We present experimental evidence for the ion-cyclotron resonant-heating (ICRH) induced trapping of ions in the edge-mirror fields of a magnetically confined plasma. Relative changes in edge-plasma density have been monitored in an end cell of the Phaedrus-B Tandem Mirror (Breun R A et 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 resonant heating. Edge-plasma density dependence upon the ICRH left-circularly-polarized electric field and on the edge-neutral density were found to be consistent with an edge rf-trapping model. A linear correlation is observed between the change in trapped edge density and the change in the applied ICRH . Furthermore, it is demonstrated that cold (less than 7 eV) ions born from atomic processes operating at or near the plasma edge are the dominant species participating in the trapping process. The results obtained are shown to be applicable to any device with mirror-like closed particle orbits at the plasma edge.

Data are presented showing the first demonstration that H mode plasmas can be produced with a biased electrode in the presence of substantial auxiliary power (the Alfven wave power was roughly twice the corresponding ohmic power). The data also show the first demonstration of Alfven wave heating of electrons during an H mode. Although the H mode has been produced in some tokamaks (without the use of a biased electrode) by auxiliary heating greater than a threshold value dependent on plasma conditions and the auxiliary heating method, for the first time, measurements presented here show that subthreshold Alfven wave power increases the edge particle transport (in both ohmic and H mode plasmas) and that this auxiliary power degrades rather than enhances the biased electrode H mode. In addition, for the first time, it is shown that Alfven waves generated by + pi /2 (as compared with a) phasing result in greater RF fuelling in H mode plasmas

Inserting a positively biased electrode to just inside the Phaedrus-T tokamak limiter results in typical H mode behaviour (i.e. H-alpha or D-alpha drop, density rise, increase in stored energy, profile steepening, and reduction of edge turbulence and radial transport) in deuterium, hydrogen and helium discharges. H-alpha or D-alpha emission suggests that the improvement in particle confinement with H mode is poloidally asymmetric, with the greatest improvement occurring on the low field side. The radial conductivity is examined and measured values are compared with theory.

Measurements of whistler-mode electron-cyclotron emission made in the Phaedrus-B tandem-mirror end cell are described. The receiving horn was located on the axis of the machine just outboard of the end cell. Under normal conditions, the signal had a component which was identified as blackbody emission, and an electron temperature was obtained which was in good agreement with electron end loss-ener...