Miniature charged particle trap with elongated trapping region for mass spectrometry - Patent Application 20070233633

Abstract

To provide a method of measuring mass spectrometry information of a sample.SOLUTION: A method of measuring mass spectrometry information of a sample includes the steps: trapping ions generated from the sample in an ion trap, the ion trap comprising a trapping region defined by a plurality of apertures in electrodes of a mass spectrometry system; selectively discharging different portions of the trapped ions from portions of the trapping region, where one or more of the portions of the trapping region is less than an entirety of the trapping region; selectively detecting the charged different portions of the trapped ions; and determining the mass spectrometry information about the sample based on the detected ions.SELECTED DRAWING: Figure 1A

Description

[Technical field]

[0001] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT This invention was made with Government support under Grant W911NF-10-1-0447 awarded by the U.S. Army Research Office. The Government has certain rights in the invention.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 13 / 840,653, filed March 15, 2013, entitled "MINIATURE CHAGED PARTICLE TRAP WITH ELONGATED TRAPPING REGION FOR MASS SPECTROMETRY," the entire contents of which are incorporated herein by reference.

[0003] The present invention relates to a miniature charged particle trap having an elongated trapping region for mass spectrometry. [Background technology]

[0004] This Background section is for informational purposes only, and no subject matter contained herein is intended to be, or is admitted to be, a prior art limitation to the present application.

[0005] Mass spectrometry (MS) is one of the most valuable analytical techniques. Due to its combination of speed, selectivity, and sensitivity, MS has a wide range of applications in areas such as trace elemental analysis, biomolecular characterization in highly complex samples, and isotopic ratio determination. However, the large size, weight, and power consumption (SWaP) of some MS systems generally restrict such analyses to laboratory settings. Applications where rapid measurements in the field are desirable or where laboratory analysis is not optimal would benefit from the development of portable, compact MS systems.

[0006] The increasing SWaP and complexity of MS work is due to the high vacuum (10 -5 ~10 -9 The SWaP is due to the vacuum system required to achieve a pressure of 10 Torr. Therefore, one approach to reducing SWaP is to be able to run the MS at higher pressures. The ion trap is -4 Ion traps can be operated at pressures above a few milliTorr and therefore can be used as mass analyzers for miniaturized systems. However, in some cases, increasing the pressure in the ion trap significantly beyond a few milliTorr has detrimental effects on resolution and signal strength. Further increasing the pressure increases the number of collisions with the buffer gas, making it difficult to control the ion trajectories with the electric field. Increasing the operating frequency of the trap (usually radio frequency or "RF") reduces the negative effects of operating at high pressures by producing fewer neutral collisions per cycle, but may require a corresponding reduction in the trap dimensions and the required RF voltage amplitude. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] U.S. Patent No. 7,847,240 [Patent Document 2] U.S. Patent No. 6,469,298 Summary of the Invention [Means for solving the problem]

[0008] Applicants have previously found that simply reducing the dimensions of conventional centimeter-scale trap geometries is problematic. As the size of the trap is reduced, it becomes increasingly difficult to manufacture the conventional hyperboloid shapes of the ion trap electrodes using conventional machining techniques. To simplify the trap geometry, these hyperboloid shapes may be replaced with planar electrodes.

[0009] However, a limitation in miniaturizing ion traps is that space charge effects reduce ion-trapping capability as the trap dimensions decrease: simulations show that 1-μm-scale traps have a charge capacity approaching that of a single ion.

[0010] Applicants have previously discovered that this limitation can be mitigated or overcome by providing a miniaturized trap with a trapping cavity that is elongated in one direction. By increasing the number of dimensions, the storage capacity can be increased over a similar trap with a symmetric trapping cavity, while still being easy to manufacture. Thus, embodiments of the ion trap described herein can provide both a high level of miniaturization and advantageously a large charge capacity.

[0011] In one aspect, a miniature electrode device for trapping charged particles is disclosed. In some embodiments, the device includes, along a longitudinal direction, a first end cap electrode, a central electrode having an aperture, and a second end cap electrode. In some embodiments, the aperture extends longitudinally through the central electrode, and the central electrode surrounds the aperture in a transverse plane perpendicular to the longitudinal direction to define a transverse cavity for trapping the charged particles.

[0012] In some embodiments, the opening in the central electrode is elongated in a lateral plane. In various embodiments, the elongated opening may be characterized in any of the following ways:

[0013] In some embodiments, an elongated aperture has a ratio of a major dimension to a minor dimension that is greater than 1.0, where the major dimension is the longest linear distance across the aperture in a lateral plane, and the minor dimension is the longest linear distance across the aperture in a lateral plane perpendicular to a line corresponding to the major dimension. In some such embodiments, the ratio of the major dimension to the minor dimension is greater than or greater than 1.5, 2.0, 3.0, 4.0, 5.0, 10.0, 50.0, 100.0. In some embodiments, the minor dimension is less than or less than 10 mm, 5 mm, 1 mm, 0.1 mm, 0.01 mm, 0.001 mm.

[0014] In some embodiments, the ratio of the major dimension to the average minor dimension of the elongate aperture is greater than 1.0, where the major dimension is the longest straight line distance across the aperture in a lateral plane, and the average minor dimension is the cumulative average of the distances along each straight line across the aperture in a lateral plane perpendicular to the line corresponding to the major dimension, at every location along the line corresponding to the major dimension. In some such embodiments, the ratio of the major dimension to the average minor dimension is greater than or greater than 1.5, 2.0, 3.0, 4.0, 5.0, 10.0, 50.0, 100.0. In some embodiments, the average minor dimension is less than or less than 10 mm, 5 mm, 1 mm, 0.1 mm, 0.01 mm, 0.001 mm.

[0015] In some embodiments, the elongated opening comprises an elongated channel having a first and second end, where the elongated channel has a ratio of channel length to channel width greater than 1.0, where the channel length is the shortest curvilinear distance across the channel in a lateral plane from the first end to the second end, and the channel width is the longest linear distance across the channel in a lateral plane perpendicular to the curve corresponding to the channel length. In some such embodiments, the ratio of channel length to channel width is greater than or greater than 1.5, 2.0, 3.0, 4.0, 5.0, 10.0, 50.0, 100.0. In some embodiments, the channel width is less than or less than 10 mm, 5 mm, 1 mm, 0.1 mm, 0.01 mm, 0.001 mm.

[0016] In some embodiments, each end cap includes a planar conductive member having a plurality of holes extending therethrough along a longitudinal direction. In some embodiments, each planar conductive member extends transversely to the longitudinal axis and is configured to be electron- or ion-transmissive. In some embodiments, each planar conductive member is a conductive mesh. In some embodiments, the conductive mesh protrudes into the central electrode along the longitudinal axis to completely surround an elongated opening in the central electrode in the transverse plane.

[0017] In some embodiments, each end cap electrode includes a conductive material having an aperture for defining a path for charged particles along a longitudinal direction through the end cap and the aperture in the central electrode, and in some embodiments, the aperture in at least one end cap is substantially filled with a conductive mesh.

[0018] In various embodiments, the opening in the at least one end cap may have any suitable shape. In some embodiments, the opening in the at least one end cap comprises a circular opening having a perimeter greater than a larger dimension of the opening in the central electrode, where the larger dimension is defined in any of the manners described above. In some embodiments, the opening in the at least one end cap comprises a circular opening having a perimeter greater than a channel length of the opening in the central electrode. In some embodiments, the opening in the at least one end cap comprises an elongated slit.

[0019] In some embodiments, the elongated aperture in the central electrode may have any suitable shape, hi some embodiments, the elongated aperture includes an elongated slit, two or more intersecting elongated slits, a serpentine portion, a spiral portion, a portion of a circular slit, and any combination thereof.

[0020] Some embodiments include a first insulating spacer disposed along the longitudinal direction between the first end cap electrode and the central electrode, and a second insulating spacer disposed between the central electrode and the second end cap electrode.

[0021] Some embodiments include a power source coupled to each electrode to generate an oscillating electromagnetic field between the central electrode and the end cap electrodes.

[0022] In some embodiments, the transverse cavity defined by the laterally elongated opening in the central electrode has a vertical dimension in the longitudinal direction from the first end cap to the second end cap that is less than or equal to about 10 mm, 10 mm, 5 mm, 1 mm, 0.1 mm, 0.01 mm, 0.001 mm. In some embodiments, the transverse cavity defined by the laterally elongated opening in the central electrode has a vertical dimension that is substantially uniform across the lateral extent of the cavity. In some embodiments, the transverse cavity defined by the laterally elongated opening in the central electrode has a vertical dimension that varies across one or more of the lateral extents of the cavity.

[0023] In some embodiments, the transverse cavity defined by the laterally elongated opening in the central electrode has a vertical dimension that is equal to or greater than the smaller dimension, the average smaller dimension, or the channel width of the elongated opening in the longitudinal direction from the first end cap to the second end cap.

[0024] In some embodiments, the elongate opening in the central electrode includes at least one channel portion having a lateral length and a lateral width, and the width is substantially uniform along the channel portion.

[0025] In some embodiments, the elongate opening in the central electrode includes at least one channel portion having a lateral length and a lateral width, and the width varies along the lateral length of the channel portion.

[0026] Some embodiments include at least one mask element configured to block transmission of electrons or ions to or from a localized region of the transverse cavity.

[0027] In some embodiments, the central electrode comprises a plurality of apertures configured to define respective transverse cavities for trapping charged particles.

[0028] In some embodiments, the elongated aperture comprises a serpentine slit in the central electrode having a plurality of substantially straight portions and a plurality of curved portions connecting pairs of the substantially straight portions. In some embodiments, the elongated aperture comprises one or more mask elements configured to block ion transmission from localized regions of the transverse cavity corresponding to the curved portions. In some embodiments, the elongated aperture comprises one or more mask elements configured to block ion transmission from localized regions of the transverse cavity corresponding to the straight portions.

[0029] In another aspect, a mass spectrometer is disclosed that includes a miniature electrode assembly for trapping charged particles, the assembly including any of the above types of devices, together with at least one electrical signal source coupled to the ion trap assembly, In some embodiments, the electrode assembly is configured to generate an electromagnetic field in response to a signal from the electrical signal source to generate an ion trapping region.

[0030] Some embodiments include a controller operably coupled to the electrical signal source and configured to adjust the signal source to effect mass selective ejection of ions from the trapping region.

[0031] In some embodiments, at least one of the end cap electrodes is configured to allow ejection of ions from the trapping region.

[0032] Some embodiments include an ion source configured to inject or form ions that are trapped in the trapping region.

[0033] Some embodiments include at least one detector configured to detect ions emitted from the assembly, hi some embodiments, the at least one detector comprises a Faraday cup detector or an electron multiplier.

[0034] In some embodiments, a chamber containing an ion trapping region is provided and, during operation, the chamber is configured to have a background pressure greater than or equal to 100 mTorr, 1 Torr, 10 Torr, 100 Torr, 500 Torr, 760 Torr, 1000 Torr.

[0035] In some embodiments, the central electrode comprises a plurality of apertures, each of which defines a transverse cavity for trapping charged particles, each cavity including a separate one of the plurality of ion trapping cavity regions. In some embodiments, the mass analyzer is configured to generate an enhanced output signal based on the combined mass-selective ion ejection output from the plurality of ion trapping cavity regions.

