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Etude et développement d'un coupleur de puissance pour les cavités supraconductrices destinées aux accélérateurs de protons de haute intensité

Abstract : The coaxial power coupler needed for superconducting RF cavities used in the high energy section of the EUROTRANS driver should transmit 150kW (CW operation) RF power to the protons beam. The calculated RF and dielectric losses in the power coupler (inner and outer conductor, RF window) are relatively high. Consequently, it is necessary to design very carefully the cooling circuits in order to remove the generated heat and to ensure stable and reliable operating conditions for the coupler cavity system. After calculating all type of losses in the power coupler, we have designed and validated the inner conductor cooling circuit using numerical simulations results. We have also designed and optimized the outer conductor cooling circuit by establishing its hydraulic and thermal characteristics. Next, an experiment dedicated to study the thermal interaction between the power coupler and the cavity was successfully performed at CRYOHLAB test facility. The critical heat load Qc for which a strong degradation of the cavity RF performance was measured leading to Qc in the range 3W-5W. The measured heat load will be considered as an upper limit of the residual heat flux at the outer conductor cold extremity. A dedicated test facility was developed and successfully operated for measuring the performance of the outer conductor heat exchanger using supercritical helium as coolant. The test cell used reproduces the realistic thermal boundary conditions of the power coupler mounted on the cavity in the cryomodule. The first experimental results have confirmed the excellent performance of the tested heat exchanger. The maximum residual heat flux measured was 60mW for a 127W thermal load. As the RF losses in the coupler are proportional to the incident RF power, we can deduce that the outer conductor heat exchanger performance is confirmed up to 800kW RF power. Heat exchanger thermal conductance has been identified using a 2D axisymetric thermal model by comparing experimental and computed temperatures. Finally, a last part of our work has been dedicated to a preliminary study of thermohydraulic behaviour of supercritical helium observed during the experiment. Then we have established a stability diagram based on dimensionless parameters. This diagram shows a good agreement between our data and those of previous similar experiments.
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Submitted on : Monday, January 28, 2008 - 3:38:03 PM
Last modification on : Wednesday, September 16, 2020 - 4:07:25 PM
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  • HAL Id : tel-00221408, version 1

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Mehdi Souli. Etude et développement d'un coupleur de puissance pour les cavités supraconductrices destinées aux accélérateurs de protons de haute intensité. Physique Nucléaire Théorique [nucl-th]. Université Paris Sud - Paris XI, 2007. Français. ⟨tel-00221408⟩

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