摘要: An edge plasma is shown to significantly absorb Ion Cyclotron Radio Frequency (ICRF) waves when a resonant triplet (a cutoff-resonance-cutoff triplet) is constructed in the evanescent region. Two-ion component plasmas in a torus a... 展开 An edge plasma is shown to significantly absorb Ion Cyclotron Radio Frequency (ICRF) waves when a resonant triplet (a cutoff-resonance-cutoff triplet) is constructed in the evanescent region. Two-ion component plasmas in a torus are considered though the plasmas are modeled by a slab in which the density changes linearly along the x-axis. The resonance is a perpendicular ion cyclotron resonance, i.e., an Alfven resonance, and is formed when the applied frequency omega is smaller than the local cyclotron frequency, at the edge of the antenna side of the lighter species of ions. Roughly the absorption rate A(b) is given by M(2) for M(2) being much greater than S(2) and S(4) for S(2) being much greater than M(2) where M = k(y)l and S is approximately = k(z)l and l is a scale length of the order of the plasma minor radius, and k(y) and k(z) are the perpendicular and the parallel components of the wave vector. It is noted that both quantities, M and S, readily become the order of unity. Since A(b) is not very sensitive to the density ratio of the two ion species, a few percent of impurities may cause significant absorption. As the mass ratio of the two ion species comes close to unity the triplet forms readily. Therefore a D-T plasma seems to suffer more easily from this kind of resonance absorption than a D-H plasma. 收起