OBSERVATION OF A PLATEAU ELECTRON-DISTRIBUTION FUNCTION DUE TO ELECTRON-CYCLOTRON HEATING FOR AN EFFICIENT PLUG POTENTIAL FORMATION

A plateau-shaped electron distribution function is observed when an electrostatic electron-trapping potential is formed by the electron cyclotron heating (ECH) in the plug region of the GAMMA 10 tandem mirror. Also, a remarkable thermal isolation effect due to a kV-range thermal barrier is observed along with the difference between distribution functions in thermally separated regions. These new findings as well as the relation between ion-confining potentials and thermal-barrier potentials in the kV range consistently support the validity of Cohens strong ECH theory. © 1990 The American Physical Society.