Predictive Integrated Modeling Simulations Using a Combination of H-mode Pedestal and Core Models Glenn Bateman, Arnold H. Kritz, Thawatchai Onjun, Alexei Pankin, Canh Nguyen Lehigh University Physics Department Bethlehem PA ITPA Meeting in St. Petersburg April 2003

Predictive Integrated Modeling Simulations Using a Combination of H-mode Pedestal and Core Models Objectives: –Predict evolution of temperature, density, and other plasma profiles in tokamak H-modes –Develop more accurate predictive models for the pedestal and ELMs at the edge of H-mode plasmas Issues: –Temperature profiles are sensitive to H-mode pedestal height as a result of the stiffness of the core transport model –Different combinations of pedestal and core models predict different fusion power production in burning plasma experiments –Does pedestal height continue to increase with heating power? –Giant ELMs expected to produce large pulses of power to divertor

H-mode Pedestal Models Models that have been proposed for the H-mode pedestal: 1.Pressure gradient limited by first ballooning mode stability Hence, pressure gradient is independent of plasma heating power For example, models developed by T. Onjun, Phys. Plasmas 9, 5018 (2002) 2.Pressure gradient limited by finite n ballooning and peeling modes Transition from first stability to second stability at high triangularity and heating power Hence, pressure gradient can make a transition as heating power is increased, but then becomes independent of heating power 3.Pressure gradient is determined by thermal conduction Hence, pressure gradient increases with plasma heating power For example, models developed by G. Cordey, IAEA 2002 The pressure at the top of the pedestal is determined by the pressure gradient and the width of the pedestal Does the pressure at the top of the H-mode pedestal increase indefinitely with plasma heating power or is it limited by instabilities?

Choice of Pedestal Model Has a Large Effect on Predicted Fusion Reactor Performance 2002 IAEA paper by Kinsey, Onjun, Bateman, Kritz, Pankin, Staebler and Waltz Cordey’s power-dependent pedestal model (solid curves) Pedestal model based on first stability limit is independent of heating power T. Onjun, et al., Phys. Plasmas 9, 5018, Dec. 2002, (dashed curves)

ITPA Collaboration Needed Experimental data scans are needed in combined profile and pedestal database: –Systematic scans over heating power and triangularity –Detailed profiles needed in pedestal before ELM crashes throughout discharge evolution ELM types can change during course of discharge –Note that early ELM crashes, right after the L to H transition, might be different from ELM crashes later in the discharge The current density profile redistributes near the edge of the plasma during the course of the discharge Detailed numerical simulation studies needed: –MHD computations using codes such as MISHKA and ELITE –Transport simulations of the H-mode pedestal including the effect of flow and magnetic shear on anomalous transport