Waveguide and related methods

Abstract

A microwave waveguide (100, 200, 300, 800) having an integral structure including integrated reinforcing ribs (124, 224, 324, 824) and cooling pipes (122, 222, 822) is disclosed. The reinforcing ribs and cooling pipes extend along the outer surface (114, 214, 314, 814) of a tube (110, 210, 310, 810) for guiding microwaves. The waveguide may be formed by extruding metal or by pultrusion of a carbon fiber composite. Additionally, a method for transmitting microwaves (600) and a geothermal drilling method (700) are disclosed.

Description

Technology Field

[0001] The present disclosure relates to a microwave waveguide, and in particular, but not exclusively, to a microwave waveguide having an integral structure having reinforcing protrusions. Background Technology

[0002] A microwave waveguide is a device used to guide microwaves from a source to a destination. Microwave waveguides can be used in a wide range of applications, from microwave ovens to nuclear fusion devices.

[0003] In a fusion device, a high-power microwave beam of about 1 MW is generated by a gyrotron, passes along a waveguide, and is injected into a vessel to heat the plasma to a fusion temperature of about 150 million °C. To reduce energy transfer losses from the microwave beam, it is desirable for the waveguide to have a high degree of straightness.

[0004] Fusion applications typically utilize vacuum circular waveguides with corrugated inner surfaces. These waveguides may be manufactured from metal bar material that is gun-drilled, corrugated, and then externally machined to attach cooling clamps. However, this manufacturing process is labor-intensive and results in significant material waste.

[0005] Therefore, improvements are required in the field of microwave waveguide technology.

[0006] During the gun drilling and corrugation process, a certain curvature may occur in the waveguide because the interior of the waveguide may differentially grip the drill bit. Consequently, this process is not only labor-intensive and wasteful of material, but it may also reduce the straightness of the existing waveguide. A straightness tolerance of less than 0.1 mm / meter is particularly desirable.

[0007] According to a first aspect of the present disclosure, a waveguide is provided. The waveguide may be configured to guide (e.g., propagate or transmit) microwaves (e.g., electromagnetic radiation having a frequency of 1 GHz to 1 THz). The waveguide may include a microwave waveguide. The waveguide may be configured to guide high-power microwaves (e.g., at least 10 kW, e.g., at least 0.5 MW, e.g., at least 1 MW, e.g., a microwave beam of up to 5 MW). The waveguide may be configured to guide microwaves over a long transmission distance (e.g., more than 1 m, e.g., at least 5 m, e.g., at least 10 m). The waveguide may be for a nuclear fusion device.

[0008] The waveguide may include a tube (e.g., an inner tube). The tube may be a tube for guiding energy (e.g., microwave energy). The tube may include an opening for guiding microwaves. For example, the tube (e.g., an inner surface) may define the opening for guiding microwaves. For example, the tube may have an inner diameter of 10 mm to 130 mm, for example, 45 mm to 55 mm (e.g., about 50 mm).

[0009] The tube may be cylindrical. The tube may include walls of uniform thickness (e.g., 2 mm to 5 mm, e.g., about 2 mm, e.g., about 5 mm). The tube may define a cylindrical inner surface. The tube may define a cylindrical outer surface. The tube may define a longitudinal axis. The length of the major axis of the tube may be longer than the diameter of the tube (e.g., may significantly exceed it). The tube may be linear (e.g., may not include bends). The tube may be an inner tube.

[0010] The waveguide may include a first end and a second end. The first end may be configured to be attached to the second end of the corresponding waveguide. The second end may be configured to be attached to the first end of the corresponding waveguide.

[0011] The waveguide may include protrusions, for example, a plurality of protrusions. Each protrusion may be provided on the outer surface of the tube. A protrusion or each protrusion may protrude or extend from the tube, for example, perpendicularly, radially, and / or at any angle from the outer surface of the tube. For example, a protrusion or each protrusion may extend at least partially radially (for example, may have a component of a geometric shape that extends radially).

[0012] A projection or each projection may extend longitudinally, such as parallel to the longitudinal axis of the tube. A projection may extend along a tube having a substantially uniform (e.g., uniform) cross section. A projection or each projection may extend from a first end to a second end (e.g., continuously). A projection or each projection and the tube may extend over the same range. Alternatively, one or more projections (e.g., a projection or each projection) may be discontinuous longitudinally (e.g., not continuously extending from a first end to a second end of the tube). For example, in one or more longitudinal coordinates, one or more projections may include a section extending longitudinally.

[0013] Multiple protrusions may be provided parallel to each other and to the major axis of the tube. Multiple protrusions may be separated from each other (e.g., separated by angle). Multiple protrusions may be spaced apart from each other around the tube. Multiple protrusions may be spaced equidistantly around the longitudinal axis of the tube. The waveguide may include at least one, for example, at least two, for example, at least three, for example, at least four, for example, at least five, for example, at least six protrusions. For example, the waveguide may include one, two, three, four, five, or six protrusions.

[0014] The protrusion may be offset by at least 30 degrees, for example, at least 45 degrees, for example, at least 60 degrees, for example, at least 90 degrees, for example, at least 120 degrees, for example, 180 degrees. For example, the protrusion may be offset by about 30 degrees, about 45 degrees, about 60 degrees, about 90 degrees, about 120 degrees, or about 180 degrees. Alternatively, the protrusion may not be offset at equal angles.

[0015] A protrusion or each protrusion may extend from a tube, for example, an inner tube, by a distance similar (e.g., equal) to the radius of the tube (e.g., vertically far, e.g. radially far).

[0016] Protrusions or each protrusion may include reinforcing structures such as ribs or pins. The ribs may be identical. The ribs or each rib may extend longitudinally and away from the outer surface of the tube. The ribs or each rib may include a uniform circumferential thickness along their length in the radial direction. For example, the ribs or each rib may be generally or substantially rectangular. The dimensions of the ribs or each rib may be determined by the space constraints of the application and also by the inner diameter of the microwave tube. The circumferential thickness dimension of the ribs or each rib may be similar (e.g., identical) to the radial thickness dimension of the tube wall. The protrusions or each protrusion may have a radial dimension between 5 and 50 mm, for example, about 25 mm, and / or a circumferential dimension of at least 2 mm (e.g., 2 to 3 mm), for example, about 5 mm. The ribs or each rib may not transport cooling fluid.

