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We report the first experimental observation of the depolarization of the Thomson scattering (TS) radiation, a relativistic effect expected to occur in very high T-e plasmas and never observed so far in a fusion machine. A set of unused optical fibers in t ...

A set of experiments was carried out in JET ILW (Joint European Torus with ITER-Like Wall) L-mode plasmas in order to study the effects of light impurities on core ion thermal transport. N was puffed into some discharges and its profile was measured by act ...

Starting from a standard single null X-point configuration, a second order null divertor (snowflake (SF)) has been successfully created on the Tokamak à Configuration Variable (TCV) tokamak. The magnetic properties of this innovative configuration have bee ...

Retarding field analyzers (RFAs) are essentially the only practical tool with which to measure the distribution of ion energies in the boundary plasma of magnetic fusion devices. The technique has long been attempted in such facilities with varying degrees of success, but, by virtue of the delicate nature of these material probes and the hostile environment in which they are inserted, its use has been limited to smaller plasma machines with easier access and more tolerable plasma conditions. This article de

The Retarding Field Analyser (REA) is essentially the only practical tool for the measurement of ion energies parallel to the total magnetic field in the tokamak scrape-off layer plasma. One such device has recently been successfully employed at JET [1]. Its bi-directional nature allows both measurements of ion temperature and plasma flow velocities. The latter are computed by collecting the ion saturation flux to negatively biased entrance slit plates which are set back inside a boron nitride protective ho

In the moderate magneticfield of TCV (1.5T), the recently installed X3 system (3 gyrotrons @118 GHz, 0.45 MW/each, 2s) broadens the operational space with the possibility of heating plasmas at high density, well above the cutoff density of the X2 system (X ...

Despite its importance in determining the calculated surface power flux predicted, for example, by scrape-off layer simulation codes, the sheath heat transmission factor, gamma remains a quantity whose theoretically predicted value has rarely been tested e ...

The First Mirror Test for ITER has been carried out in JET with mirrors exposed during: (i) the third ILW campaign (ILW-3, 2015-2016, 23.33 h plasma) and (ii) all three campaigns, i.e. ILW-1 to ILW-3: 2011-2016, 63,52 h in total. All mirrors from main cham ...

From probe measurements in the far SOL of TCV it is demonstrated that while the particle density profile becomes increasingly broader with increasing line averaged density, the radial variation of the fluctuation statistics remains the same. Excellent agre ...

In this paper, two simplified models of edge localized mode (ELM) power exhaust are developed, one based on the kinetic and the other on the fluid treatment of parallel losses. These models are found to capture many (though not all) of the salient features ...

The structure of the naturally occurring velocity shear layer and the dynamical coupling between gradients and transport have been investigated in the JET plasma boundary region. The velocity shear layer appears to organize itself to reach a condition in which the radial gradient in the poloidal phase velocity of fluctuations is comparable to the inverse of the correlation time of fluctuations (1/tau). This result suggests that E x B sheared flows organized themselves to be close to marginal stability (i.e.

During the first two years of operation, the TCV tokamak has produced a large variety of plasma shapes and magnetic configurations, with 1.0 less than or equal to B-tor less than or equal to 1.46T, I-p less than or equal to 800kA, kappa less than or equal to 2.05, -0.7 less than or equal to delta less than or equal to 1. A new shape control algorithm, based on a finite element reconstruction of the plasma current in real time, has been implemented. Vertical growth rates up to 1000 s(-1) have been stabilized

Particle transport in tokamak plasmas has been intensively studied in the past, particularly in relation to density peaking and the presence of anomalous inward particle convection in L-and H-modes. While in the L-mode case the presence of the anomalous in ...

Precise control of the shape and position of double-null divertor configurations in the TCV tokamak has been used to trigger reliably the transition from ELM-free to ELMy ohmic H mode and back. Preprogrammed modulation of the magnetic axis height (+/- 1.25 cm), with fixed shaping field, caused the plasma to evolve, during a single discharge, between double-null-upper, double-null and double-null-lower configurations, with the secondary X point remaining close to the separatrix. The transition from ELM-free

The effect of field reversal on the JET MkIIGB-SRP divertor performance has been investigated in L-mode density limit discharges. These experiments show that the direction of the magnetic field has a substantial effect on divertor physics, modifying the ch ...

Fluctuations and particle transport in the scrape-off layer of TCV plasmas have been investigated by probe measurements and direct comparison with two-dimensional interchange turbulence simulations at the outer midplane. The experiments demonstrate that wi ...

The toroidal field and plasma current were reversed in recent JET experiments to yield a large number of good forward-reversed matched pairs. The direction, magnitude and scaling of the poloidal energy transport in the SOL can be explained by (neo-)classic ...

A multi-probe system has been developed to investigate the importance of electron temperature fluctuations turbulent transport in the Joint European Torus boundary plasma. The compact five-pin triple probe has been designed to reduce the phase delay of fluctuations due to the finite pin separation in the standard triple probe technique, while still avoiding the effects of probe shadowing. This probe has been found to have advantages over the standard triple probe in the region close to the separatrix (r-r(s

First principles expressions are given for the parameters governing collisional diffusion and parallel losses of mass, momentum and energy in tokamak scrape-off layer (SOL) plasmas. These dissipative, or damping, coefficients are based on neoclassical perp ...

Examination of radial electric field (E,.) profiles in the scrape-off layer (SOL) of ASDEX Upgrade (AUG) and JET revealed large discrepancies between 2D fluid edge modelling and experiment. Experimental profiles of plasma potential (V-p) in the outer (low ...

Richard Pitts

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First observation of the depolarization of Thomson scattering radiation by a fusion plasma

Effects of nitrogen seeding on core ion thermal transport in JET ILW L-mode plasmas

Snowflake Divertor Plasmas on TCV

Retarding field energy analyzer for the JET plasma boundary

Particle-in-cell simulations of the impact of retarding field analyser probe head geometry on ion saturation current measurements

Third-harmonic X-mode, real-time controlled top-launch ECW experiments on TCV tokamak

Sheath heat transmission factors on TCV

First mirror test in JET for ITER: Complete overview after three ILW campaigns

Turbulent transport in the TCV SOL

A model of ELM filament energy evolution due to parallel losses

Experimental evidence of fluctuations and flows near marginal stability and dynamical interplay between gradients and transport in the JET plasma boundary region

Recent Results from the Tcv Tokamak

Observation of enhanced ion particle transport in mixed H/D isotope plasmas on JET

Elm Control During Double-Null Ohmic H Modes in Tcv

The effect of field reversal on the JET MkIIGB-SRP divertor performance in L-mode density limit discharges

Fluctuations and transport in the TCV scrape-off layer

Effect of B x del B direction on SOL energy transport in JET

Fluctuation measurements using a five-pin triple probe in the Joint European Torus boundary plasma

Dissipative processes in interchange driven scrape-off layer turbulence

Discrepancy between modelled and measured radial electric fields in the scrape-off layer of divertor tokamaks: a challenge for 2D fluid codes?