Publications de Ugo Siravo | EPFL Graph Search

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Earthing of electrical installations is mainly governed by safety rules. Electromagnetic compatibility also deals with earthing, among other circuit characteristics. Tokamaks are large-scale electrical installations that are known to generate large and low frequency magnetic fields as well as large and high frequency electric fields. Four European Tokamak installations have been investigated, from the earthing point of view, to identify appropriate techniques to earth the electrical equipment and to provide

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 ...

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

From the electrical point of view, the body and the anode of high power gyrotrons behave as capacitive loads. A highly dynamic power supply is, therefore, hard to achieve. The MAGY concept (Modulator for the Anode of a triode type GYrotron) embodies an inn ...

Gyrotrons and High Voltage Power Supplies (HVPS) used on electron cyclotron (EC) systems are the source of large electromagnetic interference (EMI). Arcing events inside gyrotrons is the most frequently cited issue, but fast shutdown of a HVPS can produce ...

The Tokamak a` Configuration Variable (TCV) coil converters are fed, during the plasma pulse, by a flywheel generator (FG) providing the AC voltages few seconds before the plasma pulse. The synchronization with the 120 Hz frequency delivered by the FG, var ...

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 ...

EC RF power sources will play a major role in the future operation of large scale tokamaks (ITER, DEMO). A 1MW/170GHz gyrotron is the standard RF power unit considered for ITER. Even though the efficiency of such devices has been significantly increased th ...

The EU is working towards providing 2 MW, coaxial-cavity, CW, 170 GHz gyrotrons for ITER. Their design is based on results from an experimental pre-prototype tube in operation at FZK for several years, having a pulse length of several milliseconds. The fir ...

The Tokamak Configuration Variable (TCV) tokamak (R = 0.88 m, a < 0.25 m, B < 1.54 T) programme is based on flexible plasma shaping and heating for studies of confinement, transport, control and power exhaust. Recent advances in fully sustained off-axis electron cyclotron current drive (ECCD) scenarios have allowed the creation of plasmas with high bootstrap fraction, steady-state reversed central shear and an electron internal transport barrier. High elongation plasmas, kappa = 2.5, are produced at low nor

The European Union is working toward providing 2-MW, coaxial-cavity, continuous-wave (cw) 170-GHz gyrotrons for ITER. Their design is based on results,from an experimental preprototype tube having a pulse length of several milliseconds, in operation at For ...

In noninductively driven discharges, 0.9 MW second harmonic (X2) off-axis co-electron cyclotron current drive deposition is combined with 0.45 MW X2 central heating to create an electron internal transport barrier (eITB) in steady plasma conditions resulting in a 1.6-fold increase of the confinement time (tau(Ee)) over ITER-98L-mode scaling. The eITB is associated with a reversed shear current profile enhanced by a large bootstrap current fraction (up to 80%) and is sustained for up to 10 current redistribu

A Diagnostic Neutral Beam Injector (DNBI) is operated on the TCV Tokamak since 2000. Over the years, the plasma source and the ion optical system have benefited from several upgrades, whereas the power supply system remained almost unchanged. DNBI operation is now compromised by the obsolescence of both the power components and the control infrastructure. To allow for a long-term reliable operation, a complete renew of the power supplies set is ongoing. It includes a high-speed current source rated 500A/100

The present status of operation and upgrades of the 50 keV / 3 A Diagnostic Neutral Beam Injector (DNBI) at TCV tokamak are described. The plasma grid was replaced by a new re-manufactured one with its existing design. The technology and production were performed within SPC-EPFL. The further redesign of the plasma grid was done to improve the strength and stability, accounting for the results of grid deformation measurements, and considering ANSYS thermomechanical analysis in combination with IBSimu beam si

A Diagnostic Neutral Beam Injector (DNBI) is operated on the TCV Tokamak since 2000. Over the years, the plasma source and the ion optical system have benefited from several upgrades, whereas the power supply system remained almost unchanged. DNBI operation is now compromised by the obsolescence of both the power components and the control infrastructure. To allow for a long term reliable operation, a complete renew of the power supplies set is ongoing. It includes a high-speed current source rated 500 A/10

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 ...

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 paper describes the operation and upgrade of the Heating Neutral Beam Injection (HNBI) system as well as the related infrastructure at the Tokamak Configuration Variable (TCV) during the last years. In 2023, the installation of new TCV neutron shieldin ...

The TCV tokamak continues to leverage its unique shaping capabilities, flexible heating systems and modern control system to provide a stepladder approach for extrapolations of experimental results from different ma-chines to ITER and DEMO. TCV's configura ...

Ugo Siravo

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ITER-Earthing

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

Safety factor profile requirements for electron ITB formation in TCV

ECH physics and new operational regimes on TCV

MAGY: an innovative high voltage - low current power supply for gyrotron

EMC and earthing concept of the ITER EC-system

Control upgrade for the TCV coils power supplies

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

Homogenous power distribution along gyrotron collector walls

First experimental results from the EU 2 MW coaxial cavity ITER gyrotron prototype

An overview of results from the TCV tokamak

First experimental results from the European Union 2 MW coaxial cavity ITER gyrotron prototype

Recent results from the electron cyclotron heated plasmas in Tokamak à Configuration Variable (TCV)

New ARC Power Supply for the TCV Diagnostic Neutral Beam Injector

Recent progress with Diagnostic Neutral Beam Injector at TCV tokamak

High Voltage Modulator for the TCV Diagnostic Neutral Beam Injector

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

Enhanced operation of the Eu Ec test facility

Present status of heating neutral beam injection system at TCV

Upgrade of the neutral beam heating system on the TCV tokamak - second high energy neutral beam