Thermal actuator

Abstract

According to some aspects, there is provided a thermal actuator comprising at least one first plate, the at least one first plate forming at least one wedge and at least one second plate disposed adjacent to the at least one first plate and forming at least one wedge. The at least one wedge of the at least one first plate contacts the at least one wedge the at least one second plate, the at least one first plate has a first coefficient of thermal expansion, and the at least one second plate has a second coefficient of thermal expansion that is greater than the first coefficient of thermal expansion. One or more thermal actuators may be inserted into a tokamak.

Description

PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00THERMAL ACTUATORCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. § 119(e) of U.S. Provisional Application No. 63 / 700553 filed September 27, 2024 entitled “THERMAL ACTUATOR”, under Attorney Docket No.: C1599.70069US00, which is hereby incorporated by reference in its entirety.FIELD

[0002] Aspects of the technology provided herein relate to a thermal actuator. In particular, aspects of the technology described herein relate to a thermal actuator comprising a plurality of stacked plates, and configured to be used in a tokamak.BACKGROUND

[0003] Magnetic confinement is an approach to generate fusion power that uses magnetic fields to confine a plasma to produce conditions under which the plasma will undergo fusion. Very high plasma temperatures, on the order of 150 million °C, are required to initiate fusion reactions, and the plasma may be heated through operation of the magnetic fields and using external heating methods. Magnetic confinement of a plasma is challenging, as turbulence, instabilities, and other effects within the plasma can quickly reduce the efficiency of the fusion reaction, or even stop it completely.

[0004] The fusion plant design known as a tokamak is one approach to magnetic confinement that seeks to address the problematic instabilities that can result in the plasma during heating and / or during fusion reactions. In a tokamak, the plasma is confined in a toroid, and instabilities in the plasma are controlled by arranging magnetic fields to cause particles of the plasma to transit between the inner and outer sides of the toroid multiple times per orbit. This “twist’ in the magnetic fields dramatically improves the stability of the plasma. To control the plasma in a tokamak, magnets are used to create toroidal and poloidal fields that shape and position the plasma within the toroid, as well as drive motion of the plasma around the toroid. The fusion reaction in a tokamak produces most of its energy as neutrons, which must be captured, and their kinetic energy turned into heat. Energy capture is typically performed using a1#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00 structure containing low atomic number atoms, such as lithium, which will readily collide with neutrons in inelastic collisions. This material, often called a “blanket,” can be directed to a heat exchanger to drive a conventional steam turbine or other generator.SUMMARY

[0005] According to some aspects, there is provided a thermal actuator comprising: at least one first plate, the at least one first plate forming at least one wedge; and at least one second plate disposed adjacent to the at least one first plate and forming at least one wedge, wherein: the at least one wedge of the at least one first plate contacts the at least one wedge the at least one second plate; the at least one first plate has a first coefficient of thermal expansion; and the at least one second plate has a second coefficient of thermal expansion that is greater than the first coefficient of thermal expansion.

[0006] According to some aspects, there is provided a tokamak comprising: a central solenoid; a plurality of toroidal field coils; and athermal actuator disposed between the central solenoid and a retention component coupled to the plurality of toroidal field coils, the thermal actuator including a plurality of plates being stacked together and configured such that when the thermal actuator is cooled, the plurality of plates expand outward along a vertical axis along which the plurality of plates are stacked.

[0007] According to some aspects, there is provided a method of manufacturing a tokamak including a central solenoid and a plurality of toroidal field coils, the method comprising: inserting a thermal actuator between the central solenoid and a retention component coupled to the plurality of toroidal field coils, wherein the thermal actuator includes a plurality of plates being stacked together and configured such that when the thermal actuator is cooled, the plurality of plates expand outward along a vertical axis along which the plurality of plates are stacked.

[0008] According to some aspects, there is provided a method of manufacturing a thermal actuator, the method comprising: stacking a plurality of plates, wherein the plurality of plates include: at least one first plate, the at least one first plate forming at least one wedge; at least one second plate disposed adjacent to the at least one first plate and forming at least one wedge, and wherein: the at least one wedge of the at least one first plate contacts the at least one wedge the at least one second plate; the at least one first plate has a first coefficient of thermal expansion; and the at least one second plate has a second coefficient of thermal expansion that is greater than the first coefficient of thermal expansion.

[0009] According to some aspects, there is provided a thermal actuator comprising: a first plate; and a set of second plates, each plate of the set of second plates comprising: a plurality of wedges formed on at least one face of the plate; and a slit comprising a break in a circumference of the plate; and wherein:2#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00 the set of second plates are stacked together; and the first plate is disposed within an inner diameter of the set of second plates or outside of an outer diameter of the set of second plates.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Various aspects and embodiments will be described with reference to the following figures. It should be appreciated that the figures are not necessarily drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing.

[0011] FIGS. 1A-1B depict cross-sectional views of an illustrative tokamak, according to some embodiments.

[0012] FIG. 2 illustrates a portion of an illustrative tokamak having an example thermal actuator inserted therein, according to some embodiments.

[0013] FIG. 3 illustrates a top view of an example thermal actuator, according to some embodiments.

[0014] FIG. 4A illustrates a cross-sectional view of an example thermal actuator, according to some embodiments.

[0015] FIG. 4B illustrates a cross-sectional view of another example thermal actuator, according to some embodiments.

[0016] FIG. 5 illustrates a portion of a cross-sectional view of the example thermal actuator of FIG. 4A illustrating the properties thermal expansion of the example thermal actuator, according to some embodiments.

[0017] FIG. 6 illustrates a cross-sectional of an example thermal actuator according to a second embodiment, according to some embodiments.

[0018] FIG. 7A illustrates a bottom perspective view of an upper plate of the example thermal actuator of FIG. 6, according to some embodiments.

[0019] FIG. 7B illustrates a top perspective view of an upper plate of the example thermal actuator of FIG. 6, according to some embodiments.

[0020] FIG. 7C illustrates a partial cross-sectional view of an upper plate of the example thermal actuator of FIG. 6, according to some embodiments.3#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00

[0021] FIG. 8 A illustrates a bottom perspective view of a first contraction plate of the example thermal actuator of FIG. 6, according to some embodiments.

[0022] FIG. 8B illustrates a top perspective view of a first contraction plate of the example thermal actuator of FIG. 6, according to some embodiments.

[0023] FIG. 8C illustrates a partial cross-sectional view of a first contraction plate of the example thermal actuator of FIG. 6, according to some embodiments.

[0024] FIG. 9A illustrates a bottom perspective view of an internal plate of the example thermal actuator of FIG. 6, according to some embodiments.

[0025] FIG. 9B illustrates a top perspective view of an internal plate of the example thermal actuator of FIG. 6, according to some embodiments.

[0026] FIG. 9C illustrates a partial cross-sectional view of an internal plate of the example thermal actuator of FIG. 6, according to some embodiments.

[0027] FIG. 10 illustrates a partial cross-sectional view of the example thermal actuator of FIG. 6, according to some embodiments.

[0028] FIG. 11 illustrates aspects of the example thermal actuator of FIG. 6, according to some embodiments.

[0029] FIG. 12 illustrates aspects of the example thermal actuator of FIG. 6, according to some embodiments.

[0030] FIGS. 13-15 illustrate additional views of the example thermal actuator of FIG. 6, according to some embodiments.

[0031] FIG. 16 illustrates geometry of the example thermal actuator of FIG. 6, according to some embodiments.

[0032] FIGS. 17A-17D illustrates aspects of expansion of the example thermal actuator of FIG. 6, according to some embodiments.

[0033] FIGS. 18A-18F illustrate aspects of the geometry of an example thermal actuator, according to some embodiments.

[0034] FIGS. 19A-19B illustrate aspects of expansion of an example thermal actuator, according to some embodiments.

[0035] FIG. 20 illustrates an example method for manufacturing a thermal actuator, according to some embodiments.4#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00

[0036] FIGS. 21A-D illustrate example embodiments of a thermal actuator inserted into a gap created by a toroidal field coil of a tokamak, according to some embodiments.

[0037] FIG. 22 illustrates another example embodiment of a thermal actuator, according to some embodiments.

[0038] FIG. 23 illustrates a side view of the example thermal actuator of FIG. 22, according to some embodiments.

[0039] FIGS. 24A-24B illustrate top and bottom views of the thermal actuator of FIG. 22, according to some embodiments.

[0040] FIG. 25 illustrates another view of the example thermal actuator of FIG. 22, according to some embodiments.

[0041] FIG. 26 illustrates another view of the example thermal actuator of FIG. 22, according to some embodiments.

[0042] FIGS. 27A-27C illustrate views of an outer plate of the example thermal actuator of FIG. 22, according to some embodiments.

[0043] FIG. 27D illustrates a portion of an outer plate of the example thermal actuator of FIG. 22, according to some embodiments.

[0044] FIG. 27E illustrates portions of the example thermal actuator of FIG. 22, according to some embodiments.

[0045] FIG. 28 illustrates aspects of the geometry of the example thermal actuator of FIG.22, according to some embodiments.

[0046] FIG. 29 illustrates aspects of the geometry of the example thermal actuator of FIG.22, according to some embodiments.

[0047] FIG. 30 illustrates aspects of expansion of the example thermal actuator of FIG. 22, according to some embodiments.

[0048] FIG. 31 illustrates aspects of deflection of the example thermal actuator of FIG. 22, according to some embodiments.

[0049] FIG. 32 illustrates another example thermal actuator, according to some embodiments.DETAILED DESCRIPTION5#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00

[0050] As described above, the fusion plant design known as a tokamak is one approach to magnetic confinement for fusion power. For purposes of explanation, FIG. 1A depicts a cross- sectional view of an illustrative tokamak, according to some embodiments. As shown in FIG.1A, in tokamak 100, the core plasma 110 circulates within a vacuum vessel 120, which is shaped as a toroid (or approximately as a toroid). There are numerous ports integrally formed within, or otherwise coupled to, the vacuum vessel that provide access to the vacuum vessel from outside of the tokamak, including ports 131, 132 and 133, which are situated at various points around the tokamak. The tokamak 100 also includes a plurality of toroidal field (TF) magnets 140, a plurality of poloidal field (PF) magnets 150, and one or more central solenoid (CS) magnets 160. The TF magnets 140 are D-shaped (or approximately D-shaped) magnets that are configured to confine the plasma 110 in a desired region of the vacuum vessel 120. The PF magnets 150 are roughly ring-shaped magnets that are configured to shape and position the plasma 110. The CS magnet(s) 160 are arranged in the center of the tokamak and are configured to inductively drive the plasma current. The tokamak may also comprise, or may otherwise be coupled to, a source of auxiliary heating to bring the plasma to a desired temperature (e.g., an ion cyclotron resonance heating system, alpha particles produced during fusion, and / or ohmic power).

[0051] Some of the components shown in FIG. 1A are also shown in a more detailed cross- sectional view in FIG. IB, which depicts a cross-sectional view through one side of the tokamak, according to some embodiments. In addition to the plasma 110, vacuum vessel 120, and magnets 140, 150 and 160 also shown in FIG. 1A, FIG. IB depicts a space 170 in which a blanket tank may be arranged, as described further below. During operation of the tokamak 100, an axisymmetric toroidal plasma 110 is produced in the vacuum vessel 120. This plasma carries a toroidal current, which in turn creates a poloidal magnetic field, providing confinement of the plasma. The toroidal field magnets 140 provide stability to the plasma current, with the poloidal field magnets and the central solenoid shaping and controlling the position of the plasma. The plasma is heated by the central solenoid, RF and / or high energy neutral beams to initiate fusion, and energy from the resulting neutrons are captured in the blanket as described above.

