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FEDERAL RESEARCH STATEMENT  
       [0001]     This invention was made with government support under Contract No. DE-FC26-97FT343656 awarded by the U.S. Department of Energy. The government has certain rights in the invention. 
     
    
     BACKGROUND OF INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     This invention relates to oil and gas drilling, and more particularly to apparatus and methods for reliably transmitting information along downhole drilling strings.  
         [0004]     2. Background  
         [0005]     In the downhole drilling industry, MWD and LWD tools are used to take measurements and gather information with respect to downhole geological formations, status of downhole tools, conditions located downhole, and the like. Such data is useful to drill operators, geologists, engineers, and other personnel located at the surface. This data may be used to adjust drilling parameters, such as drilling direction, penetration speed, and the like, to accurately tap into oil, gas, or other mineral bearing reservoirs. Data may be gathered at various points along the drill string. For example, sensors, tools, and the like, may be located at or near the bottom hole assembly and on intermediate tools located at desired points along the drill string.  
         [0006]     Nevertheless, data gathering and analysis do not represent the entire process. Once gathered, apparatus and methods are needed to rapidly and reliably transmit the data to the earth&#39;s surface. Traditionally, technologies such as mud pulse telemetry have been used to transmit data to the surface. However, most traditional methods are limited to very slow data rates and are inadequate for transmitting large quantities of data at high speeds.  
         [0007]     In order to overcome these limitations, various efforts have been made to transmit data along electrical or other types of cable integrated directly into drill string components, such as sections of drill pipe. In such systems, electrical contacts or other transmission elements are used to transmit data across tool joints or connection points in the drill string. Nevertheless, many of these efforts have been largely abandoned or frustrated due to unreliability and complexity.  
         [0008]     For example, one challenge is effectively integrating a transmission line into a downhole tool, such as a section of drill pipe. Due to the inherent nature of drilling, most downhole tools have a similar cylindrical shape defining a central bore. The wall thickness surrounding the central bore is typically designed in accordance with weight, strength, and other constraints imposed by the downhole environment. In some cases, milling or forming a channel in the wall of the downhole tool to accommodate a transmission line may excessively weaken the wall. Thus, in certain embodiments, the only practical route for the transmission line is through the central bore of a downhole tool.  
         [0009]     Nevertheless, routing the transmission line through the central bore may expose the transmission line to drilling fluids, cements, wireline tools, or other substances or objects passing through the central bore. This can damage the transmission line or cause interference between the transmission line and objects or substances passing through the central bore. Moreover, in directional drilling applications, downhole tools may bend slightly as a drill string deviates from a straight path. This may cause the transmission line to detach itself from the inside surface of the central bore, worsening the obstruction within the central bore.  
         [0010]     Thus, what are needed are apparatus and methods to protect a transmission line, routed through the central bore of a downhole tool, from drilling fluids, cement, wireline tools, or other components traveling through the central bore.  
         [0011]     What are further needed are reliable apparatus and methods to keep a transmission line attached to the inside surface of the central bore when the downhole tool bends from a linear path or when the transmission line encounters drilling fluids, cement, wireline tools, or other components traveling through the central bore.  
       SUMMARY OF INVENTION  
       [0012]     In view of the foregoing, it is a primary object of the present invention to provide apparatus and methods for protecting a transmission line, routed through the central bore of a downhole tool, from drilling fluids, cement, wireline tools, or other components traveling through the central bore. If is a further object to keep a transmission line attached to the inside surface of the central bore when the downhole tool bends or deviates from a straight path or encounters objects or substances traveling through the central bore.  
         [0013]     Consistent with the foregoing objects, and in accordance with the invention as embodied and broadly described herein, an apparatus for bonding a transmission line to the inside diameter of a downhole tool is disclosed in one embodiment of the invention as including a pre-formed interface for bonding a transmission line to the inside diameter of a downhole tool. The pre-formed interface includes a first surface that substantially conforms to the outside contour of a transmission line and a second surface that substantially conforms to the inside diameter of a downhole tool.  
         [0014]     In selected embodiments, the first surface is shaped to mechanically grip the transmission line. In other embodiments, the first surface is bonded directly to the transmission line. For example, in selected embodiments, the first surface is bonded to the transmission line by adhesives or welding.  
