subroutine track_sept1_end(lat,co, ix_essept, ix_magsept1,ix_magsept2, ix_extraction_fork)

       use bmad
       use ramp_parameters
       implicit none

       type (lat_struct) lat
       type (coord_struct), allocatable :: co(:),cob(:),coa(:)

       integer ix_essept, ix_magsept1,ix_magsept2, ix_extraction_fork
       integer track_state, lun
       integer i
       real(rp) s_ext_fork

      lun=lunget()
      open(unit=lun,file=trim(directory)//'/ext_line_traj.dat')

      call reallocate_coord(cob,lat%branch(1)%n_ele_track)
      call reallocate_coord(coa,size(co))
      coa = co
      coa(ix_essept-1)%vec(1) = coa(ix_essept-1)%vec(1) + x_septum(0) 
      coa(ix_essept-1)%vec(1) =  x_septum(0) 
      coa(ix_essept-1)%vec(2) =  0.
      call track_many(lat,coa,ix_essept-1,ix_extraction_fork,1, ix_branch=0, track_state=track_state)
      cob(0) = coa(ix_extraction_fork)
      call track_all(lat,cob,ix_branch=1)

      do i=1,lat%branch(0)%n_ele_track
       write(lun,'(a16,1x,8es12.4,1x,i10)')lat%branch(0)%ele(i)%name, lat%branch(0)%ele(i)%s, coa(i)%vec, lat%branch(0)%ele(i)%value(l$), lat%branch(0)%ele(i)%key
      end do
      write(lun,'(/,a1,/)')'#'
      s_ext_fork = lat%branch(0)%ele(ix_extraction_fork)%s
      do i=1,lat%branch(1)%n_ele_track
       write(lun,'(a16,1x,8es12.4,1x,i10)')lat%branch(1)%ele(i)%name, lat%branch(1)%ele(i)%s+s_ext_fork, cob(i)%vec, lat%branch(1)%ele(i)%value(l$), lat%branch(1)%ele(i)%key
      end do

      close(unit=lun)
      return
      end