Abstract:
Herein disclosed is an x-ray florescence (XRF) test system which comprises an XRF test instrument used for testing a test target&#39;s responses to X-rays, the instrument including a test window allowing the X-ray and its responsive energy to pass through, and at least one window protecting film allowing X-rays to pass through and providing protections to the window, the film being configured to be coupled with the window in a fashion to be removed from or applied or reapplied over the window. The corresponding calibration mode can be manually or automatically applied according to the specific film presently in use.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims benefit of and priority to U.S. Provisional Application entitled “REMOVABLE WINDOW PROTECTING FILMS AND A METHOD OF APPLYING SUCH TO AN XRF/XRD DEVICE” with application No. 61/810,424 filed Apr. 10, 2013 under 35 U.S.C. §§119, 120, 363, 365, and 37 C.F.R. §1.55 and §1.78 incorporated herein by this reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    In X-ray fluorescence (XRF) testing, portable testing instruments are often subject to harsh environment. The instrument test windows often need to be protected from possible dusting, intrusion and abrasion from the test material. 
         [0003]    However, applying protecting material to the test window often impedes the accuracy and sensitivity of the test result, particularly for testing elements with low atomic numbers. 
         [0004]    For example, polyethylene or polyimide is often used material for window shields or a cover. Polyethylene is more transparent and therefore less of absorbing to low energy X-rays than polyimide, but is not as resistant to punctures. 
         [0005]    It is therefore desirable to have the sensitivity that polyethylene yields for elements with lower atomic numbers, and with the same instrument to have the physical protection offered by thicker polyimide when the testing requirement for sensitivity is not as demanding, such as for testing Titanium (Ti) or other higher atomic numbers. It provides many benefits for an instrument to be equipped with a layer of window guard or protecting film that can be easily applied on or taken off for testing elements with higher or lower atomic numbers, respectively. 
         [0006]    Various shields and/or window guards have been seen in existing practice designed for X-ray devices such as handheld X-ray fluorescence (XRF) instruments. Examples include U.S. Ser. No. 13/551,232; U.S. Pat. Nos. 7,430,274; 7,375,359; 7,375,358; 6,965,118; and 7,671,350, as well as WO 00/37928, are all incorporated herein by this reference. See also U.S. Published Application No. US-2008-0152079. However, none of these background arts have been seen to provide the simple, low cost and convenient solution as described herein in the present disclosure. 
       SUMMARY OF THE INVENTION 
       [0007]    The fragile sealing window used in an X-ray analytical instrument can be protected from encounters with foreign objects by applying the protection film with embodiments of the present disclosure. 
         [0008]    It is a general object of the present disclosure to overcome the problems associated with the background art by introducing an economical, simple, easy-to-apply and re-attachable window guard that engages whenever: a) a measurement mode is for testing heavier elements, b) a penetrating object is sensed to be in close proximity to the detector sealing window during a measurement mode, c) the instrument is not in usage, or d) determined by the operator to apply, etc. 
         [0009]    The foregoing and other objects of the present disclosure may be realized with a replaceable protective film that covers the detector window, and can be removed and reapplied. 
         [0010]    In accordance with various embodiments of the invention, the protective covering or guard film may be attached on top of the detector window by adhesive means, or taken off and re-attached to the window depending on the need of the operation of the instrument. Other means of attaching, removing and re-attaching can include using other coupling means, such as magnetic coupling, thread screw coupling, etc. 
         [0011]    Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The drawings presented are not necessarily to scale. Emphasis is placed upon illustrating the principles of the preferred embodiment of the method. 
           [0013]      FIG. 1  is a schematic of an XRF instrument with a removable protective film ready to be applying over the window of the XRF instrument according to the present disclosure. 
           [0014]      FIG. 2  is a schematic of the XRF instrument in  FIG. 1  with the removable protective film applied over the window. 
           [0015]      FIG. 3  is a flowchart of the process for operating the XRF instrument accommodating the application of the protective film. 
           [0016]      FIGS. 4   a  and  4   b  exhibit the effect of the protective films on different XRF measurements, made for light elements and heavy elements respectively. 
           [0017]      FIGS. 5   a ,  5   b  and  5   c  exhibit another means of attaching and re-attaching the protective film by using magnets as couplings. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0018]    The method proposed by the preferred embodiment is herein presented by referring to  FIGS. 1-5   c.    
