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Title: Development of a non-parametric Gaussian process model in the three-dimensional equilibrium reconstruction code V3FIT

Journal Article · · Journal of Plasma Physics
ORCiD logo [1];  [2]
  1. Tech-X Corporation, Boulder, CO (United States); OSTI
  2. Auburn Univ., AL (United States). Dept. of Physics

A non-parametric Gaussian process regression model is developed in the three-dimensional equilibrium reconstruction code V3FIT. A Gaussian process is a normal distribution of functions that is uniquely defined by specifying a mean function and covariance kernel function. Gaussian process regression assumes that an unknown profile belongs to a particular Gaussian process and uses Bayesian analysis to select the function the give the best fit to measured data. The implementation in V3FIT uses a hybrid representation where Gaussian processes are used to infer some of the equilibrium profiles and standard parametric techniques are used to infer the remaining profiles. The implementation of the Gaussian process is tested using both synthetic data and experimental data from multiple machines.

Research Organization:
Auburn Univ., AL (United States); Tech-X Corporation, Boulder, CO (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
Grant/Contract Number:
FG02-03ER54692; SC0018313
OSTI ID:
1800135
Journal Information:
Journal of Plasma Physics, Journal Name: Journal of Plasma Physics Journal Issue: 1 Vol. 86; ISSN 0022-3778
Publisher:
Cambridge University PressCopyright Statement
Country of Publication:
United States
Language:
English

References (14)

Bayesian soft X-ray tomography using non-stationary Gaussian Processes journal August 2013
Design and initial operation of a two-color soft x-ray camera system on the Compact Toroidal Hybrid experiment journal November 2014
Non-axisymmetric equilibrium reconstruction of a current-carrying stellarator using external magnetic and soft x-ray inversion radius measurements journal December 2015
Three dimensional equilibrium solutions for a current-carrying reversed-field pinch plasma with a close-fitting conducting shell journal March 2016
Determination of current and rotational transform profiles in a current-carrying stellarator using soft x-ray emissivity measurements journal January 2018
Steepest-descent moment method for three-dimensional magnetohydrodynamic equilibria journal January 1983
Design, Construction, and Operation of the Compact Toroidal Hybrid journal May 2017
Equilibrium analysis of current profiles in tokamaks journal June 1990
V3FIT: a code for three-dimensional equilibrium reconstruction journal July 2009
Improved profile fitting and quantification of uncertainty in experimental measurements of impurity transport coefficients using Gaussian process regression journal January 2015
3D equilibrium reconstruction with islands journal March 2018
Bayesian electron density inference from JET lithium beam emission spectra using Gaussian processes journal January 2017
Bifurcation to 3D Helical Magnetic Equilibrium in an Axisymmetric Toroidal Device journal December 2011
The Madison Symmetric Torus journal January 1991

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