GEANT321/gphys/gefch2.F

   1 *
   2 * $Id$
   3 *
   4 * $Log$
   5 * Revision 1.1.1.1  1995/10/24 10:21:24  cernlib
   6 * Geant
   7 *
   8 *
   9 #include "geant321/pilot.h"
  10 *CMZ :  3.21/02 29/03/94  15.41.21  by  S.Giani
  11 *-- Author :
  12       FUNCTION GEFCH2(Z1,Z2,TK)
  13 C.    *******************************************************************
  14 C.    *                                                                 *
  15 C.    *  Calculates  gamma**2=( eff.charge/z1)**2 for heavy ions        *
  16 C.    *   (see e.g. F.Hubert et al. Atomic Data and Nuclear Data        *
  17 C.    *             Tables,Vol.40,1.(1990) )                            *
  18 C.    *                                                                 *
  19 C.    *  The stopping power S for a given combination of stopping       *
  20 C.    *  medium and heavy ion can be calculated according to            *
  21 C.    *  the scaling law                                                *
  22 C.    *                                                                 *
  23 C.    *            S = (gamma*Z1)**2*Sref/Zref**2                       *
  24 C.    *                                                                 *
  25 C.    *    where Z1 the ion charge , gamma*Z1 is the effective charge,  *
  26 C.    *          Sref is the stopping power of the same medium          *
  27 C.    *          for a reference ion of the same velocity and           *
  28 C.    *          of effective charge Zref.                              *
  29 C.    *                                                                 *
  30 C.    *  Input: Z1 atomic number of the ion                             *
  31 C.    *         Z2 atomic number of the medium                          *
  32 C.    *         TK E/A in GeV (ion kin.energy/atomic weight)            *
  33 C.    *                                                                 *
  34 C.    *******************************************************************
  35 C.
  36       ALZ2=LOG(Z2)
  37       TKMEV=1000.*TK
  38 C
  39       X1=1.164+0.2319*EXP(-0.004302*Z2)+1.658*EXP(-0.05170*Z1)
  40       X2=8.144+0.09876*ALZ2
  41       X3=0.3140+0.01072*ALZ2
  42       X4=0.5218+0.02521*ALZ2
  43       EE=MAX(-50.,-X2*TKMEV**X3/Z1**X4)
  44 C     .........................
  45       GA=1.-X1*EXP(EE)
  46 C
  47       GEFCH2=GA**2
  48       END