[0017] Protrusions or each protrusion may include pipes or cooling channels (e.g., cooling pipes for delivering coolant along a waveguide). The pipes or each pipe may be substantially cylindrical, or alternatively, may include other geometric shapes such as triangular or fan shapes. The pipes or each pipe may define a major axis parallel to the major axis of the tube. The wall thickness of the tube may be thicker (e.g., significantly thicker) than the wall thickness of the pipes or each pipe. The diameter of the pipes or each pipe may be thicker (e.g., about twice) than the wall thickness of the tube. The pipes or each pipe may be separated or discontinuous from the tube. For example, their internal volumes may not be communicative.

[0018] A pipe of one or more protrusions (e.g., a protrusion or the pipe of each protrusion) may include a discontinuity in its surrounding (e.g., circumferential) wall. The discontinuity may extend through the thickness of the wall. The discontinuity may extend longitudinally (e.g., along the entire length of the pipe, such as from the first end of the tube to the second end of the tube). The discontinuity may increase the deformability of the pipe in the circumferential direction. For example, the discontinuity may improve the circumferential expandability of the pipe to allow a cylindrical channel to be inserted along the length of the pipe. The discontinuity may include an opening formed by the removal or omission of an acute sector of the cylindrical wall. Alternatively, the discontinuity may include a fracture within the wall of the pipe.

[0019] The protrusions may be identical or not identical. A first set of multiple protrusions (e.g., a subset) may include ribs (e.g., composed of ribs). A second set of multiple protrusions (e.g., a subset) may include pipes (e.g., composed of pipes).

[0020] A projection or each projection may be tapered (e.g., in circumferential dimensions) according to the distance from the tube (e.g., radial distance). A projection or each projection may include pipes and ribs. Within a projection or each projection, the pipe may be provided closer to the tube than the ribs. Within a projection or each projection, the pipe may be provided at the proximal end of the projection (e.g., the end of the projection closest to the tube). Within a projection or each projection, the ribs may be provided at the distal end of the projection (e.g., the end of the projection furthest from the tube). Additionally or alternatively, a projection or each projection may include a hollow triangular cross section, the triangular cross section tapering according to the distance from the tube. The walls of the triangular cross section may be provided at an angle of about 45 degrees with respect to the radial direction.

[0021] The waveguide may further include, for example, an outer tube provided coaxially with the inner tube. The outer tube may be cylindrical. The outer tube may extend to the same extent as the inner tube and / or each protrusion. The outer tube may have a radius larger than that of the inner tube (for example, twice the radius of the inner tube). The outer tube may be spaced radially from the inner tube. The wall thickness of the outer tube may be similar (for example, the same) to the wall thickness of the inner tube.

[0022] A protrusion or each protrusion may extend from the inner surface of the outer tube. A protrusion or each protrusion may extend between the outer surface of the inner tube and the inner surface of the outer tube. A rib or each rib may be attached to the inner surface of the outer tube.

[0023] The waveguide may include multiple channels. Adjacent protrusions may be combined with coaxial inner and outer tubes to define longitudinal channels extending between the ends of the waveguide. A channel or each channel may have a geometric shape that substantially includes a prismatic annular fan or a fan of a cylindrical shell. A channel may extend over at least 30 degrees, for example, at least 45 degrees, for example, at least 60 degrees, for example, at least 90 degrees, for example, at least 120 degrees, for example, 180 degrees. For example, a channel may extend over about 30 degrees, about 45 degrees, about 60 degrees, about 90 degrees, about 120 degrees, or about 180 degrees.

[0024] The protrusions (e.g., protrusions or each protrusion) may include pipes (e.g., cooling pipes) and / or may define channels in combination with adjacent protrusions (and optionally in combination with inner and outer tubes extending between the protrusions).

[0025] The waveguide may be integral (e.g., formed integrally or formed as a single piece). The waveguide may have an integral structure (e.g., formed integrally or formed as a single piece) throughout (e.g., between the first end and the second end). The tube (e.g., inner tube) and the protrusion or each protrusion may be integral (e.g., formed integrally). The outer tube and the protrusion or each protrusion may be integral (e.g., formed integrally). The inner tube, the outer tube, and the protrusion or each protrusion may all be integral with each other (e.g., formed integrally). For example, the components may be formed simultaneously by the same process and with the same material.

[0026] The waveguide may be formed of metal (such as metal, for example, composed of metal). The tube (for example, inner tube) and the protrusions or each protrusion may be formed of metal (for example, composed of metal). The tube (for example, inner tube), outer tube, and the protrusions or each protrusion may be formed of metal (for example, composed of metal). The metal may include aluminum (for example, an aluminum alloy).

[0027] The waveguide may include a composite material (e.g., formed from a composite material) (e.g., may be composed of a composite material). A tube (e.g., an inner tube), an outer tube, and a protrusion or each protrusion may be formed from a composite material (e.g., may be composed of a composite material). A tube (e.g., an inner tube), an outer tube, and one or more protrusions or each protrusion may be formed from a composite material (e.g., may be composed of a composite material). The composite material may include a carbon fiber polymer composite (e.g., may be composed of a carbon fiber polymer composite).

[0028] The innermost surface of the tube (e.g., inner tube) may comprise a layer of conductive material (e.g., formed as a layer of conductive material). For example, if the tube comprises a metal, the innermost surface of the tube may comprise the metal or a different metal having higher conductivity. If the tube comprises a composite material (e.g., carbon fiber polymer composite), a layer of conductive material may be provided inside the tube. The layer of conductive material may be applied as a coating. Alternatively, if the tube comprises a composite material, a metal pipe or conduit may be provided inside the tube (e.g., accommodated within the tube). The metal pipe or conduit may define a cylindrical opening for guiding microwaves along a waveguide. The layer of conductive material may comprise aluminum, silver, copper, and / or gold (e.g., an alloy of one or more of these materials, e.g., an alloy of copper).

