Publications by Minh Quang Tran

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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

The operation of a 92 GHz quasi-optical gyrotron having a resonator formed by a spherical mirror and a diffraction grating placed in -1 order Littrow mount is presented. A power of 150 kW with a Gaussian output pattern was measured. The Gaussian content in the output was 98% with less than 1% of depolarization. By optimizing the magnetic field al fixed frequency a maximum efficiency of 15% was reached. (C) 1996 American Institute of Physics.

The field pattern of the resonator used in a quasi-optical gyrotron operating in the millimetre wave range is measured. Two resonators are studied: one composed of a spherical mirror and an ellipsoidal grating and the other symmetric using two mirrors with annular slots. The measurements indicate that the electric field distribution is gaussian, in spite of the complex geometry of the resonator, and thus provide an experimental basis for the assumption often used to compute the efficiency of quasi-optical g

Dynamical chaos is produced by the interaction between plasma particles and two electrostatic waves. Experiments performed in a linear magnetized plasma and a ID particle-in-cell simulation agree qualitatively: above a threshold wave amplitude, ion stochastic diffusion and heating occur on a fast time scale. Self-consistency appears to limit the extent of the heating process.

Experimental results of low-power excitation of a 118 GHz TE(22,6) rotating mode are presented. A rectangular waveguide is converted to a TE(22,6) circular waveguide mode using quasi-optical techniques. A good conversion efficiency is measured and the experimentally-observed field intensity profiles show the percentage of unwanted modes to be small.

The integration of the heating and current drive (HCD) systems in the EU DEMO tokamak must address a number of issues, namely space constraints in the tokamak building, remote handling requirements, breeding blanket penetration, neutron and photon radiatio ...

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 ...

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

A high-power sheet beam electron gun for a quasi-optical gyrotron has been developed. The gun produces two beams with rectangular cross sections, with one beam segmented into 11 beamlets. These beamlets are spaced so as to be in line with the maxima of the RF field profile in the resonator of a 120-GHz quasi-optical gyrotron. The maximum current in the segmented beam is nominally 34 A, while the that for the unsegmented beam is 68 A. The gun has been tested, and has operated essentially as predicted by 2D a

An Ion Cyclotron Range of Frequency (ICRF) system can provide power for a number of tasks, experimentally verified on present machines: heating and current drive, first wall conditioning, plasma startup, removing central impurities, controlling sawteeth an ...

The feasibility of Thomson scattering to determine the beam velocity in a gyrotron has been analyzed and preliminary experiments to implement such a system on our 100 GHz quasi-optical gyrotron are reported. Although the project had to be abandoned due to technical problems, the conclusions are that for the 90-degrees scattering arrangement discussed it should be possible to determine at least one velocity component with an acceptable signal-to-noise ratio.

DEMO is a first-of-a-kind DEMOnstration fusion power plant [1,2] and is intended to follow the ITER experimental reactor. The main goal of DEMO will be to demonstrate the possibility to produce electric energy for the grid from the fusion reaction early in ...

The effects of plasma shape on confinement and sawtooth stability are studied for positive and negative discharge triangularity and for different elongations with 1.5 MW centrally deposited ECH power

An electron cyclotron resonance heating (ECRH) system is presently under construction at Commissariat A l'Energie Atomique (CEA) Cadarache for the Tore Supra experiment. The generator is planned to be made of six gyrotrons giving RF waves with a frequency of 118 GHz and a unit power of 400 kW (500 kW) for a pulse length of 210 s (5 s); two of them are already installed: the prototype was first tested on various dummy loads and on plasma and the first series tube is still being tested on a CW load. The resul

The magnetron injection gun (MIG) is one of the most critical subcomponents in gyrotrons. The electron beam, which has the primary role on the gyrotron operation, is generated and configured at this part of the tube. The electron beam properties determine ...

For the EU DEMO Tokamak, Electron Cyclotron (EC) launching systems for plasma heating and stabilization are under development. Various concepts for the optical system are currently studied of which the Mid Steering Antenna (MSA) with a steering mirror at a ...

A mock-up gun has been manufactured as exact replica of the refurbishment first prototype EU 170 GHz/2MW/CW coaxial cavity gyrotron, but without emitter ring in order to validate the voltage standoff stability. The experimental results of the mock-up gun tests are presented.

Minh Quang Tran

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

Operation of a quasi-optical gyrotron with a Gaussian output coupler

Measurement of the Electric-Field Pattern of a Fabry-Perot Resonator Used in Quasi-Optical Gyrotrons

Stochastic Plasma-Heating by Electrostatic-Waves - a Comparison between a Particle-in-Cell Simulation and a Laboratory Experiment

Low-Power Excitation of Gyrotron-Type Modes in a Cylindrical Wave-Guide Using Quasi-Optical Techniques

Initial port integration concept for EC and NB systems in EU DEMO tokamak

Development of multimegawatt gyrotrons for fusion plasma heating and current drive

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

Design and Testing of an Electron-Gun Producing a Segmented Sheet Beam for a Quasi-Optical Gyrotron

Progress on an ion cyclotron range of frequency system for DEMO

Experimental Considerations Concerning the Velocity-Measurement of the Relativistic Electron-Beam in a Gyrotron by Means of Thomson Scattering

RAMI evaluation of the beam source for the DEMO neutral beam injectors

Energy Confinement in Shaped TCV Plasmas with Electron Cyclotron Heating

The 118 GHz ECRH experiment on Tore Supra

Overview on recent progress in magnetron injection gun theory and design for high power gyrotrons

Structural pre-conceptual design studies for an EU DEMO equatorial EC port plug and its port integration

Status of the EU 170 GHz/2 MW/CW Coaxial Cavity Gyrotron for ITER: The Dummy Gun Experiment

Electrical powering concept for ITER electron cyclotron radio-frequency sources

Experimental results of the 1-MW, 140-GHz, CW gyrotron for W7-X

Fusion: a sustainable energy source