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EP0795631A1 Expired / Lapsed EP ⏱️ 0.0 years remaining

Scintillation crystals having reduced afterglow and method of making the same

Assignee: Saint Gobain Ceramics and Plastics Inc
•
Filing: 1997-02-13
•
Granted: —
•
Expires: 2017-02-13
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Abstract

Abstract Methods of making a scintillation crystal having reduced afterglow include preparing a crystal melt according to the Czochralsky technique and doping the melt with an element or a compound which reduces afterglow without significantly reducing the luminescence light output of the crystal grown in the melt. Experiments have shown that doping the melt with any one of calcium, cobalt, germanium, niobium, sodium, and chromium significantly reduces afterglow without unduly reducing the luminescence light output of the crystal. The presently preferred dopant is cobalt, which is added to the melt in concentrations of approximately 10ppm to 50ppm. Crystals made according to the method of the invention exhibit significantly less afterglow than crystals made from the same raw materials without doping. By choice of the proper concentration of dopant, the light output of the crystal during luminescence is not adversely affected.

Inventors

  • 👤 Harold J. Murphy
  • 👤 William P. Novak
  • 👤 Alan F. Rybicki

Bibliographic Details

Application Number —
Jurisdiction EP
Data Source google_patents
Last Synchronized 2026-11-08 02:45
CPC Classifications
C; C30; C30B; C30B15/00; C30B29/00; C30B29/10; C30B29/16; C30B29/22; C30B29/32

Claims Analysis

Total Claims: 18
Claim 1
Independent Claim 42 words
A method of making a scintillation crystal, comprising: a) preparing a crystal melt; b) adding an afterglow-reducing dopant to the melt prior to growing the crystal; c) growing the crystal such that it contains a relatively low concentration of the afterglow-reducing dopant.
Claim 2
Dependent Claim 24 words
A method according to claim 1, wherein: the afterglow-reducing dopant is selected from the group consisting of calcium, cobalt, germanium, niobium, sodium, and chromium
Claim 3
Dependent Claim 27 words
A method according to claim 2, wherein: the afterglow-reducing dopant is cobalt, which is added to the melt at a concentration of less than about 50 ppm.
Claim 4
Dependent Claim 27 words
A method according to claim 3, wherein: the afterglow-reducing dopant is added to the melt at a concentration of between about 1 ppm and about 50 ppm