Determination of structure tilting in magnetized plasmas - Time delay estimation in two dimensions

Time delay estimation (TDE) is a well-known technique to investigate poloidal flows in fusion plasmas. The present work is an extension of the earlier works of A. Bencze and S. Zoletnik 2005 and B. T\'al et al. 2011. From the prospective of the comparison of theory and experiment it seem to be important to estimate the statistical properties of the TDE based on solid mathematical groundings. This paper provides analytic derivation of the variance of the TDE using a two-dimensional model for coherent turbulent structures in the plasma edge and also gives an explicit method for determination of the tilt angle of structures. As a demonstration this method is then applied to the results of a quasi-2D Beam Emission Spectroscopy (BES) measurement performed at the TEXTOR tokamak.Comment: 8 pages, 10 figure

Untersuchung zum Zerfall von Hochspin-Isomeren in den W- und Os-Isotopen und Entwicklung von Programmen zur Steuerung der Experimentlogik und der Datenerfassung

Der neue Stand der Technik erlaubt es, die Experimentelektronik durch die Verwendungvon ECL-Modulen bedeutend schneller aufzubauen. Durch den Einsatz des alten CAMAC-Standards ist man in der Lage Experimentkonfigurationen mit Hilfe eines Rechnerseinzustellen. Neue Techniken in der Herstellung von Mikroprozessoren und Speicher-IC's erlauben den Einsatz von Mikroprozessoren zur Steuerung der Experimentelektronikund tragen zur Schaffung eines von Großrechnern unabhängigen modularen undtransportablen Computers bei. Für die Kalibrierung komplexer Detektorsysteme existierenneue CAMAC-Einschübe, die eine Datenerfassung auf dem CAMAC-Bus ermöglichen.Mit den neuen Achtfach ADC's l<ann man Präzisionsmessungen durchführen. EineWeiterentwicklung solcher kleiner Datenerfassungssysteme unter Einbezug des VMEBussesist in nächster Zeit realisierbar. Dadurch können kernspektroskopische Experimentewesentlich einfacher durchgeführt werden

Turbulence propagation studies with long range correlation reflectometry

Turbulence propagation studies with long range correlation reflectometryA. Krämer-FleckenInstitut für Energie- und Klimaforschung / Plasmaphysik, Forschungszentrum Jülich GmbH,D–52425 Jülich, GermanyCEA, IRFM, F-13108 Saint-Paul-Lez-Durance, France3Southwestern Institute of Physics (SWIP) P. O. Box 432, Chengdu, Sichuan 610041, ChinaFor transport related questions it is necessary to understand the underlying turbulence and itspropagation. This needs on the one side sophisticated experiments and on the other side timeconsuming gyrokinetic simulations. Whereas simulations are performed on small time scalestoday diagnostics still suffer on temporal and spatial resolution for a detailed comparison.The scope of this presentation is to investigate the velocity of turbulent structures in all dimen-sions by using Correlation Reflectometry. The methode is outlined for measurements with acorrelation reflectometer system [1], sensitive to fluctuations of the electron density and oper-ating at two poloidal and toroidal different positions. This allows to investigate not only thepoloidal but also toroidal extension of turbulent structures as well as its propagation. For the ex-perimental conditions of the experiments near the=1 surface it it shown that quasi coherent(QC)-modes are the only one which are correlated for large toroidal distances. No indication fora correlation of low frequency turbulence is found at least for a connection length of 5 m.The poloidal velocity is easily determined from the delay time of a poloidally separated set ofantennae. The toroidal velocity can be determined if the toroidal distance travelled by the struc-ture is known. Therefore it is necessary to determine the local safety factor. Together with theknown delay times an estimation of the parallel velocity is possible. The estimation of radialvelocity will be addressed as well. Long range correlations with different poloidal separationand different propagation time yield the coherence maximum all at the same radial separationwhich is taken as evidence for a negligible radial propagation.Furthermore it could be demonstrated that QC-modes show a significant deviation from thealignment within an iso density surface. A good agreement with the symmetry axis of the QC-mode and the observation axis stemming from the two separated positions of the correlationreflectometer is found for a D r = 8 mm. If the turbulent structure is aligned to flux surfaces isstill an open question.References[1] A. Krämer-Flecken, S. Soldatov, B. Vowinkel et al., Rev. Sci. Instrum.81, 113502, (2010