Trivelpiece‐Gould‐Modes in an Axial Inhomogeneous Plasma

Abstract

SuiiiiiiaryExperiments on the propagntion of TG-modes in II weiikly inhomogeneous plasma are reported.The modes travel from the high density part (w < up#) to that of lower density (w > (I+). The wnvelength decreases ns expected but an incre;ine of t.he longitudinal fieldstrength predicted by collisionless theory could not be observed. Two nonlineur effects appear one after another with increasing n a v e amplitude. These are the sideband instability and a decay into the drift frequency riinge occuring in the whole plasma column. Neither the region (0 ' 1 : wPe nor the very vicinity of the exciter antenna are distinguished. The second inst;ibility is wcomponied by effective electron heating.

Non-resonance plasma heating by radiation in the millimetre range in toroidal devices

“…Indeed, in the experiments reported in Refs [11,12] high pumping levels & have been used. In other experiments [15,17,18] the high neutral gas pressure resulted in a frequency of electron-neutral collisions v &a which exceeded the ion sound frequency co s . Hence in these experiments, when the threshold is exceeded twofold, the condition for weak turbulence, 7p < co s , is violated.…”

“…During heating in a device with low density, $• may be comparable with the device dimensions. It can be seen from Eqs (11,17) that longitudinal spreading of pumping does not influence the instability threshold but may lead to breaking condition (20). So it is desirable not to permit the spreading of pumping.…”

Ionization Dynamics in a Pulse Disturbed Magnetically Confined Helium Plasma

“…These modes have lower phase velocities and therefore do more contribute to the energy absorption by collision-less damping than the basic mode. The wave impedance of the TB-modes gives the relation between power input and electrical fieldstrength of the wave [13]. The field measurements show that more than 50% of the power is converted into wave energy [ …”