[0036] In another aspect, a method of mass spectrometry is disclosed that includes applying an electrical signal to a miniature electrode assembly for trapping charged particles, the assembly including any of the aforementioned types of miniature electrode devices for trapping charged particles. Some embodiments include generating an electromagnetic field in response to the electrical signal with an ion trapping region located within a cavity of the ion trap assembly. Some embodiments include adjusting a signal source to perform mass selective ejection of ions from the trapping region, detecting ions ejected from the trapping region to generate a mass spectrometry signal, and outputting the mass spectrometry signal.

[0037] In some embodiments, the method includes injecting or forming ions to be trapped in the trapping region. In some embodiments, at least one of the first and second end cap electrodes comprises a planar conductive member having a plurality of holes extending therethrough, the planar conductive member configured to be electron-transparent or ion-transparent. In some embodiments, the method includes injecting ions or electrons into the trapping region through the plurality of holes in the planar conductive member.

[0038] Some embodiments include ejecting ions from a localized portion of the trapping region, which in some embodiments corresponds to a lateral end of the trapping region or a central portion of the trapping region, and some embodiments include forming or implanting ions at multiple locations within the trapping region and ejecting ions from a substantially single location within the trapping region.

[0039] Some embodiments include forming or injecting ions in a first portion of the trapping region and releasing ions from a second portion of the trapping region having a volume smaller than the volume of the first portion. In some embodiments, the trapping region includes a serpentine region extending between a pair of end points having a plurality of substantially straight portions and a plurality of curved portions connecting pairs of the substantially straight portions, the first portion corresponding to one or more of the substantially straight portions and the second portion corresponding to at least one of the curved portions and the end points.

[0040] Some embodiments include selectively blocking ions emitted from a portion of the trapping region to prevent the ions from being detected. Some embodiments include selectively blocking electrons or ions from the source from entering a portion of the trapping region.

[0041] In some embodiments, the method includes generating an electromagnetic field having a plurality of separate ion trapping regions in response to an electrical signal. In some embodiments, at least two of the ion trapping regions have different ion trapping stability characteristics. In some embodiments, each of the ion trapping regions has substantially the same ion trapping stability characteristics.

[0042] Some embodiments include adjusting the signal source to perform mass selective ejection of ions from each of the trapping regions. Some embodiments include detecting ions ejected from the multiple trapping regions with a single detector to generate a combined mass spectrometry signal. Some embodiments include detecting ions ejected from each of the multiple trapping regions with a respective detector to generate a respective mass spectrometry signal.

[0043] Various embodiments may include any of the above elements alone or in any suitable combination.

[0044] In various embodiments described herein, a miniature electrode device for trapping charged particles is disclosed. The device includes a first end cap electrode, a central electrode having an aperture, and a second end cap electrode along a longitudinal direction. The aperture extends along the longitudinal direction through the central electrode, which surrounds the aperture in a lateral plane perpendicular to the longitudinal direction to define a transverse cavity for trapping the charged particles. The aperture in the central electrode is elongated in the lateral plane. In various embodiments, the elongated aperture may be characterized in any of the following ways:

[0045] As described below, for example with reference to Figures 1-4 and 17, the elongated aperture may be any elongated shape. With reference to Figures 18A-18C, the shape may be characterized in any of the following ways.

[0046] In some embodiments, the elongated aperture has a ratio of a major dimension to a minor dimension greater than 1.0, where the major dimension is the longest linear distance across the aperture in a lateral plane and the minor dimension is the longest linear distance across the aperture in a lateral plane perpendicular to a line corresponding to the major dimension. In some such embodiments, the ratio of the major dimension to the minor dimension is greater than 1.5, 2.0, 3.0, 4.0, 5.0, 10.0, 50.0, 100.0 or more. In some embodiments, the minor dimension is less than 10 mm, 5 mm, 1 mm, 0.1 mm, 0.01 mm, 0.001 mm or less.

[0047] As shown in FIG. 18A, the major dimension of an aperture is defined as the longest straight line distance across the aperture in a lateral plane, and the minor dimension is the longest straight line distance across the aperture in a lateral plane perpendicular to a line corresponding to the major dimension. In some such embodiments, the ratio of the major dimension to the minor dimension is greater than 1.0, 1.5, 2.0, 3.0, 4.0, 5.0, 10.0, 50, 100, or more. In some embodiments, the minor dimension is less than 10 mm, 5 mm, 1 mm, 0.1 mm, 0.01 mm, 0.001 mm, or less. For the slit-shaped apertures shown in FIGS. 1A-1E, the major dimension corresponds to y0 and the minor dimension corresponds to 2x0.

[0048] As shown in Figure 18B, the major dimension of an aperture is defined as the longest straight line distance across the aperture in a lateral plane, and the average minor dimension is the cumulative average of the distances along each straight line across the aperture in a lateral plane perpendicular to the line corresponding to the major dimension at every location along the line corresponding to the major dimension. In some such embodiments, the ratio of the major dimension to the average minor dimension is greater than 1.0, 1.5, 2.0, 3.0, 4.0, 5.0, 10.0, 50, 100, 1000, or more. In some embodiments, the average minor dimension is less than 10 mm, 5 mm, 1 mm, 0.1 mm, 0.01 mm, 0.001 mm, or less.

[0049] In some embodiments, the elongated opening is an elongated channel having first and second ends, as shown in FIG. 18C. In such cases, the channel length is defined as the shortest curvilinear distance across the channel in a lateral plane from the first end to the second end, and the channel width is defined as the longest linear distance across the channel in a lateral plane perpendicular to the curve corresponding to the channel length. In some such embodiments, the ratio of channel length to channel width is greater than 1.5, 2.0, 3.0, 4.0, 5.0, 10.0, 50, 100, 1000, or more. In some embodiments, the channel width is less than 10 mm, 5 mm, 1 mm, 0.1 mm, 0.01 mm, 0.001 mm, or less. [Brief description of the drawings]

[0050] [Figure 1A] ~ [Figure 1E] 1 shows diagrams of a miniature electrode device for trapping charged particles: Fig. 1A is a perspective view; Fig. 1B is a second perspective view at another angle; Fig. 1C is a top view; Fig. 1D is a vertical cross-section along plane AA'; Fig. 1E is a perspective cross-section along plane AA'. [Figure 2A] ~ [Figure 2C] 2A, 2B, and 2C show diagrams of an ion trap including a miniature electrode device for trapping charged particles, respectively in a perspective view, a top view, and an exploded view. [Diagram 3] 1 is a photograph of an ion trap that includes a small electrode device for trapping charged particles. [Figure 4] 1A-1E show schematic diagrams of several alternative designs for the central electrode of a miniature electrode device of the type shown in FIGS. [Figure 5A] FIG. 1 is a schematic diagram of a mass spectrometer. [Figure 5B] FIG. 2 is a detailed functional diagram of a mass spectrometer. [Figure 5C] FIG. 2 is a detailed functional diagram of a mass spectrometer. [Figure 5D] FIG. 2 is an exemplary timing diagram of a mass spectrometer. [Figure 6]FIG. 1 is a schematic diagram of a mass spectrometer featuring a differentially pumped chamber. [Figure 7] Mass spectra of 10-4 Torr Xe in 30 mTorr helium buffer gas are shown, obtained using a stretched length ion trap (SLIT) where the resolution changes as the trap width is changed. [Figure 8A] ~ [Figure 8B] A comparison of the performance of a SLIT and a cylindrical ion trap (CIT) is shown. Figure 8A shows mass spectra of Xe at 10-4 Torr with 51 mTorr He buffer gas recorded using a SLIT (upper trace) and a CIT (lower trace). For reference, a bar graph of the NIST EI spectrum for Xe is shown along the bottom of the graph. The average FWHM of the five major peaks is 0.41 Th and 0.44 Th for the SLIT and CIT, respectively. Figure 8B shows the total integrated Xe signal as a function of sample pressure showing a large increase in the sensitivity of the SLIT (upper trace) over that of the CIT (lower trace). The slopes of the traces are 0.52 μV*s / Torr and 1.52 μV*s / Torr for the SLIT and CIT, respectively, a 10-fold increase in sensitivity for the SLIT. The vertical error bars represent the standard deviation of spectra taken in triplicate at each pressure, and the horizontal error bars represent the imprecision of the full-range manometer. [Figure 9] A graph of the SLIT signal as a function of the trapping length extension is shown. Each spectrum was for Xe at 10-4 Torr in He at 33 mTorr. Error bars represent the standard deviation of three consecutive spectra. [Figure 10] SLIT mass spectra of Xe obtained with He buffer gas pressures from 202 to 1002 millitorr are shown. As pressure increases, resolution and signal degrade. Signal loss is adjusted by increasing the total number of ionized electrons by adjusting ionization time, emitter bias voltage, and emitter current. The peak width of approximately 0.5 Th at low pressure degrades to an estimated 2 Th peak width at 1 Torr. [Figure 11]A table of experimental conditions for the high pressure mass spectrum shown in FIG. 10 is shown. [Figure 12] We show that mass spectra of the organic compound mesitylene were obtained by SLIT using nitrogen buffer gas at pressures between 9 mTorr and 1000 mTorr. The ionization conditions were adjusted as the pressure was increased to obtain more ionized electrons in the trap. Over this pressure range, the width of the main mesitylene peak increases from 2.3 Th to 7.2 Th. [Figure 13A] 1 shows the central electrode for a SLIT trap featuring three trapping cavities. [Figure 13B] 13B shows a mass spectrum of Xe at 10 −4 Torr in 30 mTorr helium buffer gas obtained using a SLIT trap featuring the central electrode shown in FIG. 13A. [Figure 14A] ~ [Figure 14B] 1 shows experimental results demonstrating the trapping of ions along the entire length of a serpentine slit trap. [Figure 15] 1 shows experimental results of a mass spectrometry experiment using an array of linear traps. [Figure 16] 1 shows experimental results of a mass spectrometry experiment using a single linear trap. [Figure 17] 1 shows experimental results of a mass spectrometry experiment using a tapered linear trap. [Figure 18A] ~ [Figure 18C] 1 illustrates various methods for characterizing shapes in elongated apertures. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0051] In various embodiments, for example, a stretched length ion trap (SLIT) is provided for use as a mass analyzer in a mass spectrometer. An ion trap is characterized by a trapping region that is miniaturized along two dimensions but elongated or narrow along a third dimension.

[0052] For example, Figures 1A-1E show diagrams of a miniature electrode device 100 for trapping charged particles. Figure 1A is a perspective view. Figure 1B is a second perspective view at another angle. Figure 1C is a top view. Figure 1D is a vertical cross-sectional view along plane AA'. Figure 1E is a perspective cross-sectional view along plane AA'.

[0053] The miniature electrode device 100 comprises three electrodes stacked along a longitudinal direction (shown as the z-direction in each figure). Each electrode comprises a first end cap electrode 102, a central electrode 104 and a second end cap electrode 106. The central electrode 104 comprises an elongated aperture 108 which extends along the longitudinal direction z through the central electrode and surrounds the aperture 108 in a transverse plane (shown as the xy-plane) perpendicular to the longitudinal direction to define a transverse cavity for trapping charged particles.

[0054] The center and end cap electrodes 102, 104, 106 may be made from any suitable conductive material, such as a metal (e.g., copper, gold, stainless steel) or a doped semiconductor material, such as heavily doped n- or p-type silicon. Each electrode may be formed using any suitable manufacturing technique, including, for example, milling, etching (e.g., wet etching), and laser cutting.

[0055] Aperture 108 is "elongated" or elongated in the lateral plane. For example, as shown, aperture 108 is an elongated slit that is longer in the y direction than in the x direction.

