Scintillation crystal including a co-doped rare earth silicate, a radiation detection apparatus including the scintillation crystal, and a process of forming the same

Abstract

A scintillation crystal can include a rare earth silicate, an activator, and a Group 2 co-dopant. In an embodiment, the Group 2 co-dopant concentration may not exceed 200 ppm atomic in the crystal or 0.25 at % in the melt before the crystal is formed. The ratio of the Group 2 concentration/activator atomic concentration can be in a range of 0.4 to 2.5. In another embodiment, the scintillation crystal may have a decay time no greater than 40 ns, and in another embodiment, have the same or higher light output than another crystal having the same composition except without the Group 2 co-dopant. In a further embodiment, a boule can be grown to a diameter of at least 75 mm and have no spiral or very low spiral and no cracks. The scintillation crystal can be used in a radiation detection apparatus and be coupled to a photosensor.

What is claimed is: 
     
         1 . A scintillation crystal comprising a formula of Lu (1-x) Y x SiO 5 :Ac, Me, wherein:
 Ac is a first dopant and has a first atomic concentration in the scintillation crystal of at least 20 atomic ppm based on a total rare earth content in the scintillation crystal, wherein the first dopant is Ce, Pr, Tb, or any combination thereof;   Me is a second dopant and includes Ca and has a second atomic concentration that does not exceed 200 ppm atomic based on a total rare earth content of the scintillation crystal;   wherein 0<x<1; and   the scintillation crystal has a decay time of no greater than 40 ns.   
     
     
         2 . The scintillation crystal of  claim 1 , the scintillation crystal has a decay time of no greater than 38 ns. 
     
     
         3 . The scintillation crystal of  claim 1 , the scintillation crystal has a decay time of no greater than 36 ns. 
     
     
         4 . The scintillation crystal of  claim 1 , wherein the second atomic concentration is at least 8 atomic ppm based on a total rare earth content in the scintillation crystal. 
     
     
         5 . The scintillation crystal of  claim 1 , wherein the second atomic concentration is at least 11 atomic ppm based on a total rare earth content in the scintillation crystal. 
     
     
         6 . The scintillation crystal of  claim 1 , wherein the second atomic concentration is at least 15 atomic ppm based on a total rare earth content in the scintillation crystal. 
     
     
         7 . The scintillation crystal of  claim 1 , wherein the second atomic concentration is at least 20 atomic ppm based on a total rare earth content in the scintillation crystal. 
     
     
         8 . The scintillation crystal of  claim 1 , wherein the second atomic concentration in the scintillation crystal is no greater than 160 atomic ppm based on a total rare earth content in the scintillation crystal. 
     
     
         9 . The scintillation crystal of  claim 1 , wherein the second atomic concentration in the scintillation crystal is no greater than 150 atomic ppm based on a total rare earth content in the scintillation crystal. 
     
     
         10 . The scintillation crystal of  claim 1 , wherein the second atomic concentration in the scintillation crystal is no greater than 120 atomic ppm based on a total rare earth content in the scintillation crystal. 
     
     
         11 . The scintillation crystal of  claim 1 , wherein the second atomic concentration in the scintillation crystal is no greater than 95 atomic ppm based on a total rare earth content in the scintillation crystal. 
     
     
         12 . The scintillation crystal of  claim 1 , wherein the second atomic concentration divided by the first atomic concentration is in a range of 0.4 to 2.5. 
     
     
         13 . A scintillation crystal comprising a formula of Lu (1-x) Y x SiO 5 :Ce, Ca, wherein:
 Ce has a first atomic concentration in the scintillation crystal of at least 20 atomic ppm based on a total rare earth content in the scintillation crystal;   Ca and has a second atomic concentration that does not exceed 200 ppm atomic based on a total rare earth content of the scintillation crystal;   wherein 0<x<1; and   the second atomic concentration divided by the first atomic concentration is in a range of 0.4 to 2.5.   
     
     
         14 . The scintillation crystal of  claim 13 , wherein the second atomic concentration divided by the first atomic concentration is no greater than 2.0. 
     
     
         15 . The scintillation crystal of  claim 13 , wherein the second atomic concentration divided by the first atomic concentration is no greater than 1.9. 
     
     
         16 . The scintillation crystal of  claim 13 , wherein the second atomic concentration divided by the first atomic concentration is no greater than 1.7. 
     
     
         17 . The scintillation crystal of  claim 13 , wherein the second atomic concentration divided by the first atomic concentration in the melt is no greater than 2.1. 
     
     
         18 . The scintillation crystal of  claim 13 , wherein the second dopant has a concentration in the scintillation crystal of at least 8 atomic ppm based on a total rare earth content in the scintillation crystal. 
     
     
         19 . The scintillation crystal of  claim 13 , wherein the second dopant is Ca and has a concentration in the scintillation crystal no greater than 160 atomic ppm based on a total rare earth content in the scintillation crystal. 
     
     
         20 . A radiation detection device, comprising:
 a scintillation crystal within the radiation detection device, wherein the radiation detection device is one of a Positron Emission Tomography device (PET), a Single Positron Emission Computer Tomography device (SPECT), a Time of Flight Positron Emission Tomography device, a Depth of Interaction Positron Emission Tomography device, a hybrid PET device with a Computed Tomography device, a hybrid PET device with a Magnetic Resonance device, or a hybrid PET with a SPECT device, wherein the scintillation crystal comprises a formula of Lu(1-x)YxSiO5:Ac, Me, wherein:
 Ac is a first dopant and has a first atomic concentration in the scintillation crystal of at least 20 atomic ppm based on a total rare earth content in the scintillation crystal, wherein the first dopant is Ce, Pr, Tb, or any combination thereof; 
 Me is a second dopant and includes Ca and has a second atomic concentration that does not exceed 200 ppm atomic based on a total rare earth content of the scintillation crystal; 
 wherein 0<x<1; and 
 the second atomic concentration divided by the first atomic concentration is in a range of 0.4 to 2.5.