Scintillation crystal including a rare earth halide, and a radiation detection system including the scintillation crystal

Abstract

A scintillation crystal can include Ln (1-y )RE y X 3 , wherein Ln represents a rare earth element, RE represents a different rare earth element, y has a value in a range of 0 to 1, and X represents a halogen. In an embodiment, RE is Ce, and the scintillation crystal is doped with Sr, Ba, or a mixture thereof at a concentration of at least approximately 0.0002 wt. %. In another embodiment, the scintillation crystal can have unexpectedly improved linearity and unexpectedly improved energy resolution properties. In a further embodiment, a radiation detection system can include the scintillation crystal, a photosensor, and an electronics device. Such a radiation detection system can be useful in a variety of radiation imaging applications.

1 . A scintillation crystal comprising:
 Ln( 1-y )RE y X 3 :Me 2+ , wherein:
 Ln represents a rare earth element; 
 Me 2+  represents Sr, Ba, or any mixture thereof and has a concentration of at least approximately 0.0002 wt. %; 
 RE represents a different rare earth element; 
 y has a value in a range of 0 to 1; and 
 X represents a halogen. 
   
     
     
         2 . A radiation detection system comprising:
 the scintillation crystal of  claim 1 ; and   a photosensor optically coupled to the scintillation crystal.   
     
     
         3 . A scintillation crystal comprising:
 Ln( 1-y )RE y X 3 , wherein:
 Ln represents a rare earth element; 
 RE represents a different rare earth element; 
 y has a value in a range of 0 to 1; and 
 X represents a halogen; and 
   the scintillation crystal has a property including:
 for a radiation energy range of 60 keV to 356 keV, the scintillation crystal has an averaged value for a departure from perfect linearity of no less than approximately -0.35%; 
 for a radiation energy range of 2000 keV to 2600 keV, the scintillation crystal has an averaged value for a departure from perfect linearity of no greater than approximately 0.07%; 
 for a radiation energy range of 60 keV to 356 keV, the scintillation crystal has an absolute value for a furthest departure from perfect linearity of no greater than approximately 0.7%; or 
 any combination thereof. 
   
     
     
         4 . A scintillation crystal comprising:
 Ln( 1-y )RE y X 3 , wherein:
 Ln represents a rare earth element; 
 RE represents a different rare earth element; 
 y has a value in a range of 0 to 1; and 
 X represents a halogen; and 
   an energy resolution ratio is an energy resolution of the scintillation crystal divided by a different energy resolution of a different scintillation crystal having a different composition, wherein the energy resolution ratio is:
 no greater than approximately 0.970 for energies in a range of 60 to 729 keV; 
 no greater than approximately 0.950 for energies in a range of 122 keV to 2615 keV; 
 no greater than approximately 0.920 for energies in a range of 583 keV to 2615 keV; 
 no greater than approximately 0.900 for energies in a range of 662 keV to 2615 keV; 
 no greater than approximately 0.985 for an energy of 60 keV; 
 no greater than approximately 0.980 for an energy of 122 keV; 
 no greater than approximately 0.980 for an energy of 239 keV; 
 no greater than approximately 0.970 for an energy of 511 keV; 
   no greater than approximately 0.970 for an energy of 583 keV;   no greater than approximately 0.970 for an energy of 662 keV;   no greater than approximately 0.970 for an energy of 729 keV;   no greater than approximately 0.950 for an energy of 2615 keV; or any combination thereof.   
     
     
         5  to  8 . (canceled) 
     
     
         9 . The scintillation crystal of  claim 1 ; wherein an energy resolution ratio is an energy resolution of the scintillation crystal divided by a different energy resolution of a different scintillation crystal of a different composition, wherein the energy resolution ratio is:
 no greater than approximately 0.970 for energies in a range of 60 to 729 keV;   no greater than approximately 0.950 for energies in a range of 122 keV to 2615 keV;   no greater than approximately 0.920 for energies in a range of 583 keV to 2615 keV;   no greater than approximately 0.900 for energies in a range of 662 keV to 2615 keV;   no greater than approximately 0.985 for an energy of 60 keV;   no greater than approximately 0.980 for an energy of 122 keV;   no greater than approximately 0.980 for an energy of 239 keV;   no greater than approximately 0.970 for an energy of 511 keV;   no greater than approximately 0.970 for an energy of 583 keV;   no greater than approximately 0.970 for an energy of 662 keV;   no greater than approximately 0.970 for an energy of 729 keV;   no greater than approximately 0.950 for an energy of 2615 keV; or any combination thereof.   
     
     
         10  to  21 . (canceled) 
     
     
         22 . The scintillation crystal  claim 4 , wherein an energy resolution for the scintillation crystal is determined from an energy spectrum obtained using the scintillation crystal, a photomultiplier tube, a window disposed between the scintillation crystal and the photomultiplier tube, and a multi-channel analyzer coupled to the photomultiplier tube,
 wherein:
 the scintillation crystal has a shape of a right circular cylinder with diameter of approximately 64 mm and length of approximately 75 mm, and the scintillation crystal is wrapped with a reflector on the sides and one end; 
 the window includes sapphire or quartz; 
 the photomultiplier tube includes a linearly focused, non-saturated photomultiplier; and 
 the multi-channel analyzer is configured to perform bi-polar shaping at a 0.25 micro-s shaping time; and 
   the energy resolution is no greater than approximately 6.40% at 122 keV, no greater than approximately 2.90% at 662 keV, no greater than approximatelyl.90% at 2615 keV, or any combination thereof.   
     