[0056] In various embodiments, the aperture 108 may take any elongated shape. For example, in various embodiments, the aperture has a major dimension that is the longest linear distance across the aperture in a lateral plane, and a minor dimension that is the longest linear distance across the aperture in a lateral plane perpendicular to the major dimension. In the example shown in Figures 1A-1E, the major dimension corresponds to a length y0 and the minor dimension corresponds to a distance 2x0 (best seen in Figure 1C). Note that by convention, x0 is defined herein as half the width of the aperture, and y0 is the overall length of the aperture.

[0057] In some embodiments, the ratio of the major dimension to the minor dimension is greater than or equal to 1.0, 1.5, 2.0, 3.0, 4.0, 5.0, 10.0, 20.0, 30.0, 40.0, 50.0, 100.0, 150, 200. For example, in some embodiments, the ratio of the major dimension to the minor dimension is in the range of 1.1 to 1000, or any subrange therein.

[0058] For example, the electrode device 100 may be small so that charged particle trapping operations can be performed at relatively high frequencies. For example, in some embodiments, the smaller dimension of the opening 108 is less than 50 mm, 10 mm, 5 mm, 4 mm, 3 mm, 2 mm, 1.0 mm, 0.1 mm, 0.01 mm, 0.05 mm, or 0.001 mm. For example, in some embodiments, the smaller dimension is in the range of 0.001 mm to 50 mm, or any subrange thereof. In some embodiments, the smaller dimension is small enough such that the electrode device is operative to trap only a line or surface of a single charged particle extending along the larger dimension.

[0059] In some embodiments, the vertical dimension 2z0 (best seen in FIG. 1D ) of the transverse cavity defined by the laterally elongated aperture 108 in the central electrode 104 is less than about 10 mm, 50 mm, 10 mm, 5 mm, 4 mm, 3 mm, 2 mm, 1.0 mm, 0.1 mm, 0.01 mm, 0.05 mm, or 0.001 mm. Note that z0 has been defined as half the height of the cavity, e.g., as shown in the figure, plus half the height of the aperture 108 plus the distance from the aperture to the end cap electrode. For example, in some embodiments, the smaller dimension is in the range of 0.001 mm to 50 mm, or any subrange thereof. In some embodiments, the smaller dimension is small enough that the electrode arrangement operates to trap only a single charged particle along the vertical dimension. In some embodiments, the ratio of z0 to x0 is greater than 1, e.g., in the range of 1.1 to 1.3. In various embodiments, the end cap electrodes 102 and 106 are at least partially transparent to charged particles, thereby allowing such particles to pass into and out of the transverse cavity.

[0060] For example, as shown, each end cap electrode 102 and 106 includes a planar conductive member 110 having a plurality of holes extending therethrough along a longitudinal direction. As shown, each planar conductive member 110 extends transversely to the longitudinal axis and is configured to be electron-transparent or ion-transparent.

[0061] In some embodiments, the planar conductive member 110 is a conductive mesh, such as an electroformed mesh or a woven mesh. In various embodiments, the open area of ​​the mesh (i.e., the percentage of the area of ​​the mesh surface that contains passageways extending through the mesh) can be selected to achieve a desired permeability to charged particles and a desired mechanical strength. In some embodiments, the mesh can be at least 50% open, at least 75% open, at least 80% open, at least 90% or more. For example, in some embodiments, the open area of ​​the mesh is in the range of 1% to 99%, or any subrange therein.

[0062] In some embodiments, the use of mesh 110 in end cap electrodes 102 and 106 is advantageous because it reduces the need to precisely align each electrode 102, 104, and 106. For example, as best shown in FIG. 1C, in each end cap electrode 102 and 106, the protrusion of conductive mesh 110 into the central electrode along the longitudinal axis completely surrounds the elongated aperture 108 in the central electrode 104 in the lateral plane. As shown, mesh portion 110 of end cap electrodes 102 and 106 is shaped as an elongated slit that is wider and longer than the aperture 108 in central electrode 104. In the illustrated configuration, the length of mesh portion 110 is approximately equal to the length of the aperture, but it should be noted that in other embodiments, the mesh portion may be longer (or shorter) than the aperture 108 in central electrode 104. In various embodiments, other shapes or configurations may be used. For example, as shown in FIG. 3, the mesh may be disposed in a circular opening in the end cap electrodes 102 or 106 whose diameter is longer than the larger dimension of the opening 108 in the central electrode 104.

[0063] In embodiments of the type described above, misalignment, such as lateral shifts in the xy directions and / or rotations about the longitudinal axis, does not substantially affect the operation of the ion trap. That is, because the properties of the mesh 110 are relatively uniform, such misalignment does not change the structure of the portion of the end cap electrodes 102 or 106 that faces the elongated aperture 108 in the central electrode 104. Thus, in some embodiments, the performance of the ion trap depends primarily or exclusively on the vertical alignment of the electrodes 102, 104, and 106. As described in more detail below, in some embodiments, proper vertical alignment may be easily maintained using, for example, non-conductive spacer elements disposed between each electrode.

[0064] While the use of mesh 110 may be advantageous, in some embodiments the mesh may be omitted and one or both of the end cap electrodes 102 and 106 may simply comprise an empty aperture. The aperture may have any suitable shape (e.g., an elongated slit or a cylindrical aperture). In various embodiments, the aperture in the end cap 102 or 106 may have a shape that substantially corresponds to the shape of the aperture 108 in the central electrode 104, or may have a shape that is substantially different therefrom. In some embodiments, the aperture in the end caps 102 and 106 may have a shape in the lateral plane similar to the shape of the aperture 108 in the central electrode 104, but with a length in the x-direction that is shorter than the corresponding length of the aperture 108. For example, in the embodiment shown in Figures 2A-2C, each of the electrodes 102, 104, and 106 comprises an elongated slit aperture, with the slits aligned.

[0065] In the embodiment shown in Figures 1A-1E, the transverse cavity defined by the laterally elongated aperture 108 in the central electrode 104 has a vertical dimension of 2z0 (corresponding to the spacing between the end caps), which is substantially uniform across the lateral x and y extents of the cavity. However, it should be appreciated that in some embodiments, the transverse cavity defined by the laterally elongated aperture 108 in the central electrode 104 may have a vertical dimension that varies across one or more of the lateral extents of the cavity, for example, when one of the end cap electrodes 102 or 106 is disposed at an angle relative to the central electrode 104. In some cases, this configuration is disadvantageous in that the varying alignment over the vertical extent of the cavity degrades the resolution when operating as a mass analyzer. However, in other cases (e.g., when trapped particles are selectively released from localized regions of the trapping cavity, as described below), this configuration may be advantageous.

[0066] In general, the shape of the aperture in each electrode may be modified as required for a given application. For example, in some embodiments, the elongated aperture 108 in the central electrode 104 comprises at least one channel portion having a lateral length and a width. In some cases, the width may be substantially uniform along the channel portion, and in some cases, the width varies along the lateral length of the channel portion.

[0067] 2A-2C show diagrams of an ion trap assembly 200 including a miniature electrode device 100 for trapping charged particles. Figure 2A is a perspective view, Figure 2B is a top view, and Figure 2C is an exploded view.

[0068] 1A-1E, the miniature electrode device 100 includes a first end cap electrode 102, a central electrode 104, and a second end cap electrode 106. The central electrode 104 includes an elongated aperture 108 that extends along a longitudinal direction z through the central electrode 104 and surrounds the aperture 108 in a transverse plane (shown in the xy plane) perpendicular to the longitudinal direction to define a transverse cavity for trapping charged particles.

[0069] The device 100 is disposed on a support member 201. Non-conductive spacers 202 are provided that separate the electrodes 102, 104, and 106. Any suitable non-conductive material may be used for the spacers 202, for example, polymeric films such as polyimide, polyamide, Kapton, or Teflon films, or insulating materials such as ceramic or mica. In other embodiments, a non-conductive material may be grown or deposited on one or more of the electrodes, for example, using techniques known in the art of semiconductor processing, for example, growth of silicon oxide or silicon nitride films. Although six spacers 202 are shown, any suitable number may be used in various embodiments.

[0070] The sandwich structure comprised of the electrodes 102, 104, 106 and the spacer 202 may be secured to the support member 201 using any suitable attachment mechanism, such as one or more screws that extend through the sandwich structure to the support member 201. In some embodiments, the screws may be symmetrically positioned about the longitudinal axis of the sandwich structure and tightened with equal torque to maintain parallel alignment of the electrodes 102, 104, 106.

[0071] In some embodiments, the support member 201 may include one or more alignment features to aid in mounting the device 100. For example, in some embodiments, the support member 201 may include one or more holes for mounting guide posts. The electrodes 102, 104, and 106 may then include guide holes for each electrode to slide over the guide post to maintain the desired alignment during assembly. In some embodiments, these guide posts may be removed after the electrodes are secured to the support member 201.

[0072] 3 is a photograph of an ion trap 200 including a miniature electrode arrangement 100 for trapping charged particles. As previously mentioned, in the illustrated embodiment, the mesh 110 at the end cap electrodes 102 and 106 is disposed in a circular opening in the end cap electrodes 102 and 106, the diameter of which is larger than the larger dimension of the opening 108 in the central electrode 104. Electrical connections 301 to the end cap electrodes 102 and 106. As shown, this connection is a solder connection to the trapping electrodes, although any suitable connection may be used in various embodiments.

[0073] While the above example features a single elongated aperture 108 formed as a slit in the central electrode 104, other embodiments may provide other aperture shapes and / or more than one aperture. Figure 4 shows schematic diagrams of several alternative designs for the central electrode of a miniature electrode device of the type shown in Figures 1A-1E.

[0074] The central electrode 401 includes a plurality of apertures, each defining a separate transverse cavity for trapping charged particles. As shown, each aperture is an elongated slit arranged in a regular linear array. However, in various embodiments, other aperture shapes and arrangements may be used, including a two-dimensional array of apertures, or irregular or randomly arranged apertures.

[0075] The central electrode 402 comprises a serpentine shaped aperture. As shown, the serpentine shaped aperture includes relatively long straight sections connected by relatively short curved sections. The serpentine shape is advantageous in that it allows for a trapping cavity with a very long effective length (i.e., the length that the aperture would have if the serpentine were straightened out) while still fitting into a relatively compact footprint.

[0076] Similarly, central electrode 403 comprises a spiral aperture. Central electrode 404 comprises a number of slit-shaped apertures formed as segments of a circle. In various embodiments, other curvilinear aperture shapes may be used.

[0077] In some embodiments, for example, the central electrode may include one or more intersecting slit shaped apertures. For example, central electrode 405 has two slits that meet at a common endpoint. Central electrode 406 has three intersecting slits arranged in a star shape. Any suitable number and arrangement of intersecting slits may be used in various embodiments.

[0078] It should be noted that in various embodiments, the slit-shaped portions of the apertures may have any suitable shape. For example, the vertical height, lateral length, and lateral width of each slit may be substantially uniform. In some embodiments, one or more of the vertical height, lateral length, and lateral width of each slit may vary.

