LOW-ENERGETIC HE-ATOM BEAM AS A DIAGNOSTIC PROBE FOR ELECTRIC FIELD MEASUREMENT IN THE PLASMA EDGES

摘要

Two types of low-energetic He-atom beam sources were constructed for direct measurement of electric field distribution in tokamak plasma edge region with aid of laser-induced fluorescence (LIF) technique. One is a continuous plasma flow extracted from an electron cyclotron resonance (ECR) plasma source. The plasma parameters were measured by Langmuir probes, while density profiles and velocity of metastable He atoms (2(1)S) in the plasma flow were measured by LIF methods. It was found that extremely high density metastable atoms of similar to 10(11) cm(-3) were created at 7 cm apart from the outlet of the source. Formation mechanism of such high density 2(1)S atoms was briefly discussed on the basis of atomic processes. Another is a pulsed free jet having a pair of discharge electrodes to produce the 2(1)S atoms in the jet. High density 2(1)S atoms(similar to 10(10) cm(-3)) were found to be created in the discharged jet by means of the optical absorption method. [References: 14]