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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