Publications by Stefano Alberti

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Ohmic H-mode discharges in the Tokamak Configuration Variable (TCV) have recently been heated for the first time by electron cyclotron (EC) waves at the 3rd harmonic (X3) at full power. New edge localized mode (ELM) behaviour has been found, with larger am ...

We report the experimental results of the infrared measurements of output RF beam of the European 2-MW 170-GHz coaxial cavity gyrotron for ITER. The output beam profile is measured by the infrared thermographic technique using an infrared camera and a targ ...

The first unit of the dual-frequency gyrotron, 84-126GHz/lMW/2s, for the upgrade of the TCV ECH system has been delivered and is presently being commissioned. During a first phase, long-pulse operation (TRF>0.5s) has been achieved and powers in excess of 0 ...

The unique flexibility of TCV in plasma shaping has been exploited to address different aspects of tokamak physics in which the plasma shape may play a role. This paper summarizes the experiments undertaken in the TCV tokamak ("Tokamak à Configuration Variable") over the last decade in stability and transport and offers a comprehensive and integrated view of the various effects of plasma shape observed. For each of these effects, the relation between experimental results and theoretical predictions is stres

Electron cyclotron resonance heating (ECRH) is a mature technology that has progressed constantly over a period of forty years, particularly as a tool in magnetic confinement fusion. As with other heating methods, this technique has seen a steady increase ...

Recent experiments on a 100 GHz quasioptical gyrotron have shown that for a large resonator setup [Phys. Fluids B 2, 1654 (1990)] the observed frequency up-shift between the starting current and a current of 10 A corresponds to a shift of 4-5 longitudinal modes. In this Letter it is shown that the interpretation of this frequency up-shift should involve the current-dependent electron beam voltage depression in the beam tunnel and interaction region for both the single-mode and multimode time evolution codes

In order to properly simulate cases in which gyrotrons exhibit fast temporally varying oscillations, such as non-stationary oscillations or possible dynamic After-Cavity Interaction (ACI), an adequate model for the beam-wave interaction has to be used. We will show that the commonly used assumption of considering a constant wave-field envelope during the electron transit time has to be abandoned. The appropriate model (reduced 1D Particle-In-Cell (PIC) model) is briefly presented and the implications of usi

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 (EFDA). Due to financial constraints it has recently 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. (C) 2003 Elsevier B.V. All rights reserved.

Electron cyclotron current drive (ECCD) is an important prospective tool for tailoring the current profile in nextstep devices. To fill the remaining gaps between ECCD theory and experiment, especially in the efficiency and localization of current drive, a better understanding of the physics of suprathermal electrons appears necessary. In TCV the fast electron population is diagnosed by a multichordal, spectrometric hard x-ray camera and by a highfield side electron cyclotron emission radiometer. The main m

A Test Facility (TF) has been designed and installed at SPC to allow for the commissioning of the EU gyrotrons developed in view of their integration to the ITER EC system. The first phase of operation of this TF was dedicated to the development of the EU ...

The need for an intense source of coherent, millimetre-wavelength radiation to heat a fusion plasma and control its instabilities represents a significant challenge in the development of the ITER experimental fusion reactor. This challenge may now have bee ...

The European Gyrotron Consortium (EGYC) is developing the European 1 MW, 170 GHz Continuous Wave (CW) industrial prototype gyrotron for ITER in cooperation with Thales Electron Devices (TED) and Fusion for Energy (F4E). This conventional, hollow-cavity gyr ...

This paper describes the status on the upgrade of the first European gyrotron prototype for ITER, manufactured by Thales. The upgraded prototype, TH1509U, is now being tested to verify the performance improvements and to assess the compliance with ITER ECR ...

High-frequency gyrotrons; with high output power are mainly used for microwave heating and current drive in plasmas for thermonuclear fusion. The development of high-power gyrotrons; in continuous wave (CW) operation has been in progress for several years ...

Anomalous electron transport is determined by turbulence, which in turn is affected by magnetic shear. A novel application of electron cyclotron current drive (ECCD), aiming at localized shear modulation, has been applied on the TCV tokamak for experiments ...

A detailed study of the operational capabilities of the W7-X/1MW gyrotron operated at 126GHz/TE26,7 is presented. This study is associated with the foreseen upgrade of TCV in which it is planned to add to the present EC system 3MW of additional RF power bringing the total EC-power to 7.5MW. This study is extended to a possible operation of the gyrotron at the ITER relevant frequency of 168GHz in the TE35,9 mode without implementing any further modification neither in the gyrotron nor in the gyrotron superco

Metal-coated polymers shaped by 3D stereolithography are introduced as a new manufacturing method for passive components for millimeter to terahertz electromagnetic waves. This concept offers increased design capabilities and flexibilities while shortening the manufacturing process of complex shapes, e. g., corrugated horns, mirrors, etc. Tests at 92.5, 140, and 170 GHz are reported. (C) 2012 American Institute of Physics.

An experimental study of the extraordinary mode (X mode) absorption at the third electron cyclotron harmonic frequency has been performed on the TCV tokamak in plasmas preheated by X mode at the second harmonic. Full single pass absorption of injected X3 power was measured with X2 preheating in co-current drive (CO-ECCD). The measured absorption exceeds that predicted by the linear ray tracing code TORAY-GA by more than a factor of 2 for the CO-ECCD case. Experimental evidence indicates that a large fractio

An increase in Dynamic Nuclear Polarization (DNP) signal intensity is obtained with a tunable gyrotronproducing frequency modulation around 260 GHz at power levels less than 1W. The sweep rate of frequency modulation can reach 14 kHz, and its amplitude is ...

The aim of the present work is to provide a better insight on the magnetic shear profile modification in the Switched ECCD experiments. Modelling of the plasma current density is carried on by the ASTRA transport code employed in both predictive and interp ...

Stefano Alberti

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Third harmonic EC heating of ELMy H-mode in TCV

Infrared Measurements of the RF Output of 170-GHz/2-MW Coaxial Cavity Gyrotron and Its Phase Retrieval Analysis

High-efficiency, long-pulse operation of MW-level dual-frequency gyrotron, 84/126GHz, for the TCV Tokamak

Physics Insight and Performance Benefit from Plasma Shaping Experiments in MHD and Energy Transport in the TCV Tokamak

The effect of ECRH on the electron velocity distribution function

Dc Space-Charge-Induced Frequency up-Shift in a Quasi-Optical Gyrotron

Evaluation of experimentally measured non-stationary oscillations in gyrotrons using adequate simulation methods

Design and R&D of an ECRH system on JET

Electron cyclotron current drive and suprathermal electron dynamics in the TCV tokamak

Enhanced operation of the Eu Ec test facility

Magnetic confinement fusion - Plasma heating with millimetre waves

Recent experiments with the European 1MW, 170GHz industrial CW and short-pulse gyrotrons for ITER

Th1509U European 170 Ghz 1 Mw Cw Industrial Gyrotron Upgrade

Development of multimegawatt gyrotrons for fusion plasma heating and current drive

Shear modulation experiments with ECCD on TCV

Design studies of the dual-frequency operation of the W7-X/140GHz/1MW gyrotron at 126GHz for TCV and 168GHz for ITER

Three-dimensional stereolithography for millimeter wave and terahertz applications

Full absorption of third harmonic ECH in TCV tokamak plasmas in the presence of second harmonic ECCD

Dynamic nuclear polarization by frequency modulation of a tunable gyrotron of 260 GHz

Studies of Electron Transport and Current Diffusion in Switched ECCD experiments on TCV