[0079] FIG. 5A is a schematic diagram of a mass analyzer 500. The mass analyzer 500 includes a trap 200 having a miniature electrode arrangement 100 for trapping charged particles, of the type described with reference to FIGS. 1A-2C. An electrical signal source 501 is coupled to the ion trap assembly to provide an electrical signal. The electrode arrangement 100 generates an electromagnetic field in response to the signal. The electromagnetic field includes an ion trapping region formed by the electrodes disposed in the transverse cavity. For example, in some embodiments, a signal source is coupled to the electrodes and operates as a power source to generate an oscillating electromagnetic field between the central electrode and the end cap electrodes. In some embodiments, the electromagnetic field oscillates at an RF frequency, e.g., 1 MHz to 1000 GHz, or any subrange thereof. It should be noted that for operation at high pressures, high frequencies are desirable, so that the period of oscillation of the trapping field is much shorter than the average time for a trapped particle to collide with a particle in the background gas.

[0080] The controller 502 is operatively coupled to the electrical signal source 501 and configured to adjust the signal source to perform mass selective ejection of ions from the trapping region. In various embodiments, any suitable technique may be used to achieve mass selective ejection. For example, in some embodiments, the RF potential applied to the trap 200 is ramped so that ions of mass a (>b) have stable trajectories, but ions of mass b become unstable and are ejected (e.g., via one of the end cap electrodes) on the longitudinal axis to the detector 503 (described in more detail below). In other embodiments, other techniques may be used, including applying a second axial RF signal across the end cap electrodes to generate a dipolar electric field within the trap. This dipolar electric field may eject ions when their self-perpetuating frequency is equal to the axial RF frequency.

[0081] The system 500 includes an ion source 504 configured to inject or form ions that are trapped in the trapping region. In various embodiments, any suitable source may be used. For example, in some embodiments, an electron source is used to deliver electrons to the trap 200 (e.g., via one of the end cap electrodes). These electrons may ionize analyte species in the transverse cavity of the trap 200 to form ions that are trapped in the electrode structure. The ion source 505 is operably coupled to a controller, e.g., to enable the source to be turned on and off as desired during operation.

[0082] The system 500 also includes a detector 505 configured to detect charged particles (e.g., ions) ejected from the trap 200. In various embodiments, any suitable detector may be used. In high pressure applications, it may be advantageous to use a detector that can operate at high background pressures, for example a Faraday cup type detector. In lower pressure applications, another type of detector may be used, for example an electron multiplier detector. The detector may be operatively coupled to the controller 502, for example to send signals to the controller that may be processed to generate a mass spectrum.

[0083] The system 500 may include a chamber (not shown) that contains the ion trap assembly. The chamber may be maintained at a selected background pressure. In some embodiments, the background pressure is greater than 5 mTorr, 10 mTorr, 100 mTorr, 1 Torr, 10 Torr, 100 Torr, 500 Torr, or 760 Torr. For example, in some embodiments, the background pressure is in the range of 100 mTorr to 1000 mTorr, or any subrange thereof.

[0084] In some embodiments, system 500 may include an ion trap 200 featuring two or more trapping cavities, as described above. In such cases, mass ejection from each of the cavities may be detected by a single detector 505 to generate a combined enhanced mass spectral signal. For example, in some embodiments, this signal may be generated based on the combined output from at least 2, 5, 10, 15, 20, 25, 50, or 100 or more traps.

[0085] In some embodiments, mass ejection from each of the multiple cavities (or a subset thereof) may be detected by a separate dedicated detector 505. This configuration may be useful when each cavity (or subset of cavities) has different trapping characteristics. For example, in some cases, this type of configuration may increase the range of ion masses that the system 500 can analyze.

[0086] In some embodiments featuring an elongated trapping region, ions are preferentially ejected from a localized portion of the trapping region (e.g., an end or central portion). Thus, in some embodiments, ions may be formed or injected at multiple locations within the trapping region, and ions may be ejected from a substantially single location within the trapping region. In some embodiments, ions may be formed or injected in a first portion of the trapping region, and ions may be ejected from a second portion of the trapping region having a volume smaller than the volume of the first portion.

[0087] In some cases, spatially localized emission may be advantageous. For example, in some embodiments, the resolution of the resulting mass spectrum may be improved. Without wishing to be bound by theory, in some embodiments, it is anticipated that this improved resolution is related to relatively small changes in electrode alignment in a localized region.

[0088] In some embodiments, for example where ions are preferentially ejected from a localized region, one or more mask elements may be positioned to block ions ejected from selected regions of the trap (e.g. regions other than the localized ejection region) from reaching the detector 505. In some embodiments, this may improve the resolution of the detected mass spectrum.

[0089] For example, as discussed above (see, e.g., FIG. 4), in some embodiments the trapping region may include a serpentine region extending between a pair of end points having a number of substantially straight portions and a number of curved portions connecting each pair of the substantially straight portions. In such cases, it may be advantageous to block ions emitted from the curved portions and / or end points while allowing ions emitted from the straight portions to reach the detector 505. In other embodiments, the opposite configuration may be used where ions emitted from the straight portions are blocked while allowing ions emitted from the curved portions and / or end points to reach the detector 505.

[0090] In various embodiments, the system 500 may be implemented as a portable unit, such as a handheld unit. The system 500 may be used to obtain mass spectra from any suitable analyte, including, for example, inorganic compounds, organic compounds, explosives, environmental contaminants, and hazardous materials.

[0091] In some embodiments, system 500 may be implemented as a monitoring unit disposed within a selection area to monitor a selection condition (e.g., the presence or level of one or more selected substances). In some embodiments, system 500 may include a data transmission device (e.g., a wired or wireless communication device) that can be used to communicate detection of a selection condition.

[0092] FIG. 5B shows a mass spectrometry system 7100 (e.g., a portable system) with a housing 7100h that houses a mass spectrometry assembly 710, typically within a vacuum chamber 7105 (shown by the dashed line around the assembly 710). The housing 7100h can removably mount a canister 7110 (or other source) of pressurized buffer gas "B" that is connected to the flow path into the vacuum chamber 7105. The housing 7100h can hold a control circuit 7200 and various power supplies 7205, 7210, 7215, 7220 that are connected to respective wiring to perform the ionization, mass analysis, and detection. The housing 7100h can hold one or more amplifiers, including a power amplifier 7250 that is connected to a processor 7255 to generate a mass spectral output. The system 7100 can be portable and lightweight, typically weighing between 1-15 pounds in use including the buffer gas supply 7110 (not including the vacuum pump). The housing 7100h can be configured as a handheld housing such as a game controller, notebook, smartphone, etc., and in some cases may have a pistol grip 7100g that holds the control circuitry 7200. However, other configurations of control circuitry may be used with other configurations of housing. The housing 7100h can hold a display screen and have a user interface such as a graphical user interface.

[0093] The system 7100 may also be configured to communicate with a smartphone or other popular computing device to transmit data for controlling operation, for example, using a secure APP or other programmable wireless communication protocol.

[0094] The system 7100 can be configured to operate at pressures of about 100 milliTorr or greater up to atmospheric pressure.

[0095] In some embodiments, the mass spectrometer 7100 is configured such that the ion source (ionizer) 730, the ion trap mass analyzer 720 (of any of the types described herein), and the detector 740 operate under substantially isobaric conditions and at pressures greater than 100 millitorr. The term "substantially isobaric conditions" includes conditions where the pressure between any two adjacent chambers differs by no more than 100-fold, but typically no more than 10-fold.

[0096] As shown in Figure 5C, the spectrometer 100 includes a mass analysis assembly 710 and an arbitrary function generator 215g that can provide a low voltage axial RF input 215 to the ion trap 720 during the resonance ejection mass scan. The low voltage axial RF can be between about 100 mVpp and about 8000 mVpp, typically between 200 and 2000 mVpp. To facilitate resonance ejection, the axial RF 215s can be applied to the end cap 722 or 823, typically the end cap 723, or between the two end caps 722 and 723, during the mass scan.

[0097] As shown in Figures 5B and 5C, the apparatus 7100 includes an RF power supply 7205 that provides an input signal to the central electrode 721 of the ion trap 720. The RF power supply 7205 may include an RF signal generator, an RF amplifier, and an RF power amplifier. Each of these components may be held on a circuit board within a housing 7100h that houses the ion trap 720 within the vacuum chamber 7105. In some embodiments, an amplitude ramp waveform may be provided as an input to the RF signal generator to adjust the RF amplitude. A low voltage RF may be amplified by an RF preamplifier and then a power amplifier to generate the desired RF signal. The RF signal may be between about 1 MHz and 1000 MHz depending on the size of the ring electrode arrangement. As is well known to those skilled in the art, the RF frequency may depend on the size of the aperture in the central electrode. A typical RF frequency for a slit shaped aperture of the type shown in Figures 1A-15 with a dimension x0 of 500 μm would be 5-20 MHz. The voltage may be 100 V. 0p ~about 1500V 0pTypically around 500V 0p It can be up to.

[0098] In general terms, electrons are generated by a source 30 in a well-known manner and sent to a mass analyzer (e.g., ion trap) 720 by an accelerating potential. The electrons ionize the sample gas S in the mass analyzer 720. In the ion trap configuration, RF trapping and ejection circuitry is coupled to the mass analyzer 720 to generate an alternating electric field in the ion trap 720 to first trap and then eject ions in proportion to the mass / charge ratio of the ions. The ion detector 40 records the number of ions ejected at various time intervals corresponding to specific ion masses to perform mass spectrochemical analysis. The ion trap dynamically traps ions from the measurement sample using a dynamic electric field generated by an RF drive signal 7205s. By varying the characteristics (e.g., amplitude, frequency, etc.) of the radio frequency (RF) electric field trapping the ions, ions are selectively ejected in proportion to the mass / charge ratio (mass (m) / charge (z)) of the ions. A number of these ions can be digitized for analysis and displayed as a spectrum on the on-board processor and / or remote processor 7255 .

[0099] In its simplest form, a constant RF frequency signal 205s can be applied to the central electrode 21 relative to the two end cap electrodes 22, 23. The amplitude of the central electrode signal 205s can be linearly increased to selectively destabilize ions of different m / z held in the ion trap. This amplitude ejection configuration may not provide optimal performance or resolution. However, this amplitude ejection method can be improved by applying a second signal 215s differentially across the end caps 22, 23. The use of this axial RF signal 215s results in axial excitation of the dipole, which results in resonant ejection of ions from the ion trap when the ion's permanent frequency of oscillation in the trap matches the end cap excitation frequency.

[0100] The ion trap 720 or mass filter may have an equivalent circuit that appears as approximately a pure capacitance. The amplitude of the voltage 7205s for driving the ion trap 720 may be high (e.g., 100V to 1500V) and a transformer coupling may be used to generate the high voltage. A parallel tank circuit may be formed with the inductance of the transformer secondary and the capacitance of the ion trap. It may be desirable to drive this circuit at a resonant frequency to avoid unnecessary losses and / or increased circuit size.

[0101] The vacuum chamber 7105 may be fluidly coupled to at least one pump (not shown). The pump may be any suitable pump, such as a roughing pump and / or a turbo pump, including one or both of the Varian (now Agilent Technologies) TPS Bench Compact Pump System or the TPS Compact Pump System. The pump may be fluidly coupled to the vacuum chamber 105. In some embodiments, the vacuum chamber may be at elevated pressure during operation, for example, greater than 100 millitorr up to atmospheric pressure. Operation at elevated pressure eliminates the need for high vacuum pumps, such as turbomolecular pumps, diffusion pumps, or ion pumps. Operable pressures of approximately greater than 100 millitorr may be readily achieved by mechanical positive displacement pumps, such as rotary vane pumps, reciprocating piston pumps, or scroll pumps.

