Publications de Timothy Goodman

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Confinement in TCV electron cyclotron heated discharges was studied as a function of plasma shape, i.e. as a function of elongation, 1.1 < kappa < 2.15, and triangularity, -0.65 less than or equal to delta less than or equal to 0.55. The electron energy confinement time was found to increase with elongation, owing in part to the increase of plasma current with elongation. The beneficial effect of negative triangularities was most effective at low power and tended to decrease at the higher powers used. The l

Plasma Turbulence studied by means of Correlation-ECE in the TEM domain in TCV Electron temperature fluctuations in the TEM domain have been measured in TCV using the correlation-ECE diagnostics [1]. Significant broadband electron temperature fluctuations are found radially extending between 0.3

A comparative study of X- and O-mode high field side launch for electron cyclotron heating (ECH) breakdown and startup of tokamak plasmas has been performed. It is found that X-mode power is not absorbed at the cyclotron resonance but uniquely at the upper hybrid resonance, displaced to the low field side of the cyclotron resonance. O-mode power, however, is absorbed at the cyclotron resonance as well. The displacement of the upper hybrid resonance to the low field side with O-mode launch is significantly s

Radially localized electron cyclotron heating (ECH) at the 2nd harmonic (X2) is used to tailor the current profile through the modification of the temperature, and hence conductivity, profiles. The optimal conditions for current profile broadening are inve ...

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 research activity in the Institute for Plasma Science and Technology of National Research Council (ISTP-CNR, Italy, former IFP-CNR) and in L.T. Calcoli (LTC, Italy) is aimed at the design and construction of calorimetric loads for absorption and measurem ...

A new paradigm is presented to reconstruct the plasma current density profile in a tokamak in real-time. The traditional method of basing the reconstruction on real-time diagnostics combined with a real-time Grad-Shafranov solver suffers from the difficult ...

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

In the frame of development of the ITER electron cyclotron wave (ECW) system, a two MW CW coaxial cavity gyrotron will be developed during the Sixth Framework Program (2003-2006). Such development relies on the availability of a test stand capable of providing the electrical energy and cooling capacity. This test stand will possibly be used, in a later stage, for the component test of the ITER ECW system. This paper will first present the main parameters of this new coaxial gyrotron. Then we describe the te

A small component of ECCD exists when heating off-axis with no toroidal injection due to the field helicity. The sign of the ECCD will change depending on the absorption location in a poloidal plane, the beam injection relative to delB(vac), and the direction of the toroidal magnetic field. The importance of the ECCD component can be confirmed by the behavior of the sawteeth when the ECH deposition crosses the q=1 surface. The sawtooth period is very sensitive to the local shear at q=1 and it is shown that

In the first results of electron Bernstein wave heating (EBWH) via O-X-B double mode conversion in a medium aspect ratio tokamak performed in TCV, the total power absorption efficiency was typically 60% and the deposition was made off-axis to avoid the central sawteeth perturbation that would prevent a clear detection of the deposition location. Central power deposition is however needed to maximize the global EBWH effects. Therefore, initial experiments have been started to optimize central deposition usin

An electron cyclotron resonance heating (ECRH) system has been designed for JET in the framework of the JET enhanced performance project (JET-EP) under the European fusion development agreement. Due to financial constraints it has been decided not to implement this project. Nevertheless, the design work conducted from April 2000 to January 2002 shows a number of features that can be relevant in preparation of future ECRH systems, e.g. for ITER. The ECRH system was foreseen to comprise six gyrotrons, 1 MW ea

All tokamak experiments using ECCD require setting of the beam elliptical polarization for proper coupling to the plasma. This is done either in the matching optics unit (MOU) at the output of the gyrotron, or in a couple of miter bends of the transmission line. Similarly, oblique ECE receivers require selection of the correct elliptical polarization to provide localized measurements. For the TCV tokamak at the CRPP, gyrotron and oblique-ECE polarizers are characterized during either high- or low- power tes

In the ITER Tokamak, four Electron Cyclotron Heating Upper Launchers (ECHUL) are needed to control plasma instabilities at the rational surfaces, most importantly the q = 3/2 and q = 2/1 neoclassical tearing modes (NTMs). Each ECHUL is equipped with a set ...

The European DEMO (EU-DEMO) reactor studies within EUROfusion aim to develop a fusion power plant concept. The large tokamak device needs an auxiliary heating power which, at the present stage, is provided by the Electron Cyclotron (EC) heating system with ...

Electron heat transport experiments are performed in L-mode discharges at various plasma triangularities, using radially localized electron cyclotron heating to vary independently both the electron temperature T-e and the normalized electron temperature gr ...

We report the first three-dimensional kinetic simulations that self-consistently reproduce relaxation oscillations of high-density, strongly rotating electron clouds confined in Penning-like potential wells. Using the finite element non-neutral electron clouds simulator code, we model the Trapped Electrons eXperiment (T-REX), a dedicated setup designed to study electron cloud dynamics relevant to gyrotron electron guns. The simulations are in quantitative agreement with experiment and show that the observed

In the TCV tokamak the sawtooth period and the sawtooth amplitude are observed to depend strongly on the shape of the poloidal plasma cross section. Systematic scans of plasma elongation and triangularity show small sawteeth with short periods at high elongation or low and negative triangularity, and large sawteeth with long periods at low elongation or high triangularity. Additional central electron cyclotron heating power further amplifies the shape dependence of the sawtooth properties. The sawtooth peri

A dual-frequency gyrotron has been developed within the context of the recent Tokamak à Configuration Variable (TCV) upgrade. The gyrotron is designed to generate a 1 MW, 2 seconds RF wave at 84 or 126 GHz. Before integrating the gyrotrons in the TCV tokam ...

Timothy Goodman

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Energy confinement and MHD activity in shaped TCV plasmas with localized electron cyclotron heating

Plasma Turbulence studied by means of Correlation-ECE in the TEM domain in TCV

X-Mode and O-Mode Electron-Cyclotron Heating Breakdown and Startup in Tca

Current profile tailoring using localized electron cyclotron heating in highly elongated TCV plasmas

Overview of TCV results

Operations with Spherical Calorimetric Loads in Different Configurations at Gyrotron Test Stands at EPFL and QST

Real-time physics-model-based simulation of the current density profile in tokamak plasmas

Stability and energy confinement of highly elongated plasmas in TCV

Effect of plasma shape on confinement and MHD behaviour in TCV

Design study of a test stand for ITER gyrotron

Poloidally asymmetric plasma response with ECH deposition near q=1 in TCV

Electron Bernstein Wave Core Deposition via O-X-B Double Mode Conversion in TCV

The design of an ECRH system for JET-EP

Polarization Issues with High Power Injection and Low Power Emission in Fusion Experiments

Present design of the Steering Mirror Assembly (SMA) for ITER ECHUL

Conceptual design of a modular EC heating system for EU-DEMO

Electron heat transport in shaped TCV L-mode plasmas

Relaxation oscillations driven by the diocotron instability in trapped electron clouds

Effect of triangular and elongated plasma shape on the sawtooth stability

Experimental characterization of the TCV dual-frequency gyrotron and validation of numerical codes including the effect of After Cavity Interaction