GAMCUT : Photon cutoff 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 cutoff for
 Region 5 AT EVERY CALL, and the number of calls is not known to the user.

 If name-based input is being used, the name corresponding to IR
 can be obtained via a call to routine GEOR2N:
           CALL GEOR2N (NUMREG, NAMREG, IERR)
 where NUMREG (input variable) is the region number, and NAMREG
 (returned variable) is the corresponding region name (to be declared
 as CHARACTER*8). IERR is a returned error code: if = 0, the
 conversion is successful. See example in the description of BXDRAW above.

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