Patent Publication Number: US-11665806-B2

Title: Beam alignment systems and method

Description:
BACKGROUND 
     This disclosure relates generally to a downhole tool that generates x-rays to measure formation properties and, more particularly, to a downhole tool that includes at least two detectors that measures a photon flux indicative of a position of an electron beam on a target. 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present techniques, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light and not as admissions of any kind. 
     Producing hydrocarbons from a wellbore drilled into a geological formation is a remarkably complex endeavor. During drilling operations, evaluations of the geological formation may be performed for various purposes, such as to locate hydrocarbon-producing formations and manage the production of hydrocarbons from these formations. To determine the location of hydrocarbon producing formations, as well as various geological formations, downhole tools are conveyed by various means, such as coiled tubing, drill pipe, casing or other conveyers. 
     A formation density tool may be deployed within the sub-surface to measure physical properties of a surrounding geological formation. The formation density tool may be moved within a borehole drilled in the geological formation. For example, the formation density tool may be pushed farther into the borehole and/or pulled to remove the formation density tool from the borehole. The formation density tool may include a source to emit high-energy photons into the geological formation. Some of the high-energy photons may interact with the geological formation and may then be detected by detectors on the formation density tool. The physical properties of the geological formation may be determined from the characteristics of the detected high-energy photons. 
     Determining an amount of high-energy photons being emitted by the source may improve the accuracy of the determined physical properties of the geological formation. However, conditions within the geological formation, such as pressure and temperature, mechanical stress imparted on the downhole tool, and variations in the output of the components of the downhole tool, such as the source, may make it difficult to determine the amount of high-energy photons being emitted by the source. 
     SUMMARY 
     Various refinements of the features noted above may exist in relation to various aspects of the present disclosure. Further features may also be incorporated in these various aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to one or more of the illustrated embodiments may be incorporated into any of the above-described aspects of the present disclosure alone or in any combination. The brief summary presented above is intended to familiarize the reader with certain aspects and contexts of embodiments of the present disclosure without limitation to the claimed subject matter. 
     One embodiment of the present disclosure relates to a downhole tool that includes a radiation generator that emits radiation. The downhole tool may also include a first flux detector at a first radial position about a longitudinal axis of the downhole tool, wherein the first photon detector measures a first signal indicative of a flux of the radiation. Further, the downhole tool may include a second flux detector at a second radial position about the longitudinal axis of the downhole tool, wherein the second flux detector measures a second signal indicative of the flux of the radiation. Additionally, the downhole tool may include a controller communicatively coupled to the first flux detector and the second flux detector, wherein the controller determines a condition associated with the radiation generator based at least in part on a relative flux from the first flux detector and the second flux detector. 
     Another embodiment of the present disclosure relates to a method. The method includes receiving, via a processor, a first signal from a first detector, wherein the first signal is indicative of an x-ray flux of x-ray photons emitted by a target. The method also includes receiving, via the processor, a second signal from a second detector, wherein the second signal is indicative of the x-ray flux of x-ray photons emitted by the target. Further, the method includes receiving, via the processor, a third signal from a third detector, wherein the third signal is indicative of the x-ray flux of x-ray photons emitted by the target. Further still, the method includes determining, via the processor, a condition associated with electron beam on the target based at least in part on a relative flux of the first signal, the second signal, and the third signal. 
