Abstract:
A radiation detector comprises a tool housing. The tool housing has a substantially cylindrical tubular shape. A radiation sensor generates a signal in response to detecting radiation. The radiation sensor is locatable within the tool housing. A signal processor is operably connectable with the radiation sensor. The signal processor receives the signal from the radiation sensor and generates an electrical signal as a function of the signal received. The signal processor is locatable within the tool housing. A flex-sleeve supports at least one of the radiation sensor and signal processor within the tool housing. The flex-sleeve comprises a substantially cylindrical portion and a coaxially extending polygonal portion for engagement and supportive interaction with the cylindrical portion.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates generally to radiation detectors. In particular, the invention relates to a flexible support mechanism for radiation detector components and a method of servicing the radiation detector. 
         [0002]    Radiation detectors are known in the well drilling industry for logging and measure while drilling applications. When a radiation detector is incorporated into a logging tool of a tool string used for drilling of oil, gas and water wells, the logging tool identifies, locates and differentiates geologic formations along a well bore. Tool strings and logging tools for oil wells are often exposed to harsh operating environments including temperatures in the range of 175° C. to 200° C. and pressures in the range of 10,000 to 20,000 psi along with severe shock and vibration. 
         [0003]    A known radiation detector includes a scintillator coupled to a photomultiplier tube. Radiation, such as gamma rays emitted by geologic formations adjacent to the well, is converted to light by the scintillator and conducted to the photomultiplier tube. The photomultiplier tube converts the light into an amplified electrical signal. The amplified electrical signal is then measured and used by monitoring electronics as a function of the radiation detected by the scintillator. 
         [0004]    The components of the radiation detector are sensitive pieces of equipment. The components are typically mounted in a housing to withstand the harsh operating environment they are exposed to. The components of the radiation detector also require periodic individual inspection to assure that they are providing correct and repeatable information during their service lives. However, it has been found that the typical known mounting systems do not lend themselves to easy disassembly and separation of the components. It has also been found that disassembly can damage components of the radiation detector, the housing the radiation detector is supported in and the mounting system itself. 
         [0005]    It is, therefore, advantageous to provide a radiation detector that is capable of withstanding the harsh operating environment it is exposed to while permitting ease of disassembly for inspection and repair with minimal or no damage to components of the radiation detector. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0006]    One aspect of the invention is a radiation detector that comprises a tool housing. The tool housing has a substantially cylindrical tubular shape. A radiation sensor generates a signal in response to detecting radiation. The radiation sensor is locatable within the tool housing. A signal processor is operably connectable with the radiation sensor. The signal processor receives the signal from the radiation sensor and generates an electrical signal as a function of the signal received. The signal processor is locatable within the tool housing. A flex-sleeve supports at least one of the radiation sensor and signal processor within the tool housing. The flex-sleeve comprises a substantially cylindrical portion and a coaxially extending polygonal portion for engagement and supportive interaction with the cylindrical portion. 
         [0007]    Another aspect of the invention is a radiation detector that comprises a tool housing. The tool housing has a substantially cylindrical tubular shape. A radiation scintillator sensor comprises a crystal material for generating a light signal as a function of radiation detected. The radiation scintillator sensor is locatable within the tool housing. A photomultiplier tube is operably connectable with the radiation scintillator sensor. The photomultiplier tube receives the light signal from the radiation scintillator sensor and generates an electrical signal as a function of the light signal received. The photomultiplier tube is locatable within the tool housing. A flex-sleeve supports the radiation scintillator sensor and photomultiplier tube within the tool housing. The flex-sleeve comprises a substantially cylindrical portion and a coaxially extending polygonal portion for engagement and supportive interaction with the cylindrical portion. 
