Plasma and antenna coupling characterization in ICRF-wall conditioning experiments

Paul, Manash Kumar; Lyssoivan, A.; Koch, R.; Wauters, T.; Douai, D.; Bobkov, V.; Eester, D. Van; Lerche, E.; Ongena, J.; Rohde, V.; Noterdaeme, J.‐M.; Graham, M.; Mayoral, M.‐L.; Monakhov, I.; Nightingale, M. P.; Plyusnin, V. V.

doi:10.1016/j.fusengdes.2011.10.009

Cited by 9 publications

(3 citation statements)

References 14 publications

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“…Here, caution is needed in the interpretation of the results because figure 21 was computed for a parabolic density profile and not for the observed profile in figure 22. The strong increase seen in the latter (also observed in other machines [45,47]) in the antenna region is not taken into account in the computations. Of the total power fraction absorbed by the ions P RF-i /P tot ≈ 0.10-0.25, a minor part goes to central cyclotron absorption by resonant deuterons and hydrogen molecular ions H + 2 at the fundamental ICR.…”

Section: Icwc Discharge Characterization and Optimizationmentioning

confidence: 90%

“…It is well known from ICRF coupling theory and experimental studies that the antenna coupling resistance depends on the plasma density [42][43][44]. As the density of partially ionized ICWC plasmas typically increases on increasing coupled power [19,23,45], the better coupling in monopole phasing due to the beneficial wave spectrum is thus additionally enhanced by the resulting increase in density.…”

Section: Coupling Rf Power To Low-density Icwc Plasmasmentioning

confidence: 99%

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Simulation of ITER full-field ICWC scenario in JET: RF physics aspects

Lyssoivan¹,

Douai

Koch³

et al. 2012

Plasma Phys. Control. Fusion

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ITER as a superconducting fusion machine needs efficient wall conditioning techniques for application in the presence of the permanent high toroidal magnetic field for (i) reducing the in-vessel impurity content, (ii) controlling the surface hydrogen isotopic ratio and (iii) mitigating the in-vessel long-term tritium inventory build-up. Encouraging results recently obtained with ion-cyclotron wall conditioning (ICWC) in the present-day tokamaks and stellarators have raised ICWC to the status of one of the most promising techniques available to ITER for routine inter-pulse and overnight conditioning with the ITER main ICRF heating system in the presence of the permanent high toroidal magnetic field. This paper is dedicated to a milestone experiment in ICWC research: the first simulation of ICWC operation in an equivalent ITER full-field scenario and the assessment of the wall conditioning effect on the carbon wall in the largest present-day tokamak JET. In addition, we address in this paper the following topics: (i) an analysis of the radio frequency (RF) physics of ICWC discharges, (ii) the optimization of the operation of ICRF antennas for plasma startup and (iii) an outlook for the performance of ICWC in ITER using the ICRF heating system. Important operational aspects of the conventional ICRF heating system in JET (the so-called A2 antenna system) for use in the ICWC mode are highlighted: (i) the ability of the antenna to ignite the cleaning discharge safely and reliably in different gases, (ii) the capacity of the antennas to couple a large fraction of the RF generator power (>50%) to low-density (≈10 16 -10 18 m −3 ) plasmas and (iii) the ICRF absorption schemes aimed at improved RF plasma homogeneity and enhanced conditioning effect. Successful optimization of the JET-ICWC discharge parameters

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Section: Icwc Discharge Characterization and Optimizationmentioning

confidence: 90%

Section: Coupling Rf Power To Low-density Icwc Plasmasmentioning

confidence: 99%

Simulation of ITER full-field ICWC scenario in JET: RF physics aspects

Lyssoivan¹,

Douai

Koch³

et al. 2012

Plasma Phys. Control. Fusion

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“…does not work in presence of continuous magnetic field. Ion Cyclotron Resonance Frequency (ICRF) plasma discharge assisted wall conditioning has been very promising technique for such tokamaks [3]. In Aditya and superconducting Steady State Tokamak-1 (SST-1), RF at 20-100 MHz is being used for pre-ionisation [4] and Ion Cyclotron Resonance Heating (ICRH) [5].…”

Section: Introductionmentioning

confidence: 99%

Development of liquid stub tuner and liquid phase shifter for antenna-plasma impedance matching for high power RF experiments

Singh,

Gahlaut,

Ghosh

et al. 2024

AJP

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Dedicated to Prof B N BasuTokamak plasma discharges using radio frequency (RF) power are being very extensively used for plasma pre-ionisation, breakdown, heating and current drive and wall conditioning. For RF heating of plasma, impedance matching plays an important role. Impedance of plasma consists of resistive as well as inductive part. Resistance varies in the range of 0.5 to 5 Ohm, while susceptance part varies from 10 to 200 Ohm. The impedance of RF generator is normally 50 Ohm. This necessitates the matching of plasma impedance with the source impedance for maximum power transfer. The conventional matching is done using conventional stub tuners and conventional phase shifters. At high RF power to the plasma where current is of the order of kA for Ion Cyclotron Resonance (ICR) range of frequencies, conventional stub tuner that have an electric short called plunger, moving between inner and outer conductor of coaxial rigid transmission line develops an arcing. In a similar way as in case of stub tuner, the phase shifter also has finger contacts between the moving inner and outer conductors. Theses finger contacts have spring action in order to make movement feasible between inner and outer conductors. Due to inherent ovality in copper tubes, used for inner and outer conductors, the contact between inner and outer conductors becomes non-uniform and hence many a time gets spark developed for high value of RF current flowing through these finger contacts between inner and outer conductors. In order to avoid these sparks, liquid stub tuner (LST) and liquid phase shifters (LPS) are developed where there is no metallic moving parts. In LST and LPS only liquid moves. As the dielectric constant (∈ r ) of liquid is different from the air, hence moving liquid changes the wavelength of RF wave being passed in LST and LPS. This in turn changes relative length (l/λ), where l is length and λ is wavelength of the medium in which RF wave is passing. The medium may be air or the liquid being used. This concept is used in LST and LPS for impedance matching at high power ICR frequencies. Here, in this paper we present design and simulation results of LST and LPS.

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