Accuracy of kinetic equilibrium reconstruction of NSTX and NSTX-U plasmas and its impact on the transport and stability analysis

被引:0
|
作者
Avdeeva, G. [1 ]
Thome, K. E. [1 ]
Berkery, J. W. [2 ]
Kaye, S. M. [2 ]
McClenaghan, J. [1 ]
Meneghini, O. [1 ]
Odstrcil, T. [1 ]
Sabbagh, S. A. [3 ]
Smith, S. P. [1 ]
Turnbull, A. D. [1 ]
机构
[1] Gen Atom, POB 85608, San Diego, CA 05608 USA
[2] Princeton Plasma Phys Lab, 100 Stellarator Rd, Princeton, NJ 08540 USA
[3] Columbia Univ, New York, NY 10027 USA
关键词
equilibrium reconstruction; spherical tokamaks; EFIT; TRANSP; NSTX; RADIAL ELECTRIC-FIELD; ARBITRARY COLLISIONALITY; BOOTSTRAP CURRENT; MHD STABILITY; TOKAMAK; OPERATION; CODE;
D O I
10.1088/1361-6587/ad788a
中图分类号
O35 [流体力学]; O53 [等离子体物理学];
学科分类号
070204 ; 080103 ; 080704 ;
摘要
An accurate magnetohydrodynamic (MHD) equilibrium reconstruction is an essential starting point for stability and transport plasma analysis. This work describes an approach for obtaining kinetic equilibrium reconstructions using the OMFIT framework, which has been applied for the first time to spherical tokamak data from NSTX and NSTX-U. The EFIT equilibrium solver is integrated with experimental data analysis procedures and subsequent TRANSP transport simulations to enhance the accuracy of the reconstruction, in particular, at the edge region, by adding constraints on the total pressure and current density profiles, based on the transport code solution. The accuracy of the equilibrium reconstruction depends on the uncertainty and number of constraints, as well as the choice of basis functions to represent the pressure and current density profiles. Improved fidelity of the equilibrium reconstruction is demonstrated by reducing the variability of the magnetic axis and boundary locations from several centimeters, for reconstructions based on magnetic and experimental pressure constraints, to only several millimeters, for kinetic reconstructions based on transport code constraints, when different representations of basis functions were tested. The variability of the safety factor on axis was reduced ten times in the same sensitivity study. The accuracy of the equilibrium reconstruction and subsequent mapping of the experimental kinetic profile data have a significant impact on the trapped gyro Landau fluid and linear CGYRO turbulence simulations, which predict different spectra of unstable modes and turbulent fluxes for cases with different numbers of constraints in the equilibrium reconstruction. Conversely, the stability analysis performed using the GATO code shows plasmas that are stable to n = 1 MHD modes in both equilibria using magnetic and experimental pressure constraints as well as the transport code constrained equilibrium. However, a scan of parameters away from these conditions shows considerable deviation in the threshold of unstable modes between these reconstructions. Therefore, for reliable plasma analysis and use in turbulence and stability calculations, a high-fidelity equilibrium reconstruction with accurate kinetic constraints based on transport code solutions is necessary.
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页数:25
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