     Another embodiment of the present disclosure relates to a system. The system includes an electronic photon generator having a cathode that emits an electron beam. The electronic photon generator also includes a target that generates x-ray photons when struck by the electrons. The system also includes a first photon flux detector disposed at a first radial position about a longitudinal axis of a downhole tool, wherein the first photon flux detector measures a first signal indicative of an x-ray flux of the x-ray photons. Further, the system includes a second photon flux detector disposed at a second radial position about the longitudinal axis of the downhole tool, wherein the second photon flux detector measures a second signal indicative of the x-ray flux of the x-ray photons. Further still, the system includes a third photon flux detector disposed at a third radial position about the longitudinal axis of the downhole tool, wherein the third photon flux detector measures a third signal indicative of the x-ray flux of the x-ray photons. Even further, the system includes a controller communicatively coupled to the first photon flux detector and the second photon flux detector, wherein the controller determines a condition associated with the electron beam based at least in part on a relative x-ray flux from the first photon flux detector, the second photon flux detector, and the third photon flux detector. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings in which: 
         FIG.  1    is a schematic diagram of a drilling system that includes a downhole tool to detect characteristics of a geological formation adjacent to the downhole tool, in accordance with an embodiment; 
         FIG.  2    is a schematic diagram of the downhole tool of  FIG.  1   , in accordance with an embodiment; 
         FIG.  3    is a perspective view of the target and the photon flux detectors taken along a longitudinal axis of the downhole tool, in accordance with an embodiment of the present disclosure; 
         FIG.  4    is a perspective view of the target and the photon flux detectors taken along a longitudinal axis of the downhole tool, where the electron beam is striking a first position of the target, in accordance with an embodiment of the present disclosure; 
         FIG.  5    is a perspective view of the target and the photon flux detectors taken along a longitudinal axis of the downhole tool, where the electron beam is striking a second position of the target, in accordance with an embodiment of the present disclosure; 
         FIG.  6    is a perspective view of the target and the photon flux detectors taken along a longitudinal axis of the downhole tool, where the electron beam is striking a third position of the target, in accordance with an embodiment of the present disclosure; 
         FIG.  7    is a flow chart representing an example of a process for determining a striking position of an electron beam, in accordance with an embodiment of the present disclosure; 
         FIG.  8    is a flow chart representing an example of a process for determining an alignment of the electron beam, in accordance with an embodiment of the present disclosure; 
         FIG.  9    is a flow chart representing an example of a process for modifying an alignment of the electron beam, in accordance with an embodiment of the present disclosure; and 
         FIG.  10    is a flow chart representing an example of a process for determining a relative desired x-ray flux, in accordance with an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     One or more specific embodiments of the present disclosure will be described below. These described embodiments are examples of the presently disclosed techniques. Additionally, in an effort to provide a concise description of these embodiments, not all features of an actual implementation may be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions will be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would still be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     When introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. 
     As mentioned above, a downhole tool that measures properties of a geological formation, such as a formation density. In particular, the downhole tool may include an electron beam that strikes a target, causing the target to emit photonic radiation, such as x-rays. The magnitude of the photon flux emitted by the target is used to measure the properties of the geological formation. An expected photon flux of existing downhole tools may be calibrated at the surface or a background measurement may be received downhole. That is, the downhole tool may be operated on a sample with a known composition and a known expected signal and an operator may tune the expected photon flux emitted by the downhole tool based on the performance of the downhole tool with the sample. In some cases, the photon flux may vary when the downhole tool is positioned with the wellbore due to conditions within the wellbore. Moreover, it may be difficult to determine the relative change of the flux. 
     Accordingly, the present disclosure relates to a beam alignment system for a downhole tool that measures properties of a geological formation, such as a formation density. In general, the beam alignment system includes two or more photon flux detectors disposed at different radial positions about an axis normal to a surface of the target. Each detector of the two or more detectors measures a signal indicative of a photon flux at the respective position of the respective detector. A controller communicatively coupled to the two or more detectors may determine a condition associated with the electron beam (e.g., an alignment, a striking position of the electron beam on the target, and the like) of the downhole based at least in part on the respective signal measured by the two or more detectors. In some examples, the controller may determine the condition associated with the electron beam based at least in part on a respective position of the two or more detectors. In some example, the respective position of the two or more detectors may be different or substantially equal radial distances from the axis normal to a surface of the target. In some examples, the controller may generate and/or output a signal correction factor that may modify an expected output of the photons emitted by the detector. Additionally, or alternatively, the controller may generate and/or output a control signal that modifies a condition associated with the electron beam (e.g., modifying a voltage of an electron accelerator associated with the electron beam). As such, the beam alignment system of the present disclosure may improve the accuracy of certain downhole tools as well as improve the operations of the downhole tools while the downhole tools are within a wellbore. 
     With this in mind,  FIG.  1    illustrates a well-logging system  10  that may employ the systems and methods of this disclosure. The well-logging system  10  may be used to convey a downhole tool  12  through a geological formation  14  via a wellbore  16 . The downhole tool  12  is conveyed on a cable  18  via a logging winch system  20 . Although the logging winch system  20  is schematically shown in  FIG.  1    as a mobile logging winch system carried by a truck, the logging winch system  20  may be substantially fixed (e.g., a long-term installation that is substantially permanent or modular). Any suitable cable  18  for well logging may be used. The cable  18  may be spooled and unspooled on a drum  22  and an auxiliary power source  24  may provide energy to the logging winch system  20  and/or the downhole tool  12 . 