         [0015]     In selected embodiments, the first surface is configured to completely encircle or surround the transmission line. In other embodiments, the first surface only partially encircles or encompasses the transmission line. Like the first surface, in selected embodiments, the second surface is bonded to the inside diameter of the downhole tool using adhesives or welding.  
         [0016]     The pre-formed interface may be pre-formed using various processes, including but not limited to extrusion, stamping, and casting processes. In selected embodiments, the pre-formed interface may be configured to engage one or several recesses or grooves milled or otherwise formed on the inside surface of the central bore.  
         [0017]     In another aspect of the invention, a method for bonding a transmission line to the central bore of a downhole tool includes pre-forming an interface for bonding a transmission line to the inside diameter of a downhole tool. Pre-forming includes forming a first surface substantially conforming to the outside contour of a transmission line and forming a second surface substantially conforming to the inside diameter of a downhole tool. In addition, the method includes bonding the second surface to the inside diameter of the downhole tool.  
         [0018]     In selected embodiments, the method also includes mechanically gripping the transmission line by the first surface. In other embodiments, the method includes bonding the first surface to the transmission line. For example, bonding may be achieved using adhesives or welding. In selected embodiments, the interface completely encircles or surrounds the transmission line. In other embodiments, the interface only partially encircles or surrounds the transmission line.  
         [0019]     In selected embodiments, the method includes bonding the second surface to the inside diameter of the downhole tool using adhesives or welding. The method may also include pre-forming the interface using a method including but not limited to extruding, stamping, or casting. In selected embodiments, the interface may engage one or several recesses or grooves milled or otherwise formed on the inside surface of the central bore.  
         [0020]     In another aspect of the invention, a method for bonding a transmission line to the inside diameter of a downhole tool includes positioning a transmission line near the inside wall of a downhole tool and placing a mold near the transmission line and the inside wall. The method further includes injecting a bonding material into the mold and curing the bonding material such that the bonding material bonds the transmission line to the inside wall.  
         [0021]     After the bonding material is partially or completely cured, the method includes removing the mold from the bonding material. In selected embodiments, the method includes prepping the surface of either the inside diameter of the downhole tool, the transmission line, or both, before injecting the bonding material. To facilitate bending of the downhole tool, while preventing detachment of the transmission line from the inside surface, and to prevent large pieces of bonding material from detaching from the inside surface, the method may include forming gaps in the bonding material at desired intervals along the bonding material. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0022]     The foregoing and other features of the present invention will become more fully apparent from the following description, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only typical embodiments in accordance with the invention and are, therefore, not to be considered limiting of its scope, the invention will be described with additional specificity and detail through use of the accompanying drawings.  
         [0023]      FIG. 1  is a cross-sectional view illustrating one embodiment of a drill rig in accordance with the invention.  
         [0024]      FIG. 2  is a cross-sectional view illustrating one embodiment of a transmission line integrated into a downhole tool.  
         [0025]      FIG. 3  is a cross-sectional view illustrating one embodiment of a pre-formed interface for mounting a transmission line to the inside diameter of a downhole tool.  
         [0026]      FIGS. 4A-4D  are various perspective cross-sectional views illustrating several embodiments of pre-formed interfaces in accordance with the invention.  
         [0027]      FIGS. 5A-5C  are several cross-sectional views illustrating one embodiment of a pre-formed interface that mechanically attaches to a transmission line.  
         [0028]      FIG. 6  is a cross-sectional view illustrating one embodiment of a pre-formed interface, mechanically attachable to a transmission line, that may be formed or stamped from a sheet-like material.  
         [0029]      FIGS. 7A and 7B  are cross-sectional views illustrating one embodiment of a pre-formed interface that substantially encloses a transmission line.  
         [0030]      FIG. 8  is a cross-sectional view illustrating one embodiment of a pre-formed interface that completely encloses a transmission line.  
         [0031]      FIG. 9  is a cross-sectional view illustrating one embodiment of a pre-formed interface that engages one or several recesses or grooves formed along the inside surface of the central bore.  
         [0032]      FIG. 10  is a cross-sectional view illustrating one embodiment of a tool used to attach the pre-formed interface to the inside surface of the central bore.  
         [0033]      FIG. 11  is a cross-sectional view illustrating one embodiment of a mold assembly used to attach a transmission line to the wall of the central bore by applying a bonding material to the transmission line and inside diameter of the central bore.  
