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          Institute: MPI für Plasmaphysik     Collection: Articles, Books, Inbooks     Display Documents



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ID: 60832.0, MPI für Plasmaphysik / Articles, Books, Inbooks
Signal processing techniques based on singular value decomposition applied to modulated ECH experiments
Authors:Manini, A.; Moret, J.-M.; Ryter, F.; ASDEX Upgrade Team
Language:English
Date of Publication (YYYY-MM-DD):2003
Title of Journal:Nuclear Fusion
Journal Abbrev.:Nucl. Fusion
Volume:43
Issue / Number:6
Start Page:490
End Page:511
Copyright:Copyright © Institute of Physics and IOP Publishing Limited 2003
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:The analysis and interpretation of perturbative modulated electron cyclotron heating (MECH) discharges for power deposition localization using different diagnostics, such as electron cyclotron emission (ECE) and soft x-ray (SXR) measurements, are presented. In particular, the experimental determination of the MECH power deposition is
investigated, which is a fundamental requirement, for example, for heat transport studies. The most important problem is related to the coupling between the MECH and the
sawtooth activity of the plasma, which disturbs both ECE and SXR measurements. Several techniques have been adopted to circumvent this difficulty. In particular, the singular
value decomposition (SVD) and the generalized singular value decomposition (GSVD) have been tested. However, both methods are incapable of treating the problem correctly,
which leads to potential misinterpretation of the results. A new method based on system identification using the SVD (SI-SVD) is developed and applied. This method, within reasonable limits induced by the assumption of linearity, is capable of simultaneously separating the MECH from the sawtooth contributions to both ECE electron temperature
measurements and SXR emission measurements. Such a method is in particular applied to a neutral beam injection (NBI) heated ASDEX Upgrade discharge in which MECH is added in order to analyse electron heat transport in a mostly ion-heated plasma. Since the NBI heating is also partly modulated with short pulses which coincide with the sawtooth
crashes to improve their stability, both the MECH and the NBI deposition profiles are determined. Moreover, treating the signals with the SI-SVD procedure enables a study of the
plasma dynamic response also at higher MECH harmonic numbers.
Free Keywords:PLASMA TRANSPORT, TCV TOKAMAK, RTP TOKAMAK, OSCILLATIONS, PROFILE, CONFINEMENT
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Plasmaphysik/E1
External Affiliations:Centre de Recherches en Physique des Plasmas, Association EURATOM—Confédération Suisse, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
Identifiers:DOI:10.1088/0029-5515/43/6/312
URL:http://www.iop.org/EJ/article/0029-5515/43/6/312/n...
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