Simplified injector flanges for the selected ion flow tube

Dual hole-pattern injector flanges (Venturi inlets) for a selected ion flow tube:have been fabricated and tested in order to identify an optimum balance of efficient operational characteristics and simplicity of fabrication, along with reproducible assembly. The diagnostic measurements for each configuration addressed: (a) ability to maintain pressure differences between ion selection and ion reaction regions; (b) ability to inject sufficient ions to carry out ion/molecule reaction studies; and (c) ability to not introduce turbulence in the reaction region of the flow tube. In addition, the sensitivity of these issues to different total gas flow and to partitioning of total flow between inner and outer injectors is considered. All hole-pattern injector configurations ever tried worked without requiring any adjusting. Importantly, extensive kinetic measurements of one ion/molecule reaction for many configurations, gas loads, and partitions, Indicate turbulence in the reaction region is never a problem for these injectors. An injector flange with a small total helium inlet area via 12 holes, in a planar surface, with the ion orifice slightly downstream of the helium inlet plane, has provided the best experimental data. (Int J Mass Spectrom 177 (1998) 175-186) (C) 1998 Elsevier Science B.V.