Isothermal ion source with auxiliary heater

Abstract

The ion source includes a chamber having a first end, a second end opposite the first end, a first wall extending from the first end to the second end, and a second wall opposite the first wall. The ion source also includes a source filament at the first end of the chamber and configured to emit electrons and a first amount of heat, a beam aperture in the second wall of the chamber, and one or more heaters positioned within the chamber and between the second end and the beam aperture and operable to provide a second amount of heat. The one or more heaters are positioned and operable such that the second amount of heat balances the first amount of heat to reduce or eliminate a temperature gradient within the chamber.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of and priority to U.S. Provisional Patent Application No. 63 / 122,699, filed December 8, 2020, the entire disclosure of which is incorporated herein by reference. [Background technology]

[0002] background The present disclosure relates generally to the field of heavy metal ion generation, for example, for use in medical applications. More specifically, the present disclosure relates to improving the efficiency and overall operation of ion sources, for example, ion sources for the generation of heavy metal ions such as ytterbium-176. Summary of the Invention

[0003] overview One embodiment of the present disclosure is an ion source. The ion source includes a chamber having a first end, a second end opposite the first end, a first wall extending from the first end to the second end, and a second wall opposite the first wall. The ion source also includes a source filament at the first end of the chamber, an ion source configured to emit electrons and a first amount of heat, a beam aperture at the second wall of the chamber, and one or more heaters positioned within the chamber between the second end and the beam aperture and operable to provide a second amount of heat. The term "aperture" may refer to an opening of any shape, such as a slot, a slit, a rectangular opening, a circular opening, or an opening of some other shape. The one or more heaters are positioned and operable such that the second amount of heat balances the first amount of heat, reducing or eliminating a temperature gradient within the chamber.

[0004] In some embodiments, the ion source also includes a plurality of thermocouples distributed within the chamber, and a controller configured to provide closed-loop control of one or more heaters based on outputs from the plurality of thermocouples.

[0005] In some embodiments, the ion source also includes a reflector electrode at the second end of the chamber and configured to reflect electrons away from the second end. Operation of the one or more heaters can reduce or eliminate condensation on an insulator of the reflector electrode.

[0006] In some embodiments, a gas inlet is provided in the first wall of the chamber. The gas inlet may be aligned with the beam aperture. The one or more heaters may include a first cylindrical heater extending from the second end of the chamber and along the second wall of the chamber. The one or more heaters may include a second cylindrical heater extending from the second end of the chamber and along the second wall of the chamber. The second cylindrical heater may be spaced apart from the first cylindrical heater.

[0007] In some embodiments, the ion source also includes a plurality of support posts coupled to the first wall of the chamber and extending away from the chamber. The plurality of support posts may provide a uniform path for heat transfer out of the chamber. The ion source may also include a water cooling system. The plurality of support posts extend from the chamber to the water cooling system, the water cooling system configured to remove heat from the plurality of support posts. The water cooling system may be further configured to measure heat removed from the plurality of support posts by the water cooling system.

[0008] In some embodiments, the ion source includes an oven configured to supply ytterbium gas into the chamber through an inlet in the second wall.

[0009] In some embodiments, the ion source includes a test device configured to measure plasma uniformity of the ion beam emitted from the beam aperture, and controls for the one or more heaters are adjusted based on the plasma uniformity.

[0010] In some embodiments, the second amount of heat is substantially equal to the first amount of heat. Reducing or eliminating temperature gradients within the chamber can result in reducing or eliminating non-uniform currents within the ion beam emitted from the beam aperture.

[0011] Another embodiment of the present disclosure is a method. The method includes supplying a gas (e.g., a metal gas) into a chamber and ionizing the gas by supplying power to a filament, causing the filament to emit electrons within the chamber. Supplying power to the filament causes the filament to apply heat to the chamber proximate a first end of the chamber. The method also includes reducing or eliminating a temperature gradient within the chamber by activating one or more heaters positioned within the chamber. The one or more heaters are positioned inside the chamber and extend from a second end of the chamber opposite the first end. The method also includes extracting the ion beam from the chamber through an aperture positioned between the filament and the one or more heaters.

[0012] In some embodiments, activating the one or more heaters includes causing the one or more heaters to balance heat added to the chamber by the filament. In some embodiments, the method includes measuring temperatures at multiple locations within the chamber. Activating the one or more heaters may include controlling the one or more heaters based on the temperatures at the multiple locations within the chamber. The method may also include measuring plasma uniformity of the ion beam extracted through the aperture and determining set points for temperatures at the multiple locations within the chamber based on the plasma uniformity measurements. The set points may be related to optimal plasma uniformity. The method may also include controlling the one or more heaters to bring the temperatures at the multiple locations to the set points.

[0013] In some embodiments, the method includes removing heat from the chamber by operating a water cooling system thermally coupled to the chamber by a plurality of support posts.

