CURVED ION GUIDES AND RELATED SYSTEMS AND METHODS

An ion guide includes a plurality of lenses arranged in series along a curved central axis. Each lens includes a body and a central opening, and the central openings of the plurality of disks define a curved ion guide region. The ion guide includes an ion deflector configured to apply a radial DC electric field across the ion guide region and along the curved central axis. The ion deflector includes at least one DC voltage source that is configured to apply a positive DC voltage to at least some of the plurality of lenses and a negative DC voltage to at least some of the plurality of lenses.

BACKGROUND

One or more ion guides may be used for guiding ions from a given source to a given destination in an instrument such as a mass spectrometer. The ion guide may be curved to provide ion optics with a longer length and/or more compact footprint.

SUMMARY

Some embodiments of the present technology are directed to an ion guide including a plurality of lenses arranged in series along a curved central axis. Each lens includes a body and a central opening, and the central openings of the plurality of lenses define a curved ion guide region. The curved ion guide region begins at an ion entrance and ends at an ion exit. The ion guide includes an ion deflector configured to apply a radial DC electric field across the ion guide region and along the curved central axis. The ion deflector includes at least one DC voltage source that is configured to apply a positive DC voltage to at least some of the plurality of lenses and a negative DC voltage to at least some of the plurality of lenses.

In some embodiments, the at least one DC voltage source is configured to apply DC voltage in a repeating pattern comprising applying one of a positive DC voltage and a negative DC voltage to a plurality of consecutive lenses in the series followed by applying the other one of a positive DC voltage and a negative DC voltage to at least one lens in the series that directly follow the plurality of consecutive lenses. The at least one lens may include a single lens in the series. The plurality of consecutive lenses may include at least three consecutive lenses in the series.

In some embodiments, the ion entrance and the ion exit define an angle of 90 or 180 degrees therebetween.

In some embodiments, each lens is disk shaped, and the body of each lens is continuous and surrounds the central opening. Each of the lenses may have an outer diameter of between 10 mm and 40 mm. The central opening of each of the lenses may have a diameter of between 2.5 mm and 8 mm.

In some embodiments, the lenses are spaced apart and electrically isolated from one another.

In some embodiments, the ion entrance and the ion exit define an angle of 90 degrees therebetween, and the plurality of lenses includes between 40 and 60 lenses.

In some embodiments, the at least one DC voltage source includes a plurality of DC voltage sources configured to simultaneously apply a positive DC voltage to at least some of the plurality of lenses and a negative DC voltage to at least some of the plurality of lenses.

Some other embodiments of the present technology are directed to an ion guide including a plurality of lenses arranged in series along a curved central axis. Each lens includes a body and a central opening, and the central openings of the plurality of lenses define a curved ion guide region. The ion guide includes an ion bending or deflecting device configured to bend ions along the curved ion guide region from the ion entrance to the ion exit only by DC voltage application and without applying an RF field.

Some other embodiments of the present technology are directed to a method for guiding an ion through an ion guide. The method includes: transmitting the ion into a curved ion guide region of the ion guide, the ion guide including a plurality of lenses arranged in series along a curved central axis, each lens including a body and a central opening, wherein the central openings of the plurality of lenses define the curved ion guide region, the curved ion guide region beginning at an ion entrance and ending at an ion exit; and providing an ion bending force to bend ions along the curved ion guide region from the ion entrance to the ion exit only by applying DC voltage to the plurality of lenses and without applying an RF field.

In some embodiments, providing an ion bending force includes applying a positive DC voltage to at least some of the plurality of lenses and applying a negative DC voltage to at least some of the plurality of lenses.

In some embodiments, providing an ion bending force includes applying DC voltage in a repeating pattern including applying one of a positive DC voltage and a negative DC voltage to a plurality of consecutive lenses in the series followed by applying the other one of a positive DC voltage and a negative DC voltage to at least one lens in the series that directly follow the plurality of consecutive lenses. The at least one lens may include a single lens in the series. The plurality of consecutive lenses comprises at least three consecutive lenses in the series.

In some embodiments, the method includes applying an equal DC voltage to each of the plurality of consecutive lenses in the series.

In some embodiments, the method includes applying varying DC voltages to the plurality of consecutive lenses in the series.

In some embodiments, the method includes concurrently or simultaneously applying a positive DC voltage to at least some of the plurality of lenses and applying a negative DC voltage to at least some of the plurality of lenses.

DETAILED DESCRIPTION

Mass spectrometry often uses turns to eliminate metastable molecules and other sources of noise for the system. Traditionally, ion path/optics design is axial/straight because it is much easier to manipulate ions in this direction. Bending an ion from its current trajectory/trying to deflect an ion along a curve can be challenging due to the kinetic energy of the ions. Bending/curving an ion guide, however, works to save space. Curved ion guides exist; however, an issue is that the energy is not the same for all the ions. Typically, curved ion guides use a quadripolar or multipolar design where an RF field is applied. The present inventors sought to develop a turn that has not yet been developed using DC voltage application and, in some embodiments, using DC voltage application and not using an RF field.

