Publications by Bernard Joye | EPFL Graph Search

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The Tokamak Configuration Variable (TCV) tokamak (R = 0.88 m, a < 0.25 m, B < 1.54 T) programme is based on flexible plasma shaping and heating for studies of confinement, transport, control and power exhaust. Recent advances in fully sustained off-axis electron cyclotron current drive (ECCD) scenarios have allowed the creation of plasmas with high bootstrap fraction, steady-state reversed central shear and an electron internal transport barrier. High elongation plasmas, kappa = 2.5, are produced at low nor

In noninductively driven discharges, 0.9 MW second harmonic (X2) off-axis co-electron cyclotron current drive deposition is combined with 0.45 MW X2 central heating to create an electron internal transport barrier (eITB) in steady plasma conditions resulting in a 1.6-fold increase of the confinement time (tau(Ee)) over ITER-98L-mode scaling. The eITB is associated with a reversed shear current profile enhanced by a large bootstrap current fraction (up to 80%) and is sustained for up to 10 current redistribu

Sawtooth inversion radii and profile peaking factors of a large variety of ohmic and ECH heated L mode plasmas, including, elongations up to 2.6 and triangularities between -0.5 and 0.75, have been investigated in the TCV tokamak. In ohmic plasmas, normalized inversion radii and electron temperature profile peaking factors (corrected for sawtoothing effects) depend solely on the parameter (j)/q(0)j(0), irrespective of plasma shape. With ECH this parameter remains the main scaling parameter. Density profiles

Fully noninductive, steady-state electron cyclotron current drive (ECCD) has been demonstrated for the first time in experiments carried out in the tokamak a configuration variable (TCV) [O. Sauter , Phys. Rev. Lett. 84, 3322 (2000)]. By appropriately distributing six 0.45 MW ECCD sources over the discharge cross section, fully noninductive, stable, and stationary plasmas with I-p up to 210 kA were obtained for the full discharge duration of 1.9 s, corresponding to more than 900 energy confinement times and

Within the range of plasma shapes and plasma currents investigated, the electron confinement time, tau_Ee, increases with safety factor, density and negative triangularity similar to the Ohmic heating case. There is little dependence of tau_Ee on the heating location provided power deposition occurs inside the q=1 surface; as power deposition moves out of the inversion surface, tau_Ee decreases. The power-induced energy confinement degradation exponent (tau_Ee~PaP) is as usual: alpha_P ~-0.5. As a general t

The dynamical response of a soft X ray emission profile to different external perturbations - gas feed, impurity injection, RF power, surface loop voltage - has been studied on the TCA tokamak and analysed using a single technique. The frequency dependence of the response has been exploited to distinguish between the dominant transport processes. Remarkably similar phase response profiles were obtained with different stimuli; they show a link with sawtooth activity. The model that most plausibly explains th

A 'standard', single null lower diverted discharge has been developed to enable continuous monitoring of the first wall conditions and to characterise the effectiveness and influence of wall conditioning in the TCV tokamak. Measurements over a period encompassing nearly 2000 ohmic discharges of varying configuration and input power show the global confinement time and main plasma impurity concentrations to be good general indicators of the first wall condition, whilst divertor target profiles demonstrate st

The energy confinement time of TCV Ohmic, L-mode discharges is observed to depend strongly on the plasma shape, improving slightly with elongation and degrading strongly as triangularity is increased from zero to positive values. The thermal conductivity of these plasmas is found to be independent of the shape. This observation, combined with geometrical effects on the temperature gradient and a degradation with increasing input energy flux, can explain the observed variation in the energy confinement time.

The effects of plasma shape on confinement and sawtooth stability are studied for positive and negative discharge triangularity and for different elongations with 1.5 MW centrally deposited ECH power

The energy confinement time of TCV ohmic L mode discharges depends strongly on plasma shape. For fixed average current and electron densities, confinement times increase with plasma elongation and decrease with (positive) plasma triangularity. This dependence can be explained by the geometrical effects of flux surface expansion and compression on the temperature gradients together with the effect of power degradation, without the need to invoke a shape dependence of the transport coefficients. A global fact

Bernard Joye

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An overview of results from the TCV tokamak

Recent results from the electron cyclotron heated plasmas in Tokamak à Configuration Variable (TCV)

Shape dependence of sawtooth inversion radii and profile peaking factors in TCV L mode plasmas

Steady-state fully noninductive operation with electron cyclotron current drive and current profile control in the tokamak a configuration variable (TCV)

EFFECT OF LOCALISED ELECTRON CYCLOTRON HEATING ON ENERGY CONFINEMENT AND MHD IN TCV

Investigation of Plasma Transport Processes Using the Dynamical Response of Soft-X-Ray Emission

Divertor target profiles and recycling studies in TCV single null lower standard discharges

Influence of plasma shape on transport in the TCV Tokamak

Energy Confinement in Shaped TCV Plasmas with Electron Cyclotron Heating

Effect of plasma shape on confinement and MHD behaviour in the TCV tokamak

Scrape-Off Measurements During Alfven-Wave Heating in the Tca Tokamak

Alfvén wave heating results in TCA using coated bar antennae

MHD operational limits and disruption statistics in TCV ohmic plasmas

Scrape-off measurements during Alfvén wave heating in the TCA tokamak

Influence of the shape on TCV plasma properties

Magnetic Broad-Band Turbulence Measurements and Ohmic Confinement in the Tca Tokamak

Target plasma conditions in TCA

Measurements of the tokamak safety factor profile by means of driven resonant Alfvén waves

Mode Conversion to the Kinetic Alfven-Wave in Low-Frequency Heating Experiments in the Tca Tokamak

Dynamic response analysis as a tool for investigating transport mechanisms