[0014] [The present invention 1001] a chamber having a first end, a second end opposite the first end, a first wall extending from the first end to the second end, and a second wall opposite the first wall; a source filament at the first end of the chamber and configured to emit electrons and a first amount of heat; a beam aperture in the second wall of the chamber; one or more heaters positioned within the chamber and between the second end and the beam aperture, the heaters operable to provide a second amount of heat; An ion source comprising: the one or more heaters are positioned and operable such that the second thermal mass balances the first thermal mass to reduce or eliminate a temperature gradient within the chamber; The ion source. [The present invention 1002] a plurality of thermocouples distributed within the chamber; a controller configured to provide closed-loop control of the one or more heaters based on outputs from the plurality of thermocouples; and The ion source of the present invention 1001 further comprises: [The present invention 1003] a reflector electrode at the second end of the chamber and configured to reflect the electrons away from the second end. The ion source of the present invention 1001 further comprises: [The present invention 1004] The ion source of the present invention 1003, wherein operation of the one or more heaters reduces or eliminates condensation on an insulator of the reflector electrode. [The present invention 1005] 1001. The ion source of the present invention, further comprising a gas inlet in the first wall of the chamber, the gas inlet being aligned with the beam aperture. [The present invention 1006] 1001. The ion source of claim 10, wherein the one or more heaters include a first cylindrical heater extending from the second end of the chamber and along the first wall of the chamber. [The present invention 1007] 1006. The ion source of claim 10, wherein the one or more heaters include a second cylindrical heater extending from the second end of the chamber and along the first wall of the chamber, the second cylindrical heater being spaced apart from the first cylindrical heater. [The present invention 1008] a plurality of support posts coupled to the first wall of the chamber and extending away from the chamber; 1001. The ion source of claim 10, further comprising: a plurality of support posts that provide a uniform path for heat transfer from the chamber outward. [The present invention 1009] Further comprising a water cooling system; the plurality of support posts extend from the chamber to the water cooling system; the water cooling system configured to remove heat from the plurality of support posts. The ion source of the present invention 1008. [The present invention 1010] 1009. The ion source of claim 10, wherein the water cooling system is further configured to measure heat removed from the plurality of support posts by the water cooling system. [The present invention 1011] 1001. The ion source of claim 1001, further comprising an oven configured to supply ytterbium gas into the chamber through an inlet in the first wall. [The present invention 1012] The ion source of the present invention 1001 further comprises a test device configured to measure plasma uniformity of the ion beam emitted from the beam aperture, and control for the one or more heaters is adjusted based on the plasma uniformity. [The present invention 1013] 1001. The ion source of the present invention, wherein the second amount of heat is substantially equal to the first amount of heat. [The present invention 1014] The ion source of the present invention 1001, wherein reducing or eliminating temperature gradients within the chamber results in reducing or eliminating non-uniform currents within the ion beam emitted from the beam aperture. [The present invention 1015] supplying a metal gas into the chamber; ionizing the metal gas by supplying power to a filament to cause the filament to emit electrons within the chamber, wherein supplying power to the filament causes the filament to apply heat to the chamber proximate a first end of the chamber; reducing or eliminating a temperature gradient within the chamber by activating one or more heaters positioned within the chamber, the one or more heaters being positioned inside the chamber and extending from a second end of the chamber opposite the first end; extracting the ion beam from the chamber through an aperture positioned between the filament and the one or more heaters; A method comprising: [The present invention 1016] 1015. The method of claim 1015, wherein activating the one or more heaters comprises causing the one or more heaters to balance the heat added to the chamber by the filament. [The present invention 1017] measuring temperatures at a plurality of locations within the chamber; and activating the one or more heaters includes controlling the one or more heaters based on temperatures at the plurality of locations within the chamber. The method of the present invention 1015. [The present invention 1018] measuring plasma uniformity of the ion beam extracted through the aperture; determining set points for temperatures at the plurality of locations within the chamber based on the plasma uniformity measurements, the set points being associated with optimal plasma uniformity; The method of the present invention 1017 further comprising: [The present invention 1019] 1018. The method of claim 1018, further comprising controlling said one or more heaters to bring the temperature at said plurality of locations to said setpoint. [The present invention 1020] The method of claim 1015, further comprising removing heat from said chamber by operating a water cooling system thermally coupled to said chamber by a plurality of support posts. The present disclosure will become more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which like reference numerals refer to like elements and in which: [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic diagram of an ion source in accordance with an exemplary embodiment. [Figure 2] 2 is a block diagram of a control loop for the ion source of FIG. 1 in accordance with an exemplary embodiment. [Figure 3] FIG. 2 is a block diagram of a control system for the ion source of FIG. 1 in accordance with an exemplary embodiment. [Figure 4] 2 is a perspective view of the ion source of FIG. 1 in accordance with an exemplary embodiment. [Figure 5A] 2 is another perspective view of the ion source of FIG. 1 in accordance with an exemplary embodiment. [Figure 5B] FIG. 1 is a perspective view of an ion source in accordance with an exemplary embodiment. [Figure 6] 5 is a first cross-sectional view of the ion source of FIG. 4 in accordance with an exemplary embodiment. [Figure 7] 5 is a second cross-sectional view of the ion source of FIG. 4 in accordance with an exemplary embodiment. [Figure 8] 5 is a third cross-sectional view of the ion source of FIG. 4 in accordance with an exemplary embodiment. [Figure 9] FIG. 1 is a flow diagram of a process for operating an ion source in accordance with an exemplary embodiment. [Figure 10] FIG. 1 is a flow diagram of a process for controlling an ion source in accordance with an illustrative embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] Detailed Description Before turning to the figures illustrating in detail certain exemplary embodiments, it is to be understood that the disclosure is not limited to the details or methodology set forth in the description or illustrated in the figures, and that the terminology used herein is for the purpose of description only and should not be regarded as limiting.

[0017] Generally, with reference to the figures, systems and methods relating to heavy metal ion sources are illustrated according to various exemplary embodiments, particularly the use of one or more auxiliary heaters and other thermal management features to improve the operation of the ion source. The primary embodiments illustrated below relate to a Bernas ion source, although the teachings herein may also be adapted to a Freeman ion source or other types of ion sources.

[0018] Increasing the run time of an ion source is also an objective of the systems and methods described herein. Some ion sources must be shut down frequently so that cleaning operations can be performed, for example, due to particle buildup on electrodes or other surfaces within the ion source. However, frequent shutdowns can limit production yields, create undesirable interruptions, and be energetically inefficient. The described systems and methods enable constant operation for relatively long amounts of time, for example, by efficiently ionizing metal gas within the ion source and protecting one or more electrodes or other surfaces from condensation within the ion source. In some embodiments, ion sources according to the present disclosure can operate continuously for at least several days. As described in detail below, these benefits can be achieved through the employment and operation of one or more heaters and other temperature management features.

[0019] Another objective of the systems and methods described herein is to improve the uniformity of the ion beam output from the ion source (e.g., plasma uniformity). A highly uniform ion beam can be associated with highly efficient production and extraction of desired ions and minimal contamination by undesired ions. The systems and methods described herein can provide optimal plasma uniformity. For example, the systems and methods described herein can improve plasma uniformity by reducing or eliminating temperature gradients within the ion source.

[0020] For example, some embodiments of the ion sources described herein are configured to generate beams with singly charged metal ion currents greater than 20 mA (milliamperes) with high current uniformity. In some embodiments, the ion mass of the desired isotope is greater than 176 amu (atomic mass units), e.g., 176 It is Yb.

[0021] These and other advantages of the present disclosure are described in detail below with reference to the various figures.

[0022] 1, a schematic diagram of an ion source 100 according to an exemplary embodiment is shown. The ion source 100 is configured for the production of an ion beam, for example, a heavy metal ion beam, such as a charged ytterbium isotope beam. For example, the ion source may be configured to output a beam having a singly charged metal ion current of greater than 20 mA, including ions having an ion mass of 176 amu.

[0023] The ion source 100 is shown as including a chamber 102 in which ionization of a metal gas takes place to produce an ion beam. As shown, the chamber 102 has a substantially rectangular cross-section and includes a first end 104, a second end 106 opposite the first end 104, a first wall 108 extending from the first end 104 to the second end 106, and a second wall 110 opposite the first wall 108. The chamber 102 may be formed as a closed box by including third and fourth walls (shown in subsequent figures) positioned to form a six-sided rectangular box.

[0024] As shown in FIG. 1 , the ion source 100 includes an oven 112 connected to an inlet 114 extending through the first wall 108. The oven 112 is configured to generate and deliver a metal gas into the chamber 102 via the inlet 114 in the first wall 108. For example, the oven 112 may deliver ytterbium gas. In its gaseous state, the metal gas may flow into the chamber 102 and disperse throughout the entire volume of the chamber 102. The metal gas may be uncharged when delivered into the chamber 102 by the oven 112. As the metal gas cools and condenses, it may accumulate on the interior surfaces of the chamber 102, which may be undesirable for various reasons. For example, metal vapor deposition may short out insulators within the ion source 100. As another example, surfaces coated with metal vapor may adversely affect the overall concentration of gas within the chamber 102, thus reducing the efficiency of the ion source 100. One aspect of the present disclosure includes techniques for minimizing or eliminating such condensation during operation of the ion source 100.

