Statistical study of density fluctuations in the Tore Supra tokamak
It is believed that the radial anomalous transport in tokamaks is caused by plasma turbulence. Using infra-red laser scattering technique on the Tore Supra tokamak, statistical properties of the density fluctuations are studied as a function of the scales in ohmic as well as additional heating regimes using the lower hybrid or the ion cyclotron frequencies. The probability distributions are compared to a Gaussian in order to estimate the role of intermittency, which is found to be negligible. The temporal behaviour of the three-dimensional spectrum is thoroughly discussed; its multifractal character is reflected in the singularity spectrum. The auto-correlation coefficient is shown to reflect a short-time coherence of the dissipative structures as well as their long-time incoherence and statistical independence. The existence of fluctuations transfer between two distinct but close wavenumbers is proposed. A rather clearer image is thus obtained about the way energy is transferred through the turbulent scales.
Bibliographic Reference: Report: EUR-CEA-FC-1629 EN (1998) 36pp.
Availability: Available from Association Euratom-CEA, CEN Cadarache, 13108 Saint-Paul-lez-Durance (FR)
Record Number: 199810706 / Last updated on: 1998-06-08
Original language: en
Available languages: en