Absorption of lower hybrid waves in the scrape off layer of a diverted tokamak
نویسندگان
چکیده
The goal of the Lower Hybrid Current Drive (LHCD) system on the Alcator C-Mod tokamak is to investigate current profile control under plasma conditions relevant to future devices such as ITER and DEMO. Experimental observations of an LHCD " density limit " for C-Mod are presented in this paper. Bremsstrahlung emission from relativistic fast electrons in the core plasma drops suddenly above line averaged densities of 10 20 m −3 (ω/ω LH ∼3–4), well below the density limit previously observed on other experiments (ω/ω LH ∼ 2). Electric currents flowing through the scrape off layer (SOL) between the inner and outer divertors increase dramatically across the same density range that the core bremsstrahlung emission drops precipitously. These experimental x-ray data are compared to both conventional modeling, which gives poor agreement with experiment above the density limit, and a model including collisional absorption in the SOL, which dramatically improves agreement with experiment above the observed density limit. These results show that strong absorption of LH waves in the SOL is possible on a high density tokamak and the SOL must be included in simulations of LHCD at high density.
منابع مشابه
Measurements of the parallel wavenumber of lower hybrid waves in the scrape-off layer of a high-density tokamak
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تاریخ انتشار 2010