Assessment of meander-line antenna covered with dielectric material for LHW heating

A new analysis of meander-line type antenna with dielectric cover is presented and compared with experimental results. In the case of small research tokamaks for which the lower hybrid range of frequency is relatively low, a meander-line antenna with a strip-line structure would be preferable for LHW electron heating. When the antenna is installed in the vacuum chamber, it needs an insulating cover to protect it from plasma bombardment. The comparison between the analysis and experiments agree well if the thickness of the antenna conductor is sufficiently thin and there is no vacuum gap among the substrate, conductor, and cover. We found that a slow-wave antenna may be fabricated for LHW electron heating in the small tokamak HYBTOK-II under the driving frequency of, for example, 220 MHz. (author)