     Although the downhole tool  12  is described as a wireline downhole tool, it should be appreciated that any suitable conveyance may be used. For example, the downhole tool  12  may instead be conveyed as a logging-while-drilling (LWD) tool as part of a bottom hole assembly (BHA) of a drill string, conveyed on a slickline or via coiled tubing, and so forth. For the purposes of this disclosure, the downhole tool  12  may be any suitable measurement tool that uses a detector to obtain measurements of properties of the geological formation  14 . 
     As discussed further below, the downhole tool  12  may emit radiations, such as x-rays gamma-rays, and/or neutrons, into the geological formation  14 , which are detected by the downhole tool  12  as data  26  relating to the wellbore  16  and/or the geological formation  14 . The data  26  may be sent to a data processing system  28 . The data processing system  28  may be any electronic data processing system that can be used to carry out the systems and methods of this disclosure. For example, the data processing system  28  may include a processor  30 , which may execute instructions stored in memory  32  and/or storage  34 . As such, the memory  32  and/or the storage  34  of the data processing system  28  may be any suitable article of manufacture that can store the instructions. The memory  32  and/or the storage  34  may be read-only memory (ROM), random-access memory (RAM), flash memory, an optical storage medium, or a hard disk drive, to name a few examples. A display  36 , which may be any suitable electronic display, may display the images generated by the processor  30 . The data processing system  28  may be a local component of the logging winch system  20  (e.g., within the downhole tool  12 ), a remote device that analyzes data from other logging winch systems  20 , a device located proximate to the drilling operation, or any combination thereof. In some embodiments, the data processing system  28  may be a mobile computing device (e.g., tablet, smartphone, or laptop) or a server remote from the logging winch system  20 . 
       FIG.  2    is a schematic diagram of the downhole tool  12  that detects physical characteristics of the geological formation  14 . The downhole tool  12  may include a voltage generator  40  that may generate voltages of 150 kV, 200 kV, or any other voltage suitable to form an electric field between a cathode  42  and a target  44  (e.g., anodes). 
     To determine the properties of the geological formation  14 , the downhole tool  12  may emit photons into the geological formation  14  to interact with the geological formation  14 . For example, the cathode  42  may emit electrons in an electron beam  46  (e.g., stream of electrons) between the cathode  42  and the target  44 . Due to a voltage difference between the cathode  42  and the target  44 , the electrons of the electron beam  46  may travel from the cathode  42 , through the electric field, to the target  44 . While described as being a cathode  42  that emits electrons in an electron beam, it should be noted that in some embodiments the cathode  42  may be a radiation generator that emits radiation such as neutrons. 
     As the electrons in the electron beam  46  decelerate due to contacting (e.g., colliding with) the target  44 , which may be gold (Au), Tungsten, or the like, the deceleration may cause photons  49 , such as high-energy photons (e.g., X-rays) to be emitted as Bremsstrahlung radiation. At least some of the photons  49  may be high-energy photons at an energy sufficient to cause at least a portion of the photons  49  to inelastically scatter off elements of the geological formation  14  and to be absorbed by a detector  48  (e.g., Compton scattering), such as an x-ray detector. The detector  48  may include a scintillator  50  that absorbs the photons  49  and emits light based on the energy of the absorbed photons  49 . For example, each emission of light may count as a detected photon (e.g., thereby adding one to a count rate of the detector  48 ). Further, the detector  48  may include a photomultiplier  52  operatively coupled to the scintillator  50  to detect the light emitted by the scintillator  50 . The photomultiplier  52  may output an electrical signal from the detected light of the scintillator  50  to the data processing system  28 . As mentioned above, the data processing system  28  may process the electrical signals from the photomultiplier  52  at the surface (e.g., as the data  26 ), at the downhole tool  12 , or a combination thereof. As such, the downhole tool  12  may include hardware similar to the data processing system  28  (e.g., processor  30 , memory  32 , storage  34 , etc.) In some embodiments, the detector  48  may be communicatively coupled to the data processing system  28  to communicate the data  26  related to the electrical signals indicative of the detected photons  49 . 
