Electron impact ion source for trace analysis

摘要

An apparatus for analyzing trace elements in a gas sample includes a feedback system (46, 64, 68, 70) for accurately regulating and sensing the pressure supplied to an ion chamber (32), and an ion detector (34) calibrated for accurately scaling the measurements of trace elements. The ion chamber (32) is a closed ion source which is resistant to corrosion and aids in the reduction of noise. Two filaments (96, 98) mounted outside the ion chamber (32) adjacent apertures (90) in the chamber wall are thereby shielded from the ions. A cylindrical reflector (94) is aligned to axial with and disposed around the ion chamber (32). A quadrupole analyser (23) receives the ions through an aperture (88) and is shielded by the ion chamber (32) from electrons from the filaments (96, 98).