[0025] The ion source 100 is also shown as including a filament 116 positioned at the first end 104 of the chamber 102. The filament 116 is connected to a circuit configured to supply a voltage across the filament 116, which causes the filament 116 to glow. While in a glowing state, the filament 116 emits electrons (referred to as e in FIG. 1 ). - ) and heat (shown as Q in Figure 1). filament ) in the chamber 102. In some embodiments, when the filament 116 is emitting electrons at a preferred rate for operation of the ion source 100, the filament 116 provides approximately 1 kilowatt of heat into the chamber 102. The filament 116 may be made of tungsten and may have a diameter of approximately 1.5 millimeters.

[0026] Electrons are emitted from the filament 116 into the interior of the chamber 102. Many of the electrons from the filament 116 are emitted into the chamber 102 at a velocity pointing toward the second end 106 (i.e., downward in the perspective of FIG. 1 ). The ion source 100 is shown to include a reflector electrode 118 positioned at the second end 106 that can reflect the electrons back toward the first end 104 (upward in the perspective of FIG. 1 ). That is, the reflector electrode 118 can be held at a negative voltage, such that a repulsive electric force is created between the reflector electrode 118 and the electrons. Thus, actuation of the filament 116 and the reflector electrode 118 allows the electrons to travel around the chamber 102 without collecting at the second end 106.

[0027] Thus, electrons and metal gas are both supplied into chamber 102. Interaction between the metal gas and the electrons results in ionization of the metal gas. In the example of Figure 1, inlet 114, through which gas is supplied to chamber 102, is positioned approximately equidistant from first end 104 and second end 106, and approximately equidistant from filament 116 and reflector electrode 118. This geometry can promote maximally efficient ionization of the gas supplied by oven 112.

[0028] The ionized gas can be extracted from the chamber 102 as an ion beam through an aperture 120. In various embodiments, the aperture can be an elongated slot or slit, a circular opening, or some other shape. The aperture 120 is shown positioned on the second wall 110 opposite the inlet 114. The aperture 120 can be approximately equidistant between the first end 104 and the second end 106, and approximately equidistant between the filament 116 and the reflector electrode 118. To extract the ion beam from the chamber, the aperture 120 can be part of an extraction ion device positioned outside the aperture 120 and configured to extract the ionized gas from the chamber 102 as an ion beam. For example, the extraction ion device can include a positively charged electrode that creates an electric field that extracts charged ions through the aperture 120. Various extraction ion electrode configurations are possible in various embodiments of the extraction ion device.

[0029] One aspect of the present disclosure is the determination that the uniformity of the ion beam across the vertical distance of the ion beam (from the perspective of FIG. 1 ) depends on the uniformity of the density of the metal gas within the chamber 102 across that same direction. For example, a region of higher density gas will produce more ions that are extracted from the chamber 102 and through the aperture 120 compared to a region of lower density gas. Due to the charge of those ions, this will create a current gradient that directly corresponds to the density gradient within the metal gas within the ion beam. Therefore, one objective of the ion source 100 is to minimize the density gradient of the metal gas (i.e., reduce the variation in the density of the metal gas within the chamber 102 to improve the uniformity of the ion beam extracted through the aperture 120).

[0030] One potential cause of non-uniform density of the metal gas within the ion source may be temperature variations across the metal gas. At higher temperatures, the density of the metal gas is lower, whereas at lower temperatures, the density of the metal gas is higher. That is, upon ionization, a volume at a lower temperature may contain more ions for extraction through the aperture 120 compared to a volume at a higher temperature. Thus, one aspect of the present disclosure is the recognition that temperature gradients within the chamber 102 may create non-uniformity in the ion beam generated by the ion source 100.

[0031] 1, the filament 116 glows during operation of the ion source 100, producing a first amount of heat. This filament heat is referred to herein as Q filament The filament heat is emitted proximate the first end 104 of the chamber 102, and therefore the filament heat Q filament This may tend to create a temperature gradient across the chamber 102 with areas closer to the filament 116 and first end 104 being at higher temperatures.

[0032] Filament Heat Q filamentThe ion source 100 is positioned within the chamber and provides auxiliary heat Q aux The chamber 102 includes one or more heaters 122 operable to supply a heat flux Q into the chamber 102. For example, two heaters 122 may be included. As shown in FIG. 1 , the one or more heaters 122 can extend from the second end of the chamber 102 and along the first wall 108. By being positioned proximate to the second end of the chamber 102, the one or more heaters 122 are geometrically configured to face the filament 116 without interfering with the operation of the reflector electrode 118. The one or more heaters 122 may be configured to supply a heat flux Q between the filament 116 and the first wall 108. filament to at least partially balance the auxiliary heat Q to reduce or eliminate temperature gradients within the chamber 102 that may be caused by filament heat if not in close proximity. aux For example, in some embodiments or scenarios, one or more heaters 122 may be operable to provide a temperature of Q aux =Q filament Various control strategies for the one or more heaters 122 are described in detail below.

[0033] Operation of the one or more heaters 122 can also reduce or eliminate the formation of condensation on the reflector electrode 118 (e.g., on the insulator of the reflector electrode 118) or on other surfaces within the ion source 100. When the metal gas exceeds a certain temperature, the metal gas remains gaseous and moves around the chamber 102. However, below a certain temperature, the metal gas can condense and deposit on surfaces of the ion source 100. The buildup of condensation on the reflector electrode 118 can prevent the reflector electrode 118 from operating as intended. For example, if coated with a thin film of condensation, the reflector electrode 118 can no longer be electrically insulated from the plasma. The one or more heaters 122 provide heat in close proximity to the reflector electrode 118, which keeps the temperature of the metal gas (and the reflector electrode 118 itself) high enough to prevent the buildup of metal condensate on the reflector electrode 118. The buildup of condensation on other surfaces (e.g., on the heaters 122) is similarly prevented. Thus, operation of one or more heaters 122 during ion generation can extend the operational life of the ion source 100, allowing the ion source 100 to operate for relatively long periods of time (e.g., days) without requiring intermittent cleaning as required by other designs.

[0034] 1, the ion source 100 includes multiple temperature sensors (e.g., thermocouples) 124 positioned at multiple locations within the ion source. In the example shown, five thermocouples 124 are included at various locations within the ion source. In various embodiments, other numbers of thermocouples 124 may be included. By measuring the temperature at multiple locations within the chamber 102, temperature differences and gradients across the ion source 100 can be measured. For example, a temperature sensor 124 proximate the filament 116 may measure a higher temperature than a temperature sensor 124 positioned proximate one or more heaters 122, which may require adjusting the operation of one or more heaters 122 to increase Q filamentmay indicate that the temperatures must be better balanced and that temperature gradients within the ion source 100 must be reduced or eliminated. Temperature sensors 124 may be positioned within the chamber 102 to obtain representative measurements of temperature throughout the chamber 102. Thus, multiple temperatures may be monitored in real time to facilitate control of one or more heaters 122, as described in more detail below with reference to FIGS.

