David Lindell, Brigham Young University
Engineering
Current ion detector technologies require low pressures and temperatures to achieve high sensitivity. These extra constraints result in bulky or expensive ion detection units and make a highly-portable mass spectrometer difficult or impractical to produce. A new ion detector technology that is unhampered by such constraints would allow the construction of miniaturized mass spectrometers. Such devices would have a myriad of potential applications, including use in space probes, on-site chemical weapon analyses, and in-field forensics. This research has produced solid-state ion detection devices with detection levels in the hundreds-of-ions range. The detectors are produced on a printed circuit board, are inexpensive, and are functional at room temperature and pressure. Solid-state detection capabilities were realized by adopting concepts from modern non-volatile (flash) memory and using custom-made low capacitance MOSFETs. Detection occurs as ions impact a Faraday cup and charge the gate of a MOSFET, yielding a voltage change in the circuit. In addition to refinements made by incorporating low-capacitance MOSFETs, commercial MEMS switches (which have only recently become available) are used to produce ion counts at rates up to 30 kHz. Amplification and filtering circuitry has also been added to further increase sensitivity levels. Results of this research show that ion detectors can be reduced in size and complexity, making a portable mass spectrometer more viable.