[0052] The inventors have recognized that during operation of the tokamak, certain components of the tokamak move away from each other. The toroidal field magnet 140 may stretch vertically in both upward and downward directions. For example, in operation, the toroidal field magnet 140 stretches upwards while the central solenoid 160 shrinks vertically6#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00 along its axis, creating a gap between the toroidal field magnet 140 and the central solenoid 160. A second gap may also be created at a bottom of the tokamak where the toroidal field magnet 140 stretches downward. Such gaps in the tokamak are undesirable as they may lead to issues in operation of the tokamak.

[0053] To address these gaps, the inventors have developed a thermal actuator which is configured to expand under certain conditions. In particular, the thermal actuator is configured such that the thermal actuator can expand to fill the gap described herein automatically (e.g., without electronics or user interaction). That is, the thermal actuator may be configured such that a height of the thermal actuator increases in response to a change in temperature.

[0054] The inventors have recognized that expansion of the thermal actuator can be controlled by the motion resulting from the coefficient of thermal expansion (CTE) of the material from which components of the thermal actuator are made and a change in temperature. The CTE of a material is a material property indicative of the extent to which a material changes its dimensions (e.g., expands, contracts, respectively) upon heating or cooling. The higher a CTE a material has, the more it will expand in reaction to being heated and retract in reaction to being cooled. By using materials having an appropriate CTE, the expansion of the thermal actuator can be achieved when a temperature changes, without the need to manually or programmatically control the actuator to expand.

[0055] The inventors have recognized that such a thermal actuator can be manufactured using materials having different coefficients of thermal expansion. As described herein, the thermal actuator may comprise a stack of alternating materials with the respective materials having different coefficients of thermal expansion (CTE). Components made from materials with higher CTEs will retract (e.g., shrink inward) more relative to components made from materials with a lower CTE. The upper and lower components of the thermal actuator may be made from material with lower CTE while at least some components of the thermal actuator between the upper and lower components may be made from material with a higher CTE such that the inner components between the upper and lower components shrink inwardly more when the thermal actuator cools. The inventors have recognized that the angling of surfaces of the upper, inner, and lower components which are in contact with each other can be designed to cause the upper and lower components of the thermal actuator to push away from the inner components, and thereby expand to fill the gap between the toroidal field magnet and central solenoid.7#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00

[0056] The inventors have further recognized that geometry of the thermal actuator (e.g., use of multiple angled surfaces, wedge shapes, and / or sawtooth shapes) can be used to maximize the amount of expansion of the thermal actuator that can be achieved while minimizing the height of the thermal actuator. In this way, the thermal actuator may be relatively small in its unexpanded form to fit between a retention component (e.g., a retaining ring) in contact with the toroidal field magnet and central solenoid during normal operation but expand sufficiently when necessary to fill the gap between the toroidal field magnet and central solenoid.

[0057] The aspects and embodiments described above, as well as additional aspects and embodiments, are described further below. These aspects and / or embodiments may be used individually, all together, or in any combination, as the application is not limited in this respect.

[0058] FIG. 2 illustrates a portion of an illustrative tokamak having an example thermal actuator inserted therein, according to some embodiments. As described herein, the inventors have recognized that a thermal actuator configured to expand under certain temperature conditions can be used to fill a gap between components of the tokamak which move away from each other due to such temperature conditions, or for any other reason. FIG. 2 illustrates an example schematic diagram showing a cross-section of the tokamak 100 where the thermal actuator 200 is inserted into the tokamak between (e.g., above) the central solenoid 160 and (e.g., below) the retaining ring 190 that is in contact with the toroidal field magnet 140. For example, the retaining ring 190 may be coupled to the toroidal field magnet 140. In the illustrated embodiment of FIG. 2, one thermal actuator 200 is shown, however in other embodiments, multiple thermal actuators 200 may be inserted into the tokamak 100. For example, a second thermal actuator 200 may be inserted below the central solenoid 160 and above a retention component (e.g., retaining ring 190).

[0059] In operation, the top and / or bottom of the toroidal field magnet 140 stretches vertically (e.g., downward), away from the central solenoid 160. The central solenoid 160 moves upwards away from toroidal field magnet 140. The thermal actuator expands in height (e.g., along a y-axis) to fill the gap created between the toroidal field magnet 140 and retaining ring 190, and the central solenoid 160. That is, the thermal actuator is cooled via direct conduction through contact with adjacent components of the tokamak on the top and bottom of the thermal actuator. The components of the tokamak contacting the thermal actuator are independently cooled to cryogenic temperatures, and thus through contact and conduction the thermal actuator8#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00 is cooled as well. The expansion of the thermal actuator may exert a force on adjacent components of the tokamak (e.g., the central solenoid 160, the retaining ring 190, and / or toroidal field magnet 140).

[0060] FIG. 3 illustrates a top view of an example thermal actuator 200, according to some embodiments. In the illustrated embodiment, the thermal actuator 200 comprises a stack of plates of different materials. That is, the thermal actuator 200 comprise a first plate (e.g., upper plate 202 shown in FIG. 3) having a first material with a first CTE, and a second plate disposed below the first plate (e.g., first contraction plate 206 shown in FIG. 4A) having a second material with a second CTE that is different from the first CTE. Configuration of the plates with different CTEs results in the first plate reacting differently to a change in temperature relative to the second plate. That is, the plate having the higher CTE will contract more than the plate having the lower CTE when temperature decreases. The relative difference in contraction between the plates causes the plate having the higher CTE to move further inward than the adjacent plate having the lower CTE. The inventors have recognized that the geometry of the plates can be configured such that this motion causes the thermal actuator to expand by pushing the plates away from each other, causing displacement of the thermal actuator.

[0061] The plates of the thermal actuator 200 may be any suitable shape. In some embodiments, the plates of the thermal actuator 200 are circular, as in the illustrated embodiment of FIG. 3. In some embodiments, the plates of the thermal actuator are ring shaped, as in the illustrated embodiment of FIG. 3. The ring shape of the plates in the embodiment of FIG. 3 may facilitate placement of the thermal actuator into a tokamak. In other embodiments, the plates have a different shape, such as a rectangular shape. The inventors have recognized that the plates of the thermal actuator may be designed having any shape with any corresponding vector of contraction / expansion where the angled faces (e.g., sawtooth faces forming the wedge(s) of the plate) enforce displacement perpendicular to the vector of contraction / expansion. In the illustrated embodiments, each of the plates have substantially the same shape (e.g., each of the plates are ring shaped) when viewing the thermal actuator from the top.

[0062] FIG. 4A illustrates a cross-sectional view of an example thermal actuator, according to some embodiments. The cross-sectional view shown in FIG. 4A is taken along the line A-A shown in FIG. 3.9#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00

[0063] As shown in FIG. 4A and described herein, the thermal actuator 200 of FIG. 4A comprises a plurality of plates 202, 206, 204 which are stacked together. In the illustrated embodiment of FIG. 4A, the plurality of plates are comprised of three plates, however other configurations are possible (e.g., two plates, more than three plates).

[0064] More specifically, the thermal actuator 200 of FIG. 4A comprises an upper plate 202, a lower plate 204, and a first contraction plate 206 disposed between the upper and lower plates 202, 204. The upper plate 202 may be considered a first plate and the lower plate 204 may be considered a third plate, while the first contraction plate 206 may be considered a second plate. In this way, the upper and lower plates 202, 204 may be considered “odd” plates and the first contraction plate 206 may be considered an “even” plate in the illustrated embodiment of FIG. 4A due to their positioning in the stack of plates. The upper and lower plates 202, 204 may be considered “outer” plates while the first contraction plate 206 may be considered an “inner” plate, due to the relative positions of the respective plates in the stack of plates.

[0065] As shown in FIG. 4A, each of the plurality of plates have at least one angled surface forming at least one wedge. In particular, the upper and lower plates 202, 204 have one flat surface and one angled surface. Upper plate 202 has a flat surface 213 facing way from others of the plurality of plates and an angled surface 203 facing towards others of the plurality of plates. The lower plate 204 has a flat surface 215 facing away from others of the plurality of plate and an angled surface 205 facing towards others of the plurality of plates. First contraction plate 206 has a pair of angled surfaces 207, 208 disposed on opposing sides of the first contraction plate 206 (e.g., along the y-axis). A first angled surface 208 of the first contraction plate 206 is disposed adjacent to (e.g., faces) and in contact with the angled surface 203 of the upper plate 202 and a second angled surface 207 of the first contraction plate 206 is disposed adjacent to (e.g., faces) and is in contact with the angled surface 205 of the lower plate 204.

[0066] As described herein, the thermal actuator is not limited to three plates. In other embodiments, the thermal actuator may have more than three plates (e.g., as shown in FIG. 6). In still further embodiments, the thermal actuator may comprise two plates. FIG. 4B illustrates a cross-sectional view of another example thermal actuator, according to some embodiments. In the illustrated embodiment of FIG. 4B, a thermal actuator 250 is provided having two plates: an upper plate 252 and a contraction plate 256.10#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00

[0067] The upper plate 252 may function in the same or similar way as upper plate 202. For example, upper plate 252 comprises an angled surface 253 and a flat surface 263 disposed on an opposite side of upper plate 252 relative to the angled surface 253. The angled surface 253 forms a wedge.

[0068] Contraction plate 256 may function in the same or similar way as first contraction plate 206. In the illustrated embodiment of FIG. 4B, however, only one of two opposing sides of the contraction plate 256 (e.g., the top and bottom of contraction plate 256) comprise an angled surface. In particular, contraction plate 256 comprises angled surface 258 disposed opposite flat surface 255 of contraction plate 256.

[0069] The angled surface 258 of contraction plate 256 is in contact with angled surface 253 of upper plate 252. Contraction plate 256 is made from a material having a higher CTE than a material from which upper plate 252 is made from. In this way, contraction plate 256 changes dimensions to a greater extent in response to a change in temperature than upper plate 252. For example, contraction plate 256 shrinks inwardly to a greater extent in response to a decrease in temperature than upper plate 252.

[0070] In the illustrated embodiment of FIGS. 4A-4B, the plates of the thermal actuator 200 each comprise at least one angled surface forming at least one wedge. In some embodiments, as described herein, the thermal actuator may be configured such that each plate has a plurality of angled surfaces forming a plurality of wedges. For example, each plate may have a plurality of angled surfaces on a single side of the plate, examples of which are further described herein, for example with respect to FIGS. 6-9C.

[0071] The inventors have recognized that geometry and material of the plates can be configured such that the thermal actuator expands under certain temperature conditions. FIG. 5 illustrates a portion 210 of a cross-sectional view of the example thermal actuator of FIG. 4A illustrating the properties thermal expansion of the example thermal actuator, according to some embodiments. The top panel of FIG. 5 illustrates the thermal actuator 200 in an unexpanded form. The height of the plurality of plates stacked together is Hl and the length of each plate of the thermal actuator in the portion 210 of the thermal actuator shown in FIG. 5 is LI.

[0072] The bottom panel of FIG. 5 illustrates the portion 210 of the thermal actuator in an expanded form. As described herein, when the thermal actuator undergoes a change in temperature, the thermal actuator contracts or expands in reaction to the change in temperature.11#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00More specifically, when temperature decreases, components of the thermal actuator contract. As further described herein, due to differences in CTE of the respective plates, certain plates of the thermal actuator contract to a greater extent than other plates of the thermal actuator.

[0073] In some embodiments, one or more (e.g., all) of the plates of the thermal actuator 200 may be anchored to one or more components of the tokamak. In some embodiments, the plates of the thermal actuator may not be anchored. For example, where the thermal actuator comprises a ring-shape, the thermal actuator shrinks inwardly toward a center of the plates, which is the center of mass of the thermal actuator. In this respect, all sides of the thermal actuator shrink inwardly towards the center of mass of the thermal actuator.