[0035] The ion source 100 also facilitates temperature management within the chamber 102 by including thermally conductive support posts, shown in Figure 1 as first post 126 and second post 128. Other numbers of thermally conductive support posts may be included in various embodiments (e.g., four, as shown in Figures 5-8), and the schematic diagram in Figure 1 shows first post 126 and second post 128 for illustrative purposes. The thermally conductive support posts (e.g., first post 126 and second post 128) are configured to physically support the chamber 102 (e.g., hold the chamber 102 in a desired position) and provide heat flow out of the chamber 102, as described in the following sections.

[0036] As an initial matter, the ion source 100 may have a density of, for example, approximately 6×10 -7 While the chamber 102 is in operation, positioned in a vacuum at a pressure of 2-3×10 Torr, -5 Therefore, the primary path for heat to leave the chamber 102 is through any physical structure in contact with the chamber. Therefore, the ion source 100 is designed so that the ideal heat flow is away from the chamber 102 through the support posts 126, 128.

[0037] During operation of the ion source 100, the filament 116 generates a large amount of heat Q, for example, on the order of 1 kilowatt. filament is supplied into the chamber 102. The heater 122 is filament Auxiliary heat Q that balances with aux supply, Q filament(e.g., also on the order of 1 kilowatt). Thus, Q is adjusted to a degree that the temperature within chamber 102 is maintained at a substantially constant temperature (e.g., preventing chamber 102 from forming overheat). aux +Q filament is removed from the ion source 100 through the thermally conductive support posts 126, 128.

[0038] The thermally conductive support posts 126, 128 are preferably made of a material that has high thermal conductivity and good electrical conductivity. For example, the thermally conductive support posts 126, 128 may be made of molybdenum. The chamber 102 may be electrically grounded through the support posts 126, 128. As shown, the first post 126 is electrically grounded to the thermal Q out,1 is provided to exit the chamber 102 through the first post 126, while the second post 128 is provided to allow the heat Q out,2 exits the chamber 102 via the second post 128. In the illustrated embodiment (e.g., having two posts), the thermodynamics of the ion source 100 is out,1 +Q out,2 |≒|Q aux +Q filament In another embodiment where N thermally conductive posts are provided, the thermodynamics of the ion source 100 is preferably such that |Q out,1 +Q out,2 +···Q out,N |≒|Q aux +Q filament It is preferable that |

[0039] The thermally conductive support posts 126, 128 extend from the first wall 108 of the chamber 102 to a cooling system, for example, a water cooling system 130 as shown. Because the thermally conductive support posts 126, 128 are at different locations on the first wall 108, the heat flow Q out,1 and Q out,2 For example, the second post 128 may be positioned in close proximity to one or more heaters 122, and the heaters may beout,2 The value of Q out,1 However, the support posts 126, 128 are positioned generally symmetrically with respect to the chamber 102, thereby arranging to avoid creating undesirable imbalances or temperature variations within the chamber 102 as heat flows out of the chamber 102 through the support posts 126, 128.

[0040] The water cooling system 130 is configured to circulate water (or another fluid or coolant) over the thermally conductive support posts 126, 128 to remove heat from the posts 126, 128. The posts 126, 128 may be in direct contact with the fluid or may transfer heat to the fluid through one or more intermediate structures. The water cooling system 130 is configured to dissipate heat from the ion source 100 to the ambient environment. In some embodiments, the water cooling system 130 includes a chiller or other refrigeration system to remove heat from the fluid (i.e., cooler than ambient) as it is circulated through the support posts 126, 128, absorbs heat from the support posts 126, 128, and returns to the chiller or other refrigeration system to re-cool it. In other embodiments, the water cooling system 130 includes a heat exchanger (e.g., a coil) and, optionally, a fan, to facilitate heat transfer from the fluid to the ambient environment without the use of a chiller or refrigeration system.

[0041] The water cooling system 130 may be configured to measure heat quantity, i.e., the amount of heat extracted by the water cooling. For example, the water cooling system 130 may measure the supply water temperature and the return water temperature and use those measurements in combination with data indicative of the flow rate to calculate the Q shown in FIG. out,total The amount of heat removed by the water cooling system 130 can be calculated as Q out,total The value of Q aux +Q filament Preferably, Q may be approximately equal to aux and Q filamentIn some embodiments, the water cooling system 130 is used to estimate Q out,total In some embodiments, the water cooling system 130 is controlled based at least in part on measurements from the temperature sensor 124 in the chamber 102.

[0042] Accordingly, the ion source 100 includes various elements that facilitate temperature and heat management in the ion source 100 to maximize the operating time of the ion source 100 while also optimizing the uniformity of the ion beam extracted from the chamber 102.

[0043] 2, there is shown a block diagram of a control loop 200 for one or more heaters 122 of the ion source 100, according to an exemplary embodiment. The control loop 200 is shown as including a thermocouple 124, a controller 202, and a heater circuit 204. The heater circuit 204 may include one or more power supplies or other electronic elements that are controllable to affect the operation of one or more heaters 122 of FIG. 1, particularly to vary the power (heat) output of the one or more heaters 122. When multiple heaters 122 are included, the heater circuit 204 may be configured such that the multiple heaters 122 may be independently controlled.

[0044] 2, controller 202 is configured to provide inputs (e.g., control signals) to heater circuit 204, causing heater circuit 204 to operate to affect temperature measurements collected by thermocouple 124 (i.e., via activation of heater 122). Thermocouple 124 provides its output (i.e., temperature measurements) of the physical system back to controller 202. In various embodiments, measurements, control signals, etc., can be analog or digital. In the illustration of FIG. 2, solid lines represent transfers between elements, and dashed lines indicate the thermodynamics that create control loop 200.

[0045] In some embodiments, the controller 202 generates control inputs for the heater circuit 204 based on one or more setpoints for the thermocouples 124. For example, the controller 202 can use feedback control logic (e.g., proportional-integral control, proportional-integral-derivative control) to generate control inputs configured to drive measurements from all of the thermocouples 124 toward a single shared temperature setpoint. Thus, the controller 202 can operate to minimize temperature gradients within the chamber 102. As another example, the controller 202 can use feedback control logic adapted to the generated control inputs configured to drive measurements from each thermocouple 124 toward a thermocouple-specific setpoint for each thermocouple 124. In some embodiments, the setpoints are learned based on measured characteristics of the ion beam (e.g., plasma uniformity), for example, as described in detail below with reference to FIG. 10 . Thus, the controller 202 can operate to optimize a characteristic of the ion beam, such as plasma uniformity.

[0046] In other embodiments, the controller 202 is configured to generate control inputs for the heater circuit 204 that are adapted to drive the difference between temperature setpoints to zero. For example, the controller 202 can be configured to generate control inputs that minimize an error function that compares measurements from multiple thermocouples 124 (e.g., using an extremum-seeking control technique). In such cases, the controller 202 is adapted to cause one or more heaters 122 to reduce or eliminate temperature gradients within the chamber 102 without using predetermined temperature setpoints. Various control techniques are possible in various embodiments.

[0047] In some embodiments, dynamic control of the heater circuit 204 to vary the heat output by the heater 122 is sufficient to provide the desired reduction or elimination of temperature gradients within the chamber 102 and to provide the benefits associated with that reduction or elimination as described herein. In such embodiments, the control loop 200 and controller 202 need not communicate with other elements of the ion source 100 and can be provided alone, as illustrated in Figure 2. In other embodiments, for example, as shown in Figure 3 and described in detail with reference thereto, some embodiments can provide a comprehensive, unified control system.

