DIRECT EXTRACTION OF SODIUM NEGATIVE-IONS FROM SODIUM PLASMA

Diatomic negative ions of Na(Na2-) are extracted with atomic negative ions of Na(Na-) from a low-temperature Na plasma. The extracted curren ts of these negative ions are experimentally measured as functions of discharge parameters and wall temperatures. The measured extraction ch aracteristics are discussed by comparing the results with those of neg ative hydrogen and negative lithium ions extracted from the correspond ing plasmas. The maximum current ratio of Na2- to Na- for a wall tempe rature below 235-degrees-C is on the order of 0.01, much smaller than that obtained in the sputtering experiment.