constraint_eqn_001 Subroutine

   subroutine constraint_eqn_001(tmp_cc, tmp_con, tmp_err, tmp_symbol, tmp_units)
    !! author: J Morris
    !! category: equality constraint
    !!
    !! Relationship between beta, temperature (keV) and density
    !!
    !! \begin{equation}
    !! c_i = 1 - \frac{1}{\beta}\left( \beta_{ft} + \beta_{NBI} + 2 \times 10^3 \mu_0 e
    !! \left( \frac{n_e T_e + n_i T_i}{B_{tot}^2} \right) \right)
    !! \end{equation}
    !!
    !! - \( \beta \) -- total plasma beta
    !! - \( \beta_{ft} \) -- fast alpha beta component
    !! - \( \beta_{NBI} \) -- neutral beam beta component
    !! - \( n_e \) -- electron density [m\(^3\)]
    !! - \( n_i \) -- total ion density [m\(^3\)]
    !! - \( T_e \) -- density weighted average electron temperature [keV]
    !! - \( T_i \) -- density weighted average ion temperature [keV]
    !! - \( B_{tot} \) -- total toroidal + poloidal field [T]

    use physics_variables, only: betaft, betanb, dene, ten, dnitot, tin, btot, beta
    use constants, only: echarge,rmu0

    implicit none

   !  type(constraint_args_type), intent(out) :: args
      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

    !! constraint derived type

      tmp_cc = 1.0D0 - (betaft + betanb + &
        2.0D3*rmu0*echarge * (dene*ten + dnitot*tin)/btot**2 )/beta
      tmp_con = beta * (1.0D0 - tmp_cc)
      tmp_err = beta * tmp_cc
      tmp_symbol = '='
      tmp_units  = ''

   end subroutine constraint_eqn_001