[0074] In the illustrated embodiment of FIG. 5, the upper and lower plates 202, 204, also referred to herein as a first set of plates, or the odd numbered plates, have a first CTE that is less than a second CTE of the first contraction plate 206. Due to its higher CTE, the first contraction plate 206 contracts more than the upper and lower plates 202, 204, as is illustrated in the bottom panel of FIG. 5. For example, the portion of the first contraction plate 206 shown in FIG. 6 shrinks inward, thereby contracting from an initial length of El to a second length of E2, towards a center of the plate, that is less than El. The upper and lower plates 202, 204 having a lower CTE do not contract to the same extent as the first contraction plate 206.

[0075] As is further shown in the bottom panel of FIG. 5, the contraction of the first contraction plate 206 in combination with the angled surfaces of each of the plates described herein, cause the first contraction plate 206 to push against the upper and lower plates, respectively, thereby pushing the upper plate 202 and the lower plate 204 away from the first contraction plate 206 in opposite directions. The pushing away causes displacement of the upper and lower plates 202, 204 outward, as can be seen in the bottom panel of FIG. 5, which shows that the height of the thermal actuator increases from an initial height of Hl to a second height H2 as a result of the first contraction plate 206 contracting. In this way, the configuration of the respective plates of the thermal actuator having a particular geometry and composition facilitates expansion of the thermal actuator under certain temperature conditions.

[0076] The material of the plates may be any suitable material that provides a difference in CTE between the plates. That is, the material of the plates may be any suitable material selected such that the plates other than the contraction plate (e.g., odd plates, upper and lower plates 202, 204) have a CTE that is lower than a CTE of the contraction plate(s) (e.g., the first contraction12#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00 plate 206). In some embodiments, the lower CTE plates may comprise a metallic alloy (e.g., a nickel-iron alloy such as INVAR), titanium, zirconium, and / or alloys thereof. In some embodiments, the higher CTE plates may comprise steel, stainless steel (e.g., Nitronic 30), aluminum, and / or alloys thereof.

[0077] In some embodiments, the material and / or geometry of the thermal actuator plates may be selected such that friction between the plates is sufficiently high such that the thermal actuator plates do not slip relative to each other when a force is applied to the thermal actuator. For example, in some embodiments, the friction between the plates may be selected so as to allow the plates to move along each other (e.g., via the angled surfaces) when the thermal actuator expands, as the inventors have recognized that friction can decrease the ability of the plates to move along each other. The material and / or geometry of the plates may be selected to achieve a desired stiffness of the plates. The inventors have recognized that the stiffness of the plates may be relatively high, so as to prevent deformation of the thermal actuator and reversing of the thermal actuator expansion when a force is applied to the thermal actuator.

[0078] The angle of the angled surfaces may be selected to achieve a desired amount of expansion (e.g., change in thermal actuator height between expanded and unexpanded forms) while also achieving a desired length of the thermal actuator. That is, the dimensions of the area of the tokamak into which the thermal actuator in inserted may limit the maximum length and / or height of the thermal actuator.

[0079] Having now described a first example of a thermal actuator, a second implementation of the thermal actuator is now described. FIG. 6 illustrates a cross-sectional of an example thermal actuator according to a second embodiment.

[0080] As described herein, certain variations to the thermal actuator are possible. In the illustrated embodiment of FIG. 6, the thermal actuator 600 comprises five plates: an upper plate 602, a lower plate 604, first and second contraction plates 606A, 606B, and an internal plate 610. Upper plate 602, lower plate 604, and internal plate 610 may be referred to as odd plates in the illustrated embodiment of FIG. 6, while first and second contraction plates 606A-B may be referred to as even plates, due to their positioning in the stack of the plurality of plates of the thermal actuator 600. Upper and lower plates 602, 604 may be referred to as outer plates while first and second contraction plates 606 A-B and internal plate 610 may be referred to as inner plates, due to their positioning in the stack of the plurality of plates of the thermal actuator 600.13#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00

[0081] Upper and lower plates 602, 604 may be similar to upper and lower plates 202, 204 previously described herein. For example, each of the upper and lower plates comprise a flat surface facing away from other plates of the thermal actuator 600 and at least one angled surface on an opposing side of the plate facing towards other plates of the thermal actuator. Similarly, first and second contraction plates 606A-B may be similar to first contraction plate 206 previously described herein. For example, first and second contraction plates 606A-B each comprise at least one angled surface on each of opposing sides of the plate. The internal plate 610 comprises at least one angled surface on each of opposing sides of the plate.

[0082] Like the thermal actuator 200 previously described herein, the plurality of plates of the thermal actuator 600 vary in CTE. More specifically, the CTE of the plates alternate along the stack between a first CTE and a second CTE. Like the thermal actuator 200, odd plates (upper plate 602, lower plate 604, internal plate 610) of the thermal actuator 600 have a first CTE that is lower than a second CTE of the even plates (first and second contraction plates 606A-B). Accordingly, when temperature decreases, the even plates (first and second contraction plates 606A-B) contract to a greater extent than the odd plates (upper plate 602, lower plate 604, internal plate 610) of the thermal actuator 600.

[0083] In the illustrated embodiment of FIG. 6, the thermal actuator 600 is configured with multiple angled surfaces on each plate. In particular, for each side of a plate that has an angled surface (e.g., excluding flat surfaces of upper and lower plates 602), such surfaces comprise a plurality of angled surfaces. Such surfaces may be referred to as forming a plurality of wedges and / or being in a sawtooth pattern. The wedges of adjacent plates face and contact each other and interconnect.

[0084] The inventors have recognized that the use of multiple wedges may improve the function of the thermal actuator (e.g., by increasing the actuation achieved by the thermal actuator as a whole). As described herein, in some embodiments, multiple wedges (angled surfaces) may be used in place of a single wedge of the embodiment shown in FIG. 3. The interface between each respective wedge of the thermal actuator contributes to the stiffness of the contact between adjacent plates of the thermal actuator in a region where force is applied to the thermal actuator by increasing a cross-section for the force. The use of multiple angled surfaces on a single side of a plate allows for use of a smaller (e.g., shorter height) thermal actuator. For a thermal actuator having a single wedge (e.g., only one angled surface on a side of a plate), the14#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00 height of the thermal actuator must be greater than the height of a thermal actuator having multiple angled surfaces that work together to facilitate actuation to achieve the same actuation. Accordingly, use of multiple angled surfaces on a single side of a plate allows for the overall height of the device in an unexpanded form to be decreased, thereby enabling the thermal actuator to be inserted into tokamaks even where the area of insertion is relatively short. This is illustrated by the line 625 in FIG. 11. Line 625 of FIG. 11 illustrates that continuation of a single angled surface would require a taller, less compact stack of plates. A thermal actuator having multiple wedges in place of a single wedge can be smaller than a thermal actuator having a single wedge, and the multiple wedges acting together can achieve the same amount of actuation as a thermal actuator having a single wedge.

[0085] FIGS. 7A-9C illustrate views of the respective plates of the thermal actuator 600. FIGS. 7A-7C illustrate views of an upper plate 602 of the thermal actuator 600. Although FIGS. 7A-7C illustrate views of the upper plate 602, it should be understood that FIGS. 7A-7C are also representative of the lower plate 604 which, in the illustrated embodiment of FIG. 6, shares an identical geometry as the upper plate 602.

[0086] FIG. 7A illustrates a bottom perspective view of an upper plate of the example thermal actuator of FIG. 6, according to some embodiments. FIG. 7B illustrates a top perspective view of an upper plate of the example thermal actuator of FIG. 6, according to some embodiments. FIG. 7C illustrates a partial cross-sectional view of an upper plate of the example thermal actuator of FIG. 6, according to some embodiments. FIGS. 7A-7C illustrate the angled surfaces 603 of the upper plate 602 which form the wedges 700 described herein. In addition, FIGS. 7A-7C illustrate the flat surface of the upper plate 602 which faces away from others of the plurality of plates of the thermal actuator 600.

[0087] FIGS. 8A-8C illustrate views of a first contraction plate 606A of the thermal actuator 600. Although FIGS. 8A-8C illustrate views of the first contraction plate 606A, it should be understood that FIGS. 8A-8C are also representative of the second contraction plate 606B which, in the illustrated embodiment of FIG. 6, shares an identical geometry as the first contraction plate 606A.

[0088] FIG. 8A illustrates a bottom perspective view of a first contraction plate of the example thermal actuator of FIG. 6, according to some embodiments. FIG. 8B illustrates a top perspective view of a first contraction plate 606A of the example thermal actuator of FIG. 6,15#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00 according to some embodiments. FIG. 8C illustrates a partial cross-sectional view of a first contraction plate of the example thermal actuator of FIG. 6, according to some embodiments. FIGS. 8A-8C illustrate the angled surfaces 607, 608 of the first contraction plate 606A which form the wedges 800 described herein.

[0089] FIG. 9A illustrates a bottom perspective view of an internal plate of the example thermal actuator of FIG. 6, according to some embodiments. FIG. 9B illustrates a top perspective view of an internal plate of the example thermal actuator of FIG. 6, according to some embodiments. FIG. 9C illustrates a partial cross-sectional view of an internal plate of the example thermal actuator of FIG. 6, according to some embodiments. FIGS. 9A-9C illustrate the angled surfaces 617, 618 of the internal plate 610 which form the wedges 900 described herein. As can be seen in FIGS. 8A-9C, the angled surfaces of the first contraction plate 606A and the angled surfaces of the internal plate 610 are angled in opposite directions so that the respective angled surfaces align with each other when the thermal actuator is assembled.

[0090] As described herein, the thermal actuator 600 illustrates an example where sides of the thermal actuator plates that have at least one angled surface (e.g., other than the flat surface of upper and lower plates) have multiple angled surfaces. In the illustrated embodiments, each of such sides have a same number of angled surfaces. More specifically, each of such sides have 11 angled surfaces. Any suitable number of angled surfaces may be used, and the embodiment shown in FIG. 6 is an illustrative example of one embodiment having multiple angled surfaces. Further, in some embodiments, at least some of the plates have a different number of angled surfaces than others of the plates. That is, each side of a respective plate having an angled surface may have a number of angled surfaces that is equal to a number of angled surfaces of a side of a plate that faces and is in contact with that respective plate. However, the number of angled surfaces of the respective plate may differ from a number of angles surfaces used on other plates and / or on an opposing side of the same plate.

[0091] As described herein, any suitable number of plates may be used. While the illustrated embodiment of FIG. 6 comprises five plates, other embodiments may include more or less than five plates. For example, it should be understood that in some embodiments, first contraction plate 606A, internal plate 610, and second contraction plate 606B can be duplicated, triplicated, or the like, to obtain a thermal actuator having more than five plates.16#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00

[0092] FIG. 10 illustrates a partial cross-sectional view of the example thermal actuator of FIG. 6, according to some embodiments. FIG. 10 illustrates aspects of the thermal actuator 600. In particular, FIG. 10 illustrates a distance 620 between a location where the wedges of the thermal actuator end and an inner ring of the thermal actuator 600. The distance 620 shown in the illustrated embodiments is exemplary, and in other embodiments the distance 620 may be greater than or less than the distance 620 shown in the illustrated embodiments. For example, in some embodiments, the distance 620 is less than that shown in FIG. 10, and the wedges extend to the inner ring of the thermal actuator. The distance of the thermal actuator along which the wedges extend may be selected based on what location the thermal actuator is desired to exert pressure on. That is, the configuration of the thermal actuator may be selected based on which components and the dimensions thereof of the tokamak on which it is desired for the thermal actuator to press upon.

[0093] FIG. 12 illustrate aspects of the example thermal actuator of FIG. 6, according to some embodiments. As shown in FIG. 12, the angle of the wedges on a same side of a plate vary along the length of the plate. In particular, each of the wedges may have a same height 630, while the angle of the wedges increases along the length of the plate moving from an outer diameter of the plate to the inner diameter of the plate. In other words, the angle of the angled surfaces of the plate approaches zero moving outward from a center of the plate. In the same way, the radial width of the wedges increases moving outward along the length of the plate. For example, the angle of the outer wedge 632 is less than an angle of the inner wedge 634, while the radial width of the outer wedge is greater than the radial width of the inner wedge.

