Scintillation crystal including a co-doped rare earth silicate, a radiation detection apparatus including the scintillation crystal, and a process of forming the same
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.
1. A scintillation crystal comprising a rare earth silicate, a first dopant, and a second dopant, wherein:
the first dopant is an activator and has a first atomic concentration;
the second dopant includes a Group 2 element and has a second atomic concentration that does not exceed 200 ppm atomic based on a total rare earth content of the scintillation crystal; and
the second atomic concentration divided by the first atomic concentration is in a range of 0.4 to 2.0.
2. The scintillation crystal of claim 1 , wherein the scintillation crystal has a decay time no greater than 40 ns.
3. The scintillation crystal of claim 1 , wherein the scintillation crystal has a formula of Ln 2 SiO 5 :Ac,Me or Ln 2 Si 2 O 7 :Ac,Me, wherein:
Ln includes one or more rare earth elements different from the first dopant;
Ac is the first dopant; and
Me is the second dopant.
4. The scintillation crystal of claim 1 , 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.
5. The scintillation crystal of claim 1 , wherein the second dopant is Ca, and the second atomic concentration divided by the first atomic concentration in the scintillation crystal is in a range of 0.50 to 2.0.
6. The scintillation crystal of claim 1 , wherein the second dopant is Mg.
7. The scintillation crystal of claim 1 , wherein the second dopant is Mg, and the second atomic concentration divided by the first atomic concentration in the scintillation crystal is in a range of 0.35 to 1.5.
8. The scintillation crystal of claim 1 , wherein the first concentration is no greater than 1200 atomic ppm.
9. The scintillation crystal of claim 1 , wherein the first concentration is in a range of 20 atomic ppm to 1200 atomic ppm.
10. A radiation detection apparatus comprising:
the scintillation crystal of claim 1 ; and
a photosensor optically coupled to the scintillation crystal.
11. A scintillation crystal comprising a rare earth silicate, a first dopant, and a second dopant, wherein:
the first dopant is an activator and has a first concentration;
the second dopant includes a Group 2 element and has a second concentration that does not exceed 200 ppm atomic based on a total rare earth content of the scintillation crystal; and
the scintillation crystal has a decay time no greater than 40 ns.