     As shown in the illustrated example, the downhole tool  12  includes multiple photon flux detectors  54  (e.g., flux detectors). In general, each photon flux detector of the multiple photon flux detectors  54  measures a signal indicative of a photon flux (e.g., radiation flux) of the photons  49  emitted by the target  44 . As discussed in more detail below with regards to  FIGS.  3 - 7   , the measured signal from each photon flux detector of the multiple photon flux detectors  54  may be received by the data processing system  28  (e.g., specifically the processor  30 ) and used to determine a condition of the electron beam  46  (e.g., an alignment of the electron beam  46 , a position on the target  44  where the electron beam  46  is striking) as well as to generate a correction signal (e.g., a signal correction and/or control signals to adjust an electric field generated by the electron beam steering control system  62 , causing the electron beam  46  to change alignment). In some embodiments, the data processing system  28 , in response to determining that the electron beam  46  is striking the target  44  at position that does not provide a predetermined threshold of x-ray flux, the data processing system may output an alert, such as an error signal, to an operator via a suitable display coupled to the data processing system  28 . As discussed above, in some embodiments, the downhole tool  12  may include a radiation generator that emits neutrons. In such embodiments, the photon flux detector  54  may be a flux detector that measures a radiation flux. 
     As shown in the example, the photon flux detector of the multiple photon flux detectors  54  are each disposed at a different radial position (e.g., not overlapping) about the longitudinal axis  56 , as discussed in more detail with regard to  FIG.  3   . That is, each photon flux detector of the multiple photon flux detectors  54  may be at a different position along the first transversal axis  58  and/or the second transversal axis  60 . As shown in the example, the multiple photon flux detectors  54  are disposed near the target  44 . However, it should be noted that, in some embodiments, one or all of the multiple photon flux detectors may be offset (e.g., separated) from the target along the longitudinal axis  56 . 
     As discussed above, each photon flux detector of the multiple photon flux detectors  54  may be disposed at a different radial position about the longitudinal axis  56  of the downhole tool  12 . To illustrate this,  FIG.  3    is a schematic diagram showing a perspective view of multiple photon flux detectors  54  along the longitudinal axis  56 . It should be noted that while three photon flux detectors  54  are shown, in some embodiments there may be two photon flux detectors  54  or more than three photon flux detectors (e.g., 4, 5, 6, 7, 8, etc.). As shown in the example, the photon flux detector  54   a , the photon flux detector  54   b , and the photon flux detector  54   c  are disposed at different radial positions (e.g., along the first transversal axis  58  and/or the second transversal axis  60 ) about the longitudinal axis  56 . More specifically, the photon flux detector  54   a  is disposed at a first radial position about the longitudinal axis  56  that is a first distance  64  from the center of the target  44 , the photon flux detector  54   b  is disposed at a second radial position about the longitudinal axis  56  that is a second distance  66  from the center of the target  44 , and the photon flux detector  54   c  is disposed at a third radial position about the longitudinal axis  56  that is a third distance  68  from the center of the target  44 . As discussed in more detail below, the relative photon flux measured by each photon flux detector  54  may be used to determine a condition of the electron beam  46 , such as a position where the electron beam  46  is striking the target  44 . 
     For example, by arranging multiple detectors around a target (e.g., the target  44 ) at a set distance (e.g., the first distance  64 , the second distance  66 , and the third distance  68 ) the variation of the total flux of x-rays or neutrons and the position of the center of the electron beam may be calculated. The positions of the three detectors (e.g., photon flux detectors  54 ) labeled as (a, b, and c) may be defined as (x1, y1, 0), (0, 0, 0), and (x2, 0, 0) and the center of the electron beam on the surface of the target may be defined as (x, y, 0). Each photon flux detector  54  may measure a current that is proportional to the x-ray flux and quadratic to the distance from the center of the e-beam on the surface of the target. As such, the following relationship may hold: 
     
       
         
           
             
               
                 
                   
                     
                       
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     This provides an expression of the position of the electron beam  46  on the target  44  as a function of the distance bx. To solve for the distance bx, the first equation in (2) may be substituted into (4) and the resulting quadratic equation may be solved and, thus, relating the positions of the photon flux detectors  54  to the measured signal indicative of the x-ray flux. 
