EDGE-PLASMA TRAPPING INDUCED BY ICRH IN AN END CELL OF A TANDEM MIRROR

We present experimental evidence for the ion cyclotron resonant-heatin g (ICRH) induced trapping of ions in the edge-mirror fields of a magne tically confined plasma. Relative changes in edge-plasma density have been monitored in an end cell of the Phaedrus-B Tandem Mirror (Breun R A er al 1981 Phys. Rev. Lett. 47 1833-6; Ferron J R et al 1983 Phys. Rev. Lett. 51 1955) via the use of electron cyclotron emission from a hot-edge population created by the application of electron cyclotron r esonant heating. Edge-plasma density dependence upon the ICRH left-cir cularly-polarized electric field (E+) and on the edge-neutral density were found to be consistent with an edge rf-trapping model. A linear c orrelation is observed between the change in trapped edge density and the change in the applied ICRH E+. Furthermore, if is demonstrated tha t cold (less than 7 eV) ions born from atomic processes operating at o r near the plasma edge are the dominant species participating in the t rapping process. The results obtained are shown to be applicable to an y device with mirror-like closed particle orbits at the plasma edge.