[0048] 3, a control system 300 for use with the ion source 100 is shown, according to an exemplary embodiment. In some embodiments, the control loop 200 is implemented using the control system 300. The control system 300 is shown as including a controller 302, a thermocouple 124, a water cooling system 130, a heater circuit 204, a filament circuit 304, a reflector electrode circuit 306, an oven circuit 308, an extraction circuit 310, a beam analyzer 312, and a user device 314. Various other embodiments of the control system 300 may include any combination of these elements.

[0049] Filament circuit 304 includes electronic components configured to control the amount of power provided to filament 116. Reflector electrode circuit 306 includes electronic components configured to affect the electric field provided by reflector electrode 118. Oven circuit 308 includes electronic components configured to affect the operation of oven 112, for example, to affect the temperature of gas provided in chamber 102 and / or the amount of gas provided in chamber 102. Extraction circuit 310 provides an electric field at aperture 120 configured to extract the beam from chamber 102 through aperture 120, and in some embodiments is configured to controllably modify that electric field.

[0050] The beam analyzer 312 is configured to analyze one or more characteristics of the ion beam generated by the ion source 100, i.e., extracted by the aperture 120. For example, the beam analyzer 312 may be configured to measure the plasma uniformity of the ion beam. The beam analyzer 312 may be available during online ion generation by the ion source or may be used during setup (testing, calibration, etc.) of the ion source 100.

[0051] The user device 314 is configured to allow a user to interact with the controller 302, for example, to adjust settings of the controller 302, provide commands to the controller 302, etc. The user device 314 may also be configured to display information related to the operation of the ion source 100 to the user.

[0052] 3 , the controller 302 is in communication with the thermocouple 124, the beam analyzer 312, the filament circuit 304, the reflector electrode assembly 306, the heater circuit 204, the oven circuit 308, the extraction circuit 310, the water cooling system 130, and the user device 314. The controller 302 is configured to coordinate control of the water cooling system 130, the filament circuit 304, the reflector electrode assembly 306, the heater circuit 204, the oven circuit 308, and / or the extraction circuit 310, for example, based on input from the thermocouple 124, input from the beam analyzer 312, and / or input from other elements of the control system 300. The controller 302 may be primarily configured for temperature and thermal management of the ion source 100, but may also provide various control functions related to other aspects of the operation of the ion source 100, such as ionization and extraction.

[0053] As an example of coordinated control that may be provided by the controller 302 in various embodiments, the controller 302 may control the water cooling system 130 in coordination with the control of the heater circuit 204, e.g., to vary the amount of cooling supplied to the support posts 126, 128 in proportion to changes in the amount of heat supplied to the water cooling system 130 by the one or more heaters 122. Thus, the control of the water cooling system 130 and the one or more heaters 122 may be coordinated or unified to help manage the temperature of the ion source 100.

[0054] As another example of coordinated control that can be provided by the controller 302, the controller 302 can receive a signal from the filament circuit 304 that indicates the power consumption of the filament 116. The controller 302 can use that information to generate control signals for the heater circuit 204, such as controlling one or more heaters 122 to operate at the same or similar power levels as the filament 116 (e.g., to generate the same amount of heat). The controller 302 can communicate with the oven circuit 308 to take into account the heat supplied to the chamber 102 by the oven when controlling the heater circuit 204 or other aspects of the control system 300.

[0055] 3 , the controller 302 may be able to use measurements from the beam analyzer 312 in feedback control of one or more of the water cooling system 130, the filament circuit 304, the reflector electrode circuit 306, the heater circuit 204, the oven circuit 308, and / or the extraction circuit 310. For example, the heater circuit 204 may be controlled by the controller 302 in a feedback loop that seeks to optimize a parameter, such as plasma uniformity, measured by the beam analyzer 312. As another example, the beam analyzer 312 may be used in a setup (e.g., training, configuration, calibration) phase to train the controller 302 (e.g., to determine values, weightings, etc. of algorithms used by the controller 302) so that the controller 302 can control one or more of the water cooling system 130, the filament circuit 304, the reflector electrode circuit 306, the heater circuit 204, the oven circuit 308, and / or the extraction circuit 310 to optimize the plasma uniformity (or other parameters) of the ion beam.

[0056] The control system 300 can, in various embodiments, enable a variety of such control modalities.

[0057] 4-8, there are shown various depictions of an exemplary embodiment of the ion source 100. In particular, FIG. 4 shows a cutaway perspective view of the ion source 100, FIG. 5A shows an external perspective view of the ion source 100, FIG. 5B shows an external perspective view of the ion source 100 in an alternative embodiment, and FIGs. 6-8 show perspective views of the ion source 100 from three orthogonal viewpoints.

[0058] 4-8 illustrate a chamber 102 defined by a first end 104, a second end 106 opposite the first end 104, a first wall 108 extending from the first end 104 to the second end 106, and a second wall 110 opposite the first wall, as described above with reference to FIG. 1. In FIGS. 5A-5B, a third wall 502 is visible and connects the first end 104, the second end 106, and the first wall 108 and the second wall 110. A fourth wall 702 of the chamber 102 is visible in FIGS. 7 and 8 and is positioned opposite the third wall 502 and also connects the first end 104, the second end 106, the first wall 108, and the second wall 110. Thus, the chamber 102 is formed as a six-sided rectangular box in the illustrated example. In other embodiments, other shapes are possible.

[0059] 4-9 also show a third post 426 and a fourth post 428 extending from the first wall 108 of the chamber 102. The third post 426 and the fourth post 428 are configured substantially the same as the first post 126 and the second post 128 described above. For example, the first post 126, the second post 128, the third post 426, and the fourth post 428 may have substantially similar dimensions and may provide substantially equivalent paths for heat transfer (e.g., differing by less than manufacturing tolerances). Like the first post 126, the third post 426 is positioned proximate the first end 104 of the chamber 102 and the filament 116. Like the second post 128, the fourth post 428 is positioned proximate the second end 106 of the chamber 102 and the heater 122.

[0060] The first post 126, the second post 128, the third post 426, and the fourth post 428 are shown in FIGS. 4-9 as extending from the first wall 108 of the chamber 102 to the plate 402. The plate may be thermally conductive, so that heat can flow from the posts 126, 128, 426, 428 into the plate 402. The plate 402 is then in thermal contact with the water cooling system 130, as described with reference to FIG. 1, so that the heat can dissipate to the water cooling system 130. In some embodiments, the first post 126, the second post 128, the third post 426, and the fourth post 428 can be in direct thermal contact with the interior of the chamber 102 via a channel 430 through the first wall 108, as shown in FIG. 4.

[0061] Plate 402 has a central opening 403 through which oven 112 can extend, for example, as shown in Figures 5A-5B. This allows oven 112 to be primarily positioned on the opposite side of plate 402 from chamber 102 while routing metal gas from oven 112 to chamber 102. This arrangement allows oven 112 to be much larger than shown in the schematic diagram of Figure 1.