FIG.1schematically illustrates an example ion guide or ion guide assembly100that is included in an ion processing apparatus or system10according to some embodiments of the technology. The ion guide100may include a plurality of lenses (see, e.g.,FIG.2) arranged in series along a curved central axis102. The ion guide100may include a housing or frame104and/or other structure suitable for supporting the lenses in a fixed arrangement along the central axis102. In some embodiments, the housing104may provide an evacuated, low-pressure, or less than atmospheric pressure environment. The opposite axial ends of the ion guide100respectively serve as an ion inlet106and an ion outlet108. As described in more detail herein, by the application of DC voltages to the lenses, the lenses generate a two-dimensional electrical restoring field that focuses ions generally along a curved path represented by the central axis102. Only charged particles are influenced by the DC field, so when a particle stream including ions and neutral particles (e.g., gas particles, liquid droplets, etc.) enters the ion guide100via the ion inlet106, the ions are constrained to motion in the vicinity of the central axis102while the neutral particles generally continue on a straight path. Therefore, only ions exit the ion guide100via the ion outlet108.

The ion guides described herein may be utilized in any process, apparatus, device, instrument, system or the like for which a curved focused ion beam is contemplated for guiding ions from a given source to a given destination. The ion processing system10schematically illustrated inFIG.1may represent an environment in which the ion guide may operate. Thus, for example, the ion processing system10may generally include one or more upstream devices12and14and/or one or more downstream devices16and18. The ion processing system10may be a mass spectrometry (MS) apparatus, device, or system configured to perform a desired MS technique. Thus, as a further example, the upstream device12may be an ion source and the downstream device18may be an ion detector, and the other devices14and16may represent one or more other components such as ion storage or trapping devices, mass sorting or analyzing devices, collision cells or other fragmenting devices, ion optics and other ion guiding devices, etc. Thus, for example, the ion guide may be utilized before a mass analyzer (e.g., as a Q0 device), or itself as an RF/DC mass analyzer, or as a collision or reaction cell (e.g., as a Q2 device) positioned after a first mass analyzer and before a second mass analyzer. Accordingly, the ion guide may be evacuated, or may be operated in a regime where collisions occur between ions and gas molecules (e.g., as a Q2 device in a high-vacuum GC-MS, an LC-MS, or an ICP-MS, etc.).

FIGS.2and3are top and perspective views, respectively, of an example of the ion guide100according to some embodiments. The ion guide100may, for example, be utilized as the ion guide100described above and illustrated inFIG.1and as part of the accompanying the ion processing system10.

The ion guide includes a plurality of lenses110(e.g., electrostatic lenses) arranged in series along the curved central axis102. The lenses110may be spaced apart and electrically isolated from one another.

The lenses110may be disks or disk-shaped. Referring toFIG.4, each lens110or disk includes a body112and a central opening114. However, the lenses of the present technology are not limited to disks. For example, each lens may have a polygonal shape (e.g., square) with a central opening.

Referring again toFIGS.2and3, the central openings114of the lenses110define a curved ion guide region116. The curved ion guide region116begins at the ion entrance106and ends at the ion exit108.

The curved central axis may be coextensive with an arc of a circular section. Other elliptical and hyperbolic curve shapes are contemplated.

An ion deflecting device or ion deflector20(also referred to herein as an ion bending device or ion bender) is configured to apply a radial DC electric field across the ion guide region116and along the curved central axis102. Referring toFIGS.1-3, the ion deflector20may include at least one DC voltage source22,24that is configured to apply a positive DC voltage to at least some of the plurality of lenses110and a negative DC voltage to at least some of the plurality of lenses110.FIG.1shows two DC voltage sources22,24. In some embodiments, the (first) voltage source22is configured to apply a positive DC voltage to at least some of the plurality of lenses110and the (second) voltage source24is configured to apply a negative DC voltage to at least some of the plurality of lenses110. In some other embodiments, one DC voltage source or more than two DC voltage sources may be employed. It will be understood that such “sources” may include hardware, firmware, analog and/or digital circuitry, and/or software as needed to implement the desired functions of the devices.

A controller26may be used to coordinate/execute the actions and controls of the ion deflector20(and hence the DC voltage sources22,24). The controller26may also control or coordinate with the other apparatus in the system.

In some embodiments, for positive ions, the ion deflector20is configured to apply DC voltage in a repeating pattern including applying a positive DC voltage to a plurality of consecutive lenses110A in the series followed by applying a negative DC voltage to at least one lens110B in the series that directly follow the plurality of consecutive lenses110A. In some embodiments, and as illustrated, the plurality of consecutive lenses110A includes three lenses110in the series and the at least one lens110B includes a single lens110in the series. However, in other embodiments, the plurality of consecutive lenses110A includes two, four, or more lenses110in the series and/or the at least one lens110B includes more than one consecutive lens110in the series. The number of the plurality of consecutive lenses110A may increase as the initial kinetic energy of the ions increase.

