Friso H. W. Van Amerom
SRI International, USA
Title: Experimental evaluation of micro-ion trap mass spectrometer geometries
Biography
Biography: Friso H. W. Van Amerom
Abstract
Miniaturization of mass spectrometers opens up a wide range of new applications that require portability during chemical measurements. Mass production of micro-sized mass spectrometers ultimately reduces production costs, allowing miniaturized spectrometers to be used as point-of-care medical diagnostics instruments. A new fabrication method, simulations, and experimental results for micromachined cylindrical ion trap (μ-CIT) arrays for use in miniaturized mass spectrometers is therefore presented. Simulations were performed in SIMION 7.0 to determine the optimum range of μ-CIT z0/r0 to be fabricated and tested. Micromachined μ-CIT arrays were fabricated in a silicon-on-insulator substrate. A series of z0/r0 were chosen in incremental steps of 3% for each array by changing r0 from 308 to 392 μm, while keeping z0 fixed at 355 μm, resulting in a range of z0/r0 from 1.16 to 0.92 (nine geometries in total). This resulted in fast, iterative measurements of the differences in the mass spectra from μ-CITs with different ratios of half-axial to half-radial dimensions (z0/r0). A deep reactive ion etching technique was used to create the cylindrical structures. Surface metallization created the ion trap electrodes. Symmetrical arrays of half-CITs were fabricated, diced, and bonded back-to-back to obtain complete μ-CIT array chips. Mass spectra were obtained experimentally from each trap geometry, and μ-CIT performance was found to follow the trend with respect to z0/r0 observed in the simulations. Axial modulation on one endplate electrode resulted in mass spectra with full-width-at-half-maximum peaks of 0.4 amu.