Simple heatable Langmuir probe for alkali plasmas

A new type of small, simple, indirectly heatable Langmuir probe for measurements in alkaline plasmas is presented. The heating element of this probe consists of an elogated half-loop of Ta-wire wound helically, around a thin ceramic tube that carries the probe collector. It is situated as closely as possible to the latter. The necessary heating power is a few watts. It is shown that the inevitable alkaline coating of the probe collector can be removed by sufficient heating. Various types of coating and their influence on the probe characteristic are discussed. copyright 1997 American Institute of Physics