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Title: Inference of Experimental Radial Impurity Transport on Alcator C-Mod: Bayesian Parameter Estimation and Model Selection.

Abstract

We present a fully Bayesian approach for the inference of radial profiles of impurity transport coefficients and compare its results to neoclassical, gyrofluid and gyrokinetic modeling. Using nested sampling, the Bayesian Impurity Transport InferencE (BITE) framework can handle complex parameter spaces with multiple possible solutions, offering great advantages in interpretative power and reliability with respect to previously demonstrated methods. BITE employs a forward model based on the pySTRAHL package, built on the success of the well-known STRAHL code [Dux, IPP Report, 2004], to simulate impurity transport in magnetically-confined plasmas. In this paper, we focus on calcium (Ca, Z=20) Laser Blow-Off injections into Alcator C-Mod plasmas. Multiple Ca atomic lines are diagnosed via high-resolution X-ray Imaging Crystal Spectroscopy and Vacuum Ultra-Violet measurements. We analyze a sawtoothing I-mode discharge for which neoclassical and turbulent (quasilinear and nonlinear) predictions are also obtained. We find good agreement in diffusion across the entire radial extent, while turbulent convection and density profile peaking are estimated to be larger in experiment than suggested by theory. Efforts and challenges associated with the inference of experimental pedestal impurity transport are discussed.

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
DOE Contract Number:  
SC0014264
Research Org.:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
OSTI Identifier:
1886665
DOI:
https://doi.org/10.7910/DVN/PBCZFW

Citation Formats

Sciortino, F., Howard, N. T., Marmar, E. S., Odstrcil, T., Cao, N. M., Dux, R., Hubbard, A. E., Hughes, J. W., Irby, J. H., Marzouk, Y., Milanese, L. M., Reinke, M. L., Rice, J. E., and Rodriguez-Fernandez, P. Inference of Experimental Radial Impurity Transport on Alcator C-Mod: Bayesian Parameter Estimation and Model Selection.. United States: N. p., 2021. Web. doi:10.7910/DVN/PBCZFW.
Sciortino, F., Howard, N. T., Marmar, E. S., Odstrcil, T., Cao, N. M., Dux, R., Hubbard, A. E., Hughes, J. W., Irby, J. H., Marzouk, Y., Milanese, L. M., Reinke, M. L., Rice, J. E., & Rodriguez-Fernandez, P. Inference of Experimental Radial Impurity Transport on Alcator C-Mod: Bayesian Parameter Estimation and Model Selection.. United States. doi:https://doi.org/10.7910/DVN/PBCZFW
Sciortino, F., Howard, N. T., Marmar, E. S., Odstrcil, T., Cao, N. M., Dux, R., Hubbard, A. E., Hughes, J. W., Irby, J. H., Marzouk, Y., Milanese, L. M., Reinke, M. L., Rice, J. E., and Rodriguez-Fernandez, P. 2021. "Inference of Experimental Radial Impurity Transport on Alcator C-Mod: Bayesian Parameter Estimation and Model Selection.". United States. doi:https://doi.org/10.7910/DVN/PBCZFW. https://www.osti.gov/servlets/purl/1886665. Pub date:Thu Feb 25 00:00:00 EST 2021
@article{osti_1886665,
title = {Inference of Experimental Radial Impurity Transport on Alcator C-Mod: Bayesian Parameter Estimation and Model Selection.},
author = {Sciortino, F. and Howard, N. T. and Marmar, E. S. and Odstrcil, T. and Cao, N. M. and Dux, R. and Hubbard, A. E. and Hughes, J. W. and Irby, J. H. and Marzouk, Y. and Milanese, L. M. and Reinke, M. L. and Rice, J. E. and Rodriguez-Fernandez, P.},
abstractNote = {We present a fully Bayesian approach for the inference of radial profiles of impurity transport coefficients and compare its results to neoclassical, gyrofluid and gyrokinetic modeling. Using nested sampling, the Bayesian Impurity Transport InferencE (BITE) framework can handle complex parameter spaces with multiple possible solutions, offering great advantages in interpretative power and reliability with respect to previously demonstrated methods. BITE employs a forward model based on the pySTRAHL package, built on the success of the well-known STRAHL code [Dux, IPP Report, 2004], to simulate impurity transport in magnetically-confined plasmas. In this paper, we focus on calcium (Ca, Z=20) Laser Blow-Off injections into Alcator C-Mod plasmas. Multiple Ca atomic lines are diagnosed via high-resolution X-ray Imaging Crystal Spectroscopy and Vacuum Ultra-Violet measurements. We analyze a sawtoothing I-mode discharge for which neoclassical and turbulent (quasilinear and nonlinear) predictions are also obtained. We find good agreement in diffusion across the entire radial extent, while turbulent convection and density profile peaking are estimated to be larger in experiment than suggested by theory. Efforts and challenges associated with the inference of experimental pedestal impurity transport are discussed.},
doi = {10.7910/DVN/PBCZFW},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2021},
month = {2}
}

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