         [0008]    Yet another aspect of the invention is a method of inspecting and servicing a radiation detector that has a flex-sleeve for supporting a radiation scintillator sensor and a photomultiplier tube within a tubular tool housing. The flex-sleeve has a substantially cylindrical portion located radially inward of a relatively shorter length polygonal portion. The method comprises the steps of removing the flex-sleeve, the radiation scintillator sensor and the photomultiplier tube from within the tool housing without damaging the tool housing. The radiation scintillator sensor and the photomultiplier tube are removed from within the flex-sleeve. The radiation scintillator sensor and the photomultiplier tube are inspected for serviceability. One of the radiation scintillator sensor and the photomultiplier tube are replaced if during the inspection step either is determined to be unserviceable. The radiation scintillator sensor and the photomultiplier tube are replaced within the flex-sleeve. The flex-sleeve, serviceable radiation detector and serviceable photomultiplier tube are installed in the tool housing without causing damage to the tool housing. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0009]    These and other features, aspects, and advantages of the invention will be better understood when the following detailed description is read with reference to the accompanying drawings, in which: 
           [0010]      FIG. 1  is a side elevation view, partly in section, illustrating a radiation detector according to one aspect of the invention in a tool housing; 
           [0011]      FIG. 2  is a side elevation view of the radiation detector illustrated in  FIG. 1 ; 
           [0012]      FIG. 3  is an enlarged side elevation view of a flex-sleeve of the radiation detector illustrated in  FIGS. 1 and 2 ; 
           [0013]      FIG. 4  is an end view of the flex-sleeve taken approximately along the line  4 - 4  in  FIG. 3 ; 
           [0014]      FIG. 5  is perspective view of a portion of the flex-sleeve illustrated in  FIG. 3 ; 
           [0015]      FIG. 6  is an exploded perspective view of the radiation detector illustrated in  FIG. 1 ; and 
           [0016]      FIG. 7  is a plan view of sheet material use to make the flex-sleeve of the radiation detector. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    A radiation detector  20  according to one aspect of the invention is illustrated in  FIGS. 1-2 . The radiation detector  20  may be used for detecting and measuring levels or energies of gamma radiation from various sources and in various applications. The radiation detector  20  includes a flex-sleeve  22 , according to one aspect of the invention, to mount and support the radiation detector in a tool housing  24 . The tool housing  24  is tubular and has a substantially cylindrical outer surface. The tool housing  24  is made from any suitable material, such as a metal including copper beryllium, inconel or stainless steel. The tool housing  24  protects the radiation detector  20  from the harsh environment that the radiation detector operates in. 
         [0018]    The radiation detector  20  includes major operating components, such as a radiation scintillator sensor assembly  42  ( FIG. 6 ), a photomultiplier tube assembly  44  and an electronics module assembly  48 . The radiation scintillator sensor  42  has a substantially cylindrical shape. The radiation scintillator sensor  42  includes a crystal (not shown) for generating a signal indicative of a scintillation event, such as when radiation of a certain level or energy is detected or sensed. For example, radiation, such as gamma rays, is converted to light by the crystal scintillator of the radiation scintillator sensor  42  as a function of the radiation detected. For example, the crystal may be a cylindrical sodium iodide crystal doped with thallium (NaI(Tl)). Also by way of example, the crystal may have a diameter of one inch and may be up to five inches in length. The radiation scintillator sensor  42  may include other devices capable of scintillation from radiation. 
         [0019]    The crystal of the radiation scintillator sensor  42  generates a light signal as a function of radiation detected by some of the radiation interacting with the crystal, as is known. For example, the light signal is generated as a function of the presence and amount of gamma radiation delivered to the radiation scintillator sensor  42 . The radiation scintillator sensor  42  further includes a scintillator housing for supporting a crystal. The scintillator housing may be made of any suitable material, such as titanium, prepared aluminum or stainless steel. The radiation scintillator sensor  42  may also include support structure located between the scintillator housing and the crystal. 
         [0020]    It is known that the crystal is relatively brittle and fragile. It is very important that the crystal radiation scintillator sensor  42  is properly supported within the scintillator housing and that the radiation detector  20  is properly supported in the tool housing  24  to prevent damage to the crystal during use. It is known that the crystal may react to the temperatures, pressures, shock and vibration that it is exposed to during its service life. Thus, it is desirable to periodically inspect the radiation scintillator sensor  42  by itself to determine if it is still serviceable. 