     
         23 . The scintillation crystal of  claim 22 , wherein the energy resolution is no greater than approximately 6.40%. 
     
     
         24 . (canceled) 
     
     
         25 . The scintillation crystal of  claim 22 , wherein the energy resolution is no greater than approximately 2.90% at 662 keV. 
     
     
         26 . (canceled) 
     
     
         27 . The scintillation crystal of  claim 22 , wherein the energy resolution is no greater than approximately 1.90% at 2615 keV. 
     
     
         28  to  29 . (canceled) 
     
     
         30 . The scintillation crystal of  claim 1 , wherein the scintillation crystal is doped with Sr. 
     
     
         31 . The scintillation crystal of  claim 1 , wherein the Me 2+  content in the scintillation crystal is at least approximately 0.0002 wt. %, at least approximately 0.0005 wt. %, or at least approximately 0.001 wt. %. 
     
     
         32 . The scintillation crystal of  claim 1 , wherein the Me 2+  content in the scintillation crystal is no greater than approximately 0.05 wt. %, no greater than approximately 0.03 wt. %, no greater than 0.02 wt. %, or no greater than approximately 0.009 wt. %. 
     
     
         33 - 36 . (canceled) 
     
     
         37 . The scintillation crystal of  claim 3 , wherein the averaged value for the departure from perfect linearity (DFPL average ) is determined by: 
       
         
           
             
               
                 
                   DFPL 
                   average 
                 
                 = 
                 
                   
                     
                       
                         ∫ 
                         
                           E 
                           lower 
                         
                       
                       
                         E 
                         upper 
                       
                     
                      
                     
                       
                         DFPL 
                          
                         
                           ( 
                           
                             E 
                             i 
                           
                           ) 
                         
                       
                       · 
                       
                          
                         
                           E 
                           i 
                         
                       
                     
                   
                   
                     
                       E 
                       upper 
                     
                     - 
                     
                       E 
                       lower 
                     
                   
                 
               
               , 
             
           
         
       
       where
 DFPL(Ei) is DFPL at energy E i ; 
 E upper  is the upper limit of the energy range; and 
 E lower  is the lower limit of the energy range. 
 
     
     
         38 . (canceled) 
     
     
         39 . The scintillation crystal of  claim 1 , wherein:
 Ln includes La, Gd, Lu, or any mixture thereof, and   RE includes Ce, Eu, Pr, Tb, Nd, or any mixture thereof.   
     
     
         40 - 47 . (canceled) 
     
     
         48 . The scintillation crystal of  claim 3 , wherein an energy resolution ratio is an energy resolution of the scintillation crystal divided by a different energy resolution of a different scintillation crystal of a different composition, wherein the energy resolution ratio is:
 no greater than approximately 0.970 for energies in a range of 60 to 729 keV;   no greater than approximately 0.950 for energies in a range of 122 keV to 2615 keV;   no greater than approximately 0.920 for energies in a range of 583 keV to 2615 keV;   no greater than approximately 0.900 for energies in a range of 662 keV to 2615 keV;   no greater than approximately 0.985 for an energy of 60 keV;   no greater than approximately 0.980 for an energy of 122 keV;   no greater than approximately 0.980 for an energy of 239 keV;   no greater than approximately 0.970 for an energy of 511 keV;   no greater than approximately 0.970 for an energy of 583 keV;   no greater than approximately 0.970 for an energy of 662 keV;   no greater than approximately 0.970 for an energy of 729 keV;   no greater than approximately 0.950 for an energy of 2615 keV; or any combination thereof.   
     
     
         49 . The scintillation crystal of  claim 1 , wherein the scintillation crystal is doped with Ba. 
     
     
         50 . The scintillation crystal of  claim 3 , further comprising Me 2+ , wherein an Me 2+  content in the scintillation crystal is at least approximately 0.0002 wt. %, at least approximately 0.0005 wt. %, or at least approximately 0.001 wt. %. 
     
     
         51 . The scintillation crystal of  claim 50 , wherein the Me 2+  content in the scintillation crystal is no greater than approximately 0.05 wt. %, no greater than approximately 0.03 wt. %, no greater than 0.02 wt. %, or no greater than approximately 0.009 wt. %. 
     
     
         52 . The scintillation crystal of  claim 4 , further comprising Me 2+ , wherein an Me 2+  content in the scintillation crystal is at least approximately 0.0002 wt. %, at least approximately 0.0005 wt. %, or at least approximately 0.001 wt. %. 
     
     
         53 . The scintillation crystal of  claim 52 , wherein the Me 2+  content in the scintillation crystal is no greater than approximately 0.05 wt. %, no greater than approximately 0.03 wt. %, no greater than 0.02 wt. %, or no greater than approximately 0.009 wt. %.