Patent Publication Number: US-2018033526-A1

Title: Seal for electrical passthrough

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 62/368,906, entitled “Seal for Electrical Passthrough”, by Michael Lea Bush and Michael Terrance McLaughlin II, filed Jul. 29, 2016, which is assigned to the current assignee hereof and incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure is directed to an electrical passthrough and more particularly to an electrical conductor that passes through a seal. 
     BACKGROUND 
     Scintillator-based detectors are used in a variety of applications, including research in nuclear physics, oil exploration, field spectroscopy, container and baggage scanning, and medical diagnostics. When a scintillator material of the scintillator-based detector is exposed to ionizing radiation, the scintillator material absorbs energy of incoming radiation and scintillates, remitting the absorbed energy in the form of photons. A photosensor of the scintillator-based detector detects the emitted photons. Radiation detection apparatuses can analyze pulses for many different reasons. Continued improvements are desired. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments are illustrated by way of example and are not limited in the accompanying figures. 
         FIG. 1  includes an illustration of a radiation detection assembly according to an embodiment described herein. 
         FIGS. 2 and 3  include illustrations of seals according to embodiments described herein. 
         FIG. 4  includes an illustration of an analyzer device according to an embodiment described herein. 
     
    
    
     Skilled artisans appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the invention. 
     DETAILED DESCRIPTION 
     The following description in combination with the figures is provided to assist in understanding the teachings disclosed herein. The following discussion will focus on specific implementations and embodiments of the teachings. This focus is provided to assist in describing the teachings and should not be interpreted as a limitation on the scope or applicability of the teachings. 
     As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having,” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of features is not necessarily limited only to those features but may include other features not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, “or” refers to an inclusive-or and not to an exclusive-or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present). 
     The use of “a” or “an” is employed to describe elements and components described herein. This is done merely for convenience and to give a general sense of the scope of the invention. This description should be read to include one or at least one and the singular also includes the plural, or vice versa, unless it is clear that it is meant otherwise. 
     Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The materials, methods, and examples are illustrative only and not intended to be limiting. To the extent not described herein, many details regarding specific materials and processing acts are conventional and may be found in textbooks and other sources within the scintillation and radiation detection arts. 
     A seal described herein can provide a contaminant resistant seal while allowing a body to pass through it. Typically, a body is passed directly through a seal, for example, to displace as little of the seal material as possible. However, the Inventors have discovered that an indirect pathway through the seal can provide increased contaminant resistance. Details of the improved seal that can be an electrical passthrough are provided below. 
       FIG. 1  illustrates an exemplary radiation detection assembly  100  including a scintillator module  200  and an electronics module  300 . The scintillator module  200  can include a scintillator casing  202  which encloses a scintillator  204  and a photosensor  206  optically coupled to the scintillator. The electronics module  300  can include an electronics package electrically coupled to the photosensor  206 . The scintillator module  200  and the electronics module can be separated by an interface region  400 . 
     As illustrated in  FIG. 1 , the interface region  400  can be coupled to the scintillator module  200 , such as, for example, as a partition within the scintillator casing  202  or a cap disposed at an end of the scintillator casing  202 . In an embodiment, the scintillator casing  202  together with the interface region  400  can enclose, even completely enclose, at least the scintillator  204  and possibly the photosensor  206 . Further, the scintillator casing  202  together with the interface region  400  can provide a hermetically sealed enclosure  500  for the scintillator  204 . In an embodiment, the casing  202  can include a metal casing, such as an aluminum casing. For example, the radiation detection assembly  100  can include a sealed portion and an unsealed portion separated by the seal  402 , where the body  404  extends through the seal  402  from the sealed portion to the unsealed portion. 
     The interface region  400  can include a seal  402  and a body  404  extending through the seal  402 . The seal  402  can be an electrical passthrough, and the body  404  can be a conductor, such as an electrical conductor. In a particular embodiment, the electrical conductor can include a flat cable. In a more particular embodiment, the conductor does not include a cable having a circular profile, such as a coaxial cable. In a further particular embodiment, the electrical conductor can include a multi-wire cable, such as a cable having at least two wires, or at least three wires, or at least four wires. For example, the electrical conductor can include a flat, multi-wire cable. In a particular embodiment, the electrical conductor can include a ribbon cable. In an embodiment, the body can couple the photosensor  206 , within the scintillator module  200 , to the electronics module  300 . 
     As illustrated in  FIG. 1 , the body  404  can extend through the seal  402  along an indirect pathway  406 . As used herein, the term “direct pathway” with respect to a seal refers to a pathway that has a length through a seal that is the same as the thickness of the seal, whereas the term “indirect pathway” refers to a pathway that is longer than the direct pathway. 
