In lower hybrid (LH) current drive experiments at Tore Supra and Tokamak de Varennes (TdeV), hot spots and the generation of impurities have been observed. Melting of the grill mouth has also occurred in LH current drive experiments. A possible explanation for these observations is parasitic absorption of the short-wavelength part of the LH spectrum close to the grill mouth. In this work, we investigate the parasitic absorption of the LH power in the edge plasma of Tore Supra and JET with particle-in-cell (PIC) simulations. The LH spectra are calculated with the SWAN coupling code and used in the self-consistent electrostatic PIC code XPDP2 which calculates the absorption. The absorption was calculated for different edge densities and density scale lengths when the coupled LH power densities varied between 25 MW m-2 and 50 MW m-2. The high-n|| part of the LH spectrum was found to be absorbed near the edge within a few millimetres. The absorbed power density varied from 65 kW m-2 to 420 kW m-2 which corresponds to 0.2-0.8% of the coupled power. In an edge plasma having a temperature of 25 eV, the maximum energies of the fast electrons generated by the parasitic absorption were between 0.4 keV and 1.6 keV.
在Tore Supra和Tokamak de Varennes（TdeV）的低混杂波（LH）电流驱动实验中，观察到了热点和杂质的产生。在LH电流驱动实验中也发生了炉口熔化。对这些现象的一个可能解释是，LH谱中短波长部分在炉口附近的寄生吸收。在本工作中，我们利用粒子模拟（PIC）方法研究了Tore Supra和JET边缘等离子体中LH功率的寄生吸收。LH谱由SWAN耦合程序计算，并用于自洽的静电PIC程序XPDP2中，该程序计算吸收。当耦合的LH功率密度在25 MW m⁻²至50 MW m⁻²之间变化时，计算了不同边缘密度和密度标长下的吸收。发现LH谱的高n||部分在边缘附近几毫米内被吸收。吸收的功率密度在65 kW m⁻²至420 kW m⁻²之间变化，对应于耦合功率的0.2%–0.8%。在温度为25 eV的边缘等离子体中，由寄生吸收产生的快电子的最大能量在0.4 keV至1.6 keV之间。