Methods for the detection of Zonal Flows using one-point and two-point turbulence measurements

S. Zoletnik, L. Bardoczi, A. Krämer-Flecken, Y. Xu, I. Shesterikov, S. Soldatov, G. Anda, D. Dunai, G. Petravich

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

The sensitivity of two numerical methods for the detection of zonal flows, especially geodesic acoustic modes (GAMs), through the movement of turbulence eddies is studied. One of them is the widely used time delay estimation method which determines a propagation time delay between two measurement points. The second technique is based on analyzing movements of the minimum in the autocorrelation function of a single measurement signal (ACFM method). The applicability of both methods is analyzed in detail in terms of time resolution, signal-to-noise ratio (SNR) and velocity modulation amplitude. It is found that both methods exhibit a broadband noise spectrum in the calculated velocity from inherent statistical reasons and they also underestimate the RMS velocity modulation amplitude by at least a factor of two, even under noise-free conditions. Their sensitivity to GAMs ceases below an SNR of about 2. These methods are applied to measurement signals obtained in Ohmic plasmas using correlation reflectometry, lithium beam emission spectroscopy (Li-BES) and probe diagnostics on the TEXTOR tokamak. The equivalence of the two methods is shown under these conditions experimentally. The availability of both methods considerably widens the possibility to detect zonal flows therefore the phase relationship between velocity modulations, related to GAMs, can be determined at both poloidally and toroidally well separated locations. A toroidally and poloidally symmetric m=0, n=0 velocity modulation and a coherent π/2 out of phase electron density modulation is found with odd poloidal mode number, as predicted by theory.

Original languageEnglish
Article number065007
JournalPlasma Physics and Controlled Fusion
Volume54
Issue number6
DOIs
Publication statusPublished - Jun 2012

Fingerprint

velocity modulation
Turbulence
turbulence
signal measurement
Amplitude modulation
acoustics
Modulation
signal to noise ratios
time lag
Time delay
Signal to noise ratio
sensitivity
noise spectra
autocorrelation
availability
equivalence
Emission spectroscopy
Autocorrelation
lithium
Carrier concentration

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Nuclear Energy and Engineering

Cite this

Methods for the detection of Zonal Flows using one-point and two-point turbulence measurements. / Zoletnik, S.; Bardoczi, L.; Krämer-Flecken, A.; Xu, Y.; Shesterikov, I.; Soldatov, S.; Anda, G.; Dunai, D.; Petravich, G.

In: Plasma Physics and Controlled Fusion, Vol. 54, No. 6, 065007, 06.2012.

Research output: Contribution to journalArticle

Zoletnik, S, Bardoczi, L, Krämer-Flecken, A, Xu, Y, Shesterikov, I, Soldatov, S, Anda, G, Dunai, D & Petravich, G 2012, 'Methods for the detection of Zonal Flows using one-point and two-point turbulence measurements', Plasma Physics and Controlled Fusion, vol. 54, no. 6, 065007. https://doi.org/10.1088/0741-3335/54/6/065007
Zoletnik, S. ; Bardoczi, L. ; Krämer-Flecken, A. ; Xu, Y. ; Shesterikov, I. ; Soldatov, S. ; Anda, G. ; Dunai, D. ; Petravich, G. / Methods for the detection of Zonal Flows using one-point and two-point turbulence measurements. In: Plasma Physics and Controlled Fusion. 2012 ; Vol. 54, No. 6.
@article{13b2eaa7869d48c79d2c558da2822474,
title = "Methods for the detection of Zonal Flows using one-point and two-point turbulence measurements",
abstract = "The sensitivity of two numerical methods for the detection of zonal flows, especially geodesic acoustic modes (GAMs), through the movement of turbulence eddies is studied. One of them is the widely used time delay estimation method which determines a propagation time delay between two measurement points. The second technique is based on analyzing movements of the minimum in the autocorrelation function of a single measurement signal (ACFM method). The applicability of both methods is analyzed in detail in terms of time resolution, signal-to-noise ratio (SNR) and velocity modulation amplitude. It is found that both methods exhibit a broadband noise spectrum in the calculated velocity from inherent statistical reasons and they also underestimate the RMS velocity modulation amplitude by at least a factor of two, even under noise-free conditions. Their sensitivity to GAMs ceases below an SNR of about 2. These methods are applied to measurement signals obtained in Ohmic plasmas using correlation reflectometry, lithium beam emission spectroscopy (Li-BES) and probe diagnostics on the TEXTOR tokamak. The equivalence of the two methods is shown under these conditions experimentally. The availability of both methods considerably widens the possibility to detect zonal flows therefore the phase relationship between velocity modulations, related to GAMs, can be determined at both poloidally and toroidally well separated locations. A toroidally and poloidally symmetric m=0, n=0 velocity modulation and a coherent π/2 out of phase electron density modulation is found with odd poloidal mode number, as predicted by theory.",
author = "S. Zoletnik and L. Bardoczi and A. Kr{\"a}mer-Flecken and Y. Xu and I. Shesterikov and S. Soldatov and G. Anda and D. Dunai and G. Petravich",
year = "2012",
month = "6",
doi = "10.1088/0741-3335/54/6/065007",
language = "English",
volume = "54",
journal = "Plasma Physics and Controlled Fusion",
issn = "0741-3335",
publisher = "IOP Publishing Ltd.",
number = "6",