     The indirect pathway  406  can include a linear pathway or a non-linear pathway. As used herein, the term “linear pathway” refers to a pathway that extends in one direction along the entire pathway, whereas the term “non-linear pathway” refers to a pathway that extends in a direction at a point along the pathway and at least one other non-parallel direction at another point along the pathway. 
     The seal  402  can have opposing surfaces separated a distance in a surface direction and opposing sidewalls separated a distance in a sidewall direction, and the surface and sidewall directions can be orthogonal to each other. The opposing surfaces can include an entry surface and an exit surface, as discussed below. The pathway  406  can have an entry point  408  along the entry surface, and an exit point  410  along the opposing exit surface. The entry point  408  refers to a point along an entry surface of the seal  402  where the body  404  extends into the seal  402 , and the exit point  410  refers to another point along an exit surface of the seal  402  where the body  404  extends from the seal  402 . In an embodiment, the entry surface of the seal  402  faces an interior volume of the scintillator casing  202 . In a further embodiment, the exit surface of the seal  402  faces the electronics module  300 , is opposite the entry surface, or both. 
     In an embodiment, the indirect pathway  406  can include a displacement in the sidewall direction. The displacement in the sidewall direction can be defined as the distance separating the entry point and the exit point in the sidewall direction. In a particular embodiment, the displacement can include a distance of at least 10 mm, or at least 50 mm, or at least 100 mm along the exit surface. In a further embodiment, the displacement can include a distance of no greater than 1000 mm, or no greater than 900 mm, or no greater than 800 mm. 
     Further, the displacement in the sidewall direction can be defined as a percentage of the distance separating the sidewalls, such as at least 5%, or at least 15%, or at least 25%, or at least 50% of the distance separating the sidewalls. In an embodiment, the displacement can be at most 99%, or at most 95%, or at most 90% of the distance separating the opposing sidewalls. 
     In an embodiment, the non-linear pathway can include at least one bend or at least two bends such that the electrical conductor bends in at least one or at least two directions within the seal. In an embodiment, the non-linear pathway can include a portion extending in the surface direction from the entry point, a bend followed by a portion extending in the sidewall direction, and another bend followed by a portion extending to the exit point in the surface direction. 
     In certain embodiments, the pathway can be an indirect pathway that does not include a displacement in the sidewall direction, or has a minimal displacement in the sidewall direction. For example, as illustrated in  FIG. 2 , the non-linear pathway can include at least one portion that extends away from the entry point axis and returns to the entry point axis so that the exit point lies along or near the entry point axis. In an embodiment, the indirect pathway does not include a displacement in the sidewall direction or the radial offset is at most 5% of the distance separating the sidewalls, or at most 3% of the distance separating the sidewalls, or at most 1% of the distance separating the sidewalls. 
     In certain embodiments, the pathway can be a linear pathway with a displacement in the sidewall direction. For example, as illustrated in  FIG. 3 , the linear pathway can extend in a direction oblique to the entry point axis. In an embodiment, the linear pathway can have a displacement in the sidewall direction of at least 1%, or at least 3%, or at least 5%. 
     In an embodiment, the seal can provide a light-tight seal. Light leaking through the scintillator can cause signal noise that makes the signal more difficult to read. In particular, the seal can reduce the transmission of visible light, ultraviolet light, or both. 
     In an embodiment, the seal  402  can include a polymer seal. The polymer seal can include a polymeric material. The polymeric material can include at least one of a thermoplastic polymer and a thermoset polymer. Examples of the polymeric material can include a polyamide, a polyaramide, a polyimide, a polyolefin, a polyvinylchloride, an acrylic polymer, a diene monomer polymer, a polycarbonate (PC), a polyetheretherketone (PEEK), a fluoropolymer, a polyester, a polypropylene, a polystyrene, a polyurethane, a silicone polymer, a phenolic polymer, a nylon polymer, an epoxy polymer, or any combination thereof. In a particular embodiment, the polymeric layer includes an epoxy. In an embodiment, the polymeric material can include a cationic curing polymer. 
     Further, the polymeric material can possess properties specific to the intended use. For example, the polymeric material can contain polymeric fillers, mineral fillers, metallic fillers, or any combination thereof to change the appearance, light transmission, abrasion resistance or other physical properties of the seal  402 . For example, the polymeric material can be colored in any desired color, such as a color that is resistant to light transmission. Further, the polymeric material can be textured for appearance or for low surface friction. In an embodiment, the polymeric material may have increased strength or abrasion resistance to maintain barrier integrity in the face of physical stresses. 
