SUBROUTINE  : FFTRF(DZ,Z1,S1,S2,BZEND)
 
AUTHOR : Stephen Burke
 
DATE : 26/11/96
 
LANGUAGE : FORTRAN
 
SHORT SUMMARY of PURPOSE:                                                
                                                                                
 Fast version of FKTRAN: translates track parameters from one z                 
 plane to another. There is no calculation of the Jacobian, and                 
 the z distance over which the field is assumed constant (DZMAX)                
 is 10 cm instead of 1 cm, but otherwise this is the same as                    
 FKTRAN. Bz is returned for use in FFCORR.                                      
                                                                                
LIST and DESCRIPTION of INPUT VARIABLES/ARGUMENTS:                       
                                                                                
 DZ - step length in cm (can be negative) (REAL*8)                              
 Z1 - Z coordinate of starting point in cm (REAL*8)                             
 S1 - (X,Y,q/P,Tan(Theta),Phi) = state vector at Z1 (REAL*8 5-vector)           
                                                                                
LIST and DESCRIPTION of OUTPUT VARIABLES/ARGUMENTS:                      
                                                                                
 S2    - state vector at Z1+DZ (REAL*8 5-vector)                                
 BZEND - z component of field at track end                                      
                                                                                
 Note that S2 should not be the same as S1                                      
                                                                                
 
CALLING TREE from FFTRF :
 
None
 
FUNCTIONS USED :
 
None
 
KEEP SEQUENCES USED :
 
 FKPIDP                                                                                                       
 

 
Comments from FFTRF