anchor.diff:      rcp0(j)  = rcp(j)
       ejf0v(j) = ejfv(j)
   
  +    part_hit_before_turn(j) = part_hit_turn(j)
  +    part_hit_before_pos(j)  = part_hit_pos(j)
  +
       ! For zero length element track back half collimator length
       ! DRIFT PART
  -    if(stracki == 0) then
  +    if(stracki == zero) then
         if(iexact) then
  -        zpj    = sqrt(one-rcxp(j)**2-rcyp(j)**2)
  +        zpj    = sqrt(one - rcxp(j)**2 - rcyp(j)**2)
           rcx(j) = rcx(j) - (half*c_length)*(rcxp(j)/zpj)
           rcy(j) = rcy(j) - (half*c_length)*(rcyp(j)/zpj)
         else
  
positive.code: 
    ! Copy particle data to 1-dim array and go back to meters
    do j=1,napx
      rcx(j)  = (xv1(j)-torbx(ie)) /c1e3
      rcxp(j) = (yv1(j)-torbxp(ie))/c1e3
      rcy(j)  = (xv2(j)-torby(ie)) /c1e3
      rcyp(j) = (yv2(j)-torbyp(ie))/c1e3
      rcp(j)  = ejv(j)/c1e3
      rcs(j)  = zero
      part_hit_before_turn(j) = part_hit_turn(j)
      part_hit_before_pos(j)  = part_hit_pos(j)
      rcx0(j)  = rcx(j)
      rcxp0(j) = rcxp(j)
      rcy0(j)  = rcy(j)
  
negative.code:       part_abs_pos, part_abs_turn, part_impact, part_indiv, part_linteract,             &
        onesided, nhit_type, 1, nabs_type, linside)
    end if
  #else
    call coll_doCollimator_Geant4(c_aperture,c_rotation)
  #endif
    end if
  
  