Design, microfabrication, and analysis of micrometer-sized cylindrical ion trap arrays

Abstract

A description of the design and microfabrication of arrays of micrometer-scale cylindrical ion traps is offered. Electrical characterization and initial ion trapping experiments with a massively parallel array of 5 microm internal radius (r(0)) sized cylindrical ion traps (CITs) are also described. The ion trap, materials, and design are presented and shown to be critical in achieving minimal trapping potential while maintaining minimal power consumption. The ion traps, fabricated with metal electrodes, have inner radii of 1, 2, 5, and 10 microm and range from 5 to 24 microm in height. The electrical characteristics of packaged ion trap arrays were measured with a vector network analyzer. The testing focused on trapping toluene (C(7)H(8)), mass 91, 92, or 93 amu, in the 5 microm sized CITs. Ions were formed via electron impact ionization and were ejected by turning off the rf voltage applied to the ring electrode; a current signal was collected at this time. Optimum ionization and trapping conditions, such as a sufficient pseudopotential well and high ionization to ion loss rate ratio (as determined by simulation), proved to be difficult to establish due to the high device capacitance and the presence of exposed dielectric material in the trapping region. However, evidence was obtained suggesting the trapping of ions in 1%-15% of the traps in the array. These first tests on micrometer-scale CITs indicated the necessary materials and device design modifications for realizing ultrasmall and low power ion traps.

Performance Evaluation of a Loeb-Eiber Mass Filter at 1 Torr

“…In contrast to TOFs, linear quadrupoles, and magnetic sectors [19], ion traps enjoy the ability to perform tandem mass spectrometry with a single mass analyzer [20]. The simplified geometry of a cylindrical ion trap in comparison to 3D ion traps has led to a significant research investment in the miniaturization of ion traps [21][22][23][24][25][26] and micro-fabricated ion trap arrays [27][28][29]. Lammert [30,31] and Austin [32][33][34] have studied toroidal ion traps of various geometries in an attempt to expand the quantitative dynamic range of ion traps in miniature and portable instruments.…”

Paul trapping of charged particles in aqueous solution

“…Moreover, nanoscale Paul traps may be capable of trapping a single electron (12), ions in aqueous solutions (13), as well as a long DNA polymer (14). In contrast to the 3D Paul traps, a linear Paul trap is compatible with standard microfabrication technology and can thus be mass produced (15). Linear Paul traps confine the ions radially by a 2D rf field and transport the ions axially by an applied axial electric field (16).…”

Novel ion traps using planar resistive electrodes: Implications for miniaturized mass analyzers

“…Several geometrical variations on the original quadrupole ion trap (Paul trap) have been developed, including cylindrical [12], rectilinear [13], linear [14], and toroidal [15] ion trap designs, each with advantages and disadvantages. For instance, rectilinear, linear, and toroidal traps have inherently larger storage volumes compared with quadrupole and cylindrical ion traps.…”

“…For miniaturized traps, however, machining methods have been pushed to the limit, and simpler electrode geometries such as planar and cylindrical are required. For this reason, most miniaturized and microfabricated ion traps have utilized the cylindrical trap design [12,[16][17][18][19][20].The need for a portable mass spectrometer has largely driven efforts to produce miniaturized ion traps [21]. Although the mass analyzer is just one of several components of a complete mass spectrometer system, miniaturization of the mass analyzer can often reduce the size and weight of other components.…”

“…For miniaturized traps, however, machining methods have been pushed to the limit, and simpler electrode geometries such as planar and cylindrical are required. For this reason, most miniaturized and microfabricated ion traps have utilized the cylindrical trap design [12,[16][17][18][19][20].…”