[0094] The inventors have recognized that it may be advantageous to design the thermal actuator having the change in angle of the angled surfaces along the length of thermal actuator to address a decrease in the amount of thermal contraction along the length of the thermal actuator. The angle of the angled surface required to create the same actuation (e.g., vertical displacement) increases along the length of the plate in a direction moving inward towards a center of the plate. Accordingly, using the design described herein whereby the angle of the angled surfaces increases along the length of the plates in the direction moving inwards towards the center of the plate ensures that the same vertical expansion is achieved at all points along the length of the plate. In some embodiments, the angled surfaces may not be straight lines, but instead may be curved. The inventors have recognized that use of curved lines to form the angled surfaces may17#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00 provide improved actuation. By contrast, use of straight lines (e.g., as an approximation of the curved lines) may be used to simplify manufacturing of the thermal actuator.

[0095] FIGS. 13-15 illustrate additional views of the example thermal actuator of FIG. 6, according to some embodiments. FIGS. 13-15 illustrate the example thermal actuator of FIG. 6 in assembled form. FIG. 13 is a front view of the thermal actuator 600. FIG. 14 is a side view of the thermal actuator 600. FIG. 15 is a perspective view of the thermal actuator 600.

[0096] FIG. 16 illustrates geometry of the example thermal actuator of FIG. 6, according to some embodiments. FIGS. 17A-17D illustrates aspects of expansion of the example thermal actuator of FIG. 6, according to some embodiments. In particular, FIGS. 17A-D illustrate deflection and stress results from ANSYS Finite Element (FE) analysis on the thermal actuator. The results shown in FIGS. 16-17D refer to a thermal actuator having the design of FIG. 6 and with three plates made from INVAR (“odd” plates, in the illustrated embodiment), two plates made from stainless steel (e.g., Nitronic 30)(“even” plates, in the illustrated embodiment), and four expansion interfaces (e.g., contact between angled surfaces of respective plates).

[0097] FIG. 17A illustrates initial expansion and deformation of the thermal actuator from at a cool down stage (providing a decrease in temperature). FIG. 17A shows that the thermal actuator expands uniformly. FIG. 17B illustrate net expansion and deformation of the thermal actuator after subsequent compressive load. FIG. 17C illustrates initial Von-mises stress from cool-down of the thermal actuator subsequent to compressing loading to the actuator. FIG. 17D illustrates Von-mises stress after subsequent compressive load.

[0098] The results of this experiment show 1.88 mm of expansion. The coefficient of friction between plates was 0.5. The maximum face height of the INVAR plates is 6.70 mm. As an alternative, titanium and / or zirconium can be used in place of INVAR with a maximum face height of 13.68 mm. The inventors have recognized that the greater the relative difference in CTE, the smaller the maximum ridge height that can reach the same target expansion. With 43 MN applied, which is the expected axial thrust load on central solenoid winding packs, as a subsequent step to the cooling step, the stack deflects by 0.311 mm.

[0099] FIGS. 18A-8F illustrate aspects of the geometry of an example thermal actuator, according to some embodiments. FIGS. 18A-18F illustrate cross-sectional views of portions of a thermal actuator having a first plate (e.g., upper plate shown in FIG. 18A) and a second plate (e.g., contraction plate shown in FIG. 18A). Each of the plates of the thermal actuator include18#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00 multiple wedges. In particular, each of the plates of FIG. 18A comprises three wedges. Each wedge is formed by an angled surface and a vertical face. As shown in FIG. 18 A, the upper plate is formed from material 1 and the contraction plate is formed from material 2. Material 1 has a CTE that is lower than a CTE of material 2.

[0100] Each wedge has a respective length L. A first wedge has a first length Li, a second wedge has a second length L2, and a third wedge has a third length L3.

[0101] Each wedge has a respective height H. A first wedge has a first height Hi, a second wedge has a second height H2, and a third wedge has a third height H3.

[0102] Each wedge is located a distance from an initial point (centroid, x=0) shown in FIG. 18 A. For example, an end of the first wedge is located a distance X3 from the initial point, an end of the second wedge is located a distance X2 from the initial point, and an end of a third wedge is located a distance Xi from the initial point.

[0103] Each wedge of the thermal actuator has a respective angle 9 between the angled surface and the vertical face of the wedge. In FIG. 18A, 0i, 02, 03, are shown. The angle 6 decreases as the distance from x=0 increases.

[0104] The following equation applies to the thermal actuator shown in FIG. 18A:where 0nis an angle of slope n (in radians), Hnis a height of slope n, Az is a target vertical actuation, AT is a temperature change magnitude, aHis the CTE of the higher CTE material, aLis the CTE of the lower CTE material, and xnis the distance from the plate centroid. For the thermal actuator shown in FIG. 18 A, the angle 0ndecreases as xndecreases. In the illustrated embodiment, the plate having the higher CTE material is disposed below the plate having the lower CTE material. Such a configuration may be used where the thermal actuator is expected to cool down (e.g., decrease in temperature). In other embodiments where the thermal actuator is expected to heat up (e.g., increase in temperature), the plate having the higher CTE material may be disposed above the plate having the lower CTE material. The equation for 0nmay be applicable for relatively thin plates, small target deflections, and / or large lengths. Therelationship may be applicable where — — < 0.00002. xn19#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00

[0105] The geometry and equations provided herein may be applicable to a ring-shaped thermal actuator, like the thermal actuator shown in the illustrated embodiments of FIGS. 13-16. The geometry and equations provided herein may also be applicable to a thermal actuator having another shape, such as rectangular shaped plates. In such an embodiment, the centroid, x=0, would be at the centroid of the plates or at a fixed surface of the thermal actuator. The geometry and equations provided herein may also be applicable to a thermal actuator having a hoop shape. In such an embodiment, the centroid, x=0, would be located at the centroid of the circle that is formed by the hoop-shaped thermal actuator.

[0106] FIG. 18B illustrates aspects of geometry of another thermal actuator, according to some embodiments. FIG. 18B illustrates an embodiment where the plate made from a higher CTE material is placed above the plate made from a lower CTE material. In this embodiment, the wedges have a negative slope (from a top left of the plate to a bottom right of the plate). The angle 0nis illustrated accordingly. FIG. 18B illustrates a configuration that may be used where the thermal actuator is expected to cool down (e.g., decrease in temperature). In other embodiments where the thermal actuator is expected to heat up (e.g., increase in temperature), the plate having the higher CTE material may be disposed below the plate having the lower CTE material.

[0107] Each of FIGS. 18A-B illustrate examples of thermal actuators which comprise plates which are stacked on top of each other. The displacement of each of the stacked plates add together to achieve the desired actuation.

[0108] In the illustrated examples of FIGS. 18A-B, the wedges, and particularly the angled surfaces, are formed on a single side of each plate. FIG. 18C illustrates an example thermal actuator where an interior plate includes wedges formed by angled surfaces on both of opposing sides of the thermal actuator. In particular, as seen in FIG. 18C, the interior plate has wedges on a top face and a bottom face of the interior plate. The geometry of the thermal actuator of 18C is a combination of the embodiments shown in FIGS. 18A-B. That is, the embodiment of FIG. 18C may be achieved by placing the embodiment of FIG. 18A on top of the embodiment of FIG. 18B.

[0109] FIG. 18D illustrates another example thermal actuator where an interior plate includes wedges formed by angled surfaces on both of opposing sides of the thermal actuator. In the illustrated example of FIG. 18D, in contrast to the example of FIG. 18C, the interior plate is made from a material having a lower CTE than the material from which the upper and lower20#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00 plates are made which has a higher CTE. In the illustrated embodiment of FIG. 18D, the slope of the wedges is opposite the slope of the wedges of the embodiment of FIG. 18C. The embodiment of FIG. 18D may be achieved by combining the embodiment of FIG. 18B with the embodiment of FIG. 18 A, and specifically, by placing the embodiment of FIG. 18B on top of the embodiment of FIG. 18 A.

[0110] The inventors have recognized that stacking multiple plates together to form the thermal actuator, or combining embodiments as shown in FIGS. 18C-D, has the benefit of being able to use shallower angles to achieve a target vertical deflection. If two plates are stacked to form the thermal actuator, each plate only has to deflect * of the target vertical deflection. For x number of plates, each plate would only have to deflect 1 / x of the target vertical deflection.

[0111] FIG. 18E illustrates aspects of the geometry of another example thermal actuator, according to some embodiments. FIG. 18E may be formed by duplicating the thermal actuator shown in FIG. 18A and stacking the thermal actuators together.

[0112] In the illustrated embodiment of FIG. 18E, a force F is exerted on the thermal actuator. Wedges 1, 2, and 3 labeled in FIG.18E experience the same total vertical load as wedges a, b, and c labeled in FIG. 18E. Wedges 1, 2, and 3 experience the same vertical deflection. Adding additional wedges to the plate would not increase or decrease the deflection, but would increase the width of the load path. Wedges 1, 2, and 3 would experience a portion of the target vertical deflection while wedges a, b, and c would experience the remaining portion of the target vertical deflection. If the plates of material 1 and the plates of material 2 respectively are identical (e.g., same material and angle, but not necessarily the same number of wedges), the plates would each see half of the vertical deflection.

[0113] FIG. 18F illustrates a portion of a thermal actuator, and more specifically, one wedge of the thermal actuator, according to some embodiments. In the illustrated embodiment, a force F is applied to the wedge. The force reacted by the actuator in a direction perpendicular to the force is related to the angle of the wedges. For each plate, each wedge takes a portion of the vertical load and when added up between all wedges on a single plate, the summed vertical load will be equal to the force applied to the wedge, regardless of the number of wedges of the thermal actuator. Accordingly, the decreasing angle of the wedges is beneficial as the reaction force on the plate Frwill decrease.21#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00

[0114] A large Frwill decrease the vertical displacement of the actuator once the force is applied. To avoid this, a large cross-section for the thermal actuator (high stiffness in the direction of the reaction force), and high friction between the wedges may be desired. For a thermal actuator having a hoop-shape, as is described herein, the thermal actuator takes the load in hoop tension / compression. For a thermal actuator having a rectangular shape, the thermal actuator takes the load in compression / tension in the direction of its centroid (x=0) point. For applications where the thermal actuator decreases in temperature, the higher CTE material experiences compression while the lower CTE material experiences tension. For applications where the thermal actuator increases in temperature, the lower CTE material experiences tension while the higher CTE material experiences compression.

[0115] FIGS. 19A-19B illustrate aspects of expansion of an example thermal actuator, according to some embodiments. FIG. 19A illustrates vertical deformation of the thermal actuator plates when the thermal actuator experiences a cool-down (e.g., a decrease in temperature), where no load is applied to the thermal actuator. FIG. 19B illustrates vertical deformation of the thermal actuator after the cooldown and with a load applied to the thermal actuator. The deflection of the thermal actuator decreases slightly as the plate being made from the higher CTE material (e.g., the bottom plate in the illustrated embodiments of FIGS. 19A- 19B) is squeezed out slightly.

