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Proceedings Paper

Thermal analysis and design of polarizer mirrors for waveguides in the DIII-D tokamak
Author(s): Chandrakant B. Baxi; John L. Doane; D. L. Sevier
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Paper Abstract

A new high power electron cyclotron heating (ECH) system designed to operate at 110 GHz with a power output of 2 MW has been introduced on DIII-D. All components of the system are capable of handling a 10 second pulse at an interval of 10 minutes. Transmission of ECH power from the source (a millimeter-wave gyrotron) to the plasma through waveguide miter bends may change the polarization and rotate the polarization major axis. Polarizing elements are therefore required to correct for the effect of transmission lines and also to generate proper polarization for coupling into the plasma. Rotating mirrors with different rectangular grooved gratings in two successive miter bends can generate the required wide range of elliptical polarizations. Peak heat fluxes due to ohmic losses in these mirrors are several MW/m2 for a 0.5 MW gyrotron power. The complex distribution of losses in the grooves requires a detailed thermal stress analysis to ensure that temperature and stress limits are not exceeded. The desired pulse length is 10 sec, with a cooling time of 10 min between pulses. The temperature rise in the polarizing mirrors must be limited to less than 300 degree(s)C to prevent thermal fatigue and outgassing in the vacuum lines. This paper presents an analysis for the polarizing mirrors for the DIII-D ECH system.

Paper Details

Date Published: 25 February 1993
PDF: 9 pages
Proc. SPIE 1739, High Heat Flux Engineering, (25 February 1993); doi: 10.1117/12.140505
Show Author Affiliations
Chandrakant B. Baxi, General Atomics (United States)
John L. Doane, General Atomics (United States)
D. L. Sevier, General Atomics (United States)

Published in SPIE Proceedings Vol. 1739:
High Heat Flux Engineering
Ali M. Khounsary, Editor(s)

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