         [0034]      FIG. 12  is a cross-sectional view illustrating air gaps that may be formed at desired intervals along the bonding material to allow bending of a downhole tool while preventing detachment of the transmission line from the central bore, and to prevent large pieces of bonding material from detaching from the inside surface of the central bore.  
         [0035]      FIG. 13  is a cross-sectional view illustrating one embodiment of a mold assembly used to form the air gaps described in connection with  FIG. 12 . 
     
    
     DETAILED DESCRIPTION  
       [0036]     It will be readily understood that the components of the present invention, as generally described and illustrated in the Figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of embodiments of apparatus and methods of the present invention, as represented in the Figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of various selected embodiments of the invention.  
         [0037]     The illustrated embodiments of the invention will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. Those of ordinary skill in the art will, of course, appreciate that various modifications to the apparatus and methods described herein may easily be made without departing from the essential characteristics of the invention, as described in connection with the Figures. Thus, the following description of the Figures is intended only by way of example, and simply illustrates certain selected embodiments consistent with the invention as claimed herein.  
         [0038]     Referring to  FIG. 1 , a cross-sectional view of a drill rig  10  is illustrated drilling a borehole  14  into the earth  16  using downhole tools (collectively indicated by numeral  12 ). The collection of downhole tools  12  form at least a portion of a drill string  18 . In operation, a drilling fluid is typically supplied under pressure at the drill rig  10  through the drill string  18 . The drill string  18  is typically rotated by the drill rig  10  to turn a drill bit  12   e  which is loaded against the earth  16  to form the borehole  14 .  
         [0039]     Pressurized drilling fluid is circulated through the drill bit  12   e  to provide a flushing action to carry the drilled earth cuttings to the surface. Rotation of the drill bit may alternately be provided by other downhole tools such as drill motors, or drill turbines (not shown) located adjacent to the drill bit  12   e . Other downhole tools include drill pipe  12   a  and downhole instrumentation such as logging while drilling tools  12   c , and sensor packages (not shown). Other useful downhole tools include stabilizers  12   d , hole openers, drill collars, heavyweight drill pipe, sub-assemblies, under-reamers, rotary steerable systems, drilling jars, and drilling shock absorbers, which are all well known in the drilling industry.  
         [0040]     Referring to  FIG. 2 , a downhole tool  12  may include a box end  24  and a pin end  26 . A pin end  26  may thread into a box end  24 , thereby enabling the connection of multiple tools  12  together to form a drill string  18 . Due to the inherent nature of drilling, most downhole tools  12  have a similar cylindrical shape and a central bore  28 . The central bore  28  is used to transport drilling fluids, wireline tools, cement, and the like through the drill string  18 .  
         [0041]     The wall thickness  36  surrounding the central bore  28  is typically designed in accordance with weight, strength, and other constraints, needed to withstand substantial torque placed on the tool  12 , pressure within the central bore  28 , flex in the tool  12 , and the like. Because of the immense forces placed on the tool  12 , milling or forming a channel in the wall  36  of the downhole tool  12  to accommodate a transmission line  30  may excessively weaken the wall. Thus, in most cases, the only practical route for a transmission line  30  is through the central bore  28  of the downhole tool  12 .  
         [0042]     Nevertheless, routing the transmission line  30  through the central bore  28  may expose the transmission line  30  to drilling fluids, cements, wireline tools, or other substances or objects passing through the central bore  28 . This can damage the transmission line  30  or cause interference between the transmission line  30  and objects or substances passing through the central bore  28 . Thus, in selected embodiments, a transmission line  30  is preferably maintained as close to the wall  36  of the central bore  28  as possible to minimize interference. In selected embodiments, the transmission line  30  is protected by a conduit  30  or other protective covering  30  to protect the internal transmission medium (e.g. wire, fiber, etc.).  
         [0043]     As illustrated, at or near the box end  24  and pin end  26  of the tool  12 , the central bore  28  may be narrower and the surrounding tool wall  38  may be thicker. This increases the strength of the downhole tool  12  at or near the tool joints, which undergo a great deal of stress during drilling. In addition, the added thickness  38  may enable channels  32 ,  34 , to be milled or formed in the walls  38  to accommodate a transmission line  30  without overly weakening the tool  12 . The channels  32 ,  34  may exit the downhole tool  12  at or near the ends of the tool  12 , where the transmission line  30  may be coupled to transmission elements (not shown) to transmit information across the tool joints.  