         [0019]    As seen in  FIG. 1 , a conceptual view of an XRF instrument  10  is configured to couple with a plurality of protection films  6 , one at a time during operation. A test window  4  is devised as in conventional XRF instruments. An important novel aspect of the solution herein presented includes the employment of a plurality of removable protection films  6 , with which any number can be applied over a test window  4  according to the present invention. 
         [0020]    The XRF instrument further optionally includes an X-ray source  12 , a detector  16 , a data processor  8  and a display  14 , largely in the same way as conventional XRF instruments. 
         [0021]    An immediate exemplary usage of such embodiment is to affix the commonly used polyethylene film or coating to window  4  in a non-removable fashion as conventionally done in some XRF instruments. The sensitivity that polyethylene yields for elements with lower atomic numbers is desirable for testing samples with lower atomic numbers. Therefore, no additional removable film or guard  6  is needed for such situation. However, with the same instrument  10 , in order to achieve the physical protection needed for many testing environments, thicker polyimide removable film  6 , such as polyimide 75 μm, can be applied over the existing non-removable polyethylene film or coating. This is the most desirable when the testing requirement for sensitivity is not as demanding, such as testing for Titanium (Ti) or other higher atomic numbers. 
         [0022]    It should be appreciated that the usage of any number of, and any combination of any kinds of films, collectively numerated as  6  in  FIGS. 1 and 2  should be determined by the testing specifics, and the usage of all such should be within the scope of the present disclosure. 
         [0023]    For example, the fixed layer of film is optional, and it doesn&#39;t have to be polyethylene. Polyimide with 25 μm is another often used film that can be used as the fixed layer. The removable film  6  can be also many choices. 
         [0024]    Reference is still made to  FIG. 1 . Removable film  6  is preferably attached over window  14  by using a removable attaching means. Accordingly, film  6  is shown to be configured to include an adhesive backing  6   a  encircling the edge of film  6 . Alternatively, the adhesive backing  6   a  can be applied in sections, instead of continuously encircling the edge. 
         [0025]    Continuing to refer to  FIG. 1 , film  6  can optionally have an extruded tab  6   c  allowing easy application onto and removal from window area  4 . Preferably, working area  6   b  should be left clean from adhesives and human touch. 
         [0026]    It should be appreciated that removable film  6 , adhesive backing  6   a,  tab  6   c  and working area  6   b  each and all can take any shape to suit for specific XRF instruments, and any such shape used by a removable film falls within the scope of the present invention. 
         [0027]    It should also be appreciated that the adhesive material (not shown) applied to backing  6   a  can be of any material suited for the purpose of attaching film  6  in a removable manner. 
         [0028]    Referring to  FIG. 2 , XRF instrument  10  is conceptually shown when removable film  6  is applied onto window  4 . 
         [0029]    Reference is now primarily made to  FIG. 3  with continued reference to  FIG. 1 .  FIG. 3  is a flowchart showing an operational procedure related to the usage of the embodiment shown in  FIG. 1 . 
         [0030]    In order to accommodate the usage of a plurality of removable films according to the present invention, instrument  10  is preferably devised with a plurality of corresponding calibration modes, preloaded onto processor  8 . 
         [0031]    It should be noted that the different calibration modes for different types of removable films  6  can be either designed in a new XRF instrument, or achieved by modifying an existing calibration module or functional block residing on the processor of an existing XRF product. The modified calibration module is shown in  FIG. 1  as  8   a . It can also alternatively be calibrated in a field operation or in a manufacturing set up, all of which should be within the scope of the present invention. 
         [0032]    The method of calibrating an XRF instrument for a specific window protection is commonly known. Different calibration modes can be achieved in manufacturing settings for different types of the protection films/guards. 
         [0033]    Alternatively, if the quality and thickness of the protecting films are substantially homogenous and standard, one can populate the values of different calibration modes by calculating the energy-dependent effect on the spectrum caused by the corresponding film. One can conduct sufficient number of calibration runs for a specific protecting film, which yield a calibration factor for the film by comparing to the energy reading of the same instrument without the film applied on the same set of samples. With the standard calibration factors established, using the example film Kapton 25 for element Mo testing, one can use the calibration factor associated with this specific protecting film to calculate the new calibration value with the protection film/guard based on normally known calibration values without the protection film. The result specific to this calibration mode for Kapton 25 for Mo testing can be stored in a memory (not shown) of the instrument. The following table shows an exemplary result of such calculation of the calibration mode. 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Calculating Calibration Values for Mo Testing with 
               
