Tests on a mock-up of the feedback controlled matching options for the ITER ICRH system

For the ICRH of ITER 20MW must be coupled to the plasma in the 40-55MHz frequency band via an array of 24 radiating shorted straps fed by four generators. The matching system must provide automatic matching control on the mean load provided by the plasma and be resilient (|Γ| < 0.2) to a wide range of fast antenna load excursions occurring in ELMy plasmas. Furthermore, good control of the current distribution in the strap array must be possible for the various heating and current drive scenarios. Two load resilient matching options have been considered for ITER: the 4 “Conjugate-T” (CT) and the 4 hybrids ones, the first being presently considered as a back-up option. Automatic control of these 2 options is presently developed, and tested for optimization on a low-powered scaled mock-up. Successful implementation of the simultaneous feedback control of 11 actuators for the matching of the 4CT and for the control of the toroidal phasing has already been achieved. The matching and the array current control of the 3dB hybrid option is provided by simultaneous feedback control of the decouplers and double stub tuners (in total 23 actuators) and is being progressively implemented. The simultaneous control of matching and antenna current has already been successfully tested on part of the array

Simulation of cold magnetized plasmas with the 3D electromagnetic software CST Microwave Studio ®

Detailed designs of ICRF antennas were made possible by the development of sophisticated commercial 3D codes like CST Microwave Studio® (MWS). This program allows for very detailed geometries of the radiating structures, but was only considering simple materials like equivalent isotropic dielectrics to simulate the reflection and the refraction of RF waves at the vacuum/plasma interface. The code was nevertheless used intensively, notably for computing the coupling properties of the ITER ICRF antenna. Until recently it was not possible to simulate gyrotropic medias like magnetized plasmas, but recent improvements have allowed programming any material described by a general dielectric or/and diamagnetic tensor. A Visual Basic macro was developed to exploit this feature and was tested for the specific case of a monochromatic plane wave propagating longitudinally with respect to the magnetic field direction. For specific cases the exact solution can be expressed in 1D as the sum of two circularly polarized waves connected by a reflection coefficient that can be analytically computed. Solutions for stratified media can also be derived. This allows for a direct comparison with MWS results. The agreement is excellent but accurate simulations for realistic geometries require large memory resources that could significantly restrict the possibility of simulating cold plasmas to small-scale machines

Comparaison entre l'étude expérimentale de plasmas finis cylindriques et les résultats théoriques dans l'approximation de la permittivité équivalente

Doctorat en sciences appliquéesinfo:eu-repo/semantics/nonPublishe

Comparaison entre l'étude expérimentale de plasmas finis cylindriques et les résultats théoriques dans l'approximation de la permittivité équivalente

Doctorat en sciences appliquéesinfo:eu-repo/semantics/nonPublishe

Study of a distributed ICRF antenna system in DEMO

Different feeding options for distributed ICRF antenna systems in DEMO are analysed and compared, based on detailed circuit modelling. Voltages and currents (amplitude and phase) are computed for each element of the array. The power delivered by the feeding networks is evaluated characterizing each system. Although the results presented are for a small number of radiating elements, the procedure can be scaled to any arbitrary number of straps and feeding connections. Among the three options analysed (i.e. allfed; distributed; resonant ring) the resonant ring feeding appears to be the most suitable configuration for a traveling wave array distributed antenna system in the DEMO reactor

Optimized phasing conditions to avoid edge mode excitation by ICRH antennas

An ion cyclotron resonance heating (ICRH) antenna system must launch radio frequency (RF) power with a wavenumber spectrum which maximizes the coupling to the plasma. It should also ensure good absorption while minimizing the wave interaction with the plasma edge. Such interactions lead to impurity release, whose effect has been measured far from the antenna location (Klepper et al. 2013; Wukitch et al. 2017; Perkins et al. 2019) and can involve the entire scrape-off layer. In the normal heating scenario, for which the frequency of the waves launched by the antenna is larger than the ion cyclotron frequency of the majority ions ω > ωci, maj, release of impurities due to ICRH can be affected by minimizing the lowSCOPUS: ar.jDecretOANoAutActifinfo:eu-repo/semantics/publishe

Combinaison stochastique des erreurs accidentelles et des erreurs systématiques instrumentales

info:eu-repo/semantics/publishe

Hepatic abscess likely related to Leptotrichia buccalis in an immunocompetent patient.

We present the case of a 64-year-old previously healthy man admitted for long evoluating fever. Buccal examination showed severe parodontitis. Blood cultures were positive for Leptotrichia buccalis and computed abdominal tomography discovered a hepatic abscess. So far, only exceptional cases of systemic diseases associated with Leptotrichia buccalis infections have been described in immunocompetent patients. Thus, in cases of severe parodontitis and long evoluating fever, attention must be paid to secondary anaerobic infections even in immunocompetent subjects