     It should be noted that the discussion above is not limited to when the photon flux detectors are each disposed at equal distances about a common point of the target  44  (e.g., the center of the target  44 ). That is, in some embodiments, at least two of the photon flux detectors  54  may be disposed at equal distances. For example, referring briefly back to  FIG.  3   , in some embodiments, the first distance  64  and the second distance  66  may be equal, the second distance  66  and the third distance  68  may be equal, or the first distance  64  and the third distance  68  may be equal. Alternatively, none of the distances between the photon flux detectors  54  and a (e.g., the first distance  64 , the second distance  66 , and the third distance  68 ) may be equal. In any case, the data processing system  28  may be calibrated such that the storage  34  and/or memory  32  includes the radial positions (e.g., the first distance  64  from the center of the target  44  about the longitudinal axis  56 , the second distance  66  from the center of the target  44  about the longitudinal axis  56 , and the third distance  68  from the center of the target  44  about the longitudinal axis  56 ). 
     As generally discussed above, a relative x-ray measured by each photon flux detector of the multiple photon flux detectors  54  may be used by the data processing system  28  to determine a condition of the electron beam  46 , such as a position where the electron beam  46  is striking the target  44 . 
     To illustrate this,  FIG.  4    is a schematic diagram showing a perspective view of multiple photon flux detectors  54  at different radial positions (e.g., along the first transversal axis  58  and/or the second transversal axis  60 ) about the longitudinal axis  56 . In the example, each photon flux detector  54  is disposed at an equal distance from the center of the target  44  (e.g., the first distance  64 , the second distance  66 , and the third distance  68 , as described above with regard to  FIG.  3   ). However, it should be noted that in some instances, the distances of each photon flux detector  54  from the center of the target may be different or at least two of the distances may be the same. 
     As also shown in the example, the photon flux detector  56   a  measures a first signal  70  (e.g., indicated by a direction and magnitude of the arrow) indicative of an x-ray flux of the x-rays emitted by the target  44  in response to the electron beam  46  (not shown) striking the target  44 , the photon flux detector  56   b  is measuring a second signal  72  (e.g., indicated by a direction and magnitude of the arrow) indicative of an x-ray flux of the x-rays emitted by the target  44  in response to the electron beam  46  striking the target  44 , and the photon flux detector  56   c  is measuring a third signal  74  (e.g., indicated by a direction and magnitude of the arrow) indicative of an x-ray flux of the x-rays emitted by the target  44  in response to the electron beam  46  striking the target  44 . In particular, the respective magnitude of the first signal  70 , the second signal  72 , and the third signal  74  are substantially equal (e.g., as indicated by the respective magnitude of the arrows for the first signal  70 , the second signal  72 , and the third signal  74 ). As such, the data processing system  28 , after receiving the first signal  70 , the second signal  72 , and the third signal  74 , may determine that a position  76  associated with where the electron beam  46  is striking the target. In this case, as the respective magnitude of the first signal  70 , the second signal  72 , and the third signal  74  are equal (e.g., and the distance between each photon flux detector  54  from the center is the same) the data processing system  28  may determine that the position  76  is approximately in the center of the target. 
     As another non-limiting example,  FIG.  5    is a schematic diagram showing a perspective view of multiple photon flux detectors  54  at different radial positions (e.g., along the first transversal axis  58  and/or the second transversal axis  60 ) about the longitudinal axis  56 . In the example, each photon flux detector  54  is disposed at an equal distance from the center of the target  44  (e.g., the first distance  64 , the second distance  66 , and the third distance  68 , as described above with regard to  FIG.  3   ). However, it should be noted that in some instances, the distances of each photon flux detector  54  may be different or at least two of the distances may be the same. 
     As also shown in the example, the photon flux detector  56   a  is measuring a first signal  70  indicative of an x-ray flux of the x-rays emitted by the target  44  in response to the electron beam  46  (not shown) striking the target  44 , the photon flux detector  56   b  is measuring a second signal  72  indicative of an x-ray flux of the x-rays emitted by the target  44  in response to the electron beam  46  striking the target  44 , and the photon flux detector  56   c  is measuring a third signal  74  indicative of an x-ray flux of the x-rays emitted by the target  44  in response to the electron beam  46  striking the target  44 . In particular, the respective magnitude of the first signal  70 , the second signal  72 , and the third signal  74  are different (e.g., as indicated by the respective magnitude of the arrows for the first signal  70 , the second signal  72 , and the third signal  74 ). As such, the data processing system  28 , after receiving the first signal  70 , the second signal  72 , and the third signal  74 , may determine that a position  76  associated with where the electron beam  46  is striking the target. In this case, as the respective magnitude of the first signal  70 , the second signal  72 , and the third signal  74  are different (e.g., and the distance between each photon flux detector  54  from the center is the same) the data processing system  28  may determine that the position  76  as shown in the illustrated example (e.g., generally away from the center and the distance between the position  76  and each photon flux detector  54  is not equal). 
