Thermal and mechanical analysis of ITER-relevant LHCD antenna elements

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In the frame of a R&D effort conducted by CEA toward the design and the qualification of a 5 GHz LHCD system for the ITER tokamak, two 5 GHz 500 kW/5 s windows have been designed, manufactured and tested at high power in collaboration with the National Fusion Research Institute (NFRI). The window design rely on a symmetrical pill-box concept with a cylindrical beryllium oxide ceramic brazed on an actively water cooled copper skirt. The ceramic RF properties have been measured on a test sample to get realistic values for guiding the design. Low power measurements of the manufactured windows show return losses below -32 dB and insertion losses between -0.01 dB and -0.05 dB, with an optimum frequency shifted toward lower frequencies. High power tests conducted at NFRI show unexpected total power loss for both windows. The ceramic temperature during RF pulses has been found to reach unexpected high temperature, preventing these windows to be used under CW conditions. A post-mortem RF analysis of samples taken from one window shows that the dielectric properties of the ceramic were not the ones measured on the manufacturer sample, which partly explain the differences with the reference modelling.

Section: Rf and Thermo-mechanical Designmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Design and tests of 500 kW RF windows for the ITER LHCD system

Hillairet

Kim

Faure³

et al. 2015

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“…The LH launcher design presently foreseen for ITER is a passive-active multijunction (PAM), which has been successfully validated on FTU [4] at 8 GHz and on Tore Supra [5,6] at 3.7 GHz. The nominal refractive parallel index n excited by the coupling structure has been determined from integrated simulations of propagation and absorption of LH waves in ITER for several scenarios.…”

Section: General Description Of the Iter Lh Antennamentioning

confidence: 99%

Design and testing of a 5GHz TE10–TE30 mode converter mock-up for the lower hybrid antenna proposed for ITER

Hillairet¹,

Achard²,

Brun³

et al. 2012

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a b s t r a c tThe design and overall dimensions of a 5 GHz TE 10 -TE 30 mode converter are presented. This mode converter is a RF element of a 20 MW CW lower hybrid system proposed for ITER. A low power mock-up of this device has been manufactured at CEA/IRFM and measured at low power. RF measurements indicate a return loss of 40 dB and a transmission loss of 4.78 dB ± 0.03 dB for the three outputs. The forward conversion efficiency from TE 10 mode to TE 30 has been measured from electric field probing to 99.9%. The good RF performances obtained validate the RF design of this element.

“…A thermomechanical analysis of this design can be found in Ref. [11]. For comparison, the simulated integrated losses into the Tore Supra 3.7 GHz windows is 760 W while the peak electric field inside is 2.1 MV/m for an input power of 250 kW (Fig.…”

Section: Rf Windowsmentioning

confidence: 99%

RF modeling of the ITER-relevant lower hybrid antenna

Hillairet

Ceccuzzi

Belo³

et al. 2011

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a b s t r a c tIn the frame of the EFDA task HCD-08-03-01, a 5 GHz Lower Hybrid system which should be able to deliver 20 MW CW on ITER and sustain the expected high heat fluxes has been reviewed. The design and overall dimensions of the key RF elements of the launcher and its subsystem has been updated from the 2001 design in collaboration with ITER organization. Modeling of the LH wave propagation and absorption into the plasma shows that the optimal parallel index must be chosen between 1.9 and 2.0 for the ITER steady-state scenario. The present study has been made with n || = 2.0 but can be adapted for n || = 1.9. Individual components have been studied separately giving confidence on the global RF design of the whole antenna.