         [0044]     In an effort to tap into gas, oil, or other mineral deposits, a drill string  18  may bend from a linear path. Since a drill string  18  may consist of many hundreds of sections of drill pipe  12  and other downhole tools  12 , the cumulative bend or curve in each tool  12  may enable a drill string  18  to bend from a vertical position to drill horizontally in some cases.  
         [0045]     If a transmission line  30  is routed through the central bore  28  of a tool  12 , the transmission line  30  may separate or detach from the inside surface of the central bore  28  when the downhole tool  12  bends. This may worsen the obstruction created by the transmission line  30  since it may interfere with fluids, wireline tools, concrete, or other objects or substances traveling through the central bore  28 . In fact, in some cases, when a downhole tool  12 , such as a section of drill pipe  12 , bends significantly, the transmission line  30  may actually come into contact with the opposite side  39  of the central bore  28 . Thus, apparatus and methods are needed to keep a transmission line  30  firmly attached to the inside diameter of the central bore  28  to prevent damage to the transmission line  30  and to minimize the obstruction within the central bore  28 .  
         [0046]     Referring to  FIG. 3 , to keep the transmission line  30  attached to the inside wall  36  of the central bore  28 , a pre-formed interface  40  may be attached to both the transmission line  30  and the central bore  28 . The transmission line  30  may be a combination of some transmission medium, such as coaxial cable, copper wire, optical fiber, waveguides, or the like, and a protective covering such as sheathing or conduit. In selected embodiments, the conduit may be constructed of a metal such as stainless steel. By “pre-formed,” it is meant that the interface  40  is formed previous to being inserted into the central bore  28 , as opposed to being formed within the central bore  28  as an epoxy or other like material might be. Nevertheless, an alternative embodiment, where the interface  40  is actually formed in the central bore  28  with a material such as an epoxy, is described with respect to  FIGS. 11 through 13 .  
         [0047]     The interface  40  may be used to enhance a bond between a transmission line  30  and the central bore  28  since the transmission line  30  may not naturally fit the contour of the central bore  28 . The interface  40  may include a first surface that conforms to the contour of the transmission line  30  and a second surface that conforms to the inside surface of the central bore  28 . The interface  40  need not exactly conform to the either the transmission line  30  or the central bore  28 , although a close fit may be desirable in some cases.  
         [0048]     In selected embodiments, surfaces of the central bore  28 , the interface  40 , the transmission line  30 , or a combination thereof, may be roughened or prepped by sanding, grinding, etching, or some other method, before they are attached with adhesive or welded. Likewise, the transmission line  30 , interface  40 , and central bore  28  may be glued or connected together by any of various adhesives suitable for a downhole environment, or by welding, soldering, brazing, or the like.  
         [0049]     The pre-formed interface  40  may be manufactured by any suitable means, such as by extrusion, casting, stamping, or the like, as will be described hereinafter. Since the pre-formed interface  40  may be configured to have a relatively constant cross-section, it may be desirable to use extrusion techniques to form the interface  40  since this process is relatively common and inexpensive.  
         [0050]     Moreover, the interface  40  may be constructed of any suitable material having desirable strength and weight characteristics that is able to withstand the abrasion, temperature, and corrosive nature of a downhole environment. For example, the pre-formed interface  40  may be constructed of metals, such as aluminum or other alloys, or from plastics, composites, or the like. Some of these materials may be more suitable for downhole environments than others and some may be more suitable for manufacture by extrusion. Similarly, the interface  40  may be provided in various lengths, as desired. For example, the interface  40  may be a single continuous component extending most of the length of the downhole tool  12 , or may be provided in any number of sections, as needed.  
         [0051]     Referring to  FIGS. 4A  though  4 D, various examples of pre-formed interfaces  40  are illustrated. For example, referring to  FIG. 4A , a pre-formed interface  40  may include surfaces  42 ,  44  conforming to the transmission line  30  and central bore  28 , respectively, and may have relatively straight, vertical sides  41 . Likewise, referring to  FIG. 4B , a pre-formed interface  40  may include sides  43  that slope outward. This may provide a wider surface  44  to provide greater contact and better adhesion to the surface of the central bore  28 , in addition to providing added rigidity and strength to the interface  40 . Referring to  FIG. 4C , in other embodiments, the pre-formed interface  40  may be formed to include gripping features  46   a ,  46   b  that may reach around the transmission line  30 , thereby providing a mechanical grip on the transmission line  30 . Referring to  FIG. 4D , likewise, a pre-formed interface  40  having gripping features  46   a ,  46   b  may include reinforced sides  45  to provide an improved mechanical grip on the transmission line  30 .  
