plasma_elongation_IPB Function

  function plasma_elongation_IPB()
    !! author: H Lux (UKAEA)
    !!
    !! Volume measure of plasma elongation using the IPB definition
    !!
    !! See Otto Kardaun et al 2008 Nucl. Fusion 48 099801

    ! Module variables
    use physics_variables, only : vol, rminor, rmajor
    use constants, only : pi

    real(dp) :: plasma_elongation_IPB
    !! Plasma elongation (IPB)

    plasma_elongation_IPB = vol / ( 2.0D0 * pi*pi * rminor*rminor * rmajor )
    !! \begin{equation} \kappa_{IPB} = \frac{V}{2\pi a^2 R_0} \end{equation}
    !!
    !! - \( V \) -- Plasma volume [m\(^3\)]
    !! - \( a \) -- Plasma minor radius [m]
    !! - \( R_0 \) -- Plasma major radius [m]

  end function plasma_elongation_IPB