[0116] The inventors have recognized that the thermal actuator described herein has a number of advantages. For example, the thermal actuator is easy to install into the tokamak, which may involve stacking the thermal actuator with the other components of the tokamak. The assembly process is therefore relatively non-complex and low-risk. In addition, the architecture of the thermal actuator may be relatively easy to manufacture and may be made from materials which are relatively inexpensive as compared to other solutions. Further, the expansion of the thermal actuator can be controlled to achieve the desired limit of expansion (e.g., by adding additional interfaces, changing the angles of wedge faces, and / or using different materials). Further, the thermal actuator described herein works passively with the cooling process of the tokamak and happens independently of radial pre-compression of the tokamak (making the expansion of the thermal actuator decoupled from the radial pre-compression). The expansion of the thermal actuator is reliable and dimensionally accurate.22#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00

[0117] In some embodiments, there is provided a system (e.g., a tokamak), having the thermal actuator described herein. For example, the tokamak may comprise a central solenoid, a plurality of toroidal field coils (e.g., the toroidal field magnet described herein), and a thermal actuator. The thermal actuator may be disposed between the central solenoid and the plurality of toroidal field coils, and / or a retention component (e.g., a retaining ring) that is coupled to the plurality of toroidal field coils, and may include a plurality of plates being stacked together and configured such that when the thermal actuator is cooled, the plurality of plates expand outward along a vertical axis along which the plates are stacked. In some embodiments, the tokamak may comprise multiple (e.g., a second) thermal actuators. The second thermal actuator may be disposed between the central solenoid and the plurality of toroidal field coils and / or a retention component (e.g., a retaining ring) that is coupled to the plurality of toroidal field coils.

[0118] According to some aspects of the technology described herein, there is provided methods for manufacturing the thermal actuator described herein. FIG. 20 illustrates an example method for manufacturing a thermal actuator, according to some embodiments. As shown in FIG. 20, the method 2000 for manufacturing a tokamak may begin with a method for manufacturing a thermal actuator.

[0119] For example, at act 2002, a plurality of plates may be stacked to manufacture the thermal actuator. The geometry of the plates of the thermal actuator may be designed such that adjacent plates of the thermal actuator interlock with each other via angled surfaces (e.g., wedges) of the plates, as described herein. Therefore, the manufacturing of the thermal actuator may not require fasteners or adhesives.

[0120] The plurality of plates stacked at act 2002 may include at least one first plate including an upper plate. In some embodiments, the at least one first plate may further include a lower plate. Each plate of the at least one first plate may have at least one angled surface (e.g., forming at least one wedge). The plurality of plates may further include at least one second plate including at least one angled surface. In some embodiments the at least one second plate may include at least one pair of angled surfaces, wherein respective angled surfaces of the at least one pair of angled surfaces are disposed on opposing sides of the at least one second plate. The stacking of the plurality of plates may include placing the at least one second plate beneath the upper plate. The at least one first plate may have a first coefficient of thermal expansion and the23#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00 at least one second plate may have a second coefficient of thermal expansion that is greater than the first coefficient of thermal expansion of the at least one first plate.

[0121] At act 2004, the thermal actuator manufactured at act 2002 is inserted into the tokamak. In particular, the thermal actuator is inserted between the central solenoid and a retention component (e.g., a retaining ring) of the tokamak that sits above and / or below the central solenoid and in contact with the plurality of toroidal field coils. The thermal actuator may be configured (e.g., according to the above described configuration with respect to act 2002) such that when the thermal actuator is cooled, the plurality of plates expand outward along a vertical axis along which the plurality of plates are stacked.

[0122] According to some aspects of the technology described herein, there is provided methods for operating the thermal actuator described herein. For example, a method for operating a tokamak may include the following acts. First, the central solenoid and the plurality of toroidal field coils of the tokamak, which are in contact with the thermal actuator, may be cooled.

[0123] As a result of the contact between each of the central solenoid and the plurality of toroidal field coils and the thermal actuator, the thermal actuator may be cooled. The thermal actuator may, in some embodiments, include a first set of plates including an upper plate and a lower plate, each of the first set of plates having a first coefficient of thermal expansion, and at least one second plate disposed between the upper plate and the lower plate and having a second coefficient of thermal expansion that is greater than the first coefficient of thermal expansion. In other embodiments, the first set of plates may include a single plate (e.g., the upper plate).

[0124] As a result of the cooling the thermal actuator, the thermal actuator may contract. For example, the at least on second plate of the thermal actuator may contract to a greater degree than the first set of plates, causing outward displacement of the upper plate and the lower plate of the first set of plates. As a result of the displacement, the lower plate of the thermal actuator may press upward on at least a portion of the plurality of toroidal field coils and / or a retention component (e.g., a retaining ring) that is coupled to the plurality of toroidal field coils. Further as a result of the displacement, the upper plate of the thermal actuator may press downward on at least a portion of the central solenoid.

[0125] As described herein, the thermal actuators described herein may be inserted into a tokamak to fill a gap created by the deformation of the central solenoid and the toroidal field24#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00 coils of the tokamak. For example, a thermal actuator of the type described herein may be inserted between a central solenoid and a retention component (e.g., a retaining ring) that is coupled to the toroidal field coils. However, the placement of the thermal actuators described herein is not limited to such embodiments.

[0126] According to some aspects, a thermal actuator of the type described herein may be inserted into a gap that is created between two toroidal field coil structures. FIGS. 21A-D illustrate example embodiments of a thermal actuator inserted into a gap created by a toroidal field coil of a tokamak, according to some embodiments. For example, the gap may be between two adjacent toroidal field coils, in some embodiments.

[0127] The embodiments of FIGS. 21A-D provide a method of robust and reliable connection and disconnection between adjacent toroidal field coils at the separation boundary of the tokamak without use of electric or hydraulic actuators, welding, or remote robots. The embodiments eliminate sensitive configurations such as large auto-pinners that require high degrees of alignment and high-load requirements to extract pins.

[0128] The embodiments of FIGS. 21A-D may be implemented using any of the thermal actuators described herein (e.g., the embodiments shown in FIGS. 4A, 4B, 7A-9C, 22, 32, etc.). Use of the thermal actuator adjacent at least one toroidal field coil structure may lock the toroidal field coils together with friction, which is high in a vacuum, and / or with small ridges for a direct shear connection.

[0129] At room temperature, the toroidal field coil wings overlap, but the thermal actuator is not expanded, providing a multi-mm (e.g., 1-2 mm) gap between wing structures. The thermal actuators can expand a few millimeters (e.g., 1-3 mm) to facilitate insertion and / or extraction of the toroidal field coils while providing a compression lock on the toroidal field coils when expanded. FIG. 21A illustrates schematic diagrams showing insertion / extraction of a toroidal field coil into a gap between two thermal actuators, and compression locking of the toroidal field coil when the thermal actuators expand. As shown in FIG. 21A, the thermal actuator may be provided with ridges on a surface of the thermal actuator to provide a shear grip on the toroidal field coil.

[0130] In some embodiments, the tokamak may include multiple (e.g., 18, in some embodiments) toroidal field coils. The multiple toroidal field coils cool down during operation of the tokamak. The cooling of the toroidal field coils also cause cooling of the thermal actuator(s)25#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00 which cause the thermal actuator(s) to expand. The expansion of the thermal actuator(s) lock the toroidal field coils in place. The toroidal field coils may be structurally connected for operations.

[0131] FIG. 21B illustrates example architectures of a tokamak having one or more thermal actuators and toroidal field coils. Toroidal field coils are denoted “TF” in the illustrated embodiments. Thermal actuators are denoted “TA” in the illustrated embodiments.

[0132] A first configuration is shown in a top portion of FIG. 21B. In the first configuration, a single toroidal field intercoil wings are shown with a box that spans over the TF intercoil wings. The thermal actuators are inside the box and press the components together.

[0133] A second configuration is shown in a middle portion of FIG. 21B. In the second configuration, intercoil wing box pairs, with a single slab that spans in between, are provided with thermal actuators inside pressing the components together.

[0134] A third configuration is shown in a bottom portion of FIG. 21B. In the third configuration, the second configuration is extended further to have sequentially more, smaller, thinner wings that overlap with thermal actuators in between, which create compression through the whole stack. The third configuration can be considered to work like the pages of two books alternately overlapped and in contact, which creates a high resistive force against tension when one attempts to pull the two books apart. The same compression is applied with many more friction faces to create more friction to lock the TF intercoil wings together.

[0135] Although three configurations are shown in the illustrated embodiment of FIG. 21B, it should be appreciated that other configurations are possible, including, for example, combinations of the three configurations shown in FIG. 21B. The configuration may be selected based on a balance of net intercoil wing cross-section for tension loads and friction faces to maintain lock, as well as a middle ground of manufacturability.

[0136] Advantages of the embodiments shown and described in connection with FIGS. 21A- B include use of multi-mm gaps for all insertion / extraction for connection / disconnection of toroidal field coil halves. These techniques provide a high degree of allowable error in the size of the gap which is not permissible in other techniques such as techniques which use pins and / or shear features that do not accommodate this level of variation. In addition, the embodiments do not require active actuators, welds / cuts, or robotics. The thermal contraction is inherent to any material and the embodiments utilize the inherent cooling of the toroidal field coils as the mechanism for structural connection / disconnection. The power for the actuation is a cryoplant,26#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00 which is more accessible and maintainable, as it sits outside the room where the tokamak is located. In addition, the embodiments do not require any pins or shear features or similar structures that require high precision and care to lock and engage, or prevent getting stuck on extraction. In addition, the embodiments are tolerant of manufacturing deviations in the toroidal field coil structure.

[0137] FIG. 21C illustrates further aspects of the architecture of a thermal actuator inserted into a gap created by a toroidal field coil of a tokamak. In some embodiments, as shown in the illustrated embodiment of FIG. 21C, the structural configuration of the thermal actuator and the coupling to the respective toroidal field coils is uniform across all toroidal field coils of the tokamak. In some embodiments, pins maybe used to hold toroidal field coils to each other in their general positions at room temperature. When the toroidal field coils cool, they mutually lock to each other through their major structures for the full operational capacity and loads, and thus bypass the compliant secondary pins. In other words, the toroidal field coil assembly as a whole cools and locks together to provide a stronger structure that can handle operational loads.

[0138] The seam pairs of toroidal field coils may not include secondary pins between the seam pairs of the toroidal field coils. In this way, the toroidal field coils may be held in place by the primary pins shown in FIG. 21C, but can be readily separated at the seam. The ease of performing maintenance on the toroidal field coils may be simplified in this way as the disconnection of a toroidal field coil is simplified.

[0139] FIG. 21D illustrates further aspects of the architecture of a thermal actuator inserted into a gap created by a toroidal field coil of a tokamak. In the illustrated embodiment of FIG. 21D, the thermal actuator grips onto components (e.g., surfaces of the toroidal field coils) that are angled. The inventors have recognized that this configuration could alleviate issues of gap sizes and slipping a long wing plate down a narrow gap, given actuation limits of the thermal actuator. In addition, the inventors have recognized that this configuration could reduce the required actuation of the thermal actuator and / or the accuracy of the wings of the toroidal field coils.

[0140] The angle of the thermal actuator face and of the component to which the thermal actuator grips may be slight. The angle may be selected in combination with a level of friction to ensure that the locking of the thermal actuator is effective (e.g., the thermal actuator does not slip). The inventors have recognized that given certain characteristics of the materials, thermal27#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00 actuator, and overall configuration of the structures there is an angle at which immediate loss of contact and thus friction will not occur immediately upon the application of a tension force pulling the TF structures apart, due to the self-compressed deflection of the thermal actuator upon expansion. The compressed thermal deflection acts like a spring between the TF structures, wherein even with small displacement of the structures the thermal actuator compressed deflection is not eliminated entirely, and so it still creates compression forces on each side and thus can maintain sufficient friction to resist the tension forces.

[0141] FIG. 22 illustrates another example embodiment of a thermal actuator, according to some embodiments. The thermal actuator of the embodiment shown in FIG. 22 may function in the same manner as the thermal actuators described herein. That is, the thermal actuator may deform in response to a change in temperature. In particular, the deformation of the thermal actuator may be facilitated by design of the thermal actuator using materials having different CTEs.

