Jon E. Kinsey

THEORY-BASED TRANSPORT MODELING OF TFTR

Transport simulations of TFTR temperature and density profiles have been carried out with the Nordman-Weiland transport model for ηi and trapped electron modes (including impurities and finite Larmor radius effects) combined together with resistive ballooning mode and neoclassical transport models. The Nordman-Weiland model is combined together with models for transport driven by pressure gradients to compute the coefficients for the transport of ion heat, hydrogen ions, and electron heat. The predictions of this model are compared with the experimentally observed profiles for TFTR L-mode and supershot plasmas.

Systematic comparison of a theory‐based transport model with a multi‐tokamak profile database

A theoretical model of flux‐surface‐averaged radial transport in tokamaks has been tested and re‐calibrated against a well‐documented set of temperature and density profiles from a pre‐defined set of discharges from six tokamaks. The transport theory includes neoclassical, drift/ηi, circulating electron mode, kinetic ballooning, neoclassical magnetohydrodynamic (MHD), and resistive ballooning effects. Allowing for no explicitly adjustable free parameters and no a posteriori exclusion of data subsets, the nominal theory reproduced observed temperatures and electron densities with relative error about two orders of magnitude smaller than the range over which machine parameters and resulting plasma parameters varied in the reference discharges examined. An important feature of this study is a well‐defined procedure for setting boundary conditions at an appropriate location just inside the inner‐most ‘‘closed’’ magnetic flux surface.

Resolving the mystery of transport within internal transport barriersa)

The Trapped Gyro-Landau Fluid (TGLF) quasi-linear model [G. M. Staebler, et al., Phys. Plasmas 12, 102508 (2005)], which is calibrated to nonlinear gyrokinetic turbulence simulations, is now able to predict the electron density, electron and ion temperatures, and ion toroidal rotation simultaneously for internal transport barrier (ITB) discharges. This is a strong validation of gyrokinetic theory of ITBs, requiring multiple instabilities responsible for transport in different channels at different scales. The mystery of transport inside the ITB is that momentum and particle transport is far above the predicted neoclassical levels in apparent contradiction with the expectation from the theory of suppression of turbulence by E×B velocity shear. The success of TGLF in predicting ITB transport is due to the inclusion of ion gyro-radius scale modes that become dominant at high E×B velocity shear and to improvements to TGLF that allow momentum transport from gyrokinetic turbulence to be faithfully modeled.

Testing neoclassical and turbulent effects on poloidal rotation in the core of DIII-Da)

Experimental tests of ion poloidal rotation theories have been performed on DIII-D using a novel impurity poloidal rotation diagnostic. These tests show significant disagreements with theoretical predictions in various conditions, including L-mode plasmas with internal transport barriers (ITB), H-mode plasmas, and QH-mode plasmas. The theories tested include standard neoclassical theory, turbulence driven Reynolds stress, and fast-ion friction on the thermal ions. Poloidal rotation is observed to spin up at the formation of an ITB and makes a significant contribution to the measurement of the E→×B→ shear that forms the ITB. In ITB cases, neoclassical theory agrees quantitatively with the experimental measurements only in the steep gradient region. Significant quantitative disagreement with neoclassical predictions is seen in the cores of ITB, QH-, and H-mode plasmas, demonstrating that neoclassical theory is an incomplete description of poloidal rotation. The addition of turbulence driven Reynolds stress ...

Confidence contours for calibration of a theoretical transport model against a multitokamak database

A systematic statistical model has been used to calibrate the turbulence saturation coefficients in a theory based tokamak transport model. Confidence contours are used to assess the accuracy of calibration. From the confidence contours, it is seen that the ballooning branch coefficient of this model is empirically more uncertain than that for the drift wave branch. Sensitivity studies show that the estimators obtained here are relatively insensitive to the level of prior knowledge assumed about the accuracy of theory and experiment, but the confidence regions shrink with increasing prior knowledge. The calibrated transport model is used to predict the profiles of electron density and of electron temperature and ion temperature in a large tokamak plasma. This demonstrates the potential utility of the calibrated transport model