Reconstruction of hollow areas in density profiles from frequency swept reflectometry

Rennan B MORALES; Stéphane HEURAUX; Roland SABOT; Sébastien HACQUIN; Frédéric CLAIRET; the Tore Supra Team

doi:10.1088/2058-6272/ab7b5a

Plasma Science and Technology > 2020 > 22(6): 64005-064005. > DOI: 10.1088/2058-6272/ab7b5a

Rennan B MORALES, Stéphane HEURAUX, Roland SABOT, Sébastien HACQUIN, Frédéric CLAIRET, the Tore Supra Team. Reconstruction of hollow areas in density profiles from frequency swept reflectometry[J]. Plasma Science and Technology, 2020, 22(6): 64005-064005. DOI: 10.1088/2058-6272/ab7b5a

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Reconstruction of hollow areas in density profiles from frequency swept reflectometry

¹ United Kingdom Atomic Energy Authority, Culham Centre for Fusion Energy, Culham Science Centre, Abingdon, Oxon, OX14 3DB, United Kingdom
² IJL, UMR CNRS, University of Lorraine, BP50840, Nancy, F-54011, France
³ Institute of Physics, University of Sao Paulo, Sao Paulo 05315-970, Brazil
⁴ IRFM, CEA, Cadarache, F-13108 Saint-Paul-lez-Durance, France
⁵ EUROfusion Programme Management Unit, Culham Science Centre, Culham OX14 3DB, United Kingdom

Funds: This work has been carried out with the support of the Brazilian National Council for Scientific and Technological Development (CNPq) under the Science Without Borders programme, within the framework of the French Federation for Magnetic Fusion Studies (FR-FCM) and of the EUROfusion consortium with funding from the Euratom research and training programme 2014–2018 and 2019–2020 under grant agreement No. 633 053, and also been part-funded by the RCUK Energy Programme
[grant number EP/P012450/1]. The views and opinions expressed herein do not necessarily reflect those of the European Commission.

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Received Date: October 30, 2019
Revised Date: February 27, 2020
Accepted Date: February 29, 2020

Graphical Abstract

Abstract

Abstract

The standard density profile reconstruction techniques are based on the WKB approximation of the probing wave’s phase, making them unable to properly reconstruct blind areas in the cut-off frequency profile. The reconstruction suffers a significant immediate error that is not rapidly damped. It is demonstrated that even though no reflections occur inside the hollow region causing the blind area, the higher probing frequencies that propagate through it carry information that can be used to estimate its properties. The usually ignored full-wave effects were investigated with the use of full-wave simulations in 1D, with special attention paid to the frequency band where they are dominant. A database of perturbation signals was simulated on five-dimensions of parameters and an application of the database inversion was demonstrated for a magnetic island in a Tore Supra discharge. The new adapted reconstruction scheme improved the description of the density profile inside the hollow region and also along 10 cm after it.
- FM-CW reflectometry,
- profile reconstruction,
- reflectometry density profile,
- hollowprofile, blind area

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References (28)

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