Publications by Richard Pitts | EPFL Graph Search

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This paper presents experimental results on the accessibility and the properties of plasmas with improved confinement in TCV. First, the H-mode threshold power is measured in Ohmic plasmas. Above an Ohmic threshold density, the threshold power increases with the density. A lower threshold density is found when additional electron cyclotron heating (ECH) is applied. At these low densities, the threshold power increases dramatically with decreasing density. Only a small fraction of the wide operational domain

On the Tokamak a Configuration Variable (TCV), electron internal transport barriers (eITBs) can be formed during a gradual evolution from a centrally peaked to a hollow current profile while all external actuators are held constant. The formation occurs ra ...

In this paper, we analyze heat transport in the JET tokamak using data from its high resolution ECE diagnostic and analyses based on the transfer entropy (TE). The analysis reveals that heat transport is not smooth and continuous, but is characterized by ' ...

The pressure gradient of the high confinement pedestal region at the edge of tokamak plasmas rapidly collapses during plasma eruptions called edge localised modes (ELMs), and then re-builds over a longer time scale before the next ELM. The physics that con ...

Experiments with high-power electron cyclotron heating (ECH) and current drive (ECCD) in the TCV tokamak are discussed. Power up to 2.7 MW from six gyrotrons is delivered to the tokamak at the second-harmonic frequency (82.7 GHz) in X-mode. The power is transmitted to the plasma by six independent launchers, each equipped with steerable mirrors that allow a wide variety of injection angles in both the poloidal and toroidal directions. Fully non-inductive operation of the tokamak has been achieved in steady

In this study, beryllium tiles from Joint European Torus (JET) vacuum vessel wall were analysed and compared regarding their position in the vacuum vessel and differences in the exploitation conditions during two campaigns of ITER-Like-Wall (ILW) in 2011-2 ...

The low temperature boundary layer plasma (scrape-off layer or SOL) between the hot core and the surrounding vessel determines the level of power loading, erosion and implantation of material surfaces, and thus the viability of tokamak-based fusion as an e ...

The physics of tokamak plasmas, in which electrons are heated by electron cyclotron heating (ECH) and whose current is driven by electron cyclotron current drive (ECCD), is investigated in this paper together with applications on tokamak A configuration variable (TCV) using modifications of the pressure and current profiles to improve the operational regimes. In order to explain the experimentally determined current drive efficiency and hard x-ray and electron cyclotron emission measurements, it is shown th

Accurate measurement of the nuclear environment within a test tritium breeding-blanket module of a fusion reactor is crucial to determine tritium production rates which are relevant to self-sufficiency of tritium fuel supply, tritium accountancy and also t ...

The ECW system on Tokamak a configuration variable (TCV) allows the study of a wide range of poloidal and toroidal launch angles. Both electron cyclotron heating (ECH) and electron cyclotron current drive (ECCD) experiments have been performed to demonstrate the modification of the electron temperature and current profiles. In particular a multi-channel hard X-ray camera (on loan from Cadarache) clearly shows the generation of a high energy electron tail, which increases with increasing toroidal launch angl

A series of experimental observations of light impurity profiles was carried out in JET (Joint European Torus) ITER-like wall (ILW) L-mode plasmas in order to investigate their transport mechanisms. These discharges feature the presence of He-3, Be, C, N, ...

Measurements are reported of electromagnetic emission close to the cyclotron frequency of energetic ions in JET plasmas heated by waves in the ion cylotron range of frequencies (ICRF). Hydrogen was the majority ion species in all of these plasmas. The meas ...

Significant interaction of ELM filaments with the vessel wall is now observed on JET by several diagnostics. To interpret the experimental data, a model of ELM-filament evolution was developed, with the radial velocity taken from experiment and the decay o ...

Although ohmic H-modes have long been produced on the TCV tokamak and the effects of ELMs at the divertor targets studied in some detail [1], no attempt has yet been made to model the scrape-off layer (SOL) in these plasmas. This contribution describes det ...

Understanding the details of the correlation between time series is an essential step on the route to assessing the causal relation between systems. Traditional statistical indicators, such as the Pearson correlation coefficient and the mutual information, ...

Although the most complex currently available fluid-neutral Monte-Carlo plasma boundary code package, SOLPS, has been a major player in the ITER divertor design, it has not yet been systematically used for the study of kinetic phenomena such as ELM transie ...

The large variety of plasma shapes produced in the TCV tokamak places unique demands on the plasma facing surfaces. In particular, the central column graphite armour tiles are solicited during the creation of all TCV plasmas and function as power handling surfaces for both limited and diverted discharges. The higher power flux densities accompanying the addition of electron cyclotron heating systems have necessitated a new, optimized, design for these tiles. The optimization process and the subsequent new t

Diagnostic alkali atom (e.g., lithium) beams are routinely used to diagnose magnetically confined plasmas, namely, to measure the plasma electron density profile in the edge and the scrape off layer region. A light splitting optics system was installed int ...

Two high performance JET-ILW pulses, pertaining to the 2016 experimental campaign, have been numerically simulated with the self-consistent code COREDIV with the aim of predicting the ELM-averaged power load to the target when extrapolated to DT plasmas. T ...

JET plasmas with reverse magnetic field feature a different SOL flow than those with normal field. The observed carbon fuelling efficiency from injecting methane gas was similar in reverse and normal field. EDGE2D modeling used an externally applied force ...

Richard Pitts

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Accessibility and properties of ELMy H-mode and ITB plasmas in TCV

Safety factor profile requirements for electron ITB formation in TCV

Radial variation of heat transport in L-mode JET discharges

Pedestal evolution physics in low triangularity JET tokamak discharges with ITER-like wall

High-power ECH and fully non-inductive operation with ECCD in the TCV tokamak

Comparison of the structure of the plasma-facing surface and tritium accumulation in beryllium tiles from JET ILW campaigns 2011-2012 and 2013-2014

Investigation into the formation of the scrape-off layer density shoulder in JET ITER-like wall L-mode and H-mode plasmas

ECH physics and new operational regimes on TCV

Testing of tritium breeder blanket activation foil spectrometer during JET operations

Sustained fully non-inductive scenarios using pressure and current profile control with ECCD

Light impurity transport in JET ILW L-mode plasmas

Observations and modelling of ion cyclotron emission observed in JET plasmas using a sub-harmonic arc detection system during ion cyclotron resonance heating

ELM-wall interaction on JET and ITER

SOLPS5 modelling of ELMing H-mode on TCV

On the Use of Transfer Entropy to Investigate the Time Horizon of Causal Influences between Signals

Benchmark Of Fluid And Kinetic Simulations Of Type Iii Elming H-Mode On Tcv

The design of central column protection tiles for the TCV tokamak

Sub-millisecond electron density profile measurement at the JET tokamak with the fast lithium beam emission spectroscopy system

COREDIV numerical simulation of high neutron rate JET-ILW DD pulses in view of extension to JET-ILW DT experiments

Methane screening in JET reverse field experiments