The pattern may be reversed for negative ions. For example, for negative ions, the ion deflector20may be configured to apply DC voltage in a repeating pattern including applying a negative DC voltage to the plurality of consecutive lenses110A in the series followed by applying a positive DC voltage to the at least one lens110B in the series that directly follow the plurality of consecutive lenses110A.

These types of repeating patterns have been demonstrated to work well for a large window of ion energies.

For positive ions, a positive DC voltage is applied to a majority of the lenses110. For negative ions, a negative DC voltage is applied to a majority of the lenses110.

The ion deflector20may include a plurality of DC voltage sources (e.g., voltage sources22,24shown inFIG.1) that are configured to concurrently or simultaneously apply a positive DC voltage to at least some of the plurality of lenses110(e.g., a first set) and a negative DC voltage to at least some of the plurality of lenses110(e.g., a second set).

The ion guide100does not rely on an RF field to bend ions along the curved ion guide region116. Instead, the ion deflector20is configured to bend ions along the curved ion guide region116from the ion entrance106to the ion exit108only by DC voltage application and without applying an RF field.

Referring toFIG.4, when the lens110is a disk, the body112of the disk may be continuous and surround (e.g., completely surround) the central opening114. The body112of each disk may have an outer diameter D1of between 10 and 40 mm and, in some embodiments, has an outer diameter D1of about 19 mm. The central opening114of each disk may have a diameter D2of between 2.5 and 8 mm and, in some embodiments, has a diameter D2of about 6.35 mm.

In some embodiments, and as schematically shown inFIG.1, the ion entrance106and the ion exit108define an angle of 180 degrees therebetween. In some other embodiments, and as shown inFIGS.2and3, the ion entrance106and the ion exit108define an angle of 90 degrees therebetween. However, angles other than 90 and 180 degrees are contemplated. For example, in some embodiments, the angle may be in the range from 30 degrees to 180 degrees.

For the 90 degree curve ion guide (FIGS.2and3), there may be between 40 and 60 lenses and, in some embodiments, there may be 46 lenses in the series. For the 180 degree curve ion guide (FIG.1), there may be between 80 and 120 lenses and, in some embodiments, there may be 92 lenses in the series. These counts may be for the “curved portion” or “curved region” of the ion guide. Additional lenses may be used for focusing at the beginning and the end of the curve. In some embodiments, additional lenses may be used for focusing at an intermediate region and/or middle region of the curve.

In addition to the radial DC electric field, an axial DC electric field may be applied to the ion guide100along the central axis to control ion energy (e.g., axial ion velocity). An axial DC electric field may be particularly desirable in a case where ions being transmitted through the ion guide100experience collisions with neutral gas molecules (e.g., background gas). As appreciated by those skilled in the art, such collisions may be employed for ion fragmentation or for collisional cooling. A DC voltage source or sources may be utilized to generate the axial DC electric field. The DC voltage source or sources may communicate with one or more of the lenses110or with an external field generating device such as, for example, one or more other conductive members (e.g., resistive traces) positioned along the ion guide axis102, such as outside the top and/or bottom of the ion guide100, etc. This “axial” DC voltage source may be conceptualized as being a part of one or more of the functional elements22,24schematically depicted inFIG.1.

Additionally or alternatively, there could be a gradual increase or decrease in voltage over the entire series of lenses110or along each segment of lenses110A. This can provide an electric field gradient that spans locally or along the entire length of the curve.

Rather than using an RF field, embodiments of the present technology use periodic negatively charged discs (for positive ions) angled to create a 90 degree or 180 degree turn to create the same trajectory that the ion would otherwise have with an RF field, with an added benefit that this geometry does not have the loss of sensitivity/transmission as a function of mass or energy. Simulations show that the concept can turn a wide range of masses and a wide range of energies. This shows to be an improvement over existing technologies because fewer ions are lost therefore increasing signal.

The present technology has been described herein with reference to the accompanying drawings, in which illustrative embodiments of the technology are shown. In the drawings, the relative sizes of regions or features may be exaggerated for clarity. This technology may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the technology to those skilled in the art.

It is noted that any one or more aspects or features described with respect to one embodiment may be incorporated in a different embodiment although not specifically described relative thereto. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination. Applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to be able to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner. These and other objects and/or aspects of the present technology are explained in detail in the specification set forth herein.

The foregoing is illustrative of the present technology and is not to be construed as limiting thereof Although a few example embodiments of this technology have been described, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from the teachings and advantages of this technology. Accordingly, all such modifications are intended to be included within the scope of this technology as defined in the claims. The technology is defined by the following claims, with equivalents of the claims to be included therein.