Parametric Model for the H-mode Pedestal Structure in the Presence of Micro-Turbulent Transport using IPS-FASTRAN Framework

The formation of H-mode pedestal results from a large ExB rotational shearing rate and is characterized by large gradients in the electron density, temperature, and pressure profiles. While the steep gradients in pedestal profiles are known to suppress turbulent structures of long wavelengths at plasma pedestal, a range of residual micro-instabilities, such as ion-temperature (ITG) and electron-temperature (ETG) gradients, kinetic ballooning (KBM), trapped-electron (TEM), and micro-tearing (MTM) modes, are potential sources of pedestal transport [1]. The well validated EPED1 model [2] postulates that the KBM mode sets the limit for the plasma pressure gradient in the pedestal. The ultimate limit of the pedestal pressure is set by the MHD peeling mode driven by the large bootstrap currents [3]. In this work, the evolution of the pedestal pressure, from just after the L/H transition, is calculated using time-dependent IPS-FASTRAN framework [4] with TGLF quasilinear transport model [5] that includes the full spectrum of drift-waves – except the MTM. The ELITE code [6] is employed to compute peeling-ballooning stability condition that ultimately triggers ELMs in the pedestal region as the pressure evolves. The radial electric field is assumed to have its neoclassical value since the ion-scale turbulence is largely suppressed in the H-mode phase. The parametric relation between the power balance, plasma heating, stored energy, and the pedestal structure is examined to understand how micro-instabilities limit the pressure gradient.