Patent Description:
Mass spectrometers operate in a vacuum environment that requires a pumping mechanism to establish and maintain low pressure. In various pumping methodologies, a mass spectrometer may use an ion pump (see prior art <FIG>) to achieve the internal vacuum associated with proper operation. The ion pump may achieve vacuum by ionizing molecules that drift into a cylindrical anode, then driving them to a cathode surface using an electric field. The ions thus sequestered in the cathode material may be removed from the vacuum space, and consequently, the pressure within the mass spectrometer may be reduced.

The ion pump as e. disclosed in <CIT> is a limited-life item due to, for instance, degradation of a cathode surface occurring as a consequence of ion bombardment. An increased ion pump life is desired for many mass spectrometer applications, especially for applications involving remote sensing where the mass spectrometer is not easily accessed or serviced. Consequently, improvements to the manner in which the cathode surface is consumed should increase the lifetime and durability of the ion pump. This patent describes one or more manner in which the cathode lifetime may be extended.

The present disclosure relates to ion pump systems and their components. According to various embodiments, ion pump systems according to claims <NUM>, <NUM> and <NUM> are disclosed. The ion pump system may comprise a generally cylindrical anode tube and cathode plates. The ion pump system may comprise a plurality of deflection plates. The plurality of deflection plates may be configured to steer a trajectory of an accelerated ion off the mechanical center axis of the anode tube.

The anode tube may comprise a first pair of integrally formed deflection plates and a second pair of integrally formed deflection plates. The first pair of integrally formed deflection plates may be associated with a different voltage than a voltage applied to the second pair of integrally formed deflection plates at a given time. An alternating current (AC) may be applied to at least one of the first pair of integrally formed deflection plates or the second pair of integrally formed deflection plates. The first pair of integrally formed deflection plates and the second pair of integrally formed deflection plates are substantially equivalent in size and shape.

According to various embodiments, the anode tube comprises three integrally formed deflection plates. According to various embodiments, the plurality of deflection plates are disposed between an end of the generally cylindrical anode tube and a cathode plate. According to various embodiments, a first current carrying wire and a second current carrying wire are positioned within an anode tube and configured to change a local electric field and the trajectory of accelerated ions. According to various embodiments, the anode tube comprises a heterogeneous shape. According to various embodiments, a cathode plate of an ion pump comprising a front surface, a back surface, and additional material extending in the Z axis from at least one of the front surface or the back surface is disclosed. The additional material is contained within a footprint formed by an open end of an anode tube along an axis. The additional material may form a substantially symmetrical shape along an axial center axis in the Z direction. The axial center axis is collocated with the mechanical axial center axis of an anode tube. The axial center axis is asymmetric with the mechanical axial center axis of an anode tube. The positon of the axial center axis is configured to change a local electric field and the trajectory of accelerated ions over time. The additional material is integrally formed with the cathode plate. The additional material is configured to extend the lifespan of the ion pump. There is disclosed herein a cathode plate of an ion pump comprising, a front surface; a back surface; and an additional material extending from the front surface, wherein the cathode plate is located in proximity to an anode tube, wherein the front surface is in closer proximity to the anode tube than the back surface.

Optionally, the additional material may be contained within a footprint defined by and projected to the cathode plate from an open end of the anode tube along an axis.

Optionally, the additional material forms a substantially symmetrical shape along an axial center axis in a Z direction. The axial center axis may be collocated with a mechanical axial center axis of the anode tube, and/or the axial center axis may be asymmetric with a/the mechanical axial center axis of the anode tube.

Optionally, a positon of the axial center axis of the additional material may be configured to change a local electric field and a trajectory of accelerated ions over time by varying an electric field as material of the additional material is ablated by accelerated ions.

Optionally, the additional material may be integrally formed with the cathode plate.

Also disclosed is a cathode plate of an ion pump comprising a front surface; a back surface; and an additional material extending from the back surface, wherein the cathode plate is located in proximity to an anode tube, wherein the front surface is in closer proximity to the anode tube than the back surface.

Optionally, the additional material may be contained within a footprint defined by and projected to the cathode plate from an open end of the anode tube along an axis, and/or the additional material forms a substantially symmetrical shape along an axial center axis in a Z direction.

Optionally, the axial center axis is collocated with a mechanical axial center axis of the anode tube. , and/or the axial center axis is asymmetric with a/the mechanical axial center axis of the anode tube.

Optionally, the additional material may be configured to extend a lifespan of the ion pump.

The detailed description of exemplary embodiments herein makes reference to the accompanying drawings, which show exemplary embodiments by way of illustration and their best mode. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, it should be understood that other embodiments may be realized and that logical changes may be made without departing from the scope of the disclosure. For example, the steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented.