         [0021]    The photomultiplier tube  44  is substantially cylindrical in shape. The photomultiplier tube  44  is located axially adjacent the radiation scintillator sensor  42  in the radiation detector  20 . The photomultiplier tube  44  is operably and electrically connected to the crystal of the radiation scintillator sensor  42 . The photomultiplier tube  44  receives the light signal from the crystal and generates an electrical signal as a function of the light signal received. The photomultiplier tube  44  includes a photo detector to receive the light signal from the crystal of the radiation scintillator sensor  42  and electronics to process the electrical signal. 
         [0022]    The photomultiplier tube  44  may be any of several known photomultiplier tube assemblies. In the illustrated example, the photomultiplier tube  44  has an outer diameter substantially identical to that of the radiation scintillator sensor  42 . 
         [0023]    The photomultiplier tube  44  includes a tube housing that supports the photomultiplier tube. The tube housing may be made of any suitable material, such as titanium, prepared aluminum or stainless steel. The radiation scintillator sensor  42  and photomultiplier tube  44  may have a groove  46  in its outer surface for accepting a wire or cable from the electronics module  48 . The photomultiplier tube  44  may also include structure supporting the photo detector within the tube housing. 
         [0024]    The radiation scintillator sensor  42  and the photomultiplier tube  44  are protected from the severe operating environment by the tool housing  24 . The flex-sleeve  22  supports the radiation scintillator sensor  42  and the photomultiplier tube  44  in the tool housing  24  in a manner that shock and vibration transmitted to the radiation detector  20  from the tool housing  24  is minimized. The flex-sleeve  22  according to one aspect of the invention also permits relatively easy installation and extraction of the radiation detector  20  with minimal or no damage to the tool housing  24 , the radiation scintillator sensor  42  and the photomultiplier tube  44 . 
         [0025]    The flex-sleeve  22  includes a cylindrical portion  60  ( FIGS. 3-6 ) and a polygonal portion  62 . The cylindrical portion  60  is preferably integrally formed as one piece with the polygonal portion  62 . The cylindrical portion  60  engages and interacts with the polygonal portion  62  to support the radiation scintillator sensor  42  and the photomultiplier tube  44  relative to the tool housing  24 . The polygonal portion  62  extends coaxially with and surrounds at least a portion of the cylindrical portion  60 . 
         [0026]    The cylindrical portion  60  has an inner diameter substantially equal to the outer diameters of the radiation scintillator sensor  42  and the photomultiplier tube  44 . The polygonal portion  62  has an outermost dimension substantially equal to the inner diameter of the tool housing  24 . The polygonal portion  62  has a plurality of peaks  64  ( FIGS. 4-5 ) formed at the outermost dimension of the polygonal portion between adjacent flats  66 . The illustrated aspect has nine peaks  64  and eight full flats  66 . It will be apparent that any suitable number of peaks  64  may be provided. The peaks  64  of the polygonal portion  62  engage the inner surface of the tool housing  24  to locate and support the radiation detector  20  in the tool housing. The flex-sleeve  22  is compressed within the tool housing  24  to preload the flex-sleeve spring action and provide axial damping due to friction. Maximum sensitivity of the radiation detector  20  often requires maximizing the diameter of the radiation scintillator sensor  42  while minimizing the material located between the radiation scintillator sensor and tool housing  24  for support and attenuation of vibration and shock of the radiation detector. 
         [0027]    The cylindrical portion  60  has a length L 1  ( FIG. 3 ) taken in a direction parallel to the longitudinal central axis A of the flex-sleeve  22 . The polygonal portion  62  has a length L 2  ( FIG. 3 ) taken in a direction parallel to the longitudinal central axis A of the flex-sleeve  22  that is less that the length L 1  of the cylindrical portion  60 . The flex-sleeve  22 , thus, has a pair of cylindrical protrusions  80  ( FIGS. 3 and 5 ) extending from axially opposite ends. These cylindrical protrusions  80  engage respective flanges  82  of the radiation detector  20 . 