     The seal  402  can have a thickness T from the entry surface to the exit surface. In an embodiment, the thickness T can be at most 1.5 cm, or at most 1.3 cm, or at most 1.1 cm, or at most 0.9 cm. Further, the entry surface and the exit surface can be connected by sidewalls on either side of the seal  402 , and the seal  402  can have a width W extending from one sidewall to the other sidewall. In an embodiment, the width W can be at least 0.5 cm, or at least 1 cm, or at least 1.5 cm, or at least 2 cm, or at least 2.5 cm. In an embodiment, the seal  402  can have a width W that is greater than the thickness T. In an embodiment, the ratio of width W to thickness T is greater than 1, or at least 1.4, or at least 1.8, or at least 2.2, or at least 2.6. 
     The photosensor  206  can include a photomultiplier chip or a photomultiplier tube. In an embodiment, the photomultiplier chip can include a solid-state photomultiplier, such as a semiconductor-based photomultiplier chip. In an embodiment, the photomultiplier chip includes at least one of Si, SiC, GaN, InP, CdTe, or any combination thereof. In a more particular embodiment, the photomultiplier chip can include a silicon-based photomultiplier. In an embodiment, the photomultiplier can include a photomultiplier chip disposed on a surface of the scintillator. 
     The scintillator can include at least one of an inorganic scintillator material and an organic scintillator material. In an embodiment, the scintillator material is an inorganic scintillator material. In an embodiment, the inorganic scintillator material can include a rare earth halide. For example, the inorganic scintillator material includes at least one of a sodium iodide, a cesium iodide, a bismuth germinate, a lanthanum bromide, a cerium bromide, a lanthanum chloride, a lutetium oxyorthosilicate, a lutetium yttrium oxyorthosilicate, a cesium lithium lanthanum bromide, a cesium lithium lanthanum bromo-chloride, a cesium lithium yttrium chloride. In another embodiment, the scintillator is an organic scintillator material. For example, the organic scintillator material can include an anthracene, a stilbene, or a plastic. In an embodiment, the scintillator includes a hygroscopic scintillator material. 
     The electronics package  306  can further include an analyzer device  308  electrically coupled to the photosensor  206 , as illustrated in  FIG. 4 . The analyzer device  308  can include hardware and can be at least partly implemented in software, firmware, or a combination thereof. In an embodiment, the hardware can include a plurality of circuits within an FPGA, an ASIC, another integrated circuit or on a printed circuit board, or another suitable device, or any combination thereof. The analyzer device  308  can also include a buffer to temporarily store data before the data are analyzed, written to storage, read, transmitted to another component or device, another suitable action is performed on the data, or any combination thereof. 
     In the embodiment illustrated in  FIG. 4 , the analyzer device  308  can include an amplifier  322  coupled to the photosensor  206 , such that an electronic pulse from the photosensor  206  can be amplified before analysis. The amplifier  322  can be coupled to an analog-to-digital converter (ADC)  324  that can digitize the electronic pulse. The ADC  324  can be coupled to a pulse shape discrimination (PSD) module  342 . In a particular embodiment, the PSD module  342  can include a FPGA or an ASIC. In a particular embodiment, the PSD module  342  can include circuits to analyze the shape of the electronic pulse and determine whether the electronic pulse corresponds to a neutron or gamma radiation. In a more particular embodiment, the PSD module  342  can use the electronic pulse and temperature from a temperature sensor with a look-up table to determine whether the electronic pulse corresponds to a neutron or gamma radiation. The look-up table can be part of the FPGA or ASIC or may be in another device, such as an integrated circuit, a disk drive, or a suitable persistent memory device. 
     The analyzer device  308  can include a neutron counter  362  and a gamma radiation counter  364 . If the PSD module  342  determines that an electronic pulse corresponds to a neutron, the PSD module  342  increments the neutron counter  362 . If the PSD module  342  determines that an electronic pulse corresponds to gamma radiation, the PSD module  342  increments the gamma radiation counter  364 . While  FIG. 3  illustrates a dual mode radiation detector, in other embodiments the radiation detector could be single mode radiation detector, and the analyzer could include only one of the neutron counter  362  or the gamma radiation counter  364 . 
     Any of the scintillators as previously described can be used in a variety of applications. Exemplary applications include radiation detectors for a security detection apparatus, a well-logging detection apparatus, a gamma ray spectroscopy apparatus, an isotope identification apparatus, Single Positron Emission Computer Tomography (SPECT) analysis apparatus, a Positron Emission Tomography (PET) analysis apparatus, and an x-ray imaging apparatus. 
