000120006 001__ 120006
000120006 005__ 20180913054312.0
000120006 020__ $$a0029-5515
000120006 0247_ $$2doi$$a10.1088/0029-5515/43/6/312
000120006 022__ $$a0029-5515
000120006 02470 $$2DAR$$a3936
000120006 02470 $$2ISI$$a000183917100012
000120006 037__ $$aARTICLE
000120006 245__ $$aSignal processing techniques based on singular value decomposition applied to modulated ECH experiments
000120006 260__ $$c2003
000120006 269__ $$a2003
000120006 336__ $$aJournal Articles
000120006 520__ $$aThe 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.
000120006 700__ $$0241413$$aManini, A.$$g115214
000120006 700__ $$0240130$$aMoret, J. M.$$g105910
000120006 700__ $$aRyter, F.
000120006 773__ $$j43$$k6$$q490-511$$tNuclear Fusion
000120006 909C0 $$pCRPP
000120006 909C0 $$0252028$$pSPC
000120006 909CO $$ooai:infoscience.tind.io:120006$$pSB$$particle
000120006 937__ $$aCRPP-ARTICLE-2003-052
000120006 973__ $$aEPFL$$rREVIEWED$$sPUBLISHED
000120006 980__ $$aARTICLE