     As another non-limiting example,  FIG.  6    is a schematic diagram showing a perspective view of multiple photon flux detectors  54  at different radial positions (e.g., along the first transversal axis  58  and/or the second transversal axis  60 ) about the longitudinal axis  56 . In the example, each photon flux detector  54  is disposed at an equal distance from the center of the target  44  (e.g., the first distance  64 , the second distance  66 , and the third distance  68 , as described above with regard to  FIG.  3   ). However, it should be noted that in some instances, the distances of each photon flux detector  54  may be different or at least two of the distances may be the same. 
     As also shown in the example, the photon flux detector  56   a  is measuring a first signal  70  indicative of an x-ray flux of the x-rays emitted by the target  44  in response to the electron beam  46  (not shown) striking the target  44 , the photon flux detector  56   b  is measuring a second signal  72  indicative of an x-ray flux of the x-rays emitted by the target  44  in response to the electron beam  46  striking the target  44 , and the photon flux detector  56   c  is measuring a third signal  74  indicative of an x-ray flux of the x-rays emitted by the target  44  in response to the electron beam  46  striking the target  44 . In particular, the magnitude of the first signal  70  is different that the respective magnitude of the second signal  72  and the third signal  74  (e.g., as indicated by a respective length of the arrows for the first signal  70 , the second signal  72 , and the third signal  74 ). As such, the data processing system  28 , after receiving the first signal  70 , the second signal  72 , and the third signal  74 , may determine that a position  76  associated with where the electron beam  46  is striking the target. In this case, as the magnitude of the first signal  70  is different than the respective magnitude of the second signal  72  and the third signal  74  (e.g., and the distance between each photon flux detector  54  from the center is the same) the data processing system  28  may determine the position  76  as shown in the illustrated example (e.g., approximately equal distance from the photon flux detector  54   b  and the photon flux detector  54   c ). 
     Keeping the above in mind,  FIG.  7    is a flow chart  80  representing a method for using a downhole tool  12  having at least two photon flux detectors  54  that measure radiation emitted from a target (e.g., the target  44 ). The flow chart  80  includes receiving (process block  82 ) a first signal from a first detector indicative of a first x-ray flux. For example, the data processing system  28  (e.g., the processor  30 ), or any suitable controller and/or control system having a suitable processor, may receive the first signal from the photon flux detector  54   a  at a first radial position, as described in  FIGS.  4 - 6   . The flow chart  80  also includes receiving (process block  84 ) a second signal from a second detector indicative of a second x-ray flux. For example, the data processing system  28  may receive the second signal from the photon flux detector  54   b  at a second radial position, as described in  FIGS.  4 - 6   . Then, after receiving the first signal and the second signal, the data processing system  28  may determine (process block  86 ) a striking position of an electron beam (e.g., electron beam  46 ) based at least in part on the first signal and the second signal. In some embodiments, the data processing system  28  may also receive a third signal from a third photon flux detector, such as the photon flux detector  54   c , as described in  FIGS.  4 - 6   . 
       FIG.  8    is a flow chart  90  representing a method for using a downhole tool  12  having at least two photon flux detectors  54  that measure radiation emitted from a target (e.g., the target  44 ). The flow chart  90  includes receiving (process block  92 ) a first signal from a first detector indicative of a first x-ray flux. For example, the data processing system  28  (e.g., the processor  30 ), or any suitable controller and/or control system having a suitable processor, may receive the first signal from the photon flux detector  54   a  at a first radial position, as described in  FIGS.  4 - 6   . The flow chart  90  also includes receiving (process block  94 ) a second signal from a second detector indicative of a second x-ray flux. For example, the data processing system  28  may receive the second signal from the photon flux detector  54   b  at a second radial position, as described in  FIGS.  4 - 6   . Then, after receiving the first signal and the second signal, the data processing system  28  may determine (process block  96 ) an alignment of an electron beam (e.g., electron beam  46 ), such as an angle of a collimated the electron beam  46  relative to an axis (e.g., the longitudinal axis  56 ) based at least in part on the first signal and the second signal. In some embodiments, the data processing system  28  may also receive a third signal from a third photon flux detector, such as the photon flux detector  54   c , as described in  FIGS.  4 - 6   . 
