Feasibility study of O–X coupling for overdense plasma heating through O–X–B mode conversion in FTU

Bin, W.; Bruschi, A.; D'Arcangelo, O.; Galperti, C.; Granucci, G.; Moro, A.; Nowak, S.; Pucella, G.

doi:10.1088/0029-5515/53/8/083020

Cited by 5 publications

(7 citation statements)

References 32 publications

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“…The power transmission efficiency on FTU tokamak presented in Refs. [13][14][15] indicates that for f= 140 GHz, L n ≈ 5.6 cm to L n ≈ 10 cm, and the relative fluctuation amplitude of Δn n ¼ 3%, present values of T OSX ≈ 57% to T OSX ≈ 29%. In our case, for the same parameters, we have obtained approximately the same results as depicted in Table 2.…”

Section: Power Transmission Windowmentioning

confidence: 99%

Study Electron Cyclotron Double Mode Conversion in Overdense Plasma

et al. 2019

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Double mode conversion from ordinary mode O to extraordinary mode X is used to achieve electron Bernstein wave (EBWs) for the electron cyclotron resonance heating (ECRH). The efficiency of the mode conversion depends on many parameters including the density gradient L n , magnetic field source B 0 and optimum launching angle N z. An analytical formalism together with a numerical computation have been employed, considering W7X stellarator main parameters, such as 140 GH z , k 0 = 29 cm −1 , 2.5 T and 2.4 ×10 20 m −3 , in order to investigate the efficiency of the mode conversion. The values of the density gradient Ln, obtained by numerical simulation, are from 1 to 10 cm. These values of L n correspond to the power transmission window T OSX from 88 to 29%. Moreover, the dispersion relation of the EBW mode propagation up to 10 harmonics, ω = 10ω ce , has been plotted to help a better visualization of the EBW mode heating. Finally, the power deposition profiles around the resonance layers were calculated and presented.

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Section: Power Transmission Windowmentioning

confidence: 99%

Study Electron Cyclotron Double Mode Conversion in Overdense Plasma

et al. 2019

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“…One of the two lines of the real-time front-steering antenna of FTU [5] was used to launch the probe wave and the second line was used to transmit the scattered signal. This second line has been designed either to inject ECH power or to receive radiation, for both CTS experiments and studies of the reverse OXB mode coupling scheme [6]. A beam switch installed in the line allows the received signal to leave the EC transmission line and to reach a pre-existing quasi-optical receiving line feeding the 140 GHz radiometer.…”

Section: Recent Upgrades Of the Diagnosticsmentioning

confidence: 99%

Progress And Prospects Of The Ftu Collective Thomson Scattering Diagnostics

Bin¹,

Bruschi²,

D'Arcangelo³

et al. 2016

Proceedings of 1st EPS Conference on Plasma Diagnostics — PoS(ECPD2015)

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During the last years anomalous signals have been found in the spectra analyzed with the Collective Thomson Scattering (CTS) diagnostics in tokamak devices like TEXTOR, ASDEX and FTU. The signal frequency, down-shifted with respect to the probing one, suggested the explanation of their origin in terms of Parametric Decay Instability (PDI) processes correlated with the presence of magnetic islands and taking place even for values of the pumping wave power below the threshold predicted by conventional models. A threshold lower or comparable with the power levels routinely used could pose limitations to the use of the ECRH in fusion devices. An accurate characterization of the conditions for the occurrence of this phenomenon and of its consequences is thus of primary importance. The CTS diagnostics of FTU has been recently improved for this aim with a new fast data acquisition, allowing spectra reconstruction by direct FFT of the intermediate frequency signal, added in parallel to the pre-existing multichannel spectrum analyzer. A section with polarizing mirrors has been introduced in the quasi-optical transmission line to control the polarization of the received signals. Exploiting the front-steering configuration available with the real-time launcher of FTU, the setup allows studying the anomalous emissions in conditions of density and wave injection similar to ITER. Given the possibility of the CTS in FTU to operate in both O-and X-mode, a second radiometer is being installed, to detect simultaneously signals scattered in both polarizations. The upgrades mentioned above are presented in this work as well as the first data obtained in 2014, during the experimental activity carried out under an EUROfusion Enabling Research project. 1st EPS conference on Plasma Diagnostics

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“…The launcher is shown in figure 1-left during laboratory tests at low power [13]. The upper line is designed either to inject ECH power or to collect radiation at 140 GHz for studies of reverse OXB mode coupling scheme [14,15] or for the radiometric system during CTS experiments. Two simulations of launched and received CTS beams are depicted in figure 1-right, showing, from the plasma side, the configuration of the two antennas of the front steering launcher, poloidally symmetric with respect to the equatorial plane.…”

Section: The New Cts Diagnostic In Ftu 21 Diagnostic Layoutmentioning

confidence: 99%

First operations with the new Collective Thomson Scattering diagnostic on the Frascati Tokamak Upgrade device

et al. 2015

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Anomalous emissions were found over the last few years in spectra of Collective Thomson Scattering (CTS) diagnostics in tokamak devices such as TEXTOR, ASDEX and FTU, in addition to real CTS signals. The signal frequency, down-shifted with respect to the probing one, suggested a possible origin in Parametric Decay Instability (PDI) processes correlated with the presence of magnetic islands and occurring for pumping wave power levels well below the threshold predicted by conventional models. A threshold below or close to the Electron Cyclotron Resonance Heating (ECRH) power levels could limit, under certain circumstances, the use of the ECRH in fusion devices. An accurate characterization of the conditions for the occurrence of this phenomenon and of its consequences is thus of primary importance. Exploiting the front-steering configuration available with the real-time launcher, the implementation of a new CTS setup now allows studying these anomalous emission phenomena in FTU under conditions of density and wave 1 Corresponding author.

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Feasibility study of O–X coupling for overdense plasma heating through O–X–B mode conversion in FTU

Cited by 5 publications

References 32 publications

Study Electron Cyclotron Double Mode Conversion in Overdense Plasma

Study Electron Cyclotron Double Mode Conversion in Overdense Plasma

Progress And Prospects Of The Ftu Collective Thomson Scattering Diagnostics

First operations with the new Collective Thomson Scattering diagnostic on the Frascati Tokamak Upgrade device

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