[0029] The innermost surface of the waveguide (e.g., the cylindrical inner surface of the tube) may include a series of ridges or corrugations. The ridges or corrugations have dimensions and spacing that vary depending on the frequency of the microwave to be transmitted and also the inner diameter of the tube. For example, the ridges or corrugations may have a height or radial dimension of about 0.5 mm, a longitudinal dimension of about 0.5 mm, and / or spacing of about 0.5 mm (e.g., periodicity of about 1.0 mm).

[0030] The tube (e.g., inner tube) may be hollow. The waveguide may include a cylindrical innermost surface. The tube (e.g., inner tube) may not include a structure extending radially inward (except, e.g., a ridge or corrugation). For example, if the waveguide is formed of a composite material and includes a metal conduit within the tube, a substantially cylindrical opening of the metal conduit may include the innermost surface of the waveguide. The tube may be configured to accommodate a component having an opening for microwave guidance.

[0031] According to a second aspect of the present disclosure, an assembly is provided. The assembly may include a microwave source. The assembly may include a microwave waveguide according to a first aspect.

[0032] According to a third aspect of the present disclosure, a microwave waveguide assembly comprising a first waveguide section is provided. The first waveguide section may include a waveguide according to the first aspect. The assembly may include a second waveguide section. The second waveguide section may include a waveguide according to the first aspect. The second waveguide section may be operably coupled to the first waveguide section. The second waveguide section may be identical to the first waveguide section. The waveguide assembly of the third aspect may be provided in combination with the second aspect and / or as part of the second aspect. For example, the first waveguide section of the third aspect may include the microwave waveguide of the second aspect.

[0033] According to a fourth aspect of the present disclosure, a method for forming a microwave waveguide is provided. The waveguide may be a waveguide according to a first aspect. The method may include integrally forming a waveguide according to a first aspect (e.g., integrally forming a tube and a protrusion of the first aspect). The method may include extrusion or pultrusion. The method may include extruding a metal. The method may include pultrusion forming a fiber-reinforced polymer composite (e.g., a carbon fiber-reinforced polymer composite). The method may include providing a conductive layer on the inner surface of a tube (e.g., as a coating or as a conductive conduit). The method may include corrugating the inner surface of the waveguide (e.g., corrugating the inner surface of a tube or corrugating the inner surface of a conductive conduit).

[0034] According to a fifth embodiment, a method for forming a microwave waveguide assembly (e.g., according to a third embodiment) is provided. The method may include providing a first waveguide section (e.g., including a waveguide according to a first embodiment). The method may include providing a second waveguide section (e.g., including a waveguide according to a first embodiment). The method may include operably combining the first and second microwave waveguide sections. The fifth embodiment may be provided in combination with the fourth embodiment and / or as part of the fourth embodiment.

[0035] According to a sixth embodiment, a method (e.g., a method for transmitting microwaves) is provided. The method comprises providing a microwave waveguide of a first embodiment. The method may also include injecting microwaves at a first end of the tube.

[0036] The present method may be a method for transmitting microwaves in a nuclear fusion device. The present method may include vacuuming the tube and / or passing a coolant through the cooling pipes of the waveguide.

[0037] The present method may be a drilling method. The present method may include injecting a cooling gas at a first end of the tube. The present method may include, for example, allowing and / or receiving exhaust gas at a first end of the waveguide from a channel of the waveguide provided outside the tube.

[0038] According to the seventh embodiment, an extrusion or drawing system configured to produce a waveguide according to the first embodiment (e.g., including a die) is provided.

[0039] A list of elements with "and / or" combinations is used to mean "any combination" of the elements in the list (e.g., any one or more of the elements in the list).

[0040] To avoid unnecessary duplication of effort and repetition of text in this specification, specific features are described in relation to only one or more aspects or embodiments of the present invention. However, it should be understood that, where technically possible, features described in relation to any aspect or embodiment of the present invention may also be used in conjunction with any other aspect or embodiment of the present invention. Brief explanation of the drawing

[0041] For a better understanding of the present invention and to show more clearly how it can be effectively carried out, reference is now made to the accompanying drawings as an example. FIG. 1a is a perspective view of a microwave waveguide according to the present disclosure. Figure 1b is an end view of the waveguide of Figure 1a. FIG. 2a is a perspective view of a microwave waveguide according to the present disclosure. Figure 2b is an end view of the waveguide of Figure 2a. FIG. 3 is an end view of a microwave waveguide according to the present disclosure. FIG. 4 is a flowchart illustrating a method according to the present disclosure. FIG. 5 is a flowchart illustrating a method according to the present disclosure. FIG. 6 is a flowchart illustrating a method according to the present disclosure. FIG. 7 is a flowchart illustrating a method according to the present disclosure; FIG. 8 is an end view of a microwave waveguide according to the present disclosure. Throughout the drawing, the same reference numeral is used to denote similar features. Specific details for implementing the invention

[0042] Waveguide (100)

[0043] Referring to FIGS. 1a and 1b (collectively referred to as FIG. 1), a microwave waveguide (100) for guiding high-power microwave energy (e.g., approximately 1 MW) is described. The waveguide (100) comprises a tube (110) having an opening (104) for guiding microwaves from a first end (101) to a second end (102) of the waveguide (100). The microwave energy may be limited to electromagnetic radiation having a frequency of 1 GHz to 1 THz.

[0044] The tube (110) is generally cylindrical, and its walls have a circular cross section and extend substantially uniformly and concentrically along the longitudinal axis (AA). The walls of the tube (110) have a uniform radial thickness so that the tube (110) has a substantially cylindrical inner surface (112) and a substantially cylindrical outer surface (114), and the surfaces (112, 114) extend along the longitudinal axis (AA) of the tube (110).