               
                 Kapton 25 as Window Guard 
               
             
          
           
               
                   
                 Fe Region 
                 Cu Region 
                 Mo Region 
               
               
                   
                   
               
             
          
           
               
                 Normal 
                 54.8815 
                 85.9407 
                 176244 
               
               
                 Calibration 
               
               
                 values 
               
               
                 Calibration 
                 0.9119102 
                 0.98551094 
                 0.97156215 
               
               
                 Factor for film 
               
               
                 Kapton 25 
               
               
                 Calculated 
                 50.047 
                 84.6955 
                 171232 
               
               
                 Calibration 
               
               
                 Values with WG 
               
               
                   
               
             
          
         
       
     
         [0034]    It can be understood by those skilled in the art that, wherein in Table 1, the content in the top row denotes to “energy regions” associated with known elements in a known sample. “Normal Calibration values” denote the x-ray counts per second from the standard sample without the window guard or the film. “Calculated Calibration Values with WG” denote the x-ray counts per second from the same standard sample, with the window guard or the film. 
         [0035]    Yet another note on the calibration modes is that it is preferable to prepare all possible calibration modes with corresponding calibration values for all possible combinations of using, or without using, any and any number of protection films provided with the instrument. 
         [0036]    Continuing with  FIG. 3 , the calibration procedure is preferably made in a form executable functional code, and as a module herein named “film calibration module”  8   a  shown in  FIG. 1 . The calibration procedure preferably includes steps as follows. 
         [0037]    In step  402 , the operator starts testing by starting a “Cal check” with a calibration mode mostly used for a previous session of testing. i.e., light element or heavy atomic element. “Cal check” is commonly referred in XRF as shooting a sample of known elemental composition; 
         [0038]    In step  404 , calibration module  8   a  checks the film application to determine whether film is applied, and optionally to determine automatically what kind of film is applied on window  4 . 
         [0039]    Alternatively, when the known kind of element for testing, such as Mo, is provided to the instrument, module  8   a  can be configured to determine if the detected film  6  is the right match for such testing. 
         [0040]    It should be understood that alternative step  404  can be that the calibration module  8   a  only checks if film  6  is applied or not, and prompts the operator to check if film  6  is the intended kind of film to be attached. 
         [0041]    It can be understood by those skilled in the art that after the Cal Check is initiated at step  402 , the energy reading on a known sample can indicate if a protection film is applied. And by comparing the known calibration factors stored in the instrument, such as that listed in Table-1, optionally the calibration module  8   a  can yield what kind of film is presently attached to the window. Further alternatively, the calibration module  8   a  can also yield what kind of film is presently attached to the window by comparing the ratios of a couple of know spectrum to a predetermined threshold of such ratios. 
         [0042]    In step  406 , calibration module  8   a  mostly via display  14  prompts operator whether film is applied and what kind of film is applied on window  4 , and suggests the operator whether to change or remove film or alternatively change the calibration mode. 
         [0043]    In step  408 , module  8   a  further checks what film or no film is chosen by the operator. If a specific film is chosen, the procedure moves onto step  412 . If no film is chosen, the procedure moves onto step  410 . 
         [0044]    In step  412 , a specific calibration mode suited for the chosen film is chosen by the calibration module, and executed to calibration instrument  10 . Alternatively, the operator can also choose the calibration mode via display  14 . 
         [0045]    In step  410 , if the operator determines not to use any protection film and remove the same, the existing calibration mode for window  4  without additional re-attachable protection film  6  is executed to calibrate instrument  10 . In the exemplary case shown in Table-1, the row of values of “Normal Calibration Values” is used. 
         [0046]    In step  412 , instrument  10  is ready for testing. 
         [0047]    Reference is now made to  FIGS. 4   a  and  4   b , whereby two exhibitions are shown for the effect of adding removable films, presented as “ratio of precision of Prolene window”, with Prolene (an example of a polyethylene window) exemplarily used as the fixed window base for cases. A Ti element of the lighter end of heavy atomic elements and a Mo element of the heavy atomic elements are used in  FIGS. 4   a  and  4   b , respectively. Both elements are tested within Alloy 321 for both cases. In addition, removable films Kapton 25 (an example of a polyimide window) and Kapton 75 are representatively used to compare their respective effectiveness against a fixed window with Prolene. 
         [0048]    As can be seen in  FIG. 4   a  that the lighter end of the heavier atomic elements (e.g. Ti) is affected the most by the effect of changing or adding removable films. 
         [0049]    As can be seen in  FIG. 4   b  that higher end of heavier atomic elements, such as Mo, is not as affected by adding removable films. Therefore, adding removable films for extra protection is desirable. 
         [0050]    The comparison of  FIGS. 4   a  and  4   b  indicates the benefit of versatility allowing adding or removing protection films to the text window of the XRF instruments. 
         [0051]    Reference is now made to  FIGS. 5   a ,  5   b  and  5   c , which exhibit an alternative means of attaching and re-attaching the protection film  6 . In this alternative attaching method, magnetic attraction force is used to stick or attach the film onto the window of the XRF instrument. 
         [0052]    As seen in  FIGS. 5   a ,  5   b  and  5   c , the re-attachable film  6  with magnetic coupling comprises protection film main body  6   c,  a first holder  50   a  holding film  6   c  and one set of magnets  52   a,  a second holder  50   b  holding a second set of magnets  52   b.  It should be noted that elements  52   a  and  50   b  can each be any of the permanent magnets or ferromagnetic material as long as  52   a  and  52   b  forms a magnet coupling strong enough to hold the film onto the window. Magnetic couplings  52   a  and  52   b  can also be in the forms of whole piece, such as shown in  FIG. 5   b , or of discrete discs, such as shown in  FIG. 5   c , that are configured to exert magnetic force on its corresponding counter-parts. 
         [0053]    There can be optional attaching means such as a screw thread  54  for the second holder  50   b  to be attached to window  4 , with the corresponding coupling thread on window  4  (not shown). It should be understood by those skilled in the art that other attaching means can be used instead to thread the attached to the second holder  50   b  to the window. 
         [0054]    It can be understood that this alternative magnetic coupling provides a similar advantage as that of adhesive coupling, and that it is simple and convenient for the operator to attach and re-attach the protection film onto or from the window. 
         [0055]    It should be appreciated that any other means of attaching and re-attaching, and the associated usage of corresponding calibration modes, should all be within the scope of the present disclosure.