[0062] As shown in FIGS. 4-8, the ion source includes two heaters 122, shown as a first heater 122a and a second heater 122b. The heaters 122a, b are cylindrical and are shown extending from the corners of the chamber 102. In particular, the first heater 122a extends from the second end 106 along the edge between the first wall 108 and the third wall 502, while the second heater 122b extends from the second end 106 along the edge between the first wall 108 and the fourth wall 702. The heights of the heaters 122a, b can be selected so that the heaters 122a, b terminate just below the gas inlet 114 from the oven 112. The heaters 122a, b are shown symmetrical about a centerline of the ion source. In some embodiments, the ion source is substantially symmetrical about the centerline. In some embodiments, the first heater 122a and the second heater 122b are metal-ceramic resistance heaters.

[0063] 4-8 show a first heater lead 404 extending from the first heater 122a and a second heater lead 406 extending from the second heater 122b. The first heater lead 404 provides for the transfer of power to the first heater 122a (which the first heater 122a uses to generate heat), while the second heater lead 406 provides for the transfer of power to the second heater 122b (which the second heater 122b uses to generate heat). The first heater lead 404 and the second heater lead 406 may be connected to and / or included with the heater circuit 204 shown in FIGS. 2-3, which may include electronic components configured to provide a variable and controllable amount of power to the first heater 122a and the second heater 122b. The first heater lead 404 and the second heater lead 406 are shown extending through a passage 504 formed through the second end 106 of the chamber 102. In some embodiments, a gasket or other sealing structure may be provided in the passage 504.

[0064] 4-8 also show a first wiring conduit 505 and a second wiring conduit 506 extending into the chamber 102 via ends between the second wall 110 and the third wall 502. The first wiring conduit 505 and the second wiring conduit 506 are configured to connect to temperature sensors (e.g., thermocouples) 124 positioned within the chamber 102 and to provide communication of measurements collected by the temperature sensors 124 out of the chamber 102. In some embodiments, each wiring conduit 505, 506 is connected to one temperature sensor 124. In other embodiments, each wiring conduit 505, 506 is connected to multiple temperature sensors 124, such that the first wiring conduit 505 and the second wiring conduit 506 combine to provide communication of readings from four or more temperature sensors 124 out of the chamber 102 (e.g., five temperature sensors 124 as in FIG. 1 ). First wiring conduit 505 and second wiring conduit 506 may be connected to controller 202 of FIG. 2 or controller 302 of FIG. 3 in various embodiments.

[0065] Also shown in FIGS. 5A-5B is a reflector electrode lead 508. The reflector electrode lead 508 is positioned on the exterior of the chamber 102 to provide easy access for a technician to manipulate the reflector electrode lead 508. As shown in FIGS. 5A-5B, one end of the reflector electrode lead 508 is in electrical contact with the reflector electrode 118. The reflector electrode lead 508 is also connected to the filament 116 to place the reflector electrode 118 at a potential corresponding to the potential of the filament 116. For example, the reflector electrode lead 508 may be approximately −100 V. The reflector electrode 118 may be configured to repel electrons, as described above with reference to FIG. 1 . The reflector electrode lead 508 may also be manually detached from the reflector electrode 118, so that the reflector electrode 118 is not connected to a current external to the chamber 102 and is electrically floating. This configuration may be desirable in some scenarios for use of the ion source 100.

[0066] 5A-5B also show oven leads 511 configured to connect elements of the oven 112 to control circuitry. For example, the oven leads 511 may be used to control a valve that can control the amount of metal gas supplied to the chamber 102. Figures 5A-5B also show gas lines 510 that are connected to the chamber 102 proximate the oven 112 and can supply an auxiliary gas (e.g., xenon) to the chamber 102 either during operation of the ion source 100 to generate an ion beam or during cleaning or other offline conditions of the ion source 100.

[0067] 5A-5B also show bolts 512, which are configured to hold the various components described herein together in assembly. In particular, FIGS. 5A-5B show bolts 512 as engaging the chamber proximate aperture 120 and as engaging water cooling system 130 and / or oven 112 proximate plate 402.

[0068] With respect to the aperture 120, FIGS. 4, 5A, and 6-8 depict the aperture 120 as an elongated slot aligned with the centerline of the chamber 102. In such embodiments, the aperture 120 has a length along the longitudinal axis of the second wall 110. In such embodiments, the width of the aperture 120 is significantly less than its length. For example, the aperture 120 can be formed as a slot having a width of less than 1 centimeter and a length of approximately 4 centimeters. FIG. 5B illustrates an alternative embodiment in which the circular aperture 120 has a radius of, for example, approximately 1 centimeter. Depending, for example, on the configuration of downstream processing stages for the ion beam generated by the ion source 100, various designs of the aperture 120 are possible for various applications. For example, the elongated slot embodiment of FIG. 5A may be preferred for the primary applications described herein. In some embodiments, different apertures 120 are interchangeable, for example, by removing and replacing an aperture emission plate in the second wall 110 of the chamber 102, allowing the ion source 100 to be selectively compatible with different downstream processing steps for the ion beam generated by the ion source 100.

[0069] 9, a flowchart of a process 900 for operating an ion source is shown, according to an exemplary embodiment. This process 900 can be performed using ion source 100, and for example, reference is made to that process in the following description. However, process 900 may be performable with other ion sources in various embodiments. Similarly, in some embodiments, process 900 is performed, at least in part, by operation of control loop 200 and / or control system 300 of FIGS. 2-3.

[0070] In step 902, a metal gas is supplied into the chamber. The metal gas may be, for example, ytterbium gas. In the example of the ion source 100 described above, step 902 includes operating the oven 112 to supply the metal gas into the chamber via the inlet 114. Step 902 may include controlling the amount of metal gas supplied into the chamber so that, for example, a desired flow rate of the metal gas is supplied into the chamber.

[0071] In step 904, the metal gas is ionized. In the example ion source 100, the filament 116 is activated to emit electrons that interact with and ionize the metal gas. As a result of step 904, the heavy metal ions are retained within the chamber 102, e.g., mixed with the gas that has not yet been ionized.

[0072] In step 906, one or more supplemental heaters are activated to reduce or eliminate temperature gradients within the chamber, i.e., temperature differences or ranges across multiple locations within the chamber. Step 906 may include controlling one or more heaters 122 to provide supplemental heat within the chamber 102, as described in detail above. In some embodiments, step 906 focuses on reducing or eliminating temperature gradients throughout the chamber. In other embodiments, step 906 focuses on reducing or eliminating temperature gradients within a portion of the volume of the chamber, for example, within a region proximate the aperture of the chamber from which the ion beam was extracted in step 908.

[0073] In some embodiments, step 906 includes collecting temperature measurements from multiple locations within the chamber and controlling one or more auxiliary heaters based on the measurements. For example, the auxiliary heaters may be controlled to bring the temperature measurements to a shared common setpoint to substantially eliminate or attempt to eliminate temperature gradients within the chamber. As another example, the auxiliary heaters may be controlled to bring temperature measurements from different locations within the chamber to multiple different setpoints, which may correspond to reduced temperature gradients within the chamber and may be determined through a learning or optimization process. As another example, the auxiliary heaters may be controlled using control logic configured to minimize an error function that characterizes the difference between the multiple temperature measurements. In yet another example, step 906 includes operating the auxiliary heaters at a predetermined power level selected to balance the heat generated by the incandescent filament during normal operation of the ion source.