[0045] The waveguide (100) includes a plurality of protrusions (120) that extend radially away from the outer cylindrical surface (114) of the tube (110). The protrusions (120) are further extended longitudinally along the tube (110) such that the major axis of each protrusion is parallel to the major axis (AA) of the tube (110). Each protrusion (120) includes a uniform cross-section such that the cross-section at any position along the length of the waveguide (100) has the same profile as the end view of FIG. 1b.

[0046] The protrusions (120) are evenly spaced from each other around the outer surface (114) of the tube (110) and are provided at equal angles with respect to the major axis (AA). In the example illustrated in FIG. 1, six protrusions (120) are provided at 60-degree intervals.

[0047] Each protrusion (120) includes a cooling pipe (122) provided at an end radially close to the tube (110) (when viewed from the transverse direction according to FIG. 1b) and a rib (124) provided at an end radially far from the tube (110). For the sake of understanding FIG. 1b, the cooling pipe (122) and the rib (124) are annotated on only one protrusion (120), but it is understood that each protrusion (120) of FIG. 1 includes a cooling pipe (122) and a rib (124).

[0048] A cooling pipe (122) is provided parallel to the major axis (AA) of the waveguide (100). In particular, the cooling pipe (122) is substantially cylindrical and defines a central passage of circular geometric shape. During the operation of the waveguide (100), a liquid coolant may pass along the cooling pipe (122).

[0049] Each rib (124) includes a generally rectangular cross section such that the circumferential thickness is uniform according to the radial distance from the tube (110). Accordingly, each rib (124) includes a rectangular geometric shape.

[0050] As illustrated in FIG. 1b, the diameter of each cooling pipe (122) is greater than the thickness of the wall of the tube (110) (e.g., about twice). However, the thickness of the wall of the pipe (122) is smaller than the thickness of the wall of the tube (110) (e.g., at least three times smaller). The rib (124) has a circumferential thickness dimension similar to the thickness of the wall of the tube (110). Thus, the protrusion (120) is generally tapered over the distance. The protrusion (120) extends radially by a dimension approximately equal to the radial dimension of the tube (110).

[0051] The waveguide (100) includes a narrow connection between each cooling pipe (122) and tube (110). In particular, between each cooling pipe (122) and tube (110), the waveguide (100) includes a connection having a circumferential dimension smaller than the diameter of the pipe (122).

[0052] The cylindrical inner surface (112) of the tube (110) includes a series of ridges or corrugations (not shown) that protrude radially inward from the surface (112) and are spaced apart from each other by a fixed distance along the longitudinal direction. Thus, the inner surface (112) has a series of longitudinally separated transverse circular rings. The dimensions and period of the ridges / corrugations are selected to facilitate a specific mode of microwave propagation along the waveguide (100). The tube (110) may not include additional features within the ridges or corrugations on the inner surface, so the tube (110) is essentially hollow.

[0053] In one example, the tube (110) has an opening (104) (e.g., inner diameter) of 10 mm to 130 mm, for example, about 50 mm (e.g., 45 mm to 55 mm), the wall of the tube may have a thickness of 2 mm to 5 mm, and the ridge has a radial dimension of 0.5 mm, a longitudinal dimension of 0.5 mm, and a spacing of 0.5 mm (e.g., a periodicity of 1.0 mm). However, it is understood that the exact dimensions of the tube, its wall, and the ridge may vary depending on the application of the microwave being guided and the frequency and energy.

[0054] The protrusion (120) reinforces the tube (110) to improve the bending stiffness of the waveguide (100). For example, by reducing the thickness of the wall of the inner tube (110) and providing the protrusion (120), the stiffness of the waveguide can be improved while maintaining the same mass and material volume. Thus, the straightness of the tube (110) is improved compared to an alternative tube having fewer protrusions (120) (e.g., no protrusions). For example, during subsequent drilling of the inner ridge or corrugation, the improved stiffness of the waveguide may reduce (e.g., prevent) the occurrence of curvature within the waveguide (100). In high-power microwave applications, a straighter tube (110) reduces energy loss from the microwave beam.

[0055] As described below, the waveguide (100) may be formed by extrusion (e.g., of metal) or pultrusion (e.g., of carbon fiber reinforced polymer composite), so that the tube (110) and the protrusion (120) may be formed integrally (e.g., having an integral structure). By providing a waveguide (100) with an integral structure, the conduction of heat from the wall of the tube (100) to the coolant provided in the cooling pipe (122) is improved, which means that the cooling process is more efficient. Additionally, by providing the cooling pipe (122) at the radially proximal end of the protrusion (120), the conduction of heat to the coolant in the pipe (122) may be improved compared to a protrusion having the pipe (122) at another location along the protrusion (120) (e.g., the pipe (122) at the distal end of the protrusion (120)).

[0056] Although the waveguide (100) of FIG. 1 comprises six protrusions provided at 60 degrees from each other, those skilled in the art understand that an alternative number of protrusions may be provided. For example, even a single protrusion (120) reinforces the tube (110). Additionally, the protrusions (120) do not necessarily need to be provided at equal angles. For example, the protrusions (120) may be provided such that their radial dimensions during formation and / or at the installation location have a substantial component parallel to the direction of gravity. For example, the six protrusions (120) may be clustered in groups of three in the upper and lower parts of the tube (110) against gravity.

[0057] Similarly, although the cooling pipe (122) and the rib (124) are described as being provided as part of the same protrusion (120), the cooling pipe (122) and the rib (124) may instead be provided as separate protrusions within the same waveguide (110), or may not be provided at all (for example, according to FIG. 3, only one of the cooling pipe (122) and the rib (124) may be provided). For example, the protrusion (120) does not necessarily have to be identical.

[0058] Additionally or alternatively, the geometric shape of the protrusion may differ from that of the illustrated protrusion (120). For example, the protrusion (120) may include a geometric shape such as a triangular cross section (not illustrated) that may serve as a cooling pipe or channel, other than the illustrated pipe (122) and rib (124). Similarly, the protrusion (120) does not necessarily have to extend continuously and / or uniformly from one end of the tube (110) to the other end. For example, at one or more locations along its length, one or more protrusions (120) (e.g., one or more ribs (124)) may include a cut or removed section (not illustrated) extending longitudinally.

