*-- Author : S.Burke / J.V. Morris
      SUBROUTINE FKSCAT(DZ,S,X0,D,Q)
**********************************************************************                                        
*                                                                    *                                        
* Compute the Multiple Scattering Matrix, Q, for transformation of   *                                        
* State Vector, S, from Z to Z+DZ.                                   *                                        
*                                                                    *                                        
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* TT2MIN sets the lower limit allowed for tan**2(theta) (arbitrary)                                           
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*                                                                                                             
* Test for finite step length and non-zero radiation length ....                                              
*                                                                                                             
         CALL VZERO(Q,50)                                                                              
* Fix for apparent singularity ... this should be checked further                                             
* Compute path length in medium = X ....                                                                      
*                                                                                                             
* compute the mean square scattering angle (SQMA) assuming Beta=1 ...                                         
* (this is the projection onto plane)                                                                         
*                                                                                                             
*                                                                                                             
* First compute the diagonal terms ...                                                                        
*                                                                                                             
*                                                                                                             
* Now the off-diagonal terms ...                                                                              
*                                                                                                             
*