     Embodiments as described herein can help to improve seal integrity for an electrical passthrough. The Inventors have discovered that contaminants, such as water, may migrate along an interface between an electrical conductor and a surrounding polymer seal. Migration along the interface can be significantly greater than migration through the material of the polymer seal itself. Thus, by using a more indirect path for the electrical conductor through the polymer seal, contaminants that migrate along the interface have a longer path than if the electrical conductor lies along a shortest path through the polymer seal. For example, in  FIGS. 1 to 3 , the length of the electrical conductor as it passes through the seal  402  is longer than the thickness of the seal  402 . A more tortuous path of the electrical conductor through the polymer seal can further increase the seal integrity. In a particular embodiment, most of the length of the electrical conductor passing through the polymer seal can extend in one direction and then in an opposite direction, such as illustrated in  FIG. 1 . As the length gets longer, other considerations may affect selection of the length. For example, if contaminant migration through the material of the polymer seal itself, separate from the interface, is greater than contaminant migration along an interface, lengthening the path of the electrical conductor through the polymer seal may not further improve the seal integrity. Further, parasitic electrical effects, such as resistance through the conductor may cause signal amplitude loss or signal delay for signals passing through the electrical conductor. After reading this specification, skilled artisans will be able to determine the length and path of the electrical conductor through the polymer seal to achieve the needs or desires for a particular application. 
     Many different aspects and embodiments are possible. Some of those aspects and embodiments are described herein. After reading this specification, skilled artisans will appreciate that those aspects and embodiments are only illustrative and do not limit the scope of the present invention. Additionally, those skilled in the art will understand that some embodiments that include analog circuits can be similarly implement using digital circuits, and vice versa. Embodiments may be in accordance with any one or more of the embodiments as listed below. 
     Embodiment 1 
     An electrical passthrough comprising:
         a polymer seal having an entry surface and an exit surface separated a distance in a first direction and opposing side walls separated a distance in a second direction;   an electrical conductor extending through the polymer seal, wherein the electrical conductor enters the polymer seal at an entry point along the entry surface and exits the polymer seal at an exit point along the exit surface,   wherein the entry point and the exit point have a displacement in the second direction that is at least 50% of the distance separating the opposing sidewalls.       

     Embodiment 2 
     The passthrough of embodiment 1, wherein the electrical conductor extends through the polymer seal along a non-linear pathway. 
     Embodiment 3 
     A radiation detection apparatus comprising:
         a scintillator;   a photosensor;   a seal overlying the scintillator and the photosensor and having a thickness; and   an electrical conductor extending through the seal, wherein a length of the electrical conductor as it passes through the seal is greater than the thickness of the seal.       

     Embodiment 4 
     The apparatus of embodiment 3, wherein the seal comprises a polymer seal. 
     Embodiment 5 
     The passthrough of any one of embodiments 1 and 2 or the apparatus of embodiment 4, wherein the polymer seal comprises an epoxy. 
     Embodiment 6 
     The passthrough or the apparatus of any one of embodiments 1 to 5, wherein the polymer seal comprises a cationic curing polymer. 
     Embodiment 7 
     The passthrough or the apparatus of any one of embodiments 1, 2, and 4 to 6, wherein the polymer seal is a light-tight seal. 
     Embodiment 8 
     The apparatus of any one of embodiment 3 to 7, wherein the seal has an entry surface and an exit surface separated a distance in a first direction and opposing side walls separated a distance in a second direction; wherein the electrical conductor enters the polymer seal at an entry point on the entry surface and exits the polymer seal at an exit point on the exit surface; and wherein the entry point and the exit point have a displacement in the second direction that is at least 5%, or at least 15%, or at least 25%, or at least 50% of the distance separating the opposing sidewalls. 
     Embodiment 9 
     The passthrough or the apparatus of any one of embodiments 1, 2, 5 to 8, and 10, wherein the entry point and the exit point have a displacement in the second direction that is at most 99%, or at most 95%, or at most 90% of the distance separating the opposing sidewalls. 
     Embodiment 10 
     The passthrough or the apparatus of any one of embodiments 3 to 9, wherein the photosensor is optically coupled to the scintillator. 
     Embodiment 11 
     The apparatus of any one of embodiments 3 to 10, wherein the photosensor includes a solid-state photomultiplier. 