         [0028]    Installing the radiation detector  20  within the tool housing  24  results in an axial force that will be absorbed by the cylindrical portion  60  of the flex-sleeve  22 . No assembly force will be transmitted to the polygonal portion  62  that could deform or deflect the polygonal portion. Thus, during a disassembly operation the non-deformed polygonal portion  62  allows relatively easy removal of the radiation detector  20  from the tool housing for inspection and repair, if necessary. The polygonal portion  62  is formed to function as a plurality of leaf springs between the radiation scintillator sensor  42 , the photomultiplier tube  44  and inside diameter of the tool housing  24 . The support and resilience of the leaf spring action of the polygonal portion  62  is stretched along the length of the radiation scintillator sensor  42  and the photomultiplier tube  44 . The integral cylindrical portion  60  spans any features on the outside diameter of the radiation scintillator sensor  42  and the photomultiplier tube  44 . This allows consistent suspension of the contained radiation scintillator sensor  42 , the photomultiplier tube  44  and electronics module  48 . 
         [0029]    The flex-sleeve  22  is preferably made from a substantially planar single piece  22   p  ( FIG. 7 ) of a suitable resilient sheet material, such as hardened stainless steel. By way of example, the single piece  22   p  preferably has a thickness of about 0.004 inch but can be of any suitable thickness. The single piece  22   p  is deburred and corners  84  are broken so no sharp edges or corners remain in the finished flex-sleeve  22  that could catch on the inner surface of the tool housing  24 . 
         [0030]    The area  62   p  of the single piece  22   p  that makes up the polygonal portion  62  preferably has a suitable friction reducing material (not shown) applied to what will be the outer surface of the flex-sleeve  22 . This application of friction reducing material could be before or after forming the finished configuration of the flex-sleeve  22 . One such suitable friction reducing material is polytetrafluoroethylene (PTFE). The friction reducing material on outer surface of the flex-sleeve  22  allows the flex-sleeve to remain stationary on the radiation scintillator sensor  42 , photomultiplier tube  44  and electronics module  48  while rotating within inside diameter of the tool housing  24  during installation and extraction. The friction reducing material may be sprayed on and may be applied only to areas that will form the peaks  64  for contacting the tool housing  24 . The friction reducing material may alternatively be applied to the inner surface of the tool housing  24 . 
         [0031]    By way of example, the single piece  22   p  is bent at evenly spaced locations  64   p  that will form the peaks  64  and establish the flats  66  between adjacent peaks. The polygonal portion  62  is not yet in its finished configuration. The cylindrical portion  60  is then formed. The polygonal portion  62  is then wrapped around the cylindrical portion  60 . It will be apparent that other processes and order of forming the portions of the flex-sleeve  22  can be used. 
         [0032]    Another aspect of the invention is a method of inspecting and servicing a radiation detector  20 . The radiation detector  20  is constructed as described above. The radiation detector  20  has a flex-sleeve  22  for supporting a radiation scintillator sensor  42  and a photomultiplier tube  44  within a tubular tool housing  24 . The flex-sleeve  22  has a substantially cylindrical portion  60  located radially inward of a relatively shorter length polygonal portion  62 . 
         [0033]    The method includes of removing entire radiation detector  20  from the tool housing  24 . This accomplished by removing the flex-sleeve  22 , the radiation scintillator sensor  42 , the photomultiplier tube  44  and the electronics module  48  of the radiation detector  20  as an assembly axially from the tool housing  24 . Damage to the tool housing  24  is avoided because the radiation detector  20  according to one aspect of the invention is used. 
         [0034]    The radiation scintillator sensor  42 , the photomultiplier tube  44  and the electronics module  48  are removed from within the flex-sleeve  22  of the radiation detector  20 . The radiation scintillator sensor  42 , the photomultiplier tube  44  and the electronics module  48  are separated and tested for serviceability individually. The radiation scintillator sensor  42 , the photomultiplier tube  44  and/or the electronics module  48  are replaced if during the testing/inspection step either is determined to be unserviceable. The serviceable radiation scintillator sensor  42 , the serviceable photomultiplier tube  44  and the electronics module  48  are replaced within the flex-sleeve  22 . A new flex-sleeve can be used if it is deemed unserviceable. The flex-sleeve  22 , serviceable radiation scintillator sensor  42 , serviceable photomultiplier tube  44  and serviceable electronics module  48  of the radiation detector  20  are installed in the tool housing  24  without causing damage to the tool housing. 
         [0035]    While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the systems, techniques and obvious modifications and equivalents of those disclosed. It is intended that the scope of the invention disclosed should not be limited by the particular disclosed embodiments described above.