}

TY - JOUR

T1 - Methods for the detection of Zonal Flows using one-point and two-point turbulence measurements

AU - Zoletnik, S.

AU - Bardoczi, L.

AU - Krämer-Flecken, A.

AU - Xu, Y.

AU - Shesterikov, I.

AU - Soldatov, S.

AU - Anda, G.

AU - Dunai, D.

AU - Petravich, G.

PY - 2012/6

Y1 - 2012/6

N2 - The sensitivity of two numerical methods for the detection of zonal flows, especially geodesic acoustic modes (GAMs), through the movement of turbulence eddies is studied. One of them is the widely used time delay estimation method which determines a propagation time delay between two measurement points. The second technique is based on analyzing movements of the minimum in the autocorrelation function of a single measurement signal (ACFM method). The applicability of both methods is analyzed in detail in terms of time resolution, signal-to-noise ratio (SNR) and velocity modulation amplitude. It is found that both methods exhibit a broadband noise spectrum in the calculated velocity from inherent statistical reasons and they also underestimate the RMS velocity modulation amplitude by at least a factor of two, even under noise-free conditions. Their sensitivity to GAMs ceases below an SNR of about 2. These methods are applied to measurement signals obtained in Ohmic plasmas using correlation reflectometry, lithium beam emission spectroscopy (Li-BES) and probe diagnostics on the TEXTOR tokamak. The equivalence of the two methods is shown under these conditions experimentally. The availability of both methods considerably widens the possibility to detect zonal flows therefore the phase relationship between velocity modulations, related to GAMs, can be determined at both poloidally and toroidally well separated locations. A toroidally and poloidally symmetric m=0, n=0 velocity modulation and a coherent π/2 out of phase electron density modulation is found with odd poloidal mode number, as predicted by theory.

AB - The sensitivity of two numerical methods for the detection of zonal flows, especially geodesic acoustic modes (GAMs), through the movement of turbulence eddies is studied. One of them is the widely used time delay estimation method which determines a propagation time delay between two measurement points. The second technique is based on analyzing movements of the minimum in the autocorrelation function of a single measurement signal (ACFM method). The applicability of both methods is analyzed in detail in terms of time resolution, signal-to-noise ratio (SNR) and velocity modulation amplitude. It is found that both methods exhibit a broadband noise spectrum in the calculated velocity from inherent statistical reasons and they also underestimate the RMS velocity modulation amplitude by at least a factor of two, even under noise-free conditions. Their sensitivity to GAMs ceases below an SNR of about 2. These methods are applied to measurement signals obtained in Ohmic plasmas using correlation reflectometry, lithium beam emission spectroscopy (Li-BES) and probe diagnostics on the TEXTOR tokamak. The equivalence of the two methods is shown under these conditions experimentally. The availability of both methods considerably widens the possibility to detect zonal flows therefore the phase relationship between velocity modulations, related to GAMs, can be determined at both poloidally and toroidally well separated locations. A toroidally and poloidally symmetric m=0, n=0 velocity modulation and a coherent π/2 out of phase electron density modulation is found with odd poloidal mode number, as predicted by theory.

UR - http://www.scopus.com/inward/record.url?scp=84861418795&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84861418795&partnerID=8YFLogxK

U2 - 10.1088/0741-3335/54/6/065007

DO - 10.1088/0741-3335/54/6/065007

M3 - Article

AN - SCOPUS:84861418795

VL - 54

JO - Plasma Physics and Controlled Fusion

JF - Plasma Physics and Controlled Fusion

SN - 0741-3335

IS - 6

M1 - 065007

ER -