[0059] The tube (110) may itself define the opening (104) by its inner surface (112), which may include a conductive coating (e.g., aluminum, silver, copper, and / or gold) on its inner surface (112). Alternatively, a separate component (340) (Fig. 3) may be accommodated in the tube (110), and the separate component may define the opening (104).

[0060] If a separate component (340) defines the opening (104), the reinforcement provided by the protrusion (120) may reduce (e.g., prevent) any curvature occurring within the waveguide (100) during drilling of the internal corrugation.

[0061] Waveguide (200)

[0062] Referring to FIGS. 2a and FIGS. 2b (collectively referred to as FIG. 2), a microwave waveguide (200) is described. The microwave waveguide (200) of FIG. 2 is essentially the same as the waveguide (100) of FIG. 1, except for the following exceptions.

[0063] The waveguide (200) further comprises an outer tube (230). The outer tube (230) is substantially cylindrical, has a circular cross-section that extends uniformly along its length, and is provided concentrically with the inner tube (210) so that the major axis (BB) coincides. The outer tube (230) has a radius that is about twice that of the inner tube (210).

[0064] The wall of the outer tube (230) has a uniform radial thickness, so that the tube (230) has a substantially cylindrical outer surface (234) that extends along the longitudinal axis (BB) of the waveguide (200). Thus, while the waveguide (100) has a spline outer surface, the waveguide (200) has a cylindrical outer surface. The wall of the outer tube (230) has the same thickness as the wall of the inner tube (210).

[0065] In the same manner as in the waveguide (100), the protrusion (220) extends radially away from the outer surface (114) of the tube (210). However, in the waveguide (200), the protrusion (220) extends radially inward from the inner surface (232) of the tube (210, 230) so that each protrusion (220) extends between the tubes (210, 230). As the protrusion (220) extends radially, the rib (224) forms a substantially perpendicular contact with the inner surface (232) of the outer tube (230).

[0066] Accordingly, adjacent protrusions (220) are combined with coaxial tubes (210, 230) to define a series of longitudinal channels (226) having a geometric shape that is essentially a prismatic annular fan or a fan of a cylindrical shell (e.g., a fan formed between opposing cylindrical arcs of tubes (210, 230) and between opposing radially extended protrusions (220)). Each channel (226) is continuous between the ends (201, 202) of the waveguide (200) so that fluid flow along the waveguide (200) is allowed. For the sake of understanding of FIG. 2b, only a single channel (226) is indicated in the annotation. In the example of FIG. 2, the channel (226) spans about 60 degrees, but it is understood that when a different number of protrusions (220) are provided, channels spanning different angles exist.

[0067] In the same manner as the waveguide (100), each projection (220) includes a cooling pipe (222) and a rib (224), with the cooling pipe (222) provided at the proximal end and the rib (224) provided at the distal end (224). However, each projection (220), specifically the pipe (222), has a connection with the inner tube (210) that is wider than the connection between the projection (120) of the waveguide (100) and the tube (110). For example, the pipe (222) may be provided closer to the long axis (BB) than the pipe (122) with respect to the long axis (AA). In particular, between each cooling pipe (222) and the tube (200), the waveguide (200) includes a connection having a circumferential dimension larger than the diameter of the pipe (222). In the illustrated embodiment of FIG. 2, the thickness of the rib (224) may be substantially the same as the wall thickness of the tube (210, 230).

[0068] By providing an outer tube (230) connected to an inner tube (210) through a protrusion (220), the stiffness (e.g., bending stiffness) of the waveguide (200) is improved compared to a waveguide without an outer tube (230). For example, by reducing the thickness of the wall of the inner tube (210) and providing the outer tube (230) and the protrusion (220) between them, the stiffness of the waveguide can be improved while maintaining the same mass and volume.

[0069] Waveguide (300)

[0070] Referring to FIG. 3, a microwave waveguide (300) extending along an axis (CC) is described. The waveguide (300) is substantially the same as the waveguide (200) of FIG. 2, except for the following exception.

[0071] Each protrusion (320) includes a rib (324) but does not include a cooling pipe. Accordingly, the protrusion (320) is composed of a rib (324), and the channel (326) has a geometric shape closer to a prismatic annular fan or a cylindrical shell fan.

[0072] Therefore, the protrusion (320) has a uniform circumferential thickness over its entire radial dimension, and thus the thickness of the protrusion (320) may be substantially the same as the wall thickness of the inner tube (310) and the outer tube (330).

[0073] As described later, the protrusion (320) does not include a cooling pipe, but the channel (326) limited between the tube (310, 330) and the adjacent protrusion (320) is continuous along its length, allowing fluid flow along its length.

[0074] The waveguide (300) additionally includes a conductive layer (340) inside the tube (310). The conductive layer may include a conductive coating applied to the inner surface (312) of the tube (310), or a separate component such as a conductive pipe or conduit (e.g., a copper pipe) that engages with the inner surface (312) of the tube (310). In the example where the conductive layer (340) includes a separate component, the component may be received in the tube (310) before forming a corrugation in the component (340). Including the conductive layer (340) may be particularly advantageous when the tube (110, 210, 310) is formed of a non-conductive material, but it may also be advantageous when the tube (110, 210, 310) is formed of a conductive material (e.g., the layer (340) may include a more conductive material).

[0075] Waveguide (800)

[0076] Referring to FIG. 8, a microwave waveguide (800) is described. The waveguide (800) is similar to the waveguide (200) of FIG. 2, except for the following exceptions.

[0077] The waveguide (800) is provided with four protrusions (820) distributed equidistantly around a central axis (DD), and each protrusion (820) includes a cooling pipe (822) and a rib (824). For the sake of understanding of the drawing, the cooling pipe (822) and rib (824) of only one protrusion (820) are indicated in annotation. However, it is understood that each of the remaining three protrusions (820) also includes a cooling pipe (822) and a rib (824).