The present disclosure relates to ion pump systems and their components. According to various embodiments and with reference to <FIG>, an ion pump system is depicted. The ion pump may comprise a series of generally cylindrical tubes referred to herein as anode tubes <NUM>. A positive <NUM>,<NUM> Volt bias may be applied to each anode tube <NUM>. The anode tubes <NUM> may be arranged in an array, such as a one by four or a two by four array. A cathode plate <NUM> in close proximity to an end of the anode tube may be held at a ground voltage.

Under normal operation of the ion pump, molecules drift into an open cylindrical anode, such as an anode tube having a high voltage potential. Electrons generated via the Penning effect ionize the molecules, which then accelerate toward a cathode surface. Upon impact, the ion may be sequestered in the cathode. At the same time, they may also cause ejection of material from the cathode surface. Over time, enough material is ejected to create a pit in the cathode, and eventually a hole may be drilled through the cathode, rendering it useless. If the drilling continues, it is possible to breach the vacuum housing behind the cathode and cause an ion pump failure.

The tightly focused ion beam comes out the axial center of the anode tube with minimal dispersion. This is why the burned-through portion of the cathode may be aligned with the axial center of the anode tube and result in a small footprint as compared with the diameter of the anode tube.

According to various embodiments, the ion beam is manipulated such that a wide footprint of the cathode surface is impacted. Dispersing the striking path of the electrons on the order of ½ of the conventional non-dispersed striking path may triple the life of the cathode surface and in turn extend the lifespan of the ion pump system.

With renewed reference to <FIG>, as the accelerated ions are generally accelerated along the mechanical center axis of the anode tube <NUM>, a greater percentage of the accelerated ions strike proximate this axis. Over time, a dimple may be formed in the cathode plate <NUM> generally centered along this axis for each anode tube <NUM>. Thus, in the case of <NUM> anode tubes, <NUM> dimples may be formed in the cathode plate <NUM>. This dimple may increase in depth until it progresses through the cathode plate <NUM>. Manipulating the accelerated ions' path of travel may result in an increased lifespan for the cathode plate <NUM> and ion pump.

This manipulation may be achieved by either steering the accelerated ion and/or passively defocusing the path of travel of the accelerated ion. This manipulation may be achieved in a variety of ways.

According to various embodiments and with renewed reference to <FIG>, the anode tube <NUM> may be sectioned. The anode tube <NUM> may be sectioned into deflection plates. For instance, the anode tube <NUM> may be sectioned into a pair of deflection plates. For instance, the generally cylindrical anode tube <NUM> may be comprised of <NUM> substantially equal sized sections, (e.g., first section <NUM>, second section <NUM>, third section <NUM> and fourth section <NUM>). A constant positive <NUM>,<NUM> Volts may be applied to each deflection plate, first section <NUM>, second section <NUM>, third section <NUM> and fourth section <NUM> via a power source and/or control unit <NUM> coupled to each anode tube <NUM>. A small time variant field, such as an AC field of <NUM> Volts plus or minus from the reference voltage, (e.g., <NUM>,<NUM> Volts), may be applied between a pair of deflection plates, such as between first section <NUM>, and second section <NUM> and/or between third section <NUM> and fourth section <NUM> via the power source and/or control unit <NUM> coupled to each anode tube <NUM>. This AC field may be applied at any frequency, such as <NUM>. The position of the ion within the anode tube along with the electric field at that location based on the frequency of the AC field and the reference voltage may determine a trajectory of the accelerated ion. In response to statically altering the potential on one of an opposing pair of deflection plates, the ions will move the center axis off the physical center axis (e.g., A-A') of that anode tube <NUM>. Thus, the ions path of travel will be altered from being collated with the physical center axis of the anode tube. In this way, a time varying field, such as an alternating current field, may be applied to each pair of deflection plates, such as between first section <NUM>, and second section <NUM> and/or between third section <NUM> and fourth section <NUM> at different times. Thus, there is a high probability that an ion formed and ejected through the anode tube <NUM> will not see the exact same electric field as a different ion formed in anode tube <NUM> and ejected at a different time. Consequently, the vector of the ejected ion will strike cathode plate <NUM> at a different location than an ion formed at a later time. Thus, the accelerated ion will strike the cathode plate <NUM> in a generally random pattern with respect to the X and Y axis, in contrast to along a central axis of the anode tube as was common in conventional systems such as the ion pump depicted in <FIG>.

Accelerated ions leave the center portion (near axis A-A') of the anode tube <NUM> due to the anode tube <NUM> symmetry and the generally symmetrical electric fields present. The apparent symmetry within the anode tube <NUM> may be altered by making the anode tube <NUM> longitudinally segmented and applying independent voltages to each segment, such as between first section <NUM>, and second section <NUM> and/or between third section <NUM> and fourth section <NUM>. The voltages on two adjacent segments may be time varied at different rates to achieve the same rasterizing process described above.