       FIG.  9    is a flow chart  100  representing a method for using a downhole tool  12  having at least two photon flux detectors  54  that measure radiation emitted from a target (e.g., the target  44 ). The flow chart  100  includes receiving (process block  102 ) a first signal from a first detector indicative of a first x-ray flux. For example, the data processing system  28  (e.g., the processor  30 ), or any suitable controller and/or control system having a suitable processor, may receive the first signal from the photon flux detector  54   a  at a first radial position, as described in  FIGS.  4 - 6   . The flow chart  90  also includes receiving (process block  104 ) a second signal from a second detector indicative of a second x-ray flux. For example, the data processing system  28  may receive the second signal from the photon flux detector  54   b  at a second radial position, as described in  FIGS.  4 - 6   . Then, after receiving the first signal and the second signal, the data processing system  28  may modify (process block  106 ) an alignment of an electron beam (e.g., electron beam  46 ) based at least in part on the first signal and the second signal. That is, the data processing system  28  may generate a control signal that includes instructions that cause the beam steering control system  62  to modify an alignment of the electron beam  46 . In some embodiments, the data processing system  28  may also receive a third signal from a third photon flux detector, such as the photon flux detector  54   c , as described in  FIGS.  4 - 6   . 
     To modify the alignment of the electron beam  46 , the data processing system  28  may transmit a control signal to the beam steering control system  62  causing the beam steering control system  62  to induce an electric field in a direction perpendicular to the longitudinal axis  56  (e.g., perpendicular to the x-ray tube axis) using electrodes at a variable potential. In some embodiments, the control signal may cause the electron beam steering control system  62  to modify the alignment of the electron beam  46  by applying a magnetic field via one or more coils proximate to the coil (e.g., using one or more steerer magnets disposed near and coupled to the electron beam steering control system). 
       FIG.  10    is a flow chart  110  representing a method for using a downhole tool  12  having at least two photon flux detectors  54  that measure radiation emitted from a target (e.g., the target  44 ). The flow chart  110  includes receiving (process block  112 ) a first signal from a first detector indicative of a first x-ray flux. For example, the data processing system  28  (e.g., the processor  30 ), or any suitable controller and/or control system having a suitable processor, may receive the first signal from the photon flux detector  54   a  at a first radial position, as described in  FIGS.  4 - 6   . The flow chart  90  also includes receiving (process block  114 ) a second signal from a second detector indicative of a second x-ray flux. For example, the data processing system  28  may receive the second signal from the photon flux detector  54   b  at a second radial position, as described in  FIGS.  4 - 6   . Then, after receiving the first signal and the second signal, the data processing system  28  may determine (process block  116 ) a relative desired x-ray flux based at least in part on the first signal and the second signal. That is, the data processing system  28  may determine that the x-ray flux currently indicated by the first signal and the second signal is greater than or less than a desired x-ray flux. In response to determining this, the data processing system  28  may generate a signal correction, which may indicate a determined amount of photons  49  that are being emitted into the geological formation  14 . 
     Accordingly, the present disclosure relates to a beam alignment system for a downhole tool that measures properties of a geological formation, such as a formation density. In general, the beam alignment system includes two or more photon flux detectors disposed at different radial positions about an axis normal to a surface of the target. Each detector of the two or more detectors measures a signal indicative of a photon flux at the respective position of the respective detector. A controller communicatively coupled to the two or more detectors may determine a condition associated with the electron beam (e.g., an alignment, a striking position of the electron beam on the target, and the like) of the downhole based at least in part on the respective signal measured by the two or more detectors. In some examples, the controller may determine the condition associated with the electron beam based at least in part on a respective position of the two or more detectors. In some example, the respective position of the two or more detectors may be different or substantially equal radial distances from the axis normal to a surface of the target. In some examples, the controller may generate and/or output a signal correction factor that may modify an expected output of the photons emitted by the detector. Additionally, or alternatively, the controller may generate and/or output a control signal that modifies a condition associated with the electron beam (e.g., modifying a voltage of an electron accelerator associated with the electron beam). As such, the beam alignment system of the present disclosure may improve the accuracy of certain downhole tools as well as improve the operations of the downhole tools while the downhole tools are within a wellbore. 
     The specific embodiments described above have been shown by way of example, and it should be understood that these embodiments may be susceptible to various modifications and alternative forms. It should be further understood that the claims are not intended to be limited to the particular forms disclosed, but rather to cover modifications, equivalents, and alternatives falling within the spirit and scope of this disclosure.