         [0052]     Referring to  FIGS. 5A through 5C , various views of a pre-formed interface  40  providing a mechanical grip on a transmission line  30  are illustrated. As shown, the pre-formed interface  40  may have a solid cross-section. For example, referring to  FIG. 5A , gripping features  46   a ,  46   b  may initially be too close together to receive a transmission line  30 . Nevertheless, referring to  FIG. 5B , as a force  47  is applied to the transmission line  30 , the gripping features  46   a ,  46   b  may spread apart as the transmission line  30  is urged between the features  46   a ,  46   b . The pre-formed interface  40  may be constructed of a material of sufficient elasticity and resiliency to flex or bend to accept the transmission line  30  without breaking or permanently deforming. Referring to  FIG. 5C , after the transmission line  30  slips into the interface  40 , the gripping features  46   a ,  46   b  may come together to mechanically grip and retain the transmission line  30 .  
         [0053]     Referring to  FIG. 6 , in another embodiment, the pre-formed interface  40  may be constructed from a sheet-like material. Such a configuration may be created by stamping, bending, or extruding the material and may be sufficiently lightweight and resilient. The interface  40  may be formed to include mounting surfaces  44   a ,  44   b  to directly contact and attach to the wall  36  of the central bore  28 . Likewise, the interface  40  may include gripping features  46   a ,  46   b  to mechanically grip and retain the transmission line  30 . In selected embodiments, the interface  40  may closely fit the contour of the transmission line  30 . This configuration may be desirable because the interface  40  may be attached to the inside wall of the central bore  28  before attaching the transmission line  30  to the interface  40 . Likewise, the transmission line  30  may be removed or replaced without detaching the interface  40  from the central bore  28 .  
         [0054]     Referring to  FIGS. 7A and 7B , in another embodiment, a pre-formed interface  40  may completely cover the transmission line  30 . This configuration may, in some cases, be more reliable since the transmission line  30  will only detach from the inside wall of the central bore  28  if the interface  40  detaches from the central bore  28 . In some cases, it may be possible to pre-attach the interface to the wall  36  and then feed the transmission line  30  through the opening  51 . The interface  40  may optionally include a plate  50  or cover  50  to completely surround the transmission line  30 . The interface  40  may also include surfaces  44   a ,  44   b  that may be formed to fit the contour of the wall  36 .  
         [0055]     Referring to  FIG. 8 , in another embodiment, a pre-formed interface  40  may form a closed channel  53  to accommodate the transmission line  30 . A closed channel  53  may be useful to protect the transmission line  30  from drilling fluids or other substances present in a downhole drilling environment, and may prevent the detachment of the transmission line  30  from the wall  36  except in cases where the interface  40  itself detaches.  
         [0056]     Referring to  FIG. 9 , in another embodiment, a pre-formed interface  40  may engage recesses  54   a ,  54   b , or grooves  54   a ,  54   b  formed or milled into the wall  36 . Since such grooves  54   a ,  54   b  or recesses  54   s ,  54   b  may weaken the wall, they may be very shallow, as needed, to minimize the weakening. Nevertheless, in some applications, such an embodiment may be precluded to keep the tool wall unaltered. In other applications, such as in tools having thicker walls, such grooves  54   a ,  54   b , or recesses  54   a ,  54   b , may provide an acceptable method for attaching an interface  40 .  
         [0057]     Referring to  FIG. 10 , to attach an interface  40  to the tool wall  36 , a tool  56  may be used. As illustrated, a tool  56  may straddle the interface  40 . Nevertheless, the tool  56  may take on many forms which may or may not straddle the interface  40  and the illustration is simply exemplary of a tool  56  that may be used in accordance with the invention.  
         [0058]     For example, a tool  56  may press the surfaces  48   a ,  48   b  against the wall  36  while an adhesive is curing. Or, in other embodiments, a tool  56  may be used to heat or cool the interface  40  when adhering the interface  40  to the wall  36 . In other embodiments, a tool  56  may be used to spot-weld the surfaces  48   a ,  48   b  to the tool wall  36 . In some cases, heating or welding the interface  40  to the wall  36  may weaken the wall. Nevertheless, in other cases, a suitable weld may be applied by keeping the weld localized, sufficiently thin, or the like, such that the tool wall  36  is not critically weakened.  