According to various embodiments and with reference to <FIG>, an anode tube <NUM> may be sectioned into a set of three deflection plates, a first deflection plate <NUM>, a second deflection plate <NUM> and a third deflection plate <NUM>. The first deflection plate <NUM>, the second deflection plate <NUM> and the third deflection plate <NUM> may be substantially equally sized. A reference voltage such as a positive <NUM>,<NUM> Volts, may be applied to two of the three deflection plates at any given time such as time X via a power source and/or control unit <NUM> coupled to each anode tube <NUM>. The remaining deflection plate may comprise a different amount of voltage, such as a plus or minus <NUM> Volts, such as <NUM>,<NUM> Volts, at any given time, such as time X. The deflection plate being applied the additional <NUM> volts may be time variant. This will passively steer the vector of an accelerated ion in a nearly random path away from the center axis, (axis B-B') of the anode tube <NUM> depending on which deflection plate, (the first deflection plate <NUM>, the second deflection plate <NUM> or the third deflection plate <NUM>) is being applied the additional <NUM> volts at any given time.

According to various embodiments and with reference to <FIG>, one or more current carrying wire, such as wires (first wire <NUM> and second wire <NUM>), may be positioned within a single section anode tube <NUM>. The first wire <NUM> and second wire <NUM> may be coupled to a power source and/or control unit <NUM>. The power source and/or control unit <NUM> may be coupled to each anode tube <NUM>. The single section anode tube may be similar in geometry to conventional anode tubes <NUM>. The direction of travel of the one or more wires may be spiraled, axially aligned with the center axis (axis C-C') of the anode tube <NUM> and/or randomly positioned. An AC voltage, such as <NUM> Volts plus or minus from a reference voltage, may be applied to the wires <NUM> and <NUM>. Stated another way, a periodic voltage may be applied to the wires <NUM> and <NUM>. This may alter the electric field within the anode tube away from directing an accelerated ion along axis A-A'. An ion formed at any time (and/or thus a particle cloud, such as an electron cloud) may be steered off the mechanical center axis (axis C-C') of each anode tube <NUM>. Moreover, the electron cloud may be steered off axis.

According to various embodiments and with reference to <FIG>, rather than portioning the anode tubes into sections, multiple diffusion plates and/or a plurality of pairs of diffusion plates may be positioned between the anode tube <NUM> and the cathode plate <NUM>. A reference voltage, such as a positive <NUM>,<NUM> Volts, may be applied to each anode tube <NUM>, via a control unit <NUM> and/or power source. A small time variant field, such as an AC field of <NUM> Volts plus or minus from a reference voltage, (e.g., <NUM>,<NUM> Volts), may be applied between a pair of deflection plates, such as between first deflection plate <NUM> and second deflection plate <NUM> and/or between third deflection plate <NUM> and fourth deflection plate <NUM>. Based on the disruption to the electric and magnetic fields, an ion formed at any time may be steered off the mechanical center axis (e.g., axis D-D') of each anode tube <NUM>.

Stated another way, the accelerated ion can be moved after it leaves the anode tube <NUM> using a secondary electrode disposed between the anode tube <NUM> and the cathode plate <NUM>. The secondary electrode would be segmented, allowing different time-dependent voltages to be applied to each segment, and configured to alter the electric field within the electrode and steering the accelerated ion as desired.

Three electrodes may be utilized to achieve full X axis and Y axis control of the accelerated ion, and additional segmented electrode designs are also feasible. A common set of steering electrodes could be used for a multi-anode tube ion pump. The accelerated ion may be rasterized systematically across the cathode plate <NUM> surface at high speed.

According to various embodiments and with reference to <FIG>, the shape of the anode tube <NUM>, <NUM> along the axial direction can be varied near the ends of the anode tube. In accordance with various embodiments, the various anode tubes disclosed herein may be combined with the principles of <FIG>, wherein, for example, the anode tube <NUM> may include one transition section <NUM> whereby one or more <NUM> of the anode tube may have a shape that fills gaps in the end of the array (such as in a 2x4 stacked array shown in <FIG>) wherein one end <NUM> would become square as depicted in <FIG> to fill the gaps between the cylinder portion <NUM> of adjacent anode tubes <NUM>. In accordance with various embodiments, the various anode tubes disclosed herein may be combined with the principles of <FIG>, wherein, for example, the anode tube <NUM> may include a transition section <NUM> at each end <NUM> of the anode tube <NUM> whereby each end <NUM> of the anode tube <NUM> may have a shape that fills gaps in the end of the array (such as in a 2x4 stacked array shown in <FIG>) wherein each end <NUM> would become square as depicted in <FIG> to fill the gaps between the cylinder portion <NUM> of adjacent anode tubes <NUM>. Moreover, with reference to <FIG>, an anode tube <NUM>, <NUM> may comprise any variable shape as desired. For example, the anode tube <NUM>, <NUM> may be flared to form a larger diameter (such as for a single anode design). In various embodiments, the electric field thus generated near the ends of the anode tube <NUM>, <NUM> may be radially more diffuse, increasing the radial trajectory of any off-axis ion exiting the anode tube <NUM>, <NUM> and broadening the impacted cathode area.

