Energy Confinement in Shaped TCV Plasmas with Electron Cyclotron Heating

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This paper shows the importance and feasibility of real-time tomography in fusion experiments for the example of soft X-ray (SXR) position measurements. The requirement of non-magnetic real-time diagnostics in low frequencies for ITER is discussed. This is illustrated by recent results of rapid tomographic inversion of SXR measurements on tokamak TCV. Comparison with the magnetic reconstruction data has not only shown the valuable resolution capabilities of both techniques, but also revealed a slight depend

A view of recent experimental results and progress in the characterization of the statistical properties of edge turbulence in fusion plasmas is given. The study of the dynamical interplay between fluctuations in gradients, turbulent transport and radial electric fields has shown that these parameters are strongly coupled both in tokamak and stellarator plasmas. The size of turbulent events increases when the plasma deviates from the average density gradient. The radial velocity of fluctuations is of the or

A new scenario to delay or prevent neoclassical tearing mode (NTM) onset is presented. By active sawtooth destabilization, short period and low amplitude sawteeth are generated, such that the sawtooth produced NTM seed island is reduced and the threshold normalized plasma pressure for triggering of NTMs, beta(Nonset), is increased. The scenario has been explored experimentally in the Joint European Torus (JET). Ion cyclotron resonance frequency (ICRF) waves tuned to the 2nd harmonic H-minority resonance hav

Magnetohydrodynamic (MHD) instabilities can limit the performance and degrade the confinement of tokamak plasmas. The Tokamak à Configuration Variable (TCV), unique for its capability to produce a variety of poloidal plasma shapes, has been used to analyse various instabilities and compare their behaviour with theoretical predictions. These instabilities are perturbations of the magnetic field which usually extend to the plasma edge where they can be detected with magnetic pick-up coils as magnetic fluctuat

An electron cyclotron resonance heating (ECRH) system is presently under construction at Commissariat A l'Energie Atomique (CEA) Cadarache for the Tore Supra experiment. The generator is planned to be made of six gyrotrons giving RF waves with a frequency of 118 GHz and a unit power of 400 kW (500 kW) for a pulse length of 210 s (5 s); two of them are already installed: the prototype was first tested on various dummy loads and on plasma and the first series tube is still being tested on a CW load. The resul

We report evidence of a large blue shift (up to 70 meV) in the photoluminescence spectra of InAs/InP island like quantum wells following the reduction of the InP top barrier layer thickness from 6 nm to near zero. The photoluminescence intensity only starts to decrease when the top barrier thickness falls below 1.5 nm, indicating that radiative recombinations in the islands are very efficient. These results are well understood by a model assuming a vacuum confinement energy close to 5 eV. (C) 1997 American

An analysis of the effect on the wall stabilization of external kink modes due to toroidally continuous gaps in the resistive wall is performed. The effects both with and without toroidal rotation are studied. For a high-beta equilibrium, the mode structure is localized on the outboard side. Therefore, outboard gaps greatly increase the growth rate when there is no rotation. For resistive wall stabilization by toroidal rotation, the presence of gaps has the same effect as moving the wall farther away, i.e.,

This paper presents an overview of results of the 1994/95 experimental campaign on JET with the new pumped divertor and draws implications for ITER in the areas of detached and radiative divertor plasmas, the use of beryllium as a divertor target the material, the confinement properties of discharges with the same dimensionless parameters (except for the dimensionless Larmor radius) as ITER and the effect of varying the toroidal magnetic field ripple in the ITER relevant range. Discharges with high fusion p

Ohmic H-mode has been regularly obtained on the TCV tokamak. This paper describes the change in magnetic activity occuring at the transition, the coherent activity during H-mode, a brief description of the dithering phase, and the activity associated with large and grassy ELMs.

The measurement of the tokamak plasma ion temperature can be obtained by collective Thomson scattering. This method requires a far infrared laser to achieve useful spatial resolution for typical tokamak plasma parameters. The very low Thomson scattering cross section (10-28 m2) implies the use of a pulsed far infrared laser with 1 MW power and 1 µs pulse duration. With the best technology of far infrared heterodyne receivers available today, with a noise equivalent power (NEP) below 10-18 W/Hz, it should be

Energy Confinement in Shaped TCV Plasmas with Electron Cyclotron Heating

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Present and perspective roles of soft X-ray tomography in tokamak plasma position measurements

Statistical properties of turbulence: a new approach to characterize transport in fusion plasmas

Control of sawteeth and triggering of NTMs with ion cyclotron resonance frequency waves in JET

MHD stability limits in the TCV tokamak

The 118 GHz ECRH experiment on Tore Supra

Evidence of a blue shift in near surface ultra thin InAs/InP island like quantum wells

The effect of partial poloidal wall sections on the wall stabilization of external kink modes

JET results with the new pumped divertor and implications for ITER

Mhd Activity During H-Mode Discharges on the Tcv Tokamak

Developement and use of far infrared lasers in studies of collective electron density fluctuations in a tokamak plasma by Thomson scattering