[0142] In the illustrated embodiment of FIG. 22, the thermal actuator 2200 is shown. The thermal actuator 2200 includes a plurality of plates. In particular, the thermal actuator 2200 includes a set of outer plates 2202 and at least one inner plate 2204. In operation, when the thermal actuator experiences a change in temperature, the set of outer plates 2202 move relative to each other. When the thermal actuator 2200 is cooled down, the set of outer plates shrink relatively more than the inner plate 2204 due to the difference in CTE between the inner and outer plates. The movement of the set of outer plates 2202 relative to each other is facilitated by the placement of the inner plate 2204 within an inner diameter of the set of outer plates 2202, and the fact that the inner plate 2204 shrinks comparatively less than the set of outer plates 2202 when the thermal actuator 2200 is cooled down.

[0143] The outer plates 2202 may include at least two plates stacked together. When the thermal actuator 2200 experiences a change in temperature (e.g., a decrease in temperature), the at least two stacked outer plates 2202 contract azimuthally in a direction that opens the slit 2210 in each of the outer plates 2202. The outer plates 2202 have angled surfaces comprising a plurality of wedges which, when the outer plates 2202 are stacked, interconnect. The positioning of the slit 2210 in each of the outer plates 2202 and the angling of the plurality of wedges are designed such that the azimuthal contraction of adjacent ones of the outer plates 2202 occurs in28#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00 opposite directions (e.g., in a direction that opens the slits). The contraction of the outer plates 2202 achieves the vertical actuation.

[0144] In some embodiments, each of the outer plates are made from a same material. In the illustrated embodiment of FIG. 22, the outer plates 2202 are made from a material having a CTE that is higher than a CTE of a material from which the inner plate 2204 is made. In this way, the outer plates 2202 deform to a greater degree in response to a change in temperature. The placement of the inner plate 2204 prevents radial shrinking of the outer plates 2202. In combination with the use of the slit, the placement of the inner plate 2204 achieves higher azimuthal travel of the outer plates 2202.

[0145] FIG. 23 is a side view of the example thermal actuator of FIG. 22, according to some embodiments. In the illustrated embodiment of FIG. 23, the thermal actuator 2202 comprises four outer plates 2202. The four outer plates 2202 are arranged into first and second sets of outer plates 2206 A-B. The first and second sets of outer plates 2206 A-B may be the same or similar. In the illustrated embodiment, the first and second sets of outer plates 2206A-B are identical. The first set of outer plates 2206A is stacked on top of the second set of outer plates 2206B in the illustrated embodiment. It should be appreciated that in some embodiments, the thermal actuator may comprise fewer than (e.g., one) or more than two sets of outer plates. Furthermore, in some embodiments, each set of outer plates may comprise more than two plates.

[0146] Each of the first and second sets of outer plates 2206 A-B include a first outer plate 2203 A and a second outer plates 2203B. The first outer plates 2203 A is stacked on top of the second outer plate 2203B such that the angled faces (e.g., wedges) of the first and second outer plates 2203 A-B interconnect. It should be appreciated that the first and second outer plates 2203A-B may be identical (e.g., made of a same material and having the same geometry), and may differ only in the orientation of the plate when the thermal actuator 2200 is assembled. For example, the second outer plate 2203B may be a 180 degree rotation of the first outer plate 2203 A about an axis.

[0147] FIGS. 24A-24B illustrate top and bottom view of the example thermal actuator of FIG. 22, according to some embodiments. FIG. 24A illustrates a top view of the thermal actuator 2200. FIG. 24B illustrates a bottom view of the thermal actuator 2200.

[0148] In the top view of FIG. 24A, a first outer plate 2203A of a first set of outer plates 2206A is shown. In the bottom view of FIG. 24B, a second outer plates 2203B of the second set29#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00 of outer plates 2206B is shown. FIGS. 24A-B illustrate that each of the outer plates 2203 A-B have slits 2210.. The first and second outer plates 2203A-B are arranged such that their respective slits 2210 are disposed on opposite sides of the thermal actuator. That is, when viewing the thermal actuator 2202 from the top, as shown in FIG. 24A, the slit 2210 of the first outer plate 2203 A is on a left side of the thermal actuator 2202 and the slit 2210 of the second outer plate 2203B is on a right side of the thermal actuator 2202. The slit 2210 is a break in the circumference of the plate which would otherwise form a continuous hoop (e.g., circle or oval) shape.

[0149] FIG. 25 illustrates another view of the example thermal actuator of FIG. 22, according to some embodiments. FIG. 25 further illustrates that the slits 2210 of the respective ones of the first and second outer plates 2203 A-B are disposed on opposing right and left sides of the thermal actuator.

[0150] FIG. 26 illustrates another view of the example thermal actuator of FIG. 22, according to some embodiments. As described herein, the inner plate 2204 may have a lower CTE than a CTE of the outer plates 2202. The inner plate 2204 may have a height that is greater than or equal to a height of the set of outer plates stacked together.

[0151] FIGS. 27A-27C illustrate views of an outer plate of the example thermal actuator of FIG. 22, according to some embodiments. FIG. 27A illustrates a top of the outer plate 2202. As shown in FIG. 27A, the top of the outer plate 2202 includes a plurality of angled surfaces (e.g., wedges) 2212. The number and angle of the wedges of the outer plate may be selected to achieve a desired amount of actuation of the thermal actuator within particular bounds for the dimensions of the thermal actuator.

[0152] FIG. 27B illustrates a bottom of the outer plate 2202. As shown in FIG. 27B, the bottom of the outer plate 2202 includes a flat surface 2214. In some embodiments, the bottom of the outer plate 2202 may instead include one or more angled surfaces (e.g., wedges).

[0153] FIG. 27C illustrates a top view of the outer plate 2202. FIG. 27C illustrates that the angled surfaces 2212 on the top surface of the outer plate 2202 are divided into first and second portions 2215 A-B. In the illustrated embodiment, the first and second portions 2215 A-B are equal in size, however, other embodiments are not limited to such a configuration. In the illustrated embodiment, the axis X by which the first and second portions 2215 A-B are divided passes through the slit 2210. In the illustrated embodiment of FIG. 27C, the outer plate 2202 is30#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00 symmetric about the slit 2210. The outer plate may have a relatively high stiffness and high friction, as a result of a larger cross section of plates.

[0154] The first and second portions 2215A-B differ in a direction of the slope of the angled surfaces. That is, when considering a single wedge of the plurality of angled surfaces, a wedge that decreases in slope from left to right may be considered as having a negative slope whereas a wedge that increases in slope from left to right may be considered as having a positive slope. In the illustrated embodiment of FIG. 27C, the wedges of the first portion 2215A have a negative slope while the wedges of the second portion 2215B have a positive slope. This is further illustrated in FIG. 27D which illustrates a portion of the outer plate of the thermal actuator of FIG. 22, according to some embodiments.

[0155] FIG. 27E illustrates portions of the example thermal actuator of FIG. 22, according to some embodiments. FIG. 27E illustrates the thermal actuator being assembled. In the bottom embodiment of FIG. 27E, the set of outer plates includes first and second sets of outer plates, each of the sets of outer plates including a first outer plates 2203A and a second outer plate 2203B. In the top embodiment of FIG. 27E, the set of outer plates includes three plates: a first outer plate 2203A, a second outer plate 2203B, and a third outer plate 2203C disposed between the first and second outer plates 2203 A-B. The third outer plate 2203C may be a combination of the second outer plate 2203B of the first set of outer plates disposed on top of the first outer plate 2203 A of the second set of outer plates. As described herein, any suitable number of outer plates may be used (e.g., two plates, three plates, four plates, more than four plates, etc.). A higher number of plates may increase the amount of vertical deflection and allow a shallower angle to be used for the wedges of the plates.

[0156] FIG. 28 illustrates aspects of the geometry of the thermal actuator of FIG. 22, according to some embodiments. FIG. 28 is a schematic diagram illustrating a two-dimensional example of how the thermal actuator 2200 functions. The design utilizes the following principle of two bodies with equal CTE (in this example, a high CTE). The bodies, fixed on opposite ends, will undergo a change in length proportional to the change in temperature. For all pairs of contact points between the two bodies, the relative displacement will be equal. The magnitude of this displacement is the product of the body’s length, the difference of the bars CTE and the containers CTE, and the change in temperature. Allowing the bodies to traverse vertically, but not horizontally, a slope for a wedge may then be derived which utilizes the relative motion to31#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00 enforce a vertical deflection of the two bars. In the actuator 2200, the outer plates may be fixed in the same manner at the point diametrically opposite of the slit.

[0157] In the illustrated embodiment, a first bar is fixed at a right side of the first bar and a second bar is fixed at a left side of the second bar. In another embodiment, the top and bottom bars are fixed by coupling to a component made from a material having a CTE that is lower than a CTE of the top and bottom bars. In this embodiment, the top bar is fixed on a left side of the bar and the bottom bar is fixed on a right side of the bar. The fixed boundary conditions shown in the embodiments of FIG. 28 may slide up and down.

[0158] In another embodiment, the plates may have a lower CTE relative to the rigid body, or additionally or alternatively may not experience cooldown or heating, while the rigid body has a higher CTE and experiences cooldown or heating. In this embodiment, the bodies would slip in a different direction.

[0159] In such an embodiment, the wedges of the plate would then be designed having the opposite angle, as shown in FIG. 29. FIG. 29 illustrates aspects of the geometry of the thermal actuator of FIG. 22, according to some embodiments. In an embodiment where the two fixed edges are attached to the low CTE material of the bottom example of FIG> 28, the wedges have a constant angle that is described by:where Az is the target vertical deflection, L is the body length, aHis the high CTE, aLis the low CTE, and AT is the magnitude of change in temperature.

[0160] The concepts described herein with respect to FIGS. 28-29 may be extended to a pair of ring shaped high CTE plates with a slit cut into them and a low CTE ring shaped plate disposed therebetween at the inner diameter (ID) of the high CTE plates (e.g., the thermal actuator 2200). As both bodies shrink during cooldown, the outer ring has lower hoop stiffness and is forced to take on the same ID and the outer diameter (OD) of the inner ring. To accommodate this new, larger ID with the same circumference, the outer ring uncoils itself resulting in azimuthal / theta displacement. If the second ring plate with a slit in the plate is placed above the first plate, and rotated 180 degrees, the two plates will behave similarly to the two bodies described with respect to FIGS. 28-29 where the plates will see a constant slip distance relative to each other than is equal to half the circumference of the high CTE plate times the32#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00 difference in CTE (between the high CTE and low CTE materials), times the change in temperature. FIG. 30 illustrates aspects of expansion of the thermal actuator of FIG. 22, according to some embodiments.

[0161] The angle of the slope on the plates varies across the radius of the plates, but is constant toroidally at a given radius. Due to being packaged in a small plate, a sawtooth pattern may be used to cover the whole plate. The angle of the wedges as a function of distance from the centroid r of the plate is:where r is the distance from the centroid of the ring plate, Az is the target vertical deflection, aHis the CTE of the high CTE material, aLis the CTE of the low CTE material, and AT is the magnitude of change in temperature.

[0162] FIG. 31 illustrates aspects of deflection of the example thermal actuator of FIG. 22, according to some embodiments. When a load is applied to the thermal actuator, the slit ring bends inward, in the direction of closing the slit. The inner low CTE ring helps support the outer plates and increase the stiffness of the outer plates. In other embodiments, where the inner plate has a relatively high CTE and is heated, while the outer plates have a relatively low CTE and / or are cooled, the same thermal actuation effect can be accomplished.

