A Radio-Frequency Probe for the Mass-Spectrometric Analysis of Ion Concentrations

It has become increasingly evident of recent years that a detailed study of the processes occurring in gas discharges often requires a means of analysing and studying separately the various ionic species. This is true even in the case of the inert gases. This paper describes the development, and analyses the action, of a versatile probe which can readily be moved radially into and out of a discharge tube and which is able to distinguish between ions (positive or negative) of various masses. With this instrument it is therefore now possible to make probe studies on a particular species of ion in the presence of others. Basically the instrument is a very small 12-stage linear accelerator which discriminates in favour of ions of a particular mass-charge ratio passing through its sampling orifice. It is of high sampling efficiency and this together with its mobility and the absence of a magnetic field gives it certain pronounced advantages over the magnetic method of analysis.