[0074] Thus, as a result of step 906, the chamber may become substantially isothermal, i.e., have approximately the same temperature throughout the chamber, or may be closer to an isothermal condition than a scenario in which the supplemental heaters are not activated in step 906. Because of the physical relationship between temperature and density of the metal gas, step 906 may also be characterized as activating one or more supplemental heaters to reduce or eliminate density gradients (i.e., density differences) of the ionized metal gas within the chamber. Step 906, and activation of the supplemental heaters, may thereby provide ionized gas having a substantially uniform density, at least within a region proximate the aperture of the ion chamber.

[0075] In step 908, the ion beam is extracted from the ion chamber. The ion beam can be extracted by providing an electric field at the aperture of the chamber, which draws charged heavy metal ions out of the chamber through the aperture. Successful execution of step 908 can provide a highly uniform ion beam because the density of ions is substantially uniform proximate the aperture. For example, any lateral current in the ion beam can be minimized. The ion beam extracted from the ion chamber can have optimized plasma uniformity. Thus, in various embodiments, the ion beam extracted from the ion chamber can be well suited for various purposes, such as efficient and effective processing in downstream processing steps of the ion beam. As an example, the ion beam can be well suited for efficient and precise filtering of desired isotopes from an ion beam of, for example, ytterbium-176.

[0076] 9 as a series, can be performed simultaneously to provide continuous production of a highly uniform ion beam. In this regard, operation of the auxiliary heater in step 906 can have the added benefit of reducing or preventing undesirable condensation of metal gas on surfaces within the ion source, such as on the reflector electrode. Thus, performing step 906 simultaneously with steps 902, 904, and 908 can extend the duration for which process 900 can be performed continuously. In some cases, process 900 can be performed indefinitely and / or for a continuous period of at least several days.

[0077] 10, a flow diagram of a process 1000 for controlling an auxiliary heater of an ion source is shown, according to an exemplary embodiment. This process 1000 may be performed in conjunction with the ion source 100 described above, or for some other ion sources, for example. The process 1000 may be performed by the control system 300 of FIG. 3 and / or, in some embodiments, as part of an arrangement of the control loop 200 of FIG. 2.

[0078] In step 1002, an ion source is operated to generate an ion beam. For example, step 1002 can correspond to process 900. For example, a metal gas can be ionized in a Bernas ion source, and the ions can be extracted from the ion source as a beam emitted from an aperture of the ion source.

[0079] In step 1004, the plasma uniformity of the ion beam is measured. For example, a beam analyzer device can be provided that can directly measure the plasma uniformity of the ion beam. This beam analyzer device can interrupt or prevent operation of other downstream processing steps for the ion beam, such that step 1004 is associated with start-up (configuration, calibration, testing, training) times for the ion source. Multiple measurements of plasma uniformity can be collected and stored over time, for example, in the controller 302 of FIG. 3 or in some other computer-readable medium.

[0080] In step 1006, temperatures are measured at multiple locations within the ion source. Step 1006 may be performed simultaneously with step 1004. Step 1006 may include receiving measurements from temperature sensors (e.g., thermocouples) 124 positioned at multiple locations within the chamber 102 of the ion source 100. Each temperature measurement is associated with a particular sensor and / or location and a time of collection, such that a sample of temperature measurements for a particular time can be associated with the plasma uniformity measured at that particular time.

[0081] Steps 1004 and 1006 can be performed simultaneously for a duration sufficient to collect a robust data set, including, for each of a plurality of time steps, a set of multiple temperature measurements for multiple locations within the ion source for the time step, and a measurement of plasma uniformity of the ion beam for the time step. In some embodiments, while steps 1004 and 1006 are being performed, a training experiment is performed in which the auxiliary heater is controlled to induce a wide range of temperature measurement variations at multiple locations, for example, so that the data captured in steps 1004 and 1006 includes samples spanning the entire operating volume of the auxiliary heater. The experiment should be expected to produce a corresponding change in plasma uniformity upon the effect of the temperature changes.

[0082] In step 1008, temperature setpoints for multiple locations (e.g., of multiple temperature sensors) within the ion source corresponding to optimal plasma uniformity are determined. For example, the data set collected in steps 1004 and 1006 can be searched to find the best plasma uniformity measured during data collection, and the measured temperature for the corresponding time step can be selected as the temperature setpoint. As another example, machine learning, neural networks, regression, optimization, numerical analysis, or other modeling or data processing techniques can be used to determine optimal temperature setpoints for generating an ion beam with optimal plasma uniformity based on the data collected in steps 1004 and 1006.

[0083] In other embodiments, steps 1004, 1006, and 1008 are performed simultaneously, and step 1008 includes controlling one or more heaters to search for the optimal (best, extreme, maximum) measured plasma uniformity. In such embodiments, the operation of one or more heaters is adjusted until the optimal plasma uniformity is measured by the beam analyzer. Once this optimal state is achieved, the current setpoints of the one or more heaters can be determined as the optimal setpoints for the one or more heaters. For example, the amount of power supplied to the one or more heaters at that state can be determined as the optimal setpoint for the one or more heaters and used for online control of the one or more heaters. As another example, when the ion source is adjusted to generate an ion beam with optimal plasma uniformity, temperatures measured by sensors 124 at various locations within the chamber 102 can be determined as temperature setpoints for use in online control of the one or more heaters.

[0084] In step 1010, the auxiliary heaters are controlled in a feedback loop using the temperature setpoint determined in step 1008 and temperature measurements from the ion source. For example, a control loop 200 such as that of FIG. 2 can be used. Step 1010 corresponds to online operation of the ion source to produce an ion beam that is used in downstream processing steps for the ion beam. The training phase of steps 1002, 1004, 1006, and 1008 results in the online control of one or more auxiliary heaters in step 1010 providing an ion beam with optimal plasma uniformity that can be achieved by the ion source.

[0085] Although step 1010 focuses on temperature values ​​and plasma uniformity measurements, process 1000 may be adapted to consider additional or other inputs (e.g., setpoints for, or measurements related to, operation of oven 112, filament 116, reflector electrode 118, ion extraction device, etc.) or outputs (e.g., other characteristics of the ion beam) and to train control logic for various elements of control system 300. All such variations are within the scope of this disclosure.

[0086] As used herein, the terms "approximately," "about," "substantially," and similar terms are intended to have a broad meaning consistent with common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. These terms should be understood by those of ordinary skill in the art reviewing this disclosure to indicate that the description of particular features is intended to allow those features to be described and claimed without limiting the scope of those features to the precise numerical values ​​provided, or to idealized geometric shapes. Accordingly, these terms should be interpreted as indicating that insubstantial or insignificant modifications or variations of the subject matter described and claimed are considered to be within the scope of the present disclosure, as recited in the appended claims.

