SIMPLE HEATABLE LANGMUIR PROBE FOR ALKALI PLASMAS

A new type of small, simple, indirectly heatable Langmuir probe for me asurements in alkaline plasmas is presented. The heating element of th is probe consists of an elogated half-loop of Ta-wire wound helically, around a thin ceramic tube that carries the probe collector. It is si tuated as closely as possible to the latter. The necessary heating pow er is a few watts. It is shown that the inevitable alkaline coating of the probe collector call be removed by sufficient heating. Various ty pes of coating and their influence on the probe characteristic are dis cussed. (C) 1997 American Institute of Physics.