Abstract
A verification and validation study is carried out for a sequence of reversed shear Alfvén instability time slices. The mode frequency increases in time as the minimum (qmin) in the safety factor profile decreases. Profiles and equilibria are based upon reconstructions of DIII-D discharge (#142111) in which many such frequency up-sweeping modes were observed. Calculations of the frequency and mode structure evolution from two gyrokinetic codes, GTC and GYRO, and a gyro-Landau fluid code TAEFL are compared. The experimental mode structure of the instability was measured using time-resolved two-dimensional electron cyclotron emission imaging. The three models reproduce the frequency upsweep event within ±10 of each other, and the average of the code predictions is within ±8 of the measurements; growth rates are predicted that are consistent with the observed spectral line widths. The mode structures qualitatively agree with respect to radial location and width, dominant poloidal mode number, ballooning structure, and the up-down asymmetry, with some remaining differences in the details. Such similarities and differences between the predictions of the different models and the experimental results are a valuable part of the verification/validation process and help to guide future development of the modeling efforts.
| Original language | English |
|---|---|
| Article number | 082511 |
| Journal | Physics of Plasmas |
| Volume | 19 |
| Issue number | 8 |
| DOIs | |
| State | Published - Aug 2012 |
Funding
This collaboration is supported by the US DOE SciDAC GSEP Center. Research has been sponsored by the US Department of Energy under Contract DE-AC05-00OR22725 with UT-Battelle, LLC; Cooperative Agreements DE-FC02-08ER54977 and DE-FC02-04ER54698 with General Atomics; DE-FC02-08ER54976 with UC Irvine, under DE-FG02-99ER54531, SC-G903402, DE-AC02-09CH11466, DE-AC05-00OR22725, and DE-FC-02-04ER54698 for the UC Davis/ECEI collaboration; and under DE-FG03-97ER54415 with the University of Texas at Austin. Further support was provided by NRF-201100187244, Korea, and the Association EURATOM-FOM. This research used resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Also, the resources of the Oak Ridge Leadership Computing Facility, located in the National Center for Computational Sciences at Oak Ridge National Laboratory, which is supported by the Office of Science of the Department of Energy under Contract DE-AC05-00OR22725, were used.