[0078] The cooling pipe (822) of each protrusion (820) includes a discontinuity (828) in its circumferential wall. The discontinuity (828) extends longitudinally along the entire length of the pipe (822) (such as from the first end of the waveguide (800) to the second end of the waveguide (800)) and extends radially from the inside to the outside of the cooling pipe (822) through the thickness of the circumferential wall (relative to the cooling pipe (822)). Therefore, each discontinuity (828) includes two substantially opposite surfaces that extend radially and longitudinally, respectively, relative to the cooling pipe (822). Although FIG. 8 illustrates an end view of the waveguide (800), any cross-section passing through the waveguide (800) may include the geometric shape illustrated in FIG. 8.

[0079] Additional components (e.g., aluminum or copper cooling channels for transporting coolant within the pipe (822)) may be inserted into the cooling pipe (822) before operation. By providing a discontinuity (828) within the cooling pipe (822), the circumferential and radial deformability of the pipe (822) may be increased. For example, the discontinuity (828) improves the circumferential expansion of the pipe (822), allowing additional components to be inserted more easily along the length of the pipe and enabling the pipe (822) to more securely engage or grip the components.

[0080] In FIG. 8, each discontinuity (828) is illustrated as including an opening formed by the removal or omission of an acute-angled sector of the cylindrical wall of the cooling pipe (822), so that substantially opposite faces of the discontinuity (828) are spaced apart from each other by the acute-angled sector of the cylindrical wall that was removed or omitted. Such openings may also be formed during the extrusion process.

[0081] Alternatively, in an example not illustrated, each discontinuity (828) may instead include a break between opposing circumferential faces of the wall within the wall of the pipe (822). For example, the opposing faces of the discontinuities (828) may come into contact with each other before an additional component is inserted into the cooling pipe (822). The discontinuities (828), in the form of an opening (illustrated) or a break (not illustrated), still provide the above advantages for the cooling pipe (822).

[0082] Constituent materials

[0083] In order to propagate microwaves along the waveguide (100, 200, 300, 800), the opening (104, 204, 304, 804) of the waveguide (100, 200, 300, 800) is defined by a conductive material. The tube (110, 210, 310, 810) may be formed of a conductive material (e.g., aluminum or an alloy thereof), so that the inner surface (112, 212, 312, 812) defines the opening (104, 204, 304, 804). Additionally or alternatively, the tubes (110, 210, 310, 810) may include a layer (340) of a conductive material (e.g., a conductive coating) provided on their inner surfaces (112, 212, 312, 812). For example, a tube (110, 210, 310, 810) formed of a conductive material may have a layer of a material having higher conductivity provided on its inner surface (112, 212, 312, 812). Alternatively, when the tube (110, 210, 310, 810) is formed of a non-conductive material, a layer of a conductive material may be provided on its interior (e.g., as a separate component such as a conductive conduit, or as a coating layer), and a layer of a conductive material may define an opening (104, 204, 304, 804). Materials including aluminum, silver, copper, and / or gold may be particularly beneficial for defining the openings (104, 204, 304, 804).

[0084] The composition of the waveguide (100, 200, 300, 800) may be determined by its application. If cooling is a major consideration for the waveguide (100, 200, 300, 800) (e.g., due to proximity of other components and / or environmental conditions during operation), it may be desirable to form the tube (110, 210, 310, 810) and protrusion (120, 220, 320, 820) (and optionally, if present, the outer tube (230, 330, 830)) from a material having high thermal conductivity and high electrical conductivity (e.g., aluminum or an alloy thereof). By using such materials, the conduction of heat to the cooling pipes (122, 222, 822) and / or channels (326, 826) may be improved, and thus the heat dissipation characteristics of the waveguide (100, 200, 300, 800) are improved. Such compositions may be particularly beneficial in nuclear fusion applications (described later).

[0085] When the waveguide (100, 200, 300, 800) has a very long length or is to be assembled into a waveguide assembly having a very long length, it may be desirable to form the tube (110, 210, 310, 810) and protrusion (120, 220, 320, 820) (and, if present, optionally the outer tube (230, 330, 830)) with a material having a relatively low density but high strength, such as a carbon fiber reinforced polymer composite. The polymer used may be a high-temperature resin, such as a resin capable of withstanding a temperature of up to 1000°C. Such a waveguide may include a conductive layer on the inner surface (112, 212, 312, 812) of the tube (110, 210, 310, 810). The conductive layer may be applied as a coating or may include a separate component, such as a conductive pipe or conduit inserted into the tube (110, 210, 310, 810), and the separate component may include a corrugated section. Such a composition may be particularly beneficial in geothermal drilling applications (described below).

[0086] formation process

[0087] Referring to FIG. 4, a method (400) for forming a waveguide (100, 200, 300, 800) is described. The method (400) includes extruding a metal (402). The metal may be extruded through a die having a geometric shape that is nearly identical to the end view of FIG. 1a, FIG. 2a, FIG. 3 and FIG. 8.

[0088] Alternatively, the present method (400) comprises pultrusion (404) of a carbon fiber reinforced polymer composite. The carbon fiber reinforced polymer composite may be pultrusion through a die having a geometric shape that corresponds approximately to the end views of FIG. 1a, FIG. 2a, FIG. 3 and FIG. 8. The present method (400) then comprises providing a conductive layer (340) on the inner surface (112, 212, 312, 812) (406). For example, the conductive layer may comprise a conductive coating or a separate component (e.g., a conductive conduit) accommodated in a tube (110, 210, 310, 810).

[0089] The present method (400) further comprises forming a corrugation (408) on the inner surface (112, 212, 312, 812) of the waveguide (100, 200, 300, 800). For example, if the opening (104, 204, 304, 804) is defined by a separate component accommodated in the tube (110, 210, 310, 810), the component may be inserted into the tube (110, 210, 310, 810) before drilling the corrugation portion within the component.

