Ion Cyclotron Resonance Spectrometer

A sensitive ion cyclotron resonance spectrometer designed to study low energy ion-molecule interactions in a weakly ionized gas is described. It is capable of determining simultaneously the collision frequency and average concentration of ions having a particular charge-to-mass ratio. General design considerations discussed include sensitivity, linewidth, resolution, and line broadening at high E/P. Effects of electron buildup are also discussed. The measurement chamber is intended to operate within a 1500 G, 102 cm long solenoid. Ion sources and electrode arrangements are described. Power absorption is detected by a narrow band, derivative type system for which circuit diagrams are given. The spectrometer has a resolution of about 3% and can detect an average concentration of 1–10 ions/cm3.