[0102] Sample S may be introduced into vacuum chamber 7105 along with buffer gas B through an input port toward ion trap 720. The introduction of S from the environment into housing 100h can be at any suitable location (shown from the bottom, by way of example only). One or more sample introduction ports can be used.

[0103] The buffer gas B may be provided as a pressurized canister 7110 of buffer gas as a source. However, any suitable buffer gas or buffer gas mixture including air, helium, hydrogen, or other gases may be used. If air is used, it may be drawn from the atmosphere and does not require a pressurized canister or other source. Typically, the buffer gas includes helium, typically greater than about 90% helium with suitable purity (e.g., 99% or greater). A mass flow controller (MFC) may be used to control the flow of the sample S along with the pressurized buffer gas B from the pressurized buffer gas source 110 into the chamber 105. If ambient air is used as the buffer gas, a controlled leak may be used to inject the air buffer gas and the ambient sample into the vacuum chamber. The design of the controlled leak will depend on the performance of the pump utilized and the desired operating pressure.

[0104] FIG. 9D shows an exemplary timing diagram that can be used to operate / control the various components of the mass spectrometer 7100. A gradient waveform that adjusts the RF amplitude throughout the mass scan can be used to drive the RF amplitude drive signal, and three other pulses control the ionization, detection, and applied axial RF voltages. As shown, initially, 0V can be optionally applied to the gate lens 750 (if used) to allow electrons to pass during the ionization period. Alternatively, this signal can be applied directly to the ionizer 30 to turn on / off the generation of electrons or ions. The RF amplitude drive 7205s can be held at a fixed voltage during the ionization period to trap the ions generated inside the trap 720. At the end of the ionization period, the gate lens voltage (if used) is driven to a potential to block the electron beam of the ionizer 730 and stop ionization. The RF amplitude drive 205s can then be held constant for a defined period, for example about 5 ms, to allow the trapped ions to be collisionally cooled and directed toward the center of the trap. The RF amplitude drive 7205s can be linearly increased to perform a mass instability scan and eject ions in increasing m / z order towards the detector 40. The axial RF signal 7215s can be applied synchronously at the beginning of the linear rise of the RF amplitude signal (shown at t=6 ms, but other times may be used) to gate on at substantially the same time to perform resonance ejection during the mass scan to improve resolution and mass range. Data is acquired during the mass instability scan to generate a mass spectrum. Finally, the RF amplitude drive 7205s can be reduced to a low voltage to clear remaining ions from the trap 720 and prepare it for the next scan. As is well known to those skilled in the art, several methods of ion manipulation can be applied to ion trapping devices such as CIT. All of the various methods for ejection, isolation, and collisional separation can be applied to the ion trapping structures discussed in this application.

[0105] In various embodiments, the devices described herein may be used to perform mass spectrometry techniques known in the art, including tandem mass spectrometry (e.g., as described in U.S. Patent No. 6,399,633). The devices described herein may also be used in trapping charged particles for other applications, such as quantum computing, precision time or frequency references, or any other suitable purpose. EXAMPLES

[0106] Stretch Length Ion Trap Electrode The following examples describe the use of a SLIT type trap to obtain mass spectra. For comparison, in some cases spectra were also obtained using a trap featuring a central electrode with a cylindrical symmetric trapping aperture of the type described in U.S. Pat. No. 5,399,233, issued Oct. 22, 2002. This cylindrical ion trap type will be referred to below as "CIT."

[0107] SLIT and CIT traps were constructed using the following techniques: 800 μm thick copper sheet stock for the middle electrode and 250 μm thick beryllium copper sheet stock for the end cap electrodes were photolithographically patterned and chemically wet etched to the basic shape shown in FIG. 1A (Towne Technologies, Somerville, NJ). The middle electrode space was routinely machined using a 1 mm end mill. CITs were fabricated without additional length to generate cylindrical apertures of radius r0 = 0.5 mm, and SLIT features were machined with y0 dimensions ranging from 2 mm to 6 mm. End cap support electrodes were drilled to a diameter of 5 mm, after which a 100 lines per inch (LPI), 73% transmittance electroformed mesh was bonded across the aperture (Precision Electroforming, Cortland, NY). A 250 μm spacing between the end caps and the central electrode was achieved using Kapton washers, producing a trap with critical dimensions z0 = 650 μm and x0 = 500 μm. In this example, z0 is defined to be half the thickness of the central electrode plus the spacing between the central electrode and the end caps, and x0 is half the width of the narrow dimension of the SLIT space. Other z0 / x0 ratios were also investigated by milling SLIT widths ranging from 0.94 mm to 1.17 mm and observing the change in mass spectral resolution when using a stable isotope of Xe as the sample.

[0108] Equipment design and operation The SLIT electrode assembly was placed inside a custom instrument featuring a mass analyzer of the type shown and described with reference to Figures 5B-5D and modified to include a dual chamber design suitable for use with detectors operating at high or low background pressures. A simplified instrument configuration is shown in Figure 6, which includes a custom aluminum dual chamber design for differential pressure operation with a trapping electrode that serves to limit the conductance.

[0109] Mesitylene gas samples (Sigma Aldrich) and a 10% Xe / 90% He mixture (Air Liquide, 99.999% purity) were injected through a precision leak valve (ULV-150, Vacuum Products) and measured using a full-range vacuum gauge (FRG-700, Varian) and reported as uncorrected values. Helium or nitrogen buffer gas was admitted through a 100 sccm mass flow controller (Omega FMA5408) and absolute pressure was measured using a 2 Torr scale capacitance manometer (MKS627D) with 0.12% accuracy. Operation of the instrument was performed with conventional in-trap electron ionization mode. A yttria-coated iridium disk emitter (ES-525, Kimball Physics) was used with an 80 LPI stainless steel mesh gate electrode to irradiate the trapping region with electrons. All experiments utilized a trapping frequency of 6.4 MHz and nonlinear resonant ejection around the 1 / 3 hexapole resonance with 2.23 MHz axial RF applied to the front end cap while keeping the back end cap grounded to the chamber, although resonant axial RF frequencies were observed for each individual trap. Selectively mass ejected ions were detected by a variety of methods. For operation at low pressures below 100 millitorr, ions were detected using an electron multiplier (2300, DeTech) and the resulting signal was amplified (SR570, Stanford Research Systems) and digitized via a 16-bit analog input card (PXI-6122, National Instruments). For comparison, experiments with CIT were also carried out using this experimental setup. In the experiments using nitrogen at elevated pressure as buffer gas, a Faraday cup detector was used, consisting of a 12.5 mm diameter brass plate used to collect the ions.A charge-sensitive (CoolFET A250CF, AmpTek) was used to convert the collected charge to a voltage suitable for monitoring with an analog input card. When using a Faraday cup detector, both chambers were operated at the same pressure by opening a valve in between the two chambers. For helium buffer gas experiments at higher pressures above 100 millitorr, an electron multiplier was also used. Due to the much higher gas conductance of the SLIT relative to the CIT, several modifications were made. To limit the conductance between the two chambers, a 5 mm × 0.2 mm slot was machined in the 0.250 mm thick electrode and placed behind the end cap electrode on the detector side. Additionally, the DeTech electron multiplier was replaced with a more pressure-resistant MegaSpiralton electron multiplier (Photonis, Sturbridge, Massachusetts).

[0110] Experimental Results The alignment of the three electrodes for CIT was found to have important implications for trap performance. When using rigid end cap electrodes with slots for ion ejection, the SLIT electrode structure added another degree of freedom and more complicated alignment. A fine electroformed mesh (shown in Figure 3) was used to simulate planar end cap electrodes, thus removing three degrees of freedom from the alignment: one rotational and two lateral. In all experiments described, only screw hole alignment was used for the electrode assembly. The primary alignment tolerance of concern was the distance z0 over the entire length of the trap. A variable value of z0 over the entire length of the trap would cause ion ejection to depend on its y-axis position, potentially degrading the spectral resolution.

[0111] In the absence of a DC component in the trapping field, the relationships governing ion trapping and release in a two-dimensional quadrupolar field are the same as in the three-dimensional case. The optimal electrode spacing (250 μm) was therefore believed to be the same as the optimal spacing previously determined for CIT. This was experimentally confirmed by observing the optimal spectral resolution for various z0 / x0 ratios. This particular z0 / x0 ratio was determined to be optimal by milling SLIT widths ranging from 0.94 mm to 1.17 mm and observing the resulting change in resolution of the Xe spectrum shown in FIG. 7. The experimentally observed z0 / x0 ratio value that results in the best spectral resolution is 1.3, which corresponds to a stretched configuration similar to the z0 / r0 value observed in CIT, which is described in (Patent Document 2) published on October 22, 2002. This ratio was observed to be optimal for all values ​​of y0, the length of the stretched distance of the SLIT investigated.

[0112] A representative xenon spectrum, where x0(SLIT) = r0(CIT), and for identical electrode spacing, directly compares SLIT and CIT, is shown in Figure 8A. -4Five hundred scan averages of a Xe / He mixture at 1000 torr were obtained and both were normalized to better compare the relative resolution. The average peak width at FWHM of the five major peaks in the SLIT spectrum of Xe was 0.41 Th compared to 0.44 Th for the CIT. In general, it was observed that the signal intensity of the SLIT spectrum was higher than that obtained with the CIT, while maintaining similar resolution under identical conditions. This increased sensitivity is quantified in Figure 8B, where the change in the all-integrated signal versus sample pressure is plotted for both the SLIT and the CIT. The increase in trapping capacity inherent in trapping ions along a linear range rather than a point is clearly shown by the approximately 10-fold increase in sensitivity. Furthermore, it is expected that the overall ion signal should be linearly related to the value of the y0 parameter of the SLIT, allowing electrode structures to be designed to address the sensitivity requirements. To verify this assumption, several SLIT electrodes of various lengths, i.e., y0 values, were machined with all other dimensions kept equal. The integrated ion current for the Xe spectrum as a function of the length of y0 is shown in Figure 9. These data indeed show a nearly linear dependence of the signal on the trapping length, and show that, assuming a constant trap length y0, the relative gain in signal of the SLIT over the CIT continues to increase as the length of each trap becomes narrower.

[0113] A CIT with an r value of 500 μm was demonstrated to produce mass spectra at pressures above 1 Torr. The SLIT works similarly to the CIT and is therefore expected to operate at higher pressures as well. SLIT mass spectra at He buffer gas pressures between 0.2 and 1 Torr are shown in Figure 10. By reducing the pumping speed, a mass spectrum of 1.3 × 10 -4Experiments were performed by flowing a Xe / He mixture at 1000 psig and adjusting the He buffer flow rate from 1 sccm to 70 sccm. As pressure increases, the electron flux available for ionization decreases due to increased cooling of the thermionic emitter and reduced electron mean free path. For traps of increasing pressure, we attempted to compensate for the electron ionization loss with pressure by increasing the emitter current, ionization time, and emitter bias voltage. To further improve these higher pressure spectra, the axial RF amplitude was also increased with pressure. The experimental conditions for each spectrum in Figure 10 are presented in the table shown in Figure 11. Resolution analysis shows that the peaks broaden at higher pressures, as expected, because collisions with the buffer gas compete with the electric field in controlling the ion trajectories. In agreement with the higher pressure data in CIT, the peaks for the five major isotopes are still clear, with an average peak width of 0.87 Th at heights of 400-500 mTorr.