     Embodiment 12 
     The apparatus of embodiment 11, wherein the solid-state photomultiplier includes at least one of Si, SiC, GaN, InP, CdTe, or any combination thereof. 
     Embodiment 13 
     The apparatus of any one of embodiments 3 to 12, wherein the photosensor is disposed on a surface of the scintillator. 
     Embodiment 14 
     The apparatus of any one of embodiments 3 to 13, wherein the scintillator comprises an inorganic scintillator material. 
     Embodiment 15 
     The apparatus of embodiment 14, wherein the inorganic scintillator material comprises a rare earth halide. 
     Embodiment 16 
     The apparatus of any one of embodiments 3 to 13, wherein the scintillator comprises an organic scintillator material. 
     Embodiment 17 
     The apparatus of embodiment 16, wherein the organic scintillator material comprises an anthracene, a stilbene, or a plastic. 
     Embodiment 18 
     The apparatus of any one of embodiments 3 to 17, wherein the scintillator material includes a hygroscopic material. 
     Embodiment 19 
     The passthrough or the apparatus of any one of the preceding embodiments, wherein the electrical conductor includes a flat cable. 
     Embodiment 20 
     The passthrough or the apparatus of any one of the preceding embodiments, wherein the electrical conductor includes a multi-wire cable. 
     Embodiment 21 
     The passthrough or the apparatus of any one of the preceding embodiments, wherein the electrical conductor bends in at least two directions within the seal. 
     Embodiment 22 
     The passthrough or the apparatus of any one of the preceding embodiments, wherein, a portion of the electrical conductor extends in a direction parallel to the first surface of the seal, the second surface of the seal, or both. 
     Embodiment 23 
     The apparatus of any one of embodiments 3 to 22, further comprising a casing including a sealed portion and an unsealed portion separated by the seal, the sealed portion comprising the scintillator and the photosensor, and the electrical conductor extending through the seal from the sealed portion to the unsealed portion. 
     Embodiment 24 
     The apparatus of any one of embodiments 3 to 23, wherein the casing comprises a metal casing. 
     Embodiment 25 
     The apparatus of embodiment 24, wherein the casing comprises an aluminum. 
     Embodiment 26 
     The apparatus of any one of embodiments 23 to 25, wherein the casing comprises a hermetically sealed enclosure. 
     Embodiment 27 
     The passthrough or the apparatus of any one of the preceding embodiments, wherein the width of the seal extending from one sidewall to the opposing sidewall is at least 0.5 cm, or at least 1 cm, or at least 1.5 cm, or at least 2 cm, or at least 2.5 cm. 
     Embodiment 28 
     The passthrough or the apparatus of any one of the preceding embodiments, wherein the seal has a thickness from the first surface to the second surface of no greater than 1.5 cm, or no greater than 1.3 cm, or no greater than 1.1 cm, or no greater than 0.9 cm. 
     Embodiment 29 
     The apparatus of any one of embodiments 3 to 28, wherein the apparatus includes one of a security detection apparatus, an well-logging detection apparatus, a gamma ray spectroscopy apparatus, an isotope identification apparatus, Single Positron Emission Computer Tomography (SPECT) analysis apparatus, a Positron Emission Tomography (PET) analysis apparatus, and an x-ray imaging apparatus. 
     Embodiment 30 
     A radiation detection apparatus comprising:
         a scintillator;   a photosensor;   a seal overlying the scintillator and the photosensor; and   an electrical conductor extending through the seal along a non-linear pathway.       

     Embodiment 31 
     The passthrough or the apparatus of any one of embodiments 1 to 30, wherein the electrical conductor includes a ribbon cable. 
     Note that not all of the activities described above in the general description or the examples are required, that a portion of a specific activity may not be required, and that one or more further activities may be performed in addition to those described. Still further, the order in which activities are listed is not necessarily the order in which they are performed. 
     Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any feature(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature of any or all the claims. 
     The specification and illustrations of the embodiments described herein are intended to provide a general understanding of the structure of the various embodiments. The specification and illustrations are not intended to serve as an exhaustive and comprehensive description of all of the elements and features of apparatus and systems that use the structures or methods described herein. Certain features, that are for clarity, described herein in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features that are, for brevity, described in the context of a single embodiment, may also be provided separately or in a subcombination. Further, reference to values stated in ranges includes each and every value within that range. Many other embodiments may be apparent to skilled artisans only after reading this specification. Other embodiments may be used and derived from the disclosure, such that a structural substitution, logical substitution, or another change may be made without departing from the scope of the disclosure. Accordingly, the disclosure is to be regarded as illustrative rather than restrictive.