         [0059]     Referring to  FIG. 11 , in another embodiment, a bonding material  72  (such as a high-temperature epoxy) may be formed or molded around the transmission line  30  to bond the transmission line  30  to the wall  36  of the central bore  28 . To form the bonding material  72 , a mold assembly  60  may be used to form the mold, inject, and cure the bonding material  72 . For example, in one embodiment in accordance with the invention, a mold assembly  60  may include a clamping mechanism  62 ,  64  to press the mold against the wall  36 . In one contemplated embodiment, the clamping mechanism  62 ,  64  may include a pneumatic or hydraulic cylinder  62  that exerts force against a plunger  64 . The plunger  64  may contact the opposite side of the central bore  28  to keep the mold assembly  60  firmly positioned against the tool wall  36 .  
         [0060]     In selected embodiments, the mold assembly  60  may include one or several channels  66   a ,  66   b  to convey a bonding material  72  such as an epoxy. For example, a first channel  66   a  may be used to convey one part of an epoxy, and a second channel  66   b  may be used to convey a second part of the epoxy. When the two parts are mixed together, a curing reaction may be created wherein the epoxy cures or hardens. For example, the two parts of the bonding material  72  may travel through channels  68   a ,  68   b  to a mixing chamber  70  where the two parts may be mixed and injected around the transmission line  30 .  
         [0061]     In selected embodiments, the mold assembly  60  may include a mold  78  and a frame  74 . The mold  78  may optionally include one or several heaters that may be used to heat the bonding material  72  to improve fluidity, help it cure, improve adhesion, or the like. Likewise, the frame  74  may optionally include one or several cooling channels  76  to rapidly cool the bonding material  72  or provide other functions.  
         [0062]     Referring to  FIG. 12 , in selected embodiments, a bonding material  72   a ,  72   b ,  72   c  may be configured to include one or several air gaps  82   a ,  82   b ,  82   c . One concern in downhole drilling applications is that long strips of a bonding material  72 , such as an epoxy, may detach or peel away from the tool wall  36 . Such pieces or strips may be carried downhole where they may clog or interfere with jets or other devices carrying drilling fluids, such as drilling mud. The air gaps  82   a ,  82   b ,  82   c  may help ensure that pieces of bonding material  72  that peel away remain small such that they do not detrimentally damage or clog other downhole tools  12 . Likewise, as was previously mentioned, in some cases, a drill tool  12  may bend from a linear path. The air gaps  82  may improve the adhesion of the bonding material  72  to the tool wall  36  in instances where a drill tool  12  bends by relieving stress in the bonding material  72  that may cause it to sheer or peel away from the tool wall  36 .  
         [0063]     Referring to  FIG. 13 , to form the air gaps  82  illustrated in  FIG. 12 , a modified mold  78  may be used in the mold assembly  60  in areas where air gaps  82  are inserted. For example, a modified mold  78  may be configured to closely straddle the transmission line  30  in areas of the air gaps  82  to prevent bonding material  72  from entering those areas  82 . Like the mold  78  illustrated in  FIG. 11 , the modified mold  78  may include one or several heating elements  80  or cooling conduits  80  to either heat or cool the bonding material  72 , as needed.  
         [0064]     The present invention may be embodied in other specific forms without departing from its essence or essential characteristics. The described embodiments are to be considered in all respects only as illustrative, and not restrictive. The scope of the invention is, therefore, indicated by the appended claims, rather than by the foregoing description. All changes within the meaning and range of equivalency of the claims are to be embraced within their scope.

Summary:
An apparatus for bonding a transmission line to the central bore of a downhole tool includes a pre-formed interface for bonding a transmission line to the inside diameter of a downhole tool. The pre-formed interface includes a first surface that substantially conforms to the outside contour of a transmission line and a second surface that substantially conforms to the inside diameter of a downhole tool. In another aspect of the invention, a method for bonding a transmission line to the inside diameter of a downhole tool includes positioning a transmission line near the inside wall of a downhole tool and placing a mold near the transmission line and the inside wall. The method further includes injecting a bonding material into the mold and curing the bonding material such that the bonding material bonds the transmission line to the inside wall.