Speaker
Bruno Soares Gonçalves
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.1084.pdf
Radial structure of vorticity in the plasma boundary of tokamak plasmas
B. Gonçalves1, I. Henriques1, C. Hidalgo2, C. Silva1, H. Figueiredo1, V. Naulin3, A. H.
Nielsen3
1
Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa,
1049-001 Lisboa, Portugal.
2
Euratom-Ciemat, Madrid, Spain
3
Technical University of Denmark, Department of Physics, 2800 Kgs. Lyngby, Denmark
The first experimental measurement of vorticity and vorticity flux divergence in a fusion device
is presented. This is an important achievement since vorticity plays a key role in the transport
of energy and particles in plasmas and fluids. The measurements were performed in the plasma
edge of the small tokamak ISTTOK, with an array of Langmuir probes, specifically designed
for the purpose, allowing for the first time a direct comparison with theoretical models.
Plasma profiles and turbulence have been investigated using the probe head, located on the
equatorial plane of the device. It consists of two parallel arrays of Langmuir probes separated
by Dr~3 mm allowing the simultaneous investigation of the radial structure of fluctuations on
vorticity, Reynolds stress and turbulence in the plasma boundary region. Measurements were
taken at different radial positions, both in the edge (r < alimiter) and in the scrape-off layer (r >
alimiter) on a shot by shot basis.
The experimental results presented show that the vorticity flux divergence amplifies the shear
flow in the tokamak plasma edge region. Self-similarity in the probability distribution function
of several parameters, including vorticity and vorticity flux, is also observed in ISTTOK and
indicate that there is no morphological change in the coherent structures in the plasma boundary
region and that momentum flux is regulated by blobs.