[0114] Although we have demonstrated the acquisition of spectra at higher pressures, further adjustments in the instrument operation will eventually need to be made to make a practical and highly portable mass spectrometer. One operational change would be to use nitrogen or air as a buffer gas instead of helium. Both clean nitrogen and air can be generated at the point of use, eliminating the need for a helium source. Another change would be to use a more pressure tolerant detector, such as a Faraday cup. It would therefore be useful to analyze an organic sample with nitrogen as a buffer gas and examine how the SLIT design would perform while using a pressure tolerant Faraday cup detector. Spectra of mesitylene collected at 9 mTorr, 80 mTorr, and 1000 mTorr in nitrogen buffer gas are shown in Figure 12. Even at lower pressures, the peak widths are broader than those in the He buffer gas due to the greater momentum transfer associated with collisions of nitrogen molecules. Again, the peak widths increase significantly with pressure. Note that the irregular shape of the background is an artifact of how the CoolFET preamplifier for the detector works and can be easily accounted for in other experimental designs.

[0115] By forming a parallel array of multiple SLITs from one intermediate electrode and two end cap electrodes, the number of ions trapped and therefore the final detected signal is increased without any operational difference from a single trap device. For example, FIG. 13A shows the intermediate electrode of a three SLIT array. This was fabricated by machining three identical SLIT features, 1 mm wide and separated by 0.5 mm. The SLIT array utilizes the same electroformed mesh end cap as previously described. FIG. 13B shows the mass spectrum obtained using this configuration for 30 mTorr xenon and He buffer. The data shows good signal. The moderate broadening of the peak width compared to a single trap is due to slight differences in trap tolerances due to machining accuracy.

[0116] With reference to FIG. 14A, experiments were performed in which the central electrode for the SLIT was routinely machined with a 1.0 mm end mill to provide a serpentine aperture with three straight sections (4 mm) and two connecting curved sections. Each straight section was separated from the others by a 0.5 mm wide post. The trap was constructed with the same end cap electrodes and spacers as the conventional SLIT described above and placed inside the chamber shown in FIG. 6. The 8.0×10 -5 Mass spectrometry of 1000 torr of Xe was performed to obtain the spectrum shown in the figure. Sufficient resolution and good signal intensity were observed.

[0117] Referring to FIG. 14B, the following experiment was set up using the same set of electrodes as shown in FIG. 14A to observe ions moving through the entire length of the serpentine trap. Additional charged particle mask elements were added to control the ionization and ion ejection locations. A single copper mask element was placed on the ionization end cap to allow ionization of only the top third of the trapping volume. A second copper mask element was placed on the detector end cap to block ion emission from all but the bottom third of the trap. In this way, the only way an ion signal can be seen is if ions are formed in the top third of the serpentine SLIT structure and at least a portion of the ions move into the bottom third before ejection. 3.5×10 ions in 30 mTorr He buffer gas. -5 This was observed using 2000 torr of Xe, the spectrum of which is shown in Figure 14B.

[0118] The same experimental setup was used to test the shortest time it takes for ions to fill the entire trapping volume. The time between the onset of ionization and the first emitted Xe peak was shortened as much as possible. Ions were still ejected and observed at the detector in as little as 1.5 ms, which is the experimental limit of this setup. Therefore, it may be concluded that ions can be formed and travel the entire length of this serpentine trap at least as fast as 1.5 ms.

[0119] Referring to FIG. 15, an array of three SLITs identical to the 5 mm single SLIT described above was machined with one intermediate electrode separated by 0.50 mm. In the experiment shown, ion ejection occurs at various points in the mass gradient by varying z0 across the three traps. Taking every precaution to ensure the most parallel end caps, the trap (top insert) was assembled using this intermediate electrode. The resulting 3.0×10 traps in 30 mTorr He were -5 The Xe spectrum at 1000 Hz is shown in the top graph. The chamber was then opened and, without any other modifications, the top SLIT alignment screws (bottom inserts) shown were over-torqued to provide a tilt in the two end caps with respect to the middle electrode, resulting in different values ​​of z0 in each of the traps. As theoretically predicted, during mass analysis operation, ions are ejected at various points within the RF gradient, such that the overall spectrum is composed of three individual spectra that overlap each other. This experiment also shows that this over-torque technique produces sufficient change in the z dimension to have a noticeable effect on the mass spectrum.

[0120] Referring to Figure 16, an additional experiment was performed to show the effect of varying the z0 dimension along a single trap. A standard 5 mm SLIT of the type described above was assembled and tested in the same manner as the three SLIT array in the previous slide, with the exception that this single SLIT was rotated 90°, so that the variation in z0 was along its y0 dimension. In this case, a 3.0 x 10 trap in 30 mTorr He was used. -5 The spectra obtained at 2000 torr of Xe were identical whether the end caps were parallel or tilted. This was true for both moderately trapped ions (1 ms ionization) and for large amounts of trapped ions (50 ms ionization).

[0121] 17, a single aperture SLIT was fabricated where the x0 dimension was varied by 10% across the y0 dimension, resulting in a complementary experiment to that described in FIG 16. Again, a basic mass spectrometry experiment was performed, with a 3.0×10 -5 1000 torr of Xe was analyzed. The resulting spectrum is shown. This spectrum is not as well sharpened as the previously shown spectra, and theory suggests that the width of a single peak would be greater than 5 Th, which would completely blur the spectrum. This experiment combined with the results shown in the experiment in Figure 16 shows that the SLIT geometry is much less susceptible to poor mechanical tolerances than initially anticipated.

[0122] It is believed that the tolerance of SLIT performance to variations in both the x0 and z0 dimensions, in some configurations, is due to spatially specific ion ejection, i.e., all ions are ejected over a narrow range of the y0 dimension. The x0 and z0 dimensions can be seen to vary significantly over the entire y0 range in the experiments described in Figures 16 and 17, but this variation is negligible over the range of y0 where ions are actually ejected. This spatially specific ejection was further investigated using the setup shown in Figure 16 by placing a copper shim electrode behind one half of the trap to sufficiently block all ion ejection from that section. The experiment was repeated on the other half of the trap, and it was determined that the entire ion signal observed in the entire trap was the result of ejection from only one half. It is believed that, in some configurations, the trap dimensions can be tuned for ion ejection from any desired point, and the resolution of the device is determined by the geometry of the trap in the ejection region and is relatively insensitive to the geometry of the regions where ions are not being ejected. Furthermore, such a structure is less sensitive to overall trapping electrode structure alignment tolerances, yet still achieves the overall dimensional charge capacity of the SLIT structure.

[0123] Retrospectively, we have successfully developed a high capacity ion trap by stretching the CIT in the horizontal direction. This trap has critical dimensions z0=0.650 μm, x0=500 μm, and y0=5.00 mm and has been characterized and compared to a similar sized CIT operating under similar conditions. The signal appeared to increase by an order of magnitude while maintaining the same resolution as the CIT. The trapping volume appeared to increase linearly with extension in the y direction.

[0124] Operation of the SLIT at elevated buffer gas pressures has been successfully performed using both helium and nitrogen at buffer gas pressures up to 1 Torr. Both xenon and mesitylene were analyzed using a high-voltage electron multiplier in a differentially pumped vacuum chamber and a Faraday cup in an isobaric chamber, respectively.

[0125] Although various inventive embodiments have been described and illustrated herein, those skilled in the art will readily envision various other means and / or structures for performing the functions and / or obtaining the results and / or one or more of the advantages described herein, and such variations and / or modifications are deemed to be within the scope of the inventive embodiments described herein. More specifically, those skilled in the art will readily appreciate that any parameters, dimensions, materials, and configurations described herein are meant to be exemplary, and that the actual parameters, dimensions, materials, and / or configurations will depend on the specific application for which the inventive teachings are used. Those skilled in the art will recognize or be able to ascertain using no more than routine experimentation numerous equivalents to the specific inventive embodiments described herein. Thus, the foregoing embodiments are presented by way of example only, and it will be understood that within the scope of the appended claims and their equivalents, the inventive embodiments may be practiced otherwise than as specifically described and claimed. The inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and / or method described herein. Furthermore, any combination of two or more such features, systems, articles, materials, kits, and / or methods is included within the inventive scope of the present disclosure, if such features, systems, articles, materials, kits, and / or methods are not mutually inconsistent.

[0126] The above-described embodiments can be implemented in any of numerous ways. For example, each embodiment may be implemented using hardware, software, or a combination thereof. When implemented in software, the software code can be executed on any suitable processor, or collection of processors, whether located on a single computer or distributed among multiple computers.

[0127] A computer may also have one or more input and output devices. These devices may be used, among other things, to provide a user interface. Examples of output devices that may be used to provide a user interface include a printer or display screen for visually presenting output, and a speaker or other sound generating device for audibly presenting output. Examples of input devices that may be used for a user interface include keyboards and pointing devices such as mice, touch pads, digitizing tablets, etc. As another example, a computer may receive input information via speech recognition or in other acoustic forms.

[0128] Such computers may be interconnected by one or more networks in any suitable manner, including local or wide area networks, such as an enterprise network, an Intelligent Network (IN), the Internet, etc. Such networks may be based on any suitable technology and operate according to any suitable protocol, and may include wireless networks, wired networks, or fiber optic networks.

[0129] A computer utilized to perform at least a portion of the functionality described herein may include a memory, one or more processing units (also referred to herein simply as a "processor"), one or more communication interfaces, one or more display units, and one or more user input devices. The memory may include any computer-readable medium and may store computer instructions (also referred to herein as "processor-executable instructions") for performing various functions described herein. The processing units may be used to execute the instructions. The communication interfaces may be coupled to a wired or wireless network, bus, or other communication means, thus allowing the computer to send and / or receive communication information to and from other devices. A display unit may be provided, for example, to allow a user to view various information in connection with the execution of the instructions. A user input device may be provided, for example, to allow a user to manually adjust, select, input data or various other information, and / or interact with the processor in any of a variety of ways during execution of the instructions.

[0130] The various methods or processes outlined herein may be coded as software executable on one or more processors utilizing various operating systems or platforms. Further, such software may be written using any suitable programming language and / or programming or scripting tools, and compiled as executable machine code or intermediate code that runs on a framework or virtual machine.

[0131] In this regard, the various inventive concepts may be embodied as a computer readable storage medium (or multiple computer readable storage media) (e.g., a computer memory, one or more floppy disks, compact disks, optical disks, magnetic tapes, flash memory, circuitry on a field programmable gate array or other semiconductor device, or other non-transitory or tangible computer storage medium) that is encoded with one or more programs that, when executed on one or more computers or processors, perform methods that implement the various embodiments of the invention as discussed above. The computer readable media may be portable such that the programs stored thereon can be loaded onto one or more different computers or other processors to implement various aspects of the invention as previously discussed.

[0132] The terms "program" or "software" are used herein in a generic sense to refer to any type of computer code or set of computer-executable instructions that can be used to program a computer or other processor to perform various aspects of the embodiments as described above. It should be further understood that, according to one aspect, one or more computer programs that, when executed, perform the methods of the present invention need not reside on a single computer or processor, but may be distributed in a modular manner among several different computers or processors to perform various aspects of the present invention.

[0133] Computer-executable instructions may be in many forms, such as program modules, executed by one or more computers or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc., that perform particular tasks or implement particular abstract data types. Typically the functionality of the program modules may be combined or distributed as desired in various embodiments.

[0134] Additionally, the data structure may be stored in any suitable form on the computer-readable medium. For ease of explanation, the data structure may be depicted as having fields that are related via their locations within the data structure. Furthermore, such relationships may be achieved by allocating storage for the fields with their locations in the computer-readable medium that conveys the relationships between each of the fields. However, any suitable mechanism may be used to establish relationships between information in the fields of the data structure, including the use of pointers, tags, or other mechanisms that establish relationships between data elements.

