Modeling of lower hybrid antennas using the ALOHA code and comparisons with Tore Supra experiments

Hillairet, J.; Voyer, Damien; Frincu, B.; Meneghini, O.; Ekedahl, A.; Goniche, M.

doi:10.1016/j.fusengdes.2008.12.058

Cited by 18 publications

(12 citation statements)

References 9 publications

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“…The disconnect between edge coupling, treated by coupling codes such as GRILL [26] or ALOHA [27], and core propagation/absorption, treated by traditional ray tracing/Fokker-Planck codes such as GENRAY/CQL3D, must be bridged and the two problems treated together. Recent advances in full wave simulations with codes such as TORIC-LH [28,29] and COMSOL [30,31] allow proper treatment of both edge coupling (including penetration through the pedestal) and core propagation/absorption in a seamless manner.…”

Section: Implications For Lhcd In H-mode On Alcator C-modmentioning

confidence: 99%

Absorption of lower hybrid waves in the scrape off layer of a diverted tokamak

Wallace¹,

Parker²,

Bonoli³

et al. 2010

Physics of Plasmas

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133

126

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The goal of the Lower Hybrid Current Drive (LHCD) system on the Alcator C-Mod tokamak is to investigate current profile control under plasma conditions relevant to future devices such as ITER and DEMO. Experimental observations of an LHCD "density limit" for C-Mod are presented in this paper. Bremsstrahlung emission from relativistic fast electrons in the core plasma drops suddenly above line averaged densities of 10 20 m −3 (ω/ω LH ∼3-4), well below the density limit previously observed on other experiments (ω/ω LH ∼ 2). Electric currents flowing through the scrape off layer (SOL) between the inner and outer divertors increase dramatically across the same density range that the core bremsstrahlung emission drops precipitously. These experimental x-ray data are compared to both conventional modeling, which gives poor agreement with experiment above the density limit, and a model including collisional absorption in the SOL, which dramatically improves agreement with experiment above the observed density limit. These results show that strong absorption of LH waves in the SOL is possible on a high density tokamak and the SOL must be included in simulations of LHCD at high density.

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Section: Implications For Lhcd In H-mode On Alcator C-modmentioning

confidence: 99%

Absorption of lower hybrid waves in the scrape off layer of a diverted tokamak

Wallace¹,

Parker²,

Bonoli³

et al. 2010

Physics of Plasmas

Self Cite

133

126

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“…To study the coupling properties of a LH antenna with a cold inhomogeneous tokamak plasma, the ALOHA (Advanced LOwer Hybrid Antenna) code is extensively used in this paper [9,10]. ALOHA calculates the coupling between the twodimensional radiating structure (waveguides in vacuum) and the magnetized plasma edge where both slow and fast waves propagate.…”

Section: Linear Theory Of Lh Coupling Within the Framework Of The Alo...mentioning

confidence: 99%

“…Indeed, the presence of passive waveguides in the PAM waveguide array has an important impact on the coupling properties in terms of power radiated spectrum along the parallel direction of the magnetic field, the electric field at the mouth of the antenna E and the power reflection coefficient RC at the input of the PAM. The coupling characteristics of the PAM and a FAM launcher have been compared using the linear simulation performed initially with the SWAN (Slow Wave ANtenna) code and, more recently, with the ALOHA code [1,9,10]. Different coupling features between these two concepts have been predicted.…”

Section: Main Differences With a Fully Active Multijunction Antennamentioning

confidence: 99%

Coupling characteristics of the ITER-relevant lower hybrid antenna in Tore Supra: experiments and modelling

et al. 2011

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A new concept of lower hybrid antenna for current drive has been proposed for ITER (Bibet et al 1995 Nucl. Fusion 35 1213–23): the passive active multijunction (PAM) antenna that relies on a periodic combination of active and passive waveguides. An actively cooled PAM antenna at 3.7 GHz has recently been installed on the tokamak Tore Supra. This paper summarizes the comprehensive experimental characterization of the coupling properties of the PAM antenna to the Tore Supra plasmas. In this paper, the electromagnetic properties of the antenna are measured at a reduced power (<1 MW) to allow a systematic comparison with linear wave coupling theory and the associated modelling based on the linear ALOHA code. In a wide range of edge electron densities at the antenna aperture (spanning a factor 20 from 0.5 × n c to 10 × n c where n c is the slow wave density cut-off, n c = 1.7 × 1017 m−3 at 3.7 GHz) and antenna phasing, the ALOHA simulations reproduce the experimental results observed on Tore Supra. In addition, reduced power reflection coefficients (<5%) are measured at a low edge density, close to n c, i.e. in the range 0.5–3 × n c. Measurement and analysis with ALOHA of the antenna–plasma scattering matrices provide explanation of the good coupling properties of the PAM antenna close to n c by highlighting the crucial role of the slow wave intercoupling between active and passive waveguides through the plasma edge. This detailed validation of the coupling modelling is an important step towards the validation of the PAM concept in view of further optimizing the electromagnetic properties of the future ITER antenna.

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“…In Advanced LOwer Hybrid Antenna (ALOHA) [1], antennas are fully described by their scattering matrix and the electromagnetic problem is formulated in terms of rectangular waveguide modes.…”

Section: Codes Descriptionmentioning

confidence: 99%