Microliter-Sized, Metastable-Helium Ionization Detector with Novel Electrodes

For flight experiments in low earth orbits and planetary missions, an innovative electrode structure is proposed to obtain a metastable helium ionization detector of active volume down to a fraction of a microliter for use with microbore and microchannel gas chromatographs. Such a small detector volume is achieved by the special electrode structure and gas flow pattern. In Phase I, the detector structure and function will be optimized with the use of a test fixture which examines the metastable helium ionization performance with a coupled mass spectrometer for mass identification. A new generation of micro-sized gas chromatograph columns requires a micro-volume detector for the measurement of organic chemicals, oxygen and water, down to parts-per-billion. A theoretical model for understanding the detector's operation can be based in part on the research results already achieved by PCP, inc. under Contracts NAS2-12997 and NAS2-13276, entitled Ion Mobility Sensing of Extraterrestrial Volatiles from a Gas Chromatograph. For NASA, the further reduction in detector size leads to a reduction in utilities (gas) requirements and weight in space flight instrumentation.