[0163] FIG. 32 illustrates another example thermal actuator, according to some embodiments. In the example embodiment of FIG. 32, the thermal actuator 3200 comprises a set of plates 3202. The set of plates 3202 may be configured in the same manner as outer plates 2202 (e.g., having a slit 3210) of thermal actuator 2200. Therefore, further description of the set of plates 3202 is omitted. In the embodiment of FIG. 32, the thermal actuator includes an exterior plate 3204. The exterior plate may function in the same manner as inner plate 2204 of the thermal actuator 2200, except that the exterior plate is disposed outside of the plates 3202. That is, an inner diameter of the exterior plate 3204 is in contact with an outer diameter of the plates 3202, in contract to the thermal actuator 2200 where an outer diameter of the inner plate 2204 is in contact with an inner diameter of the plates 2202.

[0164] In the illustrated embodiment of FIG 32, the exterior plate 3204 may be made from a material having a CTE that is higher than a CTE of a material from which the plates 3202 are made. In the illustrated embodiment, the thermal actuator 3200 may be cooled down. In the33#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00 embodiment of FIG. 32, wedges of the plates 3202 may be angled towards the slit. The slit may be designed to be large enough to compensate for azimuthal movement of the thermal actuator. In embodiments where the thermal actuator 3200 is heated, the plates 3202 may be made from a material having a CTE that is higher than a material from which the exterior plate 3204 is made to achieve actuation.

[0165] Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated that various alterations, modifications, and improvements will readily occur to those skilled in the art.

[0166] Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. Further, though advantages of the present invention are indicated, it should be appreciated that not every embodiment of the technology described herein will include every described advantage. Some embodiments may not implement any features described as advantageous herein and in some instances one or more of the described features may be implemented to achieve further embodiments. Accordingly, the foregoing description and drawings are by way of example only.

[0167] Various aspects of the present invention may be used alone, in combination, or in a variety of arrangements not specifically described in the embodiments described in the foregoing and is therefore not limited in its application to the details and arrangement of components set forth in the foregoing description or illustrated in the drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments.

[0168] Also, the invention may be embodied as a method, of which an example has been provided. The acts performed as part of the method may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include performing some acts simultaneously, even though shown as sequential acts in illustrative embodiments.

[0169] (1) A thermal actuator comprising: at least one first plate, the at least one first plate forming at least one wedge; and at least one second plate disposed adjacent to the at least one first plate and forming at least one wedge, wherein: the at least one wedge of the at least one first plate contacts the at least one wedge the at least one second plate; the at least one first plate has a34#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00 first coefficient of thermal expansion; and the at least one second plate has a second coefficient of thermal expansion that is greater than the first coefficient of thermal expansion.

[0170] (2) The thermal actuator of (1), wherein the at least one first plate comprises a first set of plates including an upper plate and a lower plate.

[0171] (3) The thermal actuator of (2), wherein the at least one second plate includes a plurality of plates.

[0172] (4) The thermal actuator of (3), wherein the first set of plates further includes at least one internal plate disposed between the upper plate and the lower plate.

[0173] (5) The thermal actuator of (4), wherein the at least one second plate includes a first plate and a second plate, each of the first and second plates being disposed between the upper plate and the lower plate of the first set of plates and the at least one internal plate of the first set of plates is disposed between the first and second plates of the at least one second plate.

[0174] (6) The thermal actuator of (2), wherein: the at least one wedge of the at least one second plate is formed by a pair of angled surfaces of the second plate disposed on opposing sides of the second plate; and the at least one wedge of the upper plate is formed by an angled surface of the upper plate disposed on a side of the upper plate opposing a flat surface of the upper plate, wherein the angled surface of the upper plate is in contact with a first angled surface of the pair of angled surfaces of the second plate; and the at least one wedge of the lower plate is formed by an angled surface of the lower plate disposed on a side of the lower plate opposing a flat surface of the lower plate, wherein the angled surface of the lower plate is in contact with a second angled surface of the pair of angled surfaces of the second plate.

[0175] (7) The thermal actuator of (1) or any other preceding embodiment, wherein the at least one second plate forms a plurality of wedges.

[0176] (8) The thermal actuator of (2), wherein each of the upper plate and the lower plate comprise a plurality of wedges, wherein each of the plurality of wedges of the upper plate comprise an angled surface disposed on a same side of the upper plate and each of the plurality of wedges of the lower plate comprise an angled surface disposed on a same side of the lower plate.

[0177] (9) The thermal actuator of (1) or any other preceding embodiment, wherein the at least one first plate includes a titanium material and / or a zirconium material.35#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00

[0178] (10) The thermal actuator of (1) or any other preceding embodiment, wherein the at least one first plate includes a nickel-iron material.

[0179] (11) The thermal actuator of (1) or any other preceding embodiment, wherein the at least one second plate includes a steel material.

[0180] (12) The thermal actuator of (7), wherein the plurality of wedges of the at least one second plate comprise a plurality of angled surfaces, and respective ones of the plurality of angled surfaces vary in an angle of elevation relative to a first axis, the first axis being perpendicular to a direction in which the at least one first plate and the at least one second plate are stacked together.

[0181] (13) The thermal actuator of (12), wherein the respective ones of the plurality of angled surfaces decrease in the angle of elevation relative to the first axis in a direction away from a center of the at least one second plate.

[0182] (14) The thermal actuator of (1) or any other preceding embodiment, wherein the at least one first plate and the at least one second plate are circular.

[0183] (15) The thermal actuator of (1) or any other preceding embodiment, wherein the at least one first plate and the at least one second plate are ring-shaped.

[0184] (16) A tokamak comprising: a central solenoid; a plurality of toroidal field coils; and a thermal actuator disposed between the central solenoid and a retention component coupled to the plurality of toroidal field coils, the thermal actuator including a plurality of plates being stacked together and configured such that when the thermal actuator is cooled, the plurality of plates expand outward along a vertical axis along which the plurality of plates are stacked.

[0185] (17) The tokamak of (16), further comprising a second thermal actuator disposed between the central solenoid and a second retention component coupled to the plurality of toroidal field coils.

[0186] (18) The tokamak of (16) or any other preceding embodiment, wherein the plurality of claims include: at least one first plate, the at least one first plate forming at least one wedge; and at least one second plate disposed adjacent to the at least one first plate and forming at least one wedge, wherein: the at least one wedge of the at least one first plate contacts the at least one wedge the at least one second plate; the at least one first plate has a first coefficient of thermal expansion; and the at least one second plate has a second coefficient of thermal expansion that is greater than the first coefficient of thermal expansion.36#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00

[0187] (19) The tokamak of (18), wherein the at least one first plate comprises a first set of plates including an upper plate and a lower plate.

[0188] (20) The tokamak of (19), wherein the at least one second plate includes a plurality of plates.

[0189] (21) The tokamak of (20), wherein the first set of plates further includes at least one internal plate disposed between the upper plate and the lower plate.

[0190] (22) The tokamak of (21), wherein the at least one second plate includes a first plate and a second plate, each of the first and second plates being disposed between the upper plate and the lower plate of the first set of plates and the at least one internal plate of the first set of plates is disposed between the first and second plates of the at least one second plate.

[0191] (23) The tokamak of (18), wherein: the at least one wedge of the at least one second plate is formed by a pair of angled surfaces of the second plate disposed on opposing sides of the second plate; and the at least one wedge of the upper plate is formed by an angled surface of the upper plate disposed on a side of the upper plate opposing a flat surface of the upper plate, wherein the angled surface of the upper plate is in contact with a first angled surface of the pair of angled surfaces of the second plate; and the at least one wedge of the lower plate is formed by an angled surface of the lower plate disposed on a side of the lower plate opposing a flat surface of the lower plate, wherein the angled surface of the lower plate is in contact with a second angled surface of the pair of angled surfaces of the second plate.

[0192] (24) The tokamak of (18), wherein the at least one second plate forms a plurality of wedges.

[0193] (25) The tokamak of (19), wherein each of the upper plate and the lower plate comprise a plurality of wedges, wherein each of the plurality of wedges of the upper plate comprise an angled surface disposed on a same side of the upper plate and each of the plurality of wedges of the lower plate comprise an angled surface disposed on a same side of the lower plate.

[0194] (26) The tokamak of (18), wherein the at least one first plate includes a titanium material and / or a zirconium material.

[0195] (27) The tokamak of (18), wherein the at least one first plate includes a nickel-iron material.37#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00

[0196] (28) The tokamak of (18), wherein the at least one second plate includes a steel material.

[0197] (29) The tokamak of (24), wherein the plurality of wedges of the at least one second plate comprise a plurality of angled surfaces, and respective ones of the plurality of angled surfaces vary in an angle of elevation relative to a first axis, the first axis being perpendicular to a direction in which the at least one first plate and the at least one second plate are stacked together.

[0198] (30) The tokamak of (29), wherein the respective ones of the plurality of angled surfaces decrease in the angle of elevation relative to the first axis in a direction away from a center of the at least one second plate.

[0199] (31) The tokamak of (18), wherein the at least one first plate and the at least one second plate are circular.

[0200] (32) The tokamak of (18), wherein the at least one first plate and the at least one second plate are ring-shaped.

[0201] (33) The tokamak of (16), wherein the thermal actuator is the thermal actuator of any one of claims 39-50.

[0202] (34) A method of manufacturing a tokamak including a central solenoid and a plurality of toroidal field coils, the method comprising: inserting a thermal actuator between the central solenoid and a retention component coupled to the plurality of toroidal field coils, wherein the thermal actuator includes a plurality of plates being stacked together and configured such that when the thermal actuator is cooled, the plurality of plates expand outward along a vertical axis along which the plurality of plates are stacked.

[0203] (35) The method of (34), wherein the thermal actuator is the thermal actuator of any one of claims 1-15.

[0204] (36) The method of (34), wherein the thermal actuator is the thermal actuator of any one of claims 39-50.

[0205] (37) A method of manufacturing a thermal actuator, the method comprising: stacking a plurality of plates, wherein the plurality of plates include: at least one first plate, the at least one first plate forming at least one wedge; at least one second plate disposed adjacent to the at least one first plate and forming at least one wedge, and wherein: the at least one wedge of the at least one first plate contacts the at least one wedge the at least one second plate; the at least one38#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00 first plate has a first coefficient of thermal expansion; and the at least one second plate has a second coefficient of thermal expansion that is greater than the first coefficient of thermal expansion.

[0206] (38) The method of (36), wherein the thermal actuator is the thermal actuator of any one of claims 1-15.

[0207] (39) A thermal actuator comprising: a first plate; and a set of second plates, each plate of the set of second plates comprising: a plurality of wedges formed on at least one face of the plate; and a slit comprising a break in a circumference of the plate; and wherein: the set of second plates are stacked together; and the first plate is disposed within an inner diameter of the set of second plates or outside of an outer diameter of the set of second plates.

[0208] (40) The thermal actuator of (39), wherein the first plate is disposed within the inner diameter of the set of second plates.

[0209] (41) The thermal actuator of any of (39)-(40), wherein the first plate is disposed outside of the outer diameter of the set of second plates.

[0210] (42) The thermal actuator of any of (39)-(41), wherein the set of second plates are ring-shaped.

[0211] (43) The thermal actuator of (42), wherein the first plate is ring-shaped.

[0212] (44) The thermal actuator of any of (39)-(43), wherein the first plate comprises a first material having a first coefficient of thermal expansion (CTE) and the set of second plates comprise a second material having a second CTE that is different than the first CTE.

[0213] (45) The thermal actuator of (44), wherein the first CTE is greater than the secondCTE.

[0214] (46) The thermal actuator of (44), wherein the first CTE is less than the second CTE.

[0215] (47) The thermal actuator of any of (39)-(46), wherein the set of second plates comprises at least three plates.

[0216] (48) The thermal actuator of (47), wherein at least one plate of the set of second plates comprises the plurality of wedges formed on both of two opposing faces of the at least one plate.

[0217] (49) The thermal actuator of any of (39)-(48), wherein each plate of the set of second plates is symmetric.

