Speaker
Description
Several reduced models exist for predicting anomalous energetic particle (EP) transport that may be induced by instabilities such as Alfven Eigenmodes, spanning a wide spectrum of fidelity and computational cost. However, these models have typically been validated against isolated experimental discharges instead of databases, providing an incomplete assessment of their reliability and sensitivity to input uncertainty. In this poster, progress is presented on the validation of the TGLF-EP+Alpha critical gradient model [1] against a set of carefully analyzed, high q-min, high β, DIII-D steady-state scenario discharges where substantial EP transport has been observed [2,3]. TGLF-EP iteratively solves a gyro-Landau fluid system, balancing the fast-ion drive of the most unstable mode against thermal damping at each radial grid point to determine the critical EP density gradient corresponding to marginal stability. Under the assumption of stiff transport, the Alpha code relaxes the EP density profile to the critical gradient, also yielding a corresponding fast-ion diffusivity profile that can be used in TRANSP with the Monte Carlo code NUBEAM for integrated modeling and experimental validation. The ability of TGLF-EP+Alpha to reproduce the experimental observations in these plasmas is evaluated in two ways. First, TRANSP/NUBEAM is used to calculate the neutron rate due to the relaxed EP density and compare it to the measured neutron rate. Second, the NUBEAM-calculated EP distribution, including the diffusivity from Alpha, is used with FIDASIM forward modeling to compare the predicted to measured EP density profile. Moreover, the TGLF-EP+Alpha model sensitivity to equilibrium and kinetic profile input uncertainty is assessed in these discharges. Ongoing work and future plans towards large scale, quantitative validation of TGLF-EP+Alpha against a large and diverse database of DIII-D discharges will be discussed.
[1] R.E. Waltz, E.M. Bass, W.W. Heidbrink, and M.A. Van Zeeland, Nucl. Fusion 55, 123012 (2015)
[2] W.W. Heidbrink, J.R. Ferron, C.T. Holcomb, et al., Plasma Phys. Control. Fusion 56, 095030 (2014)
[3] C.T. Holcomb, W.W. Heidbrink, J.R. Ferron, et al., Phys. Plasmas 22, 055904 (2015)
*Work supported by US DOE under DE-FC02-04ER54698 and DE-SC0020337