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[u/mrichter/AliRoot.git] / GEANT321 / neutron / evaplr.F

*
* $Id$
*
* $Log$
* Revision 1.1.1.1  1995/10/24 10:21:56  cernlib
* Geant
*
*
#include "geant321/pilot.h"
*CMZ :  3.21/04 23/02/95  14.46.01  by  S.Giani
*-- Author :
      SUBROUTINE EVAPLR(E,Q,SQ,ATAR,CB,EX)
C       THIS ROUTINE SAMPLES AN EXIT ENERGY FROM AN
C       EVAPORATION SPECTRUM FOR AN LR-FLAG (N,N-PRIME X) REACTION
#include "geant321/minput.inc"
      SAVE
C       CONVERT THE COULOMB BARRIER (CB) TO UNITS OF EV
      CB=CB*1.00E+06
C       SET THE EXCITATION ENERGY (Q) TO ITS ABSOLUTE VALUE
      QA=ABS(Q)
C       CALCULATE THE MAXIMUM ENERGY AVAILABLE
      CBI=CB
      EMAX=QA+SQ-CB
      IF(EMAX.GT.0.0)GO TO 10
      CB=0.5*CB
      EMAX=QA+SQ-CB
      IF(EMAX.GT.0.0)GO TO 10
      CB=0.0
      EMAX=QA+SQ-CB
      IF(EMAX.GT.0.0)GO TO 10
      WRITE(IOUT,10000)E,EMAX,QA,SQ,CBI
10000 FORMAT(' MICAP: NEGATIVE MAXIMUM ENERGY CALCULATED IN ROUTINE ',
     1'EVAPLR --- INDICATING PROBABLE CROSS SECTION ERROR ALLOWING ',
     2'THE REACTION TO OCCUR',/,10X,'E,EMAX,QA,SQ,CB=',1P5E13.5)
      WRITE(6,*) ' CALOR: ERROR in EVAPLR ====> STOP '
      STOP
C       CALCULATE THE NUCLEAR TEMPERATURE (THETA)
   10 THETA=4.0161E+03*(SQRT(QA+SQ-CB)/(ATAR**0.8333333))
C       SELECT THE EXIT ENERGY FROM AN EVAPORATION SPECTRUM
   20 R1=FLTRNF(0)
      R2=FLTRNF(0)
      W=-ALOG(R1*R2)
      EX=THETA*W
      IF(EX.LE.EMAX)RETURN
C       RESAMPLE 75% OF THE TIME IF EX IS GREATER THAN EMAX
      R=FLTRNF(0)
      IF(R.LE.0.75)GO TO 20
#if defined(CERNLIB_MDEBUG)
      WRITE(IOUT,10100)EX,EMAX
10100 FORMAT(' MICAP: WARNING-EX,EMAX=',1P2E13.5,' IN ROUTINE EVAPLR')
#endif
      EX=EMAX
      RETURN
      END