[0087] As used herein, the term "coupled" and variations thereof refer to the joining of two members directly or indirectly to one another. Such joining may be static (e.g., permanent or fixed) or movable (e.g., removable or releasable). Such joining may be achieved using two members directly joined to one another, a separate intermediate member, and any additional intermediate member joined to one another, or two members joined to one another using an intermediate member integrally formed with one of the two members as a single body. When "coupled" or variations thereof are modified by additional terms (e.g., directly coupled), the inclusive definition of "coupled" provided above is modified by the ordinary linguistic meaning of the additional terms (e.g., "directly coupled" means the joining of two members without any separate intermediate member), resulting in a definition narrower than the inclusive definition of "coupled" provided above. Such joining may be mechanical, electrical, or fluid.

[0088] References herein to the location of elements (e.g., "top," "bottom," "upper," "lower") are used merely to describe the orientation of various elements within the drawings. It should be noted that the orientation of various elements may differ according to other exemplary embodiments, and such variations are intended to be encompassed by the present disclosure.

[0089] The hardware and data processing components used to implement the various processes, operations, exemplary logic, logic blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed using general-purpose single- or multi-chip processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs) or other programmable logic devices, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, or any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In some embodiments, particular processes and methods may be performed by circuitry specific to a given function. Memory (e.g., memory, memory unit, storage device) may include one or more devices (e.g., RAM, ROM, flash memory, hard disk storage) for storing data and / or computer code for completing or facilitating the various processes, layers, and modules described in this disclosure. Memory may be or include volatile or non-volatile memory and may include database components, object code components, script components, or any other type of information structure for supporting the various activities and information structures described in this disclosure. According to an exemplary embodiment, the memory is communicatively coupled to the processor via a processing circuit and includes computer code for executing (e.g., by the processing circuit or processor) one or more processes described herein.

[0090] The present disclosure contemplates methods, systems, and program products on any machine-readable medium for accomplishing various operations. Embodiments of the present disclosure can be implemented using existing computer processors, or by dedicated computer processors for suitable systems incorporated for this or another purpose, or by hardwired systems. Embodiments within the scope of the present disclosure include program products comprising machine-readable media for carrying or having machine-executable instructions or data structures stored thereon. Such machine-readable media can be any available medium that can be accessed by a general-purpose computer or special-purpose computer, or other machine with a processor. By way of example, such machine-readable media can include RAM, ROM, EPROM, EEPROM, or other optical disk storage, magnetic disk storage, or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of machine-executable instructions or data structures and that can be accessed by a general-purpose computer or special-purpose computer, or other machine with a processor. Combinations of the above are also included within the scope of machine-readable media. Machine-executable instructions include, for example, instructions and data that cause a general-purpose computer, special-purpose computer, or special-purpose processing machine to perform a certain function or group of functions.

[0091] Although the figures and description may illustrate a particular order of method steps, the order of such steps may differ from that shown and described unless otherwise specified. Also, two or more steps may be performed concurrently or with partial concurrence unless otherwise specified. Such variations may depend, for example, on the software and hardware systems selected and the designer's choice. All such variations are within the scope of this disclosure. Similarly, software implementations of the described methods may be achieved using standard programming techniques involving rule-based logic and other logic to accomplish the various connecting, processing, comparing, and determining steps.

Claims

1. a chamber having a first end, a second end opposite the first end, a first wall extending from the first end to the second end, and a second wall opposite the first wall; a source filament at the first end of the chamber and configured to emit electrons and a first amount of heat; a beam aperture in the second wall of the chamber; one or more heaters positioned within the chamber and between the second end and the beam aperture and operable to provide a second amount of heat; An ion source comprising: the one or more heaters are positioned and operable such that the second thermal quantity balances the first thermal quantity to reduce or eliminate a temperature gradient within the chamber; The ion source.

2. a plurality of thermocouples distributed within the chamber; a controller configured to provide closed-loop control of the one or more heaters based on outputs from the plurality of thermocouples; and The ion source of claim 1 further comprising:

3. a reflector electrode at the second end of the chamber and configured to reflect the electrons away from the second end. The ion source of claim 1 further comprising:

4. The ion source of claim 3 , wherein activation of the one or more heaters reduces or eliminates condensation on an insulator of the reflector electrode.

5. 10. The ion source of claim 1, further comprising a gas inlet in the first wall of the chamber, the gas inlet aligned with the beam aperture.

6. 2. The ion source of claim 1, wherein the one or more heaters include a first cylindrical heater extending from the second end of the chamber and along the first wall of the chamber.

7. 7. The ion source of claim 6, wherein the one or more heaters include a second cylindrical heater extending from the second end of the chamber and along the first wall of the chamber, the second cylindrical heater being spaced apart from the first cylindrical heater.

8. a plurality of support posts coupled to the first wall of the chamber and extending away from the chamber; 10. The ion source of claim 1, further comprising: a plurality of support posts providing a uniform path for heat transfer out of the chamber.

9. Further comprising a water cooling system; the plurality of support posts extend from the chamber to the water cooling system; the water cooling system configured to remove heat from the plurality of support posts. The ion source of claim 8 .

10. 10. The ion source of claim 9, wherein the water cooling system is further configured to measure heat removed from the plurality of support posts by the water cooling system.

11. 10. The ion source of claim 1, further comprising an oven configured to supply ytterbium gas into the chamber through an inlet in the first wall.

12. 10. The ion source of claim 1, further comprising a test device configured to measure a plasma uniformity of the ion beam emitted from the beam aperture, and wherein controls for the one or more heaters are adjusted based on the plasma uniformity.

13. 2. The ion source of claim 1, wherein the second amount of heat is substantially equal to the first amount of heat.

14. 10. The ion source of claim 1, wherein reducing or eliminating temperature gradients within the chamber results in reducing or eliminating non-uniform currents within the ion beam emitted from the beam aperture.

15. supplying a metal gas into the chamber; ionizing the metal gas by supplying power to a filament to cause the filament to emit electrons within the chamber, wherein supplying power to the filament causes the filament to apply heat to the chamber proximate a first end of the chamber; reducing or eliminating a temperature gradient within the chamber by activating one or more heaters positioned within the chamber, the one or more heaters being positioned inside the chamber and extending from a second end of the chamber opposite the first end; extracting the ion beam from the chamber through an aperture positioned between the filament and the one or more heaters; A method comprising:

16. 16. The method of claim 15, wherein activating the one or more heaters comprises causing the one or more heaters to balance the heat added to the chamber by the filament.

17. measuring temperatures at a plurality of locations within the chamber; and operating the one or more heaters includes controlling the one or more heaters based on temperatures at the plurality of locations within the chamber.

16. The method of claim 15.

18. measuring plasma uniformity of the ion beam extracted through the aperture; determining set points for temperatures at the plurality of locations within the chamber based on the plasma uniformity measurements, the set points being associated with optimal plasma uniformity; 20. The method of claim 17, further comprising:

19. 20. The method of claim 18, comprising controlling the one or more heaters to bring the temperature at the plurality of locations to the setpoint.

20. The method of claim 15 , further comprising removing heat from the chamber by operating a water cooling system thermally coupled to the chamber by a plurality of support posts.

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