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Visualization of electron temperature and density isosurfaces or isocurves in T...

In this paper are described two programs that allow the easy visualization of isosurfaces S(r,t) or isocurves C(r,t), time and space profiles from electron temperature and density of Tokamak plasmas, used in research of thermonuclear fusion of light nucleus. The programs are written in IDL and they run in two European laboratories, JET (Joint European Torus) that is the largest Tokamak in the world, based in t...

Density Profile Evolution during Dynamic Processes in ASDEX Upgrade

The impact of ELM activity and density limit disruptions on the plasma density as well as the use of reflectometry for plasma position and shape control are discussed here. Fast density measurements allow the definition of three characteristic phases of the ELM: precursor, collapse and recovery. At the precursor phase low frequency oscillations starting approximately 3 ms prior to the ELM collapse are observed ...

Runaway electrons in JET disruptions

Behavior of Density Fluctuations and Electron Temperature Profiles in JET Densi...

The sudden degradation of the energy confinement characterizing major density limit disruptions, has been observed to initiate close to the q=2 surface, in a small and medium size tokamak. A flattening of the electron temperature profile spreads inwards from the outboard O-point of the 2/1 mode. This initiates the destruction of the energy confinement. This paper reports on observations of this sequence of ev...

Observations of the Onset of the Energy Quench in ASDEX Upgrade Density Limit D...

Tokamak major density limit disruptions are usually preceded by a m/n=2/1 tearing mode, that may or may not lock to the vessel wall. The complete destruction of energy confinement in these major disruptions is known to have a characteristic m/n=1/1 form. Initially only a small degradation of the confinement occurs, as is observed by the slow increase of the electron temperature at the plasma edge. But at some ...

Sawtooth, Neo-Classical Tearing Mode and Error Field Studies in JET

A range of ITER relevant plasma stability issues have been studied in the JET tokamak; these include the effects of fast particles on sawteeth, control of NTMs via sawteeth seeds, scaling of (2,1) NTM thresholds and the effect of error fields on plasma rotation and vice-versa. The sawtooth studies have examined both the effects of ICRF and NBI fast particles, and models used for ITER predictions have been valid...

The effect of ECRH on the stability of the radiation induced m=2 mode and on th...

The results of a series of experiments done in RTP which had the purpose to avoid or ameliorate radiative density-limit disruptions, will be reported. Avoidance of disruptions was achieved by stabilizing the m = 2 radiation induced tearing mode (RTM) with electron cyclotron resonance heating (ECRH). Both continuous and modulated power deposition was studied. It was found that stabilization with modulated ECRH i...

Exponentially growing tearing modes in Rijnhuizen Tokamak Project plasmas

The local measurement of the island width w, around the resonant surface, allowed a direct test of the extended Rutherford model [P. H. Rutherford, PPPL Report-2277 (1985)], describing the evolution of radiation-induced tearing modes prior to disruptions of tokamak plasmas. It is found that this model accounts very well for the observed exponential growth and supports radiation losses as being the main driving ...

High Resolution Ne and Te Profiles During the Energy Quench of Density Limit Di...

Electron temperature, Te and density, ne profiles were measured during the energy quench of a major density limit disruption in RTP (a=0.164 m, R0=0.72 m, qa=4). The evolution of the Te profile was followed with high temporal resolution (1 us) with a 20 channels ECE radiometer. High spatial (3 mm) Te and ne profiles were measured at different times during the energy quench with a Thomson scattering. With these ...