Date of Award
Master of Science in Electrical Engineering - (M.S.)
Electrical and Computer Engineering
William N. Carr
Kenneth Rudolph Farmer
Robert Boris Marcus
This thesis describes a design for a microengineered mass spectrometer. This mass spectrometer device uses VLSI processing techniques to scale down the dimensions of an existing mass spectrometer and make it portable. It can be manufactured economically and has the potential to be integrated with more complex structures and including transistor integrated circuits. An optimized device is proposed. This device is to be fabricated using two silicon substrates approximately 1cm by 1cm, where one is a cathode electron source and the other is the ion collector. External ion sources are not needed. Electrons are emitted from the array of cathode tips by field emission. Gas molecules near the cathode are bombarded by electrons and ionized. An electrostatic field and a uniform magnetic field of 3000 Gauss are used to establish separate trajectories for each mass isotope. Each mass isotope ion is collected at a different location on the ion collector plane. Voltage supply levels are 0 and 50V. The 3000 Gauss magnetic field permits collection of ions of up to 222amu (radon) for the spatial dimensions selected for this design Analyses of electron and ion trajectories were carried out using the SIMION simulation program. Many different structures were simulated and the optimized geometry of the microengineered mass spectrometer was determined. Sensitivities of the device have been modeled and calculated for the molecular range up to 222amu. The minimum detectable density level for an isotope is proportional to the active ionizing volume and is limited by the input noise level of the ion collection detector circuits. Fabrication procedures are detailed in this thesis.
Sun, Chao, "Microengineered mass spectrometer with field emission ionization source" (1993). Theses. 2273.