[0135] Also, various inventive concepts may be embodied as one or more methods from which examples are derived. The operations performed as part of a method may be ordered in any suitable manner. Thus, embodiments may be constructed in which operations are performed in an order different from that described, which may include performing some operations simultaneously even though they are shown as sequential operations in an example embodiment.

[0136] All definitions defined and used herein should be understood to be controlling in light of dictionary definitions, definitions in documents incorporated by reference, and / or ordinary meaning of the defined terms.

[0137] The indefinite articles "a" and "an," as used in the specification and claims, should be understood to mean "at least one," unless clearly indicated to the contrary.

[0138] The phrase "and / or" as used in the specification and claims should be understood to mean "either or both" of the elements so conjoined, i.e., elements that are present in a conjunctive manner and elements that are present in a disjunctive manner. Multiple elements listed with "and / or" should be construed in the same manner, i.e., "one or more" of the elements so conjoined. In some cases, other elements may be present other than the elements specifically named by the "and / or" clause, whether related or unrelated to the specifically named element. Thus, as a non-limiting example, reference to "A and / or B" when used in connection with open-ended terminology such as "comprising" may refer, for example, in one embodiment to only A (optionally including elements other than B), in another embodiment to only B (optionally including elements other than A), and in yet another embodiment to both A and B (optionally including other elements).

[0139] As used herein and in the claims, "or" should be understood to have the same meaning as "and / or" above. For example, when separating items in a list, "or" or "and / or" is to be construed to be inclusive, i.e., including at least one of, but also including more than one, possibly including additional unlisted items, of a number or list of elements. Terms clearly indicated to the contrary, such as "only one of" or "exactly one of," or, when used in the claims, "consisting of," refer to the inclusion of exactly one element of a number or list of elements. In general, the term "or" as used herein is to be construed as indicating exclusively exclusive alternatives (i.e., "either," "one of," "only one of," "exactly one of," etc.) when preceded by exclusive terms, such as "either," "one of," "exactly one of," "exclusive of," etc. "Consisting essentially of," as used in the claims, shall have its original meaning as used in the field of patent law.

[0140] As used herein and in the claims, the phrase "at least one" in reference to a list of one or more elements should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed in the list of elements, and not excluding any combination of each element in the list of elements. Also, by this definition, in some cases there may be elements other than those specifically named in the list of elements to which the phrase "at least one" refers, whether related or unrelated to the specifically named element. Thus, as a non-limiting example, "at least one of A and B" (or, similarly, "at least one of A or B" or, similarly, "at least one of A and / or B") refers, for example, in one embodiment to at least one (possibly including more than one) A and no B (possibly including elements other than B), in another embodiment to at least one (possibly including more than one) B and no A (possibly including elements other than A), and in yet another embodiment to at least one (possibly including more than one) A and at least one (possibly including more than one) B (and also possibly including other elements).

[0141] In the claims, as well as in the foregoing specification, any transitional phrases such as "comprising," "including," "carrying," "having," "containing," "holding," "composed of," and the like, are to be understood to be open-ended, i.e., to mean inclusive of, but not limited to. Only the transitional phrases "consisting of" and "consisting essentially of" shall be exclusive or semi-exclusive transitional phrases, as respectively set forth in Section 2111.03 of the United States Patent Office Manual of Patent Search Procedures.

[0142] [Appendix 1] A small electrode device for trapping charged particles, the small electrode device having a longitudinal direction: a first end cap electrode; a central electrode having an aperture; a second end cap electrode; Equipped with the aperture extends along the longitudinal direction through the central electrode, and the central electrode surrounds the aperture in a transverse plane perpendicular to the longitudinal direction to define a transverse cavity for trapping charged particles; The opening in the central electrode is elongated in the lateral plane. [Appendix 2] the ratio of the major dimension to the minor dimension of the elongated aperture is greater than 1.0; 2. The apparatus of claim 1, wherein the larger dimension is the longest straight line distance across the opening in the lateral plane and the smaller dimension is the longest straight line distance across the opening in the lateral plane perpendicular to the line corresponding to the larger dimension. [Appendix 3] 2. The apparatus of claim 1, wherein the ratio of the larger dimension to the smaller dimension is greater than 1.5. [Appendix 4] 2. The apparatus of claim 1, wherein the ratio of the larger dimension to the smaller dimension is greater than 2.0. [Appendix 5] 2. The apparatus of claim 1, wherein the ratio of the larger dimension to the smaller dimension is greater than 3.0. [Appendix 6] 2. The apparatus of claim 1, wherein the ratio of the larger dimension to the smaller dimension is greater than 5.0. [Appendix 7] 2. The apparatus of claim 1, wherein the ratio of the larger dimension to the smaller dimension is greater than 10.0. [Appendix 8] the ratio of the elongated aperture's major dimension to its average minor dimension is greater than 1.0; 2. The apparatus of claim 1, wherein the larger dimension is the longest straight line distance across the opening in the lateral plane, and the average smaller dimension is the integrated average of the distances along each straight line across the opening in the lateral plane perpendicular to the line corresponding to the larger dimension, at every location along the line corresponding to the larger dimension. [Appendix 9] 9. The apparatus of claim 8, wherein the ratio of the larger dimension to the average of the smaller dimensions is greater than 1.5. [Appendix 10] 9. The apparatus of claim 8, wherein the ratio of the larger dimension to the average smaller dimension is greater than 2.0. [Appendix 11] 9. The apparatus of claim 8, wherein the ratio of the larger dimension to the average smaller dimension is greater than 3.0. [Appendix 12] 9. The apparatus of claim 8, wherein the ratio of the larger dimension to the average smaller dimension is greater than 4.0. [Appendix 13] 9. The apparatus of claim 8, wherein the ratio of the larger dimension to the average smaller dimension is greater than 5.0. [Appendix 14] 9. The apparatus of claim 8, wherein the ratio of the larger dimension to the average smaller dimension is greater than 10.0. [Appendix 15] the elongated opening comprises an elongated channel having first and second ends, the elongated channel having a ratio of channel length to channel width greater than 1.0; 2. The device of claim 1, wherein the channel length is the shortest curvilinear distance across the channel in the lateral plane from the first end to the second end, and the channel width is the longest straight line distance across the channel in the lateral plane perpendicular to the curve corresponding to the channel length. [Appendix 16] 16. The device of claim 15, wherein a ratio of the channel length to the channel width is greater than 1.5. [Appendix 17] 16. The device of claim 15, wherein a ratio of the channel length to the channel width is greater than 2.0. [Appendix 18] 16. The device of claim 15, wherein a ratio of the channel length to the channel width is greater than 3.0. [Appendix 19] 16. The device of claim 15, wherein a ratio of the channel length to the channel width is greater than 4.0. [Appendix 20] 16. The device of claim 15, wherein a ratio of the channel length to the channel width is greater than 5.0. [Appendix 21] 16. The device of claim 15, wherein a ratio of the channel length to the channel width is greater than 10.0. [Appendix 22] 22. The device of any one of claims 1 to 21, wherein the smaller dimension is less than 10 mm. [Appendix 23] 15. The device of any one of claims 8 to 14, wherein the smaller average dimension is less than 10 mm. [Appendix 24] 15. The device of any one of claims 8 to 14, wherein the average channel width is less than 10 mm. [Appendix 25] 15. The device of any one of claims 8 to 14, wherein the smaller dimension is less than 5 mm. [Appendix 26] 15. The device of any one of claims 8 to 14, wherein the smaller average dimension is less than 5 mm. [Appendix 27] 22. The device of any one of claims 15 to 21, wherein the average channel width is less than 5 mm. [Appendix 28] 8. The device of any one of claims 1 to 7, wherein the smaller dimension is less than 1 mm. [Appendix 29] 15. The device of any one of claims 8 to 14, wherein the smaller average dimension is less than 1 mm. [Appendix 30] 22. The device of any one of claims 15 to 21, wherein the average channel width is less than 1 mm. [Appendix 31] 8. The device of any one of claims 1 to 7, wherein the smaller dimension is less than 0.1 mm. [Appendix 32] 15. The device of any one of claims 8 to 14, wherein the smaller average dimension is less than 0.1 mm. [Appendix 33] 22. The device of any one of claims 15 to 21, wherein the average channel width is less than 0.1 mm. [Appendix 34] 34. The apparatus of any one of claims 1-33, wherein each end cap comprises a planar conductive member having a plurality of holes extending therethrough along the longitudinal direction. [Appendix 35] 35. The apparatus of claim 34, wherein each planar conductive member extends transversely to the longitudinal axis and is configured to be electron transparent or ion transparent. [Appendix 36] 36. The apparatus of claim 35, wherein each planar conductive member is a wire mesh. [Appendix 37] 37. The apparatus of claim 36, wherein the conductive mesh protrudes into the central electrode along the longitudinal axis to completely surround the elongated opening in the central electrode in the lateral plane. [Appendix 38] 38. The apparatus of any one of claims 1-37, wherein each end cap electrode comprises a conductive material having an opening to define a path for the charged particles along the longitudinal direction through the openings in the end cap and central electrode. [Appendix 39] 39. The apparatus of claim 38, wherein the opening in at least one end cap comprises a circular opening having a perimeter greater than the larger dimension of the opening in the central electrode. [Appendix 40] 39. The apparatus of claim 38, wherein the opening in at least one end cap comprises a circular opening having a perimeter greater than the channel length of the opening in the central electrode. [Appendix 41] 41. The apparatus of claim 39 or 40, wherein the opening in at least one end cap comprises an elongated slit. [Appendix 42] 42. The apparatus of any one of claims 39 to 41, wherein the opening in at least one end cap is substantially filled with a conductive mesh. [Appendix 43] 43. The device of any one of claims 1 to 42, wherein the elongated opening comprises an elongated slit. [Appendix 44] 44. The device of any one of claims 1-43, wherein the elongated opening comprises a serpentine portion. [Appendix 45] 45. The device of any one of claims 1-44, wherein the elongated opening comprises a spiral portion. [Appendix 46] 46. ​​The device of any one of claims 1 to 45, wherein the elongated opening comprises a portion of a circular slit. [Appendix 47] 47. The apparatus of any one of claims 1 to 46, further comprising a first insulating spacer disposed along the longitudinal direction between the first end cap electrode and the central electrode, and a second insulating spacer disposed between the central electrode and the second end cap electrode. [Appendix 48] 48. The apparatus of any one of claims 1-47, further comprising a power source coupled to the electrodes to generate an oscillating electromagnetic field between the central electrode and the end cap electrodes. [Appendix 49] 49. The apparatus of any one of claims 1-48, wherein the transverse cavity defined by the laterally elongated opening in the central electrode has a vertical dimension 2z0 of less than about 10 mm. [Appendix 50] 50. The apparatus of any one of claims 1-49, wherein the transverse cavity defined by the laterally elongated opening in the central electrode has a vertical dimension 2z0 of less than about 1 mm. [Appendix 51] 51. The apparatus of any one of claims 1 to 50, wherein the transverse cavity defined by the laterally elongated opening in the central electrode has a vertical dimension 2z0 of less than about 0.5 mm. [Appendix 52] 52. The apparatus of any one of claims 1 to 51, wherein the transverse cavity defined by the laterally elongated opening in the central electrode has a vertical dimension 2z0 of less than about 0.1 mm. [Appendix 53] 53. The apparatus of any one of claims 1 to 52, wherein the transverse cavity defined by the laterally elongated opening in the central electrode has a vertical dimension 2z0 that is substantially uniform across the lateral dimension of the cavity. [Appendix 54] 54. The apparatus of any one of claims 1 to 53, wherein the transverse cavity defined by the laterally elongated opening in the central electrode has a vertical dimension 2z0 that varies across one or more of the lateral dimensions of the cavity. [Appendix 55] 55. The device of any one of claims 1-54, wherein the elongated opening in the central electrode includes at least one channel portion having a lateral length and a lateral width, and the width is substantially uniform along the channel portion. [Appendix 56] 56. The device of any one of claims 1-55, wherein the elongated opening in the central electrode includes at least one channel portion having a lateral length and a lateral width, and the width varies along the lateral length of the channel portion. [Appendix 57] 57. The apparatus of any one of claims 1 to 56, further comprising at least one mask element configured to block transmission of electrons or ions to or from a localized region of the transverse cavity. [Appendix 58] 58. The apparatus of any one of claims 1 to 57, wherein the central electrode comprises a plurality of apertures, the plurality of apertures being configured to define respective transverse cavities for trapping charged particles. [Appendix 59] 59. The apparatus of any one of claims 1-58, wherein the elongated aperture comprises a serpentine slit in the central electrode having a plurality of substantially straight portions and a plurality of curved portions connecting pairs of the substantially straight portions. [Appendix 60] 37. The apparatus of claim 36, comprising one or more mask elements configured to block ion transmission from a localized region of the transverse cavity corresponding to the curved portion. [Appendix 61] 37. The apparatus of claim 36, comprising one or more mask elements configured to block ion transmission from a localized region of the transverse cavity corresponding to the straight portion. [Appendix 62] A small electrode assembly for trapping charged particles, the small electrode assembly comprising a device according to any one of claims 1 to 61; at least one electrical signal source coupled to the ion trap assembly; A mass spectrometer comprising: A mass spectrometer, wherein the electrode assembly is configured to generate an electromagnetic field in response to a signal from the electrical signal source to generate an ion trapping region disposed within the transverse cavity. [Appendix 63] 63. The mass spectrometer of claim 62, further comprising a controller operably coupled to the electrical signal source and configured to adjust the signal source to perform mass selective ejection of ions from the trapping region. [Appendix 64] 64. The mass spectrometer of claim 63, wherein at least one of the end cap electrodes is configured to enable ejection of ions from the trapping region. [Appendix 65] 65. The mass spectrometer of claim 64, further comprising an ion source configured to inject or form ions that are trapped within the trapping region. [Appendix 66] 46. ​​The mass spectrometer of any one of claims 62 to 45, further comprising at least one detector configured to detect ions emitted from the assembly. [Appendix 67] 67. The mass spectrometer of claim 66, wherein the at least one detector comprises a Faraday cup detector. [Appendix 68] 67. The mass spectrometer of claim 66, wherein the at least one detector comprises an electron multiplier. [Appendix 69] 69. The mass spectrometer of any one of claims 62 to 68, comprising a chamber including the ion trapping region, the chamber being configured such that during operation, the chamber has a background pressure greater than 100 milliTorr. [Appendix 70] 69. The mass spectrometer of any one of claims 62 to 68, comprising a chamber including the ion trapping region, the chamber being configured such that during operation, the chamber has a background pressure greater than 1 Torr. [Appendix 71] 69. The mass spectrometer of any one of claims 62 to 68, comprising a chamber including the ion trapping region, the chamber being configured such that during operation, the chamber has a background pressure greater than 10 Torr. [Appendix 72] 69. The mass spectrometer of any one of claims 62 to 68, comprising a chamber including the ion trapping region, the chamber being configured such that during operation, the chamber has a background pressure greater than 100 Torr. [Appendix 73] 69. The mass spectrometer of any one of claims 62 to 68, comprising a chamber including the ion trapping region, the chamber being configured such that during operation, the chamber has a background pressure greater than 500 Torr. [Appendix 74] 69. The mass spectrometer of any one of claims 62 to 68, comprising a chamber including the ion trapping region, the chamber being configured to have a background pressure greater than 760 Torr during operation. [Appendix 75] the central electrode having a plurality of apertures, each of the apertures defining a transverse cavity for trapping charged particles, each cavity including a separate region of the plurality of ion trapping cavity regions; 75. The mass analyzer of any one of claims 62 to 74, wherein the mass analyzer is configured to generate an enhanced output signal based on the combined mass-selective ion ejection output from the multiple ion trapping cavity regions. [Appendix 76] applying an electrical signal to a small electrode assembly for trapping charged particles, the assembly including a device according to any one of claims 1 to 61; generating an electromagnetic field in response to the electrical signal, the electromagnetic field having an ion trapping region located within the cavity of the ion trap assembly; Mass spectrometry, including [Appendix 77] adjusting the signal source to effect mass selective ejection of ions from the trapping region; detecting ions ejected from the trapping region to produce a mass spectrometry signal; outputting said mass spectrometry signal; 77. The method of claim 76, further comprising: [Appendix 78] 80. The method of claim 77, further comprising the step of implanting or forming ions that are trapped in the trapping region. [Appendix 79] 80. The method of claim 78, wherein at least one of the first and second end cap electrodes comprises a planar conductive member having a plurality of holes extending therethrough, the planar conductive member configured to be electron-transparent or ion-transparent; injecting ions or electrons into the trapping region through the plurality of holes in the planar conductive member. [Appendix 80] 80. The method of any one of claims 76 to 79, comprising ejecting ions from a localized portion of the trapping region. [Appendix 81] 81. The method of claim 80, wherein the localized portions correspond to lateral ends of the trapping region. [Appendix 82] forming or implanting ions at a plurality of locations within a trapping region; ejecting ions from a substantially single location within the trapping region; 82. The method of claim 80 or 81, comprising: [Appendix 83] forming or implanting ions in a first portion of the trapping region; ejecting ions from a second portion of the trapping region having a volume smaller than the volume of the first portion; 82. The method of claim 80 or 81, comprising: [Appendix 84] the trapping region includes a serpentine region extending between a pair of end points having a plurality of substantially straight portions and a plurality of curved portions connecting pairs of the substantially straight portions; the first portion corresponds to one or more of the substantially straight portions; and 84. The method of claim 83, wherein the second portion corresponds to at least one of the curved portion and the end point. [Appendix 85] 85. The method of any one of claims 77 to 84, comprising selectively blocking ions released from a portion of the trapping region to prevent the ions from being detected. [Appendix 86] 86. The method of any one of claims 77 to 85, comprising selectively blocking electrons or ions from a source from entering a portion of the trapping region. [Appendix 87] 87. The method of any one of claims 76 to 86, comprising generating an electromagnetic field having a plurality of separate ion trapping regions in response to the electrical signal. [Appendix 88] 88. The method of claim 87, wherein at least two of the ion trapping regions have different ion trapping stability characteristics. [Appendix 89] 88. The method of claim 87, wherein each of the ion trapping regions has substantially the same ion trapping stability characteristics. [Appendix 90] 90. The method of any one of claims 87 to 89, further comprising adjusting the signal source to perform mass selective ejection of ions from each of the trapping regions. [Appendix 91] 91. The method of claim 90, comprising detecting ions ejected from multiple trapping regions with a single detector to produce a combined mass spectrometry signal. [Appendix 92] 91. The method of claim 90, comprising detecting ions ejected from each of a plurality of trapping regions with a respective detector to generate a respective mass spectrometry signal.