Thickening the cathode plate <NUM>, with reference to <FIG>, in desired areas may result in an increased lifespan for the cathode plate and ion pump. While the entire cathode plate <NUM> may be thickened to increase the lifespan for the cathode plate and ion pump, in some applications the material weight may be undesirable, such as in aerospace applications.

According to various embodiments and with reference to <FIG>, additional material <NUM> may be integrally formed in the cathode plate back surface <NUM>, such as the surface farthest to an exit of the anode tube. In this way, additional material <NUM> formed from the same material and integral to the cathode plate <NUM> may extend from the cathode plate back surface <NUM> in a direction along the Z axis away from an exit of the anode tube. The additional material <NUM> may form a Gaussian toroid shape. The additional material <NUM> may form a cylinder aligned with the footprint of the anode tube. The additional material <NUM> may form a symmetrical shape along axis A-A' which may be the mechanical center axis of an anode tube. The additional material <NUM> may form a cylinder of any desired radius with a center axis aligned with the mechanical center axis A-A' of the anode tube.

According to various embodiments and with reference to <FIG>, additional material <NUM> may be integrally formed in the cathode plate front surface <NUM>, such as the surface closest to an exit of the anode tube. In this way, additional material <NUM> formed from the same material and integral to the cathode plate <NUM> may extend from the cathode plate front surface <NUM> in a direction along the Z axis proximate from an exit of the anode tube. The additional material <NUM> may form a Gaussian toroid shape. The additional material <NUM> may form a cylinder aligned with the footprint of an anode tube. The additional material <NUM> may form a symmetrical shape along axis A-A' which may be the mechanical center axis of an anode tube. The additional material <NUM> may form a cylinder of any desired radius with a center axis aligned with the mechanical center axis A-A' of the anode tube.

According to various embodiments and with reference to <FIG>, additional material <NUM> may extend in a direction along the Z axis from the cathode plate front surface <NUM> or cathode plate back surface <NUM>. The additional material <NUM> may be generally symmetrical about additional material <NUM> along a centerline E-E', wherein the centerline is offset from the mechanical center axis of the anode tube A-A'.

A cathode plate with an extension that is offset from the mechanical center axis of the anode tube A-A' distorts the electric field felt by the incoming accelerated ion. Thus, the vector of the accelerated ion is off center. Over time, the ions will impact the additional material <NUM>. The ions will impact the additional material <NUM> a relatively higher percentage of the time near the mechanical center axis of the anode tube A-A' but offset from the mechanical center axis of the anode tube A-A'. Over time, the additional material <NUM> may be ablated away, which will alter the shape of the electric field experienced by incoming accelerated ions. In this way, by ablating the additional material <NUM> over time, the electric field experienced by incoming accelerated ions is passively changed. Thus, the accelerated ions will be steered into different sections of the cathode plate <NUM>, generally within the footprint of the anode tube over time.

In this way the deformity to the cathode surface (e.g., the additional material <NUM>), may be axially asymmetric to the ion beam axis A-A'. This arrangement may be configured to distort the electric field and alter the trajectory of the accelerated ion. As the accelerated ion interacts with and/or ablated the additional material <NUM> with the cathode over time and material is removed, the deformity will be altered as well, changing the local electric field, and consequently, the trajectory of the accelerated ion.

The concepts described herein may apply to terrestrial ion pumps and/or aerospace based ion pumps, such as sputter ion pumps.

Claim 1:
An ion pump comprising:
an anode tube (<NUM>) sectioned into a first deflection plate (<NUM>), a second deflection plate (<NUM>), and a third deflection plate (<NUM>);
a cathode plate (<NUM>; <NUM>; <NUM>;<NUM>); and
wherein a mechanical axial center axis of the anode tube intersects the cathode plate, wherein the first deflection plate (<NUM>), the second deflection plate (<NUM>), and the third deflection plate (<NUM>) are disposed around the mechanical axial center axis, wherein a control unit is configured to apply a time variant electric current to the first deflection plate to alter the trajectory of accelerated ions moving toward the cathode plate, wherein the cathode plate comprises a front surface and a back surface.