[0218] (50) The thermal actuator of any of (39)-(49), wherein the set of second plates comprises an upper plate and a lower plate, the lower plate has a same geometry as the upper39#14432232v2PCT / US25 / 48134 26 September 2025 (26.09.2025)Attorney Docket No.: C1599.70069WO00 plate, and when the set of second plates are stacked together, the lower plate is rotated approximately 180 degrees about at least one axis.

[0219] Some actions are described as taken by a “user.” It should be appreciated that a “user” need not be a single individual, and that in some embodiments, actions attributable to a “user” may be performed by a team of individuals and / or an individual in combination with computer-assisted tools or other mechanisms.

[0220] Use of ordinal terms such as “first,” “second,” “third,” etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.

[0221] The terms “approximately” and “about” may be used to mean within ±20% of a target value in some embodiments, within ±10% of a target value in some embodiments, within ±5% of a target value in some embodiments, and yet within ±2% of a target value in some embodiments. The terms “approximately” and “about” may include the target value. The term “substantially equal” may be used to refer to values that are within ±20% of one another in some embodiments, within ±10% of one another in some embodiments, within ±5% of one another in some embodiments, and yet within ±2% of one another in some embodiments.

[0222] The term “substantially” may be used to refer to values that are within ±20% of a comparative measure in some embodiments, within ±10% in some embodiments, within ±5% in some embodiments, and yet within ±2% in some embodiments. For example, a first direction that is “substantially” perpendicular to a second direction may refer to a first direction that is within ±20% of making a 90° angle with the second direction in some embodiments, within ±10% of making a 90° angle with the second direction in some embodiments, within ±5% of making a 90° angle with the second direction in some embodiments, and yet within ±2% of making a 90° angle with the second direction in some embodiments.

[0223] Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having,” “containing,” “involving,” and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.40#14432232v2

Claims

1. Attorney Docket No.: C1599.70069WO00CLAIMSWhat is claimed is:

1. A thermal actuator comprising: at least one first plate, the at least one first plate forming at least one wedge; and at least one second plate disposed adjacent to the at least one first plate and forming at least one wedge, wherein: the at least one wedge of the at least one first plate contacts the at least one wedge the at least one second plate; the at least one first plate has a first coefficient of thermal expansion; and the at least one second plate has a second coefficient of thermal expansion that is greater than the first coefficient of thermal expansion.

2. The thermal actuator of claim 1, wherein the at least one first plate comprises a first set of plates including an upper plate and a lower plate.

3. The thermal actuator of claim 2, wherein the at least one second plate includes a plurality of plates.

4. The thermal actuator of claim 3, wherein the first set of plates further includes at least one internal plate disposed between the upper plate and the lower plate.

5. The thermal actuator of claim 4, wherein the at least one second plate includes a first plate and a second plate, each of the first and second plates being disposed between the upper plate and the lower plate of the first set of plates and the at least one internal plate of the first set of plates is disposed between the first and second plates of the at least one second plate.

6. The thermal actuator of claim 2, wherein: the at least one wedge of the at least one second plate is formed by a pair of angled surfaces of the second plate disposed on opposing sides of the second plate; and the at least one wedge of the upper plate is formed by an angled surface of the upper plate disposed on a side of the upper plate opposing a flat surface of the upper plate, wherein the41 14432232v2Attorney Docket No.: C1599.70069WO00 angled surface of the upper plate is in contact with a first angled surface of the pair of angled surfaces of the second plate; and the at least one wedge of the lower plate is formed by an angled surface of the lower plate disposed on a side of the lower plate opposing a flat surface of the lower plate, wherein the angled surface of the lower plate is in contact with a second angled surface of the pair of angled surfaces of the second plate.

7. The thermal actuator of claim 1 or any other preceding claim, wherein the at least one second plate forms a plurality of wedges.

8. The thermal actuator of claim 2, wherein each of the upper plate and the lower plate comprise a plurality of wedges, wherein each of the plurality of wedges of the upper plate comprise an angled surface disposed on a same side of the upper plate and each of the plurality of wedges of the lower plate comprise an angled surface disposed on a same side of the lower plate.

9. The thermal actuator of claim 1 or any other preceding claim, wherein the at least one first plate includes a titanium material and / or a zirconium material.

10. The thermal actuator of claim 1 or any other preceding claim, wherein the at least one first plate includes a nickel-iron material.

11. The thermal actuator of claim 1 or any other preceding claim, wherein the at least one second plate includes a steel material.

12. The thermal actuator of claim 7, wherein the plurality of wedges of the at least one second plate comprise a plurality of angled surfaces, and respective ones of the plurality of angled surfaces vary in an angle of elevation relative to a first axis, the first axis being perpendicular to a direction in which the at least one first plate and the at least one second plate are stacked together.42 14432232v2Attorney Docket No.: C1599.70069WO0013. The thermal actuator of claim 12, wherein the respective ones of the plurality of angled surfaces decrease in the angle of elevation relative to the first axis in a direction away from a center of the at least one second plate.

14. The thermal actuator of claim 1 or any other preceding claim, wherein the at least one first plate and the at least one second plate are circular.

15. The thermal actuator of claim 1 or any other preceding claim, wherein the at least one first plate and the at least one second plate are ring-shaped.

16. A tokamak comprising: a central solenoid; a plurality of toroidal field coils; and a thermal actuator disposed between the central solenoid and a retention component coupled to the plurality of toroidal field coils, the thermal actuator including a plurality of plates being stacked together and configured such that when the thermal actuator is cooled, the plurality of plates expand outward along a vertical axis along which the plurality of plates are stacked.

17. The tokamak of claim 16, further comprising a second thermal actuator disposed between the central solenoid and a second retention component coupled to the plurality of toroidal field coils.

18. The tokamak of claim 16 or any other preceding claim, wherein the plurality of claims include: at least one first plate, the at least one first plate forming at least one wedge; and at least one second plate disposed adjacent to the at least one first plate and forming at least one wedge, wherein: the at least one wedge of the at least one first plate contacts the at least one wedge the at least one second plate; the at least one first plate has a first coefficient of thermal expansion; and the at least one second plate has a second coefficient of thermal expansion that is greater than the first coefficient of thermal expansion.43 14432232v2Attorney Docket No.: C1599.70069WO0019. The tokamak of claim 18, wherein the at least one first plate comprises a first set of plates including an upper plate and a lower plate.

20. The tokamak of claim 19, wherein the at least one second plate includes a plurality of plates.

21. The tokamak of claim 20, wherein the first set of plates further includes at least one internal plate disposed between the upper plate and the lower plate.

22. The tokamak of claim 21, wherein the at least one second plate includes a first plate and a second plate, each of the first and second plates being disposed between the upper plate and the lower plate of the first set of plates and the at least one internal plate of the first set of plates is disposed between the first and second plates of the at least one second plate.

23. The tokamak of claim 18, wherein: the at least one wedge of the at least one second plate is formed by a pair of angled surfaces of the second plate disposed on opposing sides of the second plate; and the at least one wedge of the upper plate is formed by an angled surface of the upper plate disposed on a side of the upper plate opposing a flat surface of the upper plate, wherein the angled surface of the upper plate is in contact with a first angled surface of the pair of angled surfaces of the second plate; and the at least one wedge of the lower plate is formed by an angled surface of the lower plate disposed on a side of the lower plate opposing a flat surface of the lower plate, wherein the angled surface of the lower plate is in contact with a second angled surface of the pair of angled surfaces of the second plate.

24. The tokamak of claim 18, wherein the at least one second plate forms a plurality of wedges.

25. The tokamak of claim 19, wherein each of the upper plate and the lower plate comprise a plurality of wedges, wherein each of the plurality of wedges of the upper plate comprise an44 14432232v2Attorney Docket No.: C1599.70069WO00 angled surface disposed on a same side of the upper plate and each of the plurality of wedges of the lower plate comprise an angled surface disposed on a same side of the lower plate.

26. The tokamak of claim 18, wherein the at least one first plate includes a titanium material and / or a zirconium material.

27. The tokamak of claim 18, wherein the at least one first plate includes a nickel-iron material.

28. The tokamak of claim 18, wherein the at least one second plate includes a steel material.

29. The tokamak of claim 24, wherein the plurality of wedges of the at least one second plate comprise a plurality of angled surfaces, and respective ones of the plurality of angled surfaces vary in an angle of elevation relative to a first axis, the first axis being perpendicular to a direction in which the at least one first plate and the at least one second plate are stacked together.

30. The tokamak of claim 29, wherein the respective ones of the plurality of angled surfaces decrease in the angle of elevation relative to the first axis in a direction away from a center of the at least one second plate.

31. The tokamak of claim 18, wherein the at least one first plate and the at least one second plate are circular.

32. The tokamak of claim 18, wherein the at least one first plate and the at least one second plate are ring-shaped.

33. A method of manufacturing a tokamak including a central solenoid and a plurality of toroidal field coils, the method comprising: inserting a thermal actuator between the central solenoid and a retention component coupled to the plurality of toroidal field coils, wherein the thermal actuator includes a plurality of plates being stacked together and configured such that when the thermal actuator is cooled, the45 14432232v2Attorney Docket No.: C1599.70069WO00 plurality of plates expand outward along a vertical axis along which the plurality of plates are stacked.

34. The method of claim 33, wherein the thermal actuator is the thermal actuator of any one of claims 1-15.

35. A method of manufacturing a thermal actuator, the method comprising: stacking a plurality of plates, wherein the plurality of plates include: at least one first plate, the at least one first plate forming at least one wedge; at least one second plate disposed adjacent to the at least one first plate and forming at least one wedge, and wherein: the at least one wedge of the at least one first plate contacts the at least one wedge the at least one second plate; the at least one first plate has a first coefficient of thermal expansion; and the at least one second plate has a second coefficient of thermal expansion that is greater than the first coefficient of thermal expansion.

36. The method of claim 35, wherein the thermal actuator is the thermal actuator of any one of claims 1-15.

37. A thermal actuator comprising: a first plate; and a set of second plates, each plate of the set of second plates comprising: a plurality of wedges formed on at least one face of the plate; and a slit comprising a break in a circumference of the plate; and wherein: the set of second plates are stacked together; and the first plate is disposed within an inner diameter of the set of second plates or outside of an outer diameter of the set of second plates.46 14432232v2Attorney Docket No.: C1599.70069WO0038. The thermal actuator of claim 37, wherein the first plate is disposed within the inner diameter of the set of second plates.

39. The thermal actuator of any of claims 37-38, wherein the first plate is disposed outside of the outer diameter of the set of second plates.

40. The thermal actuator of any of claims 37-39, wherein the set of second plates are ringshaped.

41. The thermal actuator of claim 40, wherein the first plate is ring-shaped.

42. The thermal actuator of any of claims 37-41, wherein the first plate comprises a first material having a first coefficient of thermal expansion (CTE) and the set of second plates comprise a second material having a second CTE that is different than the first CTE.

43. The thermal actuator of claim 42, wherein the first CTE is greater than the second CTE.

44. The thermal actuator of claim 42, wherein the first CTE is less than the second CTE.

45. The thermal actuator of any of claims 37-44, wherein the set of second plates comprises at least three plates.

46. The thermal actuator of claim 45, wherein at least one plate of the set of second plates comprises the plurality of wedges formed on both of two opposing faces of the at least one plate.

47. The thermal actuator of any of claims 37-46, wherein each plate of the set of second plates is symmetric.

48. The thermal actuator of any of claims 37-47, wherein the set of second plates comprises an upper plate and a lower plate, the lower plate has a same geometry as the upper plate, and when the set of second plates are stacked together, the lower plate is rotated approximately 180 degrees about at least one axis.47 14432232v2Attorney Docket No.: C1599.70069WO0049. The tokamak of claim 16, wherein the thermal actuator is the thermal actuator of any one of claims 37-48.

50. The method of claim 33, wherein the thermal actuator is the thermal actuator of any one of claims 37-48. 14432232v2

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