Claims

1. 1. An ion trap for mass spectrometry, comprising: a planar electrode, the planar electrode including one or more openings extending therethrough; end cap electrodes disposed on either side of the planar electrode, each of the end cap electrodes including at least one aperture; at least one of the one or more apertures has a cross-sectional shape in the plane of the planar electrode that has an elongated curved trapping region within the planar electrode; Ion trap.

2. The ion trap of claim 1 , wherein at least a portion of the elongated curved trapping region is an arc in the plane of the planar electrode.

3. The ion trap of claim 1 , wherein at least a portion of the elongated curved trapping region has a circular or spiral aperture.

4. The ion trap of claim 1 , wherein at least one of the one or more apertures comprises an elongated linear trapping region in the planar electrode.

5. The ion trap of claim 4 wherein at least a portion of the elongated straight trapping region is connected to at least a portion of the elongated curved trapping region.

6. The ion trap of claim 5 , wherein the elongated straight trapping region and the elongated curved trapping region combined form a serpentine trapping region within the planar electrode.

7. The ion trap of claim 1 , wherein at least one of the one or more apertures has a cross-sectional shape that is generally non-linear.

8. The ion trap of claim 1 , wherein at least one of the one or more apertures comprises a plurality of apertures.

9. The ion trap of claim 8 , wherein the plurality of apertures are arranged concentrically about a common point of the planar electrode.

10. The ion trap of claim 1 , further comprising a mask positioned to selectively obscure portions of the one or more apertures to control the location within the planar electrode from which ions are ejected.

11. The ion trap of claim 1 , wherein each of the end cap electrodes includes a plurality of apertures aligned axially of the ion trap with the one or more apertures in the planar electrode.

12. The ion trap of claim 11 , wherein at least a portion of the plurality of apertures in each of the end cap electrodes have a cross-sectional shape that corresponds to a cross-sectional shape of the one or more apertures in the planar electrode.

13. 1. A mass spectrometry system comprising: An ion source; An ion trap according to claim 1 or 2; An ion detector; 1. An electronic processor comprising: applying one or more potentials to eject trapped ions from the at least one of the one or more apertures; determining mass spectral information about the sample based on an ion signal produced by the ion detector and corresponding to the ejected ions; the electronic processor configured to A mass spectrometry system comprising:

14. 14. The system of claim 13, wherein the electronic processor is configured to apply the one or more potentials to selectively eject trapped ions from only a portion of the one or more apertures.

15. 1. A method for analyzing a sample, comprising: Ions are generated from the sample; trapping the generated ions in an ion trap comprising a planar electrode including one or more apertures extending therethrough, where at least one of the one or more apertures has a cross-sectional shape in the plane of the planar electrode that has an elongated curved trapping region within the planar electrode; releasing at least a portion of the trapped ions from the ion trap; measuring an ion signal corresponding to at least a portion of the released trapped ions; determining mass spectral information about the sample based on the measured ion signals; The method includes:

16. The method of claim 15 , wherein at least a portion of the elongated curved trapping region is arcuate in the plane of the planar electrode.

17. The method of claim 15 , wherein at least a portion of the elongated curved trapping region has a circular or spiral opening.

18. The method of claim 15 , wherein at least one of the one or more apertures comprises an elongated linear trapping region in the planar electrode.

19. The method of claim 15 , wherein at least a portion of the elongated straight trapping region is connected to at least a portion of the elongated curved trapping region.

20. 20. The method of claim 19, wherein the elongated straight trapping region and the elongated curved trapping region combined form a serpentine trapping region within the planar electrode.

21. The method of claim 15 , wherein at least one of the one or more openings has a cross-sectional shape that is generally non-linear.

22. The method of claim 15 , wherein at least one of the one or more apertures comprises a plurality of apertures.

23. The method of claim 22 , wherein the plurality of apertures are concentrically disposed about a common point of the planar electrode.

24. 16. The method of claim 15, further comprising a mask positioned to selectively obscure portions of the one or more apertures to control the location within the planar electrode at which at least some of the trapped ions are released from the ion trap.

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