subroutine write_transfermatrix(lat,nbranch)

  use bmad
  use parameters_bmad
  implicit none

  type (lat_struct), target :: lat
  type (branch_struct), pointer :: branch 
  type (ele_struct) ele
  type (coord_struct) co
  
  character *2 cbranch
  real(rp) temp(6,6),m(6,6)
  integer lun, i, j
  integer nbranch

!compute branch matrix (injection line or full turn) 
  temp = 0.
  forall(i=1:6)temp(i,i) = 1.
  branch => lat%branch(nbranch)
  do i = 1, branch%n_ele_track
    m = matmul(branch%ele(i)%mat6, temp)
    temp= m
  end do   
  lat%branch(nbranch)%ele(0)%mat6=temp
  write(cbranch,'(i2.2)')nbranch
  lun = lunget()
  open(unit = lun, file = trim(directory)//'/'//'transfer_matrix_file_branch'//trim(cbranch)//'.dat')
   write(lun,'(/,a,i10)')' Element =  Branch ', nbranch
   write(lun,'(4es12.4)')(temp(j,1:4),j=1,4)
  
  do i=0,lat%branch(nbranch)%n_ele_track
   write(lun,'(/,a,a)')' Element = ', trim(lat%branch(nbranch)%ele(i)%name)
   write(lun,'(4es12.4)')(lat%branch(nbranch)%ele(i)%mat6(j,1:4),j=1,4)
   call create_taylor_ele(lat%branch(nbranch)%ele(i),co)
  end do
  close(unit=lun)
return
end