Study of Low-Frequency Microturbulence in the Microtor Tokamak by Far-Infrared Laser Scattering

Abstract

terns where the above effect can be seen. A candidate for the first case would be the excited line in Cu 2 0 where the values of the parameters predict a large effect with crucial consequences on the interpretation of some experiments on the excitons and biexcitonic states using counterpropagating beams. In a different context the soft modes near a paraelectric-to-ferroelectric transition in a crystal will be another interesting system; these modes are highly anharmonic and the damping will play a very crucial role.(a . 7 When one takes into account damping but still neglects the out-of-phase component inQ 0 , r\ near r 2 approaches 9A 2 T 2 . The out-of-phase component cannot be neglected near r 1 . At and very near the critical points, the expansion Q =Q 0 + 6Q and Eqs. (4) and (8) as well as the mean-field approximation cannot be used. The detailed behavior near the critical points and the implications of the near-field approximation are being investigated and the results will be reported elsewhere. 8 B. A. Huberman and J. P 0 Crutchfield, Phys. Rev.

Scale-selective turbulence reduction in H-mode plasmas in the TJ-II stellarator

“…For the core region (d), the turbulence level is higher than in all spectra towards the edge. These measurements compare well to existing literature: far-infrared measurements in a tokamak plasma (Mictrotor tokamak) were made in 1980 by Semet et al and yielded α = −3.5 in the range 6 cm −1 < k ⊥ < 20 cm −1 [61]. Devynck et al investigated k ⊥ spectra in 1993 in the Tore Supra tokamak with collective infrared laser scattering and obtained spectral indices α = −3 at k ⊥ > 6 cm −1 [24].…”

Impact of collisionality on fluctuation characteristics of micro-turbulence

“…At the largest scales measured ͑k Ͻ 2 cm −1 ͒, an anisotropy is observed between the radial and the poloidal directions 30,32,35 while for higher wavenumbers ͑but still k i Շ 1͒ the fluctuation energy follows, in both directions, a power law S͑k͒ = ␦n 2 ϰ k −␣ where ␣ Ϸ −3.5Ϯ 1. [36][37][38][39][40] Thanks to the extension of the spatial scale range of the measurements, a faster decrease of the energy of fluctuations at high wavenumbers has been observed, first on Tore Supra using CO2 laser scattering system: the spectrum is composed of two power laws, at small k, S͑k͒ = k −3 while from k i = ͓1−2͔, S͑k͒ = k −6 . 28 This observation has been confirmed on W7-AS ͑k −2.8 and k −8.5 ͒ ͑Ref.…”

Theoretical interpretation of experimental dibaryon resonance data

“…(8), the spectrum at large mode numbers is of the form <| ii m I 2 > ro * k£ 4 [9] to be compared with the Microtor observations kg 3 -5 [36] in low-ion-temperature plasma. It can be shown [9] that the spectral index (= 4) is compatible with the hypothesis of an inertial subrange, similar to Obukhoff s in Navier-Stokes turbulence [37], in which only energy cascade occurs.…”