constraint_eqn_020 Subroutine

   subroutine constraint_eqn_020(tmp_cc, tmp_con, tmp_err, tmp_symbol, tmp_units)
      !! Equation for neutral beam tangency radius upper limit
      !! author: P B Lloyd, CCFE, Culham Science Centre
      !! args : output structure : residual error; constraint value;
      !! residual error in physical units; output string; units string
      !! Equation for neutral beam tangency radius upper limit
      !! #=# current_drive
      !! #=#=# fportsz, rtanmax
      !! and hence also optional here.
      !! Logic change during pre-factoring: err, symbol, units will be assigned only if present.
      !! fportsz : input real : f-value for neutral beam tangency radius limit
      !! rtanmax : input real : maximum tangency radius for centreline of beam (m)
      !! rtanbeam : input real : neutral beam centreline tangency radius (m)
      use constraint_variables, only: fportsz
      use current_drive_variables, only: rtanmax, rtanbeam
      implicit none
            real(dp), intent(out) :: tmp_cc
      real(dp), intent(out) :: tmp_con
      real(dp), intent(out) :: tmp_err
      character(len=1), intent(out) :: tmp_symbol
      character(len=10), intent(out) :: tmp_units

      tmp_cc =  1.0D0 - fportsz * rtanmax/rtanbeam
      tmp_con = rtanmax * (1.0D0 - tmp_cc)
      tmp_err = rtanbeam * tmp_cc
      tmp_symbol = '<'
      tmp_units = 'm'

   end subroutine constraint_eqn_020