Publications de Richard Pitts | EPFL Graph Search

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The radial electric field in known to be one of the drivers of parallel ion flow in the SOL. It contributes to the ion Pfirsch-Schluter flow and also determines the 'return parallel flow' that can arise to compensate poloidal E x B drift. It was establishe ...

The EUROfusion Work Package JET3 programme, established to enable the technological exploitation of the JET experiments over the next years, includes, within the NEXP subproject, a novel Shutdown Dose Rate (SDR) experiment. Considering its ITER-relevance, ...

Operation of the JET tokamak with beryllium and tungsten ITER-like wall provides unique opportunity for detailed studies on dust generation: quantity, morphology, location, etc. The programme carried out in response to ITER needs for safety assessment comp ...

In the preparation for the Deuterium-Tritium campaign, JET will operate with a tritium plasma. The T + T reaction consists of two notable channels: (1) T + T -> He-4 + 2n, (2) T + T -> He-5 + n -> He-4 + 2n. The reaction channel (1) is the reaction with th ...

The TCV tokamak (R = 0.88 in, a < 0.25 in, BT < 1.54 T) is equipped with six 0.5 MW gyrotron sources operating at 82.7 GHz for second harmonic X mode ECH. By distributing the ECCD current sources over the discharge cross section, fully driven stationary plasmas with I-p = 210 kA, n(e0) = 2 x 10(19) m(-3), T-e0 approximate to 4 keV, were obtained for the full discharge duration of 2 s. Highly peaked electron temperature profiles with T-e0 up to 12 keV were obtained in central counter-current drive scenarios

A theoretical model for isotopologues of beryllium monohydride, BeH, BeD and BeT, A (2)Pi to X (2)Sigma(+) visible and X (2)Sigma(+) to X (2)Sigma(+) infrared rovibronic spectra is presented. The MARVEL procedure is used to compute empirical rovibronic ene ...

The stationary edge localized mode (ELM)-free 'Quiescent H-mode' (QH-mode) regime, obtained with counter neutral beam injection, is studied in ASDEX Upgrade and Joint European Torus. QH-mode plasmas have high pedestal and core ion temperatures together wit ...

Total radiative powers measured by foil bolometer and AXUV camera systems are compared to SOLPS5 simulations in low and high density deuterium and helium diverted discharges on the TCV tokamak. For low density the match between simulation and measurements ...

The deuterium and helium dynamics in the plasma and subdivertor regions of JET are compared during a sequence of similar ohmic and ICRH pulses where 100% He gas is injected into the JET vacuum vessel, whose graphite walls were previously saturated with deuterium. After the first six He fueled change-over discharges, only He plasma operation was performed. Following this investigation, the situation is reversed and the change-over from an initially saturated He wall is investigated when only D-2 plasma fuell

The first divertor was installed in the JET machine between 1992 and 1994 and was operated with carbon tiles and then beryllium tiles in 1994-5. Post-mortem studies after these first experiments demonstrated that most of the impurities deposited in the div ...

Tungsten (W) melting due to transient power loads, for example those delivered by edge localised modes (ELMs), is a major concern for next step fusion devices. A series of experiments has been performed on JET to investigate the dynamics of Type-I ELM-indu ...

This paper details progress in experimental characterisation work at JET for the long-term irradiation station, conducted as part of a project to perform activation experiments using ITER materials. The aim is to take advantage of the significant 14 MeV ne ...

Beryllium oxide (BeO) and deuteroxide (BeOxDy) have been found on the melted zone of a beryllium tile extracted from the upper dump plate of JET-ILW (2011-2012 campaign). Results have been obtained using Raman microscopy, which is sensitive to both the che ...

The operating space of the TCV tokamak has been extended to higher elongation, kappa = 2.8, and higher normalized current, I-N = I-p/aB = 3.6MA/mT, than were previously attainable. This has been achieved by optimizing the parameters of the vertical position control system and by optimizing the plasma shape. Experimental current and beta limits were found to be consistent with ideal MHD stability calculations, using measured plasma shapes and profiles. The sawtooth period was measured as a function of elonga

The TCV tokamak (B-T < 1.5 T, R approximate to 0.88 m, a < 0.25 m) has produced a wide variety of plasma configurations, both diverted and limited, with elongations kappa(a), ranging from 0.9 to 2.58, triangularities delta(a) from -0.7 to 1 as well as discharges with nearly rectangular cross sections. Plasma currents of 1 MA have been obtained in elongated discharges (kappa(a) approximate to 2.3). Ohmic discharges with delta(a) < 0 have smaller sawteeth and higher levels of MHD mode activity than plasmas wi

This work aims at establishing the parameter space for the existence of geodesic acoustic modes (GAMs) on JET as well as investigating their driving and damping mechanisms predicted by different theoretical models. This was achieved using an experimental d ...

The issue of first wall and divertor target lifetime represents one of the greatest challenges facing the successful demonstration of integrated tokamak burning plasma operation, even in the case of the planned next step device, ITER, which will run at a r ...

The MHD response and the penetration of a deuterium shattered pellet into a JET plasma is investigated via the non-linear reduced MHD code JOREK with the neutral gas shielding (NGS) ablation model. The dominant MHD destabilizing mechanism by the injection ...

To ensure sufficient divertor target lifetime, the loss in plasma stored energy due to ELMs in ITER should be restricted to Delta W-ELM

Recently at JET a pure helium campaign has been performed. The exploration of the density limit in L-mode limiter as well as L-mode and H-mode diverted plasmas was one of the main objectives. In L-mode plasmas the density can be increased until the total radiated power equals the heating power, hence the density limit is determined by a radiative collapse. When compared to deuterium plasmas the L-mode density limit in helium is twice as high. In H-mode no significant difference in the density limit process

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A possible role of radial electric field in driving parallel ion flow in scrape-off layer of divertor tokamaks

Shutdown dose rate measurements after the 2016 Deuterium-Deuterium campaign at JET

Dust generation in tokamaks: Overview of beryllium and tungsten dust characterisation in JET with the ITER-like wall

Activation material selection for multiple foil activation detectors in JET TT campaign

Overview of TCV results

Synthetic spectra of BeH, BeD and BeT for emission modeling in JET plasmas

Studies of the 'Quiescent H-mode' regime in ASDEX Upgrade and JET

Radiation distributions in TCV

Deuterium to helium plasma-wall change-over experiments in the JET MkII-gas box divertor

Material migration and fuel retention studies during the JET carbon divertor campaigns

Heat flux analysis of Type-I ELM impact on a sloped, protruding surface in the JET bulk tungsten divertor

Activation of ITER materials in JET: nuclear characterisation experiments for the long-term irradiation station

Identification of BeO and BeOxDy in melted zones of the JET Be limiter tiles: Raman study using comparison with laboratory samples

Stability and energy confinement of highly elongated plasmas in TCV

Effect of plasma shape on confinement and MHD behaviour in TCV

Scaling of the geodesic acoustic mode amplitude on JET

Material erosion and migration in tokamaks

3D non-linear MHD simulation of the MHD response and density increase as a result of shattered pellet injection

The impact of large ELMs on JET

Density limits in helium plasmas at JET