Speaker
Description
See full abstract here
http://ocs.ciemat.es/EPS2019ABS/pdf/P4.1019.pdf
For the JET tokamak, standard equilibrium reconstructions find solutions of the Grad-Shafranov equation given diverse constraints on plasma pressure and/or magnetic field [1]. The most basic reconstruction neglects plasma pressure entirely and constraints the magnetic field via measurements of pick-up coils located around the plasma. A more advanced reconstruction exploits polarimetry and motional-stark-effect diagnostics which provide information about the magnetic field inside the plasma. These conventional approaches provide different results, estimating to some extent the systematic uncertainties of the reconstruction. An alternative approach uses Bayes' theorem to estimate the equilibrium quantities [2] by a joint posterior probability. This allows to obtain a joint solution of the Grad-Shafranov equation consistent with the underlying physics model and with uncertain data measured by magnetic and motional-stark-effect diagnostics.
The work presented infers probabilistically the axisymmetric equilibrium of an Ohmic JET plasma, relying on data measured with broadband ECE diagnostics and an extra-ordinary mode reflectometer [3]. Besides probing the plasma centrally, the data of both diagnostics constrain the local electron pressure and the magnetic field.
References
[1] M. Gelfusa et al., "Influence of plasma diagnostics and constraints on the quality of equilibrium reconstructions on Joint European Torus", Rev. Sci. Instrum., 84, 103508 (2013).
[2] J. Svensson, A. Werner, and JET EFDA contributors, "Current tomography for axisymmetric plasmas", Plasma Phys. Control. Fusion, 50, 085002 (2008).
[3] S. Schmuck, J. Svensson, L. Figini, D. Micheletti, "Bayesian Inference Using JET's Microwave Diagnostic System", Submitted to IFP and JET pinboards, (2019).
