subroutine write_log(lat, chrom_x, chrom_y)
  use bmad
  use parameters_bmad
  implicit none
  type(lat_struct) lat
  integer lun, nbranch, j
  real(rp) chrom_x, chrom_y

  lun=lunget()
  print *,' write to file:', trim(directory)//'/'//'log.dat'
  open(unit=lun, file=trim(directory)//'/'//'log.dat',access='append')
  write (lun, '(4a)')    'parameter[particle]               = ', trim(species_name(lat%param%particle))
  print '(a,es12.4,a,es12.4)','Horizontal tune = ',lat%a%tune/twopi,' Vertical tune = ',lat%b%tune/twopi
  print '(a,es12.4,a,es12.4)','Horiz chromaticity = ' ,chrom_x,' Vertical chromaticity = ',chrom_y
  write(lun,'(a,es12.4,a,es12.4)')'Horizontal tune = ',lat%a%tune/twopi,' Vertical tune = ',lat%b%tune/twopi
  write(lun,'(a,es12.4,a,es12.4)')'Horiz chromaticity = ' ,chrom_x,' Vertical chromaticity = ',chrom_y
  write(lun,'(a16,1x,4a12,a12)')'Name','x1_limit','x2_limit','y1_limit','y2_limit','limit_on'
  do nbranch=0,size(lat%branch)-1
   if(nbranch==0)write(lun,'(a)')'Injection line'
   if(nbranch==1)write(lun,'(a)')'Ring'
   do j=1,lat%branch(nbranch)%n_ele_track
    write(lun,'(a16,1x,4es12.4,5x,l)')lat%branch(nbranch)%ele(j)%name, lat%branch(nbranch)%ele(j)%value(x1_limit$), lat%branch(nbranch)%ele(j)%value(x2_limit$), &
                              lat%branch(nbranch)%ele(j)%value(y1_limit$), lat%branch(nbranch)%ele(j)%value(y2_limit$), bmad_com%aperture_limit_on  
   end do
  end do
  close(unit=lun)
  return
  end