[0090] When the opening (104, 204, 304, 804) is limited by a tube (110, 210, 310, 810), a corrugation may be formed on the inner surface (112, 212, 312, 812) of the tube (110, 210, 310, 810). However, the application of a conductive coating to the tube (110, 210, 310, 810) may be performed before or after the formation of the corrugation.

[0091] Therefore, the tubes (110, 210, 310, 810) and protrusions (120, 220, 320, 820) (and optionally, if present, the outer tube (230, 330, 830)) are formed integrally, thus having an integral structure. For example, the waveguide (100, 200, 300, 800) may be formed by extruding metal through a die having a geometric shape corresponding to the end view of FIG. 1b, FIG. 2b, FIG. 3, and FIG. 8. Thus, the waveguide (100, 200, 300, 800) may be formed integrally (e.g., from a single material) and thus have an integral structure throughout.

[0092] Alternatively, the waveguide (100, 200, 300, 800) may be formed by pultrusion of a carbon fiber composite or similar material through a die having a geometric shape corresponding to the end views of FIG. 1b, FIG. 2b, FIG. 3, and FIG. 8. Thus, the waveguide (100, 200, 300, 800) may be formed integrally, except for an optional conductive coating and an optional conductive conduit provided inside the tube (110, 210, 310, 810).

[0093] Forming a waveguide (100, 200, 300, 800) by drawing or extrusion provides a higher output of the waveguide, reduces material waste, and may be less labor-intensive.

[0094] waveguide assembly

[0095] Waveguides (100, 200, 300, 800) are provided in sections and may be assembled into a waveguide assembly (not shown). For example, waveguides (100, 200, 300, 800) may be extruded / drawn into sections several meters in length and then attached to each other by flanges provided at both ends.

[0096] Referring to FIG. 5, a method (500) for forming a microwave waveguide assembly is described. The method (500) includes providing a first waveguide section (502). For example, the method step (502) may include performing the method (400) of FIG. 4. The method (500) includes providing a second waveguide section (504). For example, the method step (504) may include performing the method (400) of FIG. 4. Then, the method (500) comprises operably joining the first waveguide section (100, 200, 300, 800) and the second waveguide section (100, 200, 300, 800) as by means of a flange (e.g., so that the waveguide may be transmitted from the first waveguide section to the second waveguide section). The flange may be attached to the waveguide section after formation.

[0097] nuclear fusion

[0098] Waveguides (100, 200, 300, 800) may also be used in nuclear fusion applications. Due to their cooling pipes (122, 222, 822), waveguides (100, 200, 800) may be particularly useful in nuclear fusion when formed from a metal such as aluminum (e.g., aluminum alloy) or other materials having high thermal conductivity. By forming the protrusions (120, 220, 820) and the tubes (110, 210, 810) as a single unit, heat conduction from the tubes (110, 210, 810) to the coolant flowing through the pipes (122, 222, 822) may be improved.

[0099] Referring to FIG. 6, a method (600) is described. The method (600) may be a method of transmitting microwaves from a source, such as a gyrotron, to a destination, such as a fusion vessel.

[0100] The present method (600) comprises providing (602) a microwave waveguide (100, 200, 300, 800) (e.g., as part of a waveguide assembly). For example, the method step (602) may include performing the method (400) of FIG. 4. Then, the present method (600) comprises vacuum evacuating the tube (110, 210, 310, 810) (604) and passing a coolant through the cooling pipe (122, 222, 322, 822) of the waveguide (100, 200, 300, 800) (606). After that, the present method (600) includes injecting microwaves (608) at the first end (101, 201, 301, 801) of the tube (110, 210, 310, 810).

[0101] Geothermal drilling

[0102] Waveguides (300) may be particularly beneficial in geothermal drilling, especially when formed from carbon fiber composites. During geothermal drilling, it may be necessary to drill into the crust up to 20 km. Since this is a vertical drill hole, the break length of the waveguide and other material properties may be important considerations. For example, conventional waveguide materials may not be suitable for hanging vertically over a kilometer scale.

[0103] However, when formed from a carbon fiber composite (having a break length several times greater than 20 km), material limitations may be relaxed (e.g., by processing). For example, in an embodiment in which the waveguide (300) comprises a tube (310, 330) and a protrusion (320) integrally formed from a carbon fiber composite by pultrusion, the break length of the conductive conduit housed in the tube (310) may be improved by reinforcement provided by the carbon fiber composite of the waveguide (300). In other words, the weight of the copper pipe relative to the interior of the tube (110, 210, 310, 810) may be partially supported by the carbon fiber composite, thereby increasing the break length of the copper pipe.

[0104] Additionally, a carbon fiber composite containing a high-temperature resistant resin (e.g., a resin capable of withstanding a temperature of at least 1,000°C, such as at least 2,000°C) may withstand a temperature of about 700°C at its distal end during the drilling process.

[0105] Referring to FIG. 7, a method (700) of drilling (e.g., geothermal drilling) is described. The method (700) comprises providing (702) a microwave waveguide (100, 200, 300, 800) (e.g., as part of a waveguide assembly). For example, the method step (702) may include performing the method (400) of FIG. 4. The method (700) subsequently comprises injecting a cooling gas (e.g., an inert gas) into a first end (101, 201, 301, 801) of a tube (110, 210, 310, 810) (704). The present method (700) subsequently includes injecting microwaves (706) into the first end (101, 201, 301, 801) of the tube (110, 210, 310, 810). The present method (700) subsequently includes receiving exhaust gas (708) from the first end (101, 201, 301, 801) from the channel (226, 326, 826) of the waveguide (200, 300, 800). For example, vaporized soil from the drilled end of the waveguide may pass upward along the channel (226, 326, 826) toward the upper end of the waveguide assembly.

[0106] Experimental data

[0107] Finite Element Analysis (FEA) was performed on a waveguide (300) of the type shown in FIG. 3 having a different number of ribs (324). The waveguide has an inner tube (310) with an inner diameter of 50 mm, an outer tube (330) with an outer diameter of 100 mm, and all walls with a uniform thickness of 3 mm.

