Design of a 5 GHz window in a lower hybrid r.f. system

Maebara, S.; Ikeda, Yoshitaka; Seki, M.; Imai, T.

doi:10.1016/0920-3796(94)00200-q

Cited by 5 publications

(3 citation statements)

References 5 publications

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“…The proposed ITER 5 GHz RF window is based on a pill-box window concept [10] [11], i.e. a thin ceramic disc brazed in the middle of a short straight section of a circular waveguide axially connected on both sides to rectangular waveguides.…”

Section: Rf and Thermo-mechanical Designmentioning

confidence: 99%

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

Hillairet

Kim

Faure³

et al. 2015

Fusion Engineering and Design

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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.

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Section: Rf and Thermo-mechanical Designmentioning

confidence: 99%

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

Hillairet

Kim

Faure³

et al. 2015

Fusion Engineering and Design

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“…The worst-case scenario for power density handling for the windows would be placing them directly at the launcher mouth, where they would have to handle approximately 7.7 kW cm −2 of power density. Windows that can handle that power density, however, have been designed and operated [29,30] implying that this is not an unsolvable issue. Another concern for the windows that must be analyzed in the future is the high-temperature operation of the vacuum vessel, which could cause degradation of the ceramic windows if they are exposed to the high temperature region.…”

Section: Conceptual Design Of Lhcd Systemmentioning

confidence: 99%

The lower hybrid current drive system for steady-state operation of the Vulcan tokamak conceptual design

Podpaly

Olynyk

Garrett

et al. 2012

Fusion Engineering and Design

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“…copper + stainless steel + copper) linked by explosive diffusion [87,143]; assembled by stacking and bolting plates [137,142], by vacuum brazing pre-machined plates [143,146], by electron beam welding and laser beam techniques [143]; most rely on inertial cooling but some use water cooling [87,143,144]. Windows have been made of different ceramic materials (BeO, Al 2 O 3 , sapphire) and designs (those close to plasma using ceramic 'bricks' in a flange that match the waveguide array [141]; those far from plasma using a pill-box type [143,152]). Klystrons have been made for different frequencies and output powers: from 150 kW at 800 MHz [9] up to 500 kW CW at 5.0 GHz [153] and 200 kW at 8.2 GHz [135].…”

Section: The Multijunctionmentioning

confidence: 99%

An ITER-relevant passive active multijunction launcher for lower hybrid current drive in JET-grade plasmas

et al. 2011

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Lower hybrid current drive (LHCD) has been demonstrated to be an important actuator for controlling the current profiles of advanced tokamak plasmas, either in fully non-inductive or in hybrid regimes. To continue such scenario development in JET, and most notably towards extrapolations for ITER, an upgrade of its LH launcher is required to deliver more power (>5 MW) and to deal with a broad array of density situations at the plasma edge more consistently. These may range from steep gradients to ELM activity; extend from as low as the cut-off density nec to large and fast density variations and give rise to strong and rapid reflections of RF power. The passive active multijunction (PAM), advocated as the LH launcher concept for ITER, is claimed to be more resilient to such conditions, run with increased efficiency near nec and even with a small vacuum gap, being also specially appropriate for long pulse operation—all conditions hampering traditional designs. In addition, some of this leverage has been confirmed experimentally at the ITER-relevant FTU with the first PAM ever deployed, and more recently with Tore Supra's PAM. The JET version addressed in this study, with the latter focusing on the physics that drives and supports the adopted technical solutions, allows the injection of up to 5.2 MW at 3.7 GHz and N||peak = 1.9. With directivities better than 70%, reflection coefficients below 2% even for ∼nec and power densities comparable to those foreseen for ITER at 5 GHz, it would validate this concept in ITER-relevant scenarios.

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Design of a 5 GHz window in a lower hybrid r.f. system

Cited by 5 publications

References 5 publications

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

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

The lower hybrid current drive system for steady-state operation of the Vulcan tokamak conceptual design

An ITER-relevant passive active multijunction launcher for lower hybrid current drive in JET-grade plasmas

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