Direct measurements of E x B flow and its impact on edge turbulence in the CASTOR tokamak using an optimized Gundestrup probe

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F61389021%3A_____%2F01%3A00556780" target="_blank" >RIV/61389021:_____/01:00556780 - isvavai.cz</a>

Result on the web

<a href="https://link.springer.com/article/10.1023/A:1012885815332" target="_blank" >https://link.springer.com/article/10.1023/A:1012885815332</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1023/A:1012885815332" target="_blank" >10.1023/A:1012885815332</a>

Result language

angličtina

Original language name

Direct measurements of E x B flow and its impact on edge turbulence in the CASTOR tokamak using an optimized Gundestrup probe

Original language description

New experimental evidence of the correlation between edge sheared ExB flow and reduction of turbulence has been measured in the CASTOR tokamak (R = 0.4m, a = 0.085 m, B-T = 1 T). A biasing electrode is placed at the separatrix in a configuration which has demonstrated strongly sheared electric fields and consequent improvement of the global particle confinement. A set of movable electrostatic probes (rake, Langmuir, Gundestrup, and rotating Mach) provide redundant, simultaneous measurements of poloidal flow, toroidal flow, electron temperature, density, and radial electric field with high temporal resolution and at the same poloidal location. Particular effort has been made in the optimization of the Gundestrup probe collector geometry in order to reduce the relative uncertainty of Mach number measurements in plasmas with weak flow (M-parallel to, M-perpendicular to < 0.1). The measurements from the rake, Gundestrup, and rotating Mach probes give three independent radial profiles of E x B shear in ohmic and biased modes. Good agreement is obtained both for the profile shape and its absolute magnitude. The plasma flows, especially the poloidal ExB drift velocity, are strongly modified in the sheared region, reaching Mach numbers as high as half the sound speed. The corresponding shear rates (<approximate to> 5 x 10(6) s(-1)) derived from both the flow and electric field profiles are in excellent agreement and are at least an order of magnitude higher than the growth rate of unstable turbulent modes as estimated from fluctuation measurements. In addition, we compare the measured ExB ion mass flow with the phase velocity of fluctuations moving poloidally across the Gundestrup collectors. Given the poloidal separation of the collecting plates and the sampling frequency (5 MHz), the maximum detectable phase velocity turns out to be rather modest compared to the measured bulk poloidal flow speed. Therefore the two quantities are only compared when the poloidal speed is low - in that case, they show similar behaviour in response to the applied bias.

Czech name

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Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

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OECD FORD branch

10305 - Fluids and plasma physics (including surface physics)

Project

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Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2001

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Czechoslovak Journal of Physics

ISSN

0011-4626

e-ISSN

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Volume of the periodical

51

Issue of the periodical within the volume

10

Country of publishing house

US - UNITED STATES

Number of pages

10

Pages from-to

1001-1010

UT code for WoS article

000172493000005

EID of the result in the Scopus database

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