[0108] Next, the deflection behavior of a waveguide (300) having different lengths and different numbers of ribs (324) was determined. For the deflection calculation of Table 1, the FEA boundary conditions included a waveguide (300) having a fixed support at one end and a frictionless support at the other end. To reduce calculation time, the internal corrugations were omitted from the FEA (it was separately determined that the corrugations do not affect the deflection behavior of the waveguide). The result data is shown in Table 1 below.

[0109]

[0110] [Table 1] Bias Analysis Using FEA

[0111] As described above, it was found that the deflection of the waveguide increased with the number of ribs for both 2m and 4m lengths. However, the waveguide (300) still exhibited a smaller deflection compared to the previously proposed waveguide structure, and thus exhibited improved stiffness and straightness compared to the previously proposed waveguide structure.

[0112] Afterwards, thermal analysis was performed on waveguides (200) of the type shown in FIG. 2, having different numbers of ribs, and at different coolant mass flow rates. The results are shown in Table 2.

[0113] It was found that cooling improves as the number of ribs increases, but if the number of ribs exceeds 4, the additional improvement effect decreases.

[0114] Next, a circularity analysis was performed to determine the degree of deflection according to orientation. It was found that the deflection of the waveguide having four ribs does not change according to orientation when rotated about the central axis. In particular, it was found that the 4m waveguide having four ribs is deflected by the same amount when the line of gravity is parallel to the rib (324) and when the line of gravity bisects an adjacent rib (324) (i.e., the deflection does not change according to a rotation over 45 degrees). Therefore, the 4-rib waveguide (300) may be installed in a rotation-invariant or direction-invariant manner.

[0115]

[0116] [Table 2] Thermal Analysis Using FEA

[0117] In light of the above data, it was concluded that although all proposed microwave waveguides provide improvements over previously proposed waveguides, the waveguide with four ribs is the most advantageous when deflection behavior is a major consideration and according to specific boundary conditions of the analyses performed.

[0118] Those skilled in the art will understand that although the present invention has been described by way of example with reference to one or more exemplary examples, it is not limited to the disclosed examples and alternative examples may be constructed without departing from the scope of the invention as defined by the appended claims.

Claims

Claim 1 A microwave waveguide comprising: a tube including an opening for guiding microwave energy; and a waveguide including a protrusion extending longitudinally along the outer surface of the tube. Claim 2 A waveguide according to claim 1, comprising a plurality of protrusions spaced apart from each other around the tube. Claim 3 In claim 1 or 2, the protrusion or each protrusion is a waveguide extending parallel to the longitudinal axis of the tube. Claim 4 In any one of claims 1 to 3, the protrusion or the cross-section of each protrusion is uniform over the entire length of the waveguide. Claim 5 A waveguide according to any one of claims 1 to 4, wherein the protrusion or each protrusion includes a rib, and the rib extends away from the outer surface of the tube. Claim 6 In any one of claims 1 to 5, the protrusion or each protrusion is a waveguide comprising a pipe. Claim 7 A waveguide according to any one of claims 1 to 6, wherein the projection or each projection comprises a pipe and a rib, the pipe being provided at the proximal end of the projection and / or the rib being provided at the distal end. Claim 8 A waveguide according to any one of claims 1 to 7, wherein the protrusion or each protrusion is integrally formed with the tube. Claim 9 A waveguide according to any one of claims 2 to 8, wherein the protrusion is provided at an equal angle with respect to the longitudinal axis of the tube. Claim 10 A waveguide according to any one of claims 1 to 9, wherein the tube is an inner tube, and the waveguide further comprises an outer tube provided coaxially with the inner tube. Claim 11 In claim 10, the above protrusion or each protrusion is a waveguide extending from the inner surface of the outer tube. Claim 12 In any one of claims 1 to 11, the protrusion or each protrusion is an integrally formed guide tube with the tube. Claim 13 A waveguide according to any one of claims 1 to 12, wherein the protrusion or each protrusion and the tube are formed of metal. Claim 14 In any one of claims 1 to 13, the waveguide comprises a first end and a second end, and the waveguide has an integral structure between the first end and the second end. Claim 15 A waveguide according to any one of claims 1 to 12, wherein the protrusion or each protrusion and the tube are formed of a carbon fiber polymer composite. Claim 16 In any one of claims 1 to 15, the tube is cylindrical and is a waveguide having an inner diameter of 10 mm to 30 mm. Claim 17 A waveguide according to any one of claims 1 to 16, wherein the tube limits the opening, or the opening is limited by a conductive conduit contained within the tube. Claim 18 An assembly comprising a microwave source and a waveguide described in any one of claims 1 to 17. Claim 19 A microwave waveguide assembly comprising a first waveguide section including a waveguide described in any one of claims 1 to 17, and a second waveguide section including a waveguide described in any one of claims 1 to 17, wherein the second waveguide section is operably coupled to the first waveguide section. Claim 20 A method for forming a microwave waveguide as described in any one of claims 1 to 17, comprising extruding a metal or pultrusion molding a carbon fiber reinforced polymer composite. Claim 21 A method for forming a microwave waveguide according to claim 20, comprising forming a corrugation on the inner surface of a tube and / or providing a conductive layer on the inner surface of a tube. Claim 22 A method for forming a microwave waveguide assembly as described in claim 19, comprising: providing a first waveguide section comprising a waveguide as described in any one of claims 1 to 17; providing a second waveguide section comprising a waveguide as described in any one of claims 1 to 17; and operably combining the first and second waveguide sections. Claim 23 A method comprising providing a microwave waveguide as described in any one of claims 1 to 17, and injecting microwaves at a first end of the tube. Claim 24 A method according to claim 23, comprising vacuuming the tube and / or passing a coolant through the cooling pipe of the waveguide. Claim 25 In claim 23, the method is a drilling method comprising injecting a cooling gas at a first end of a tube and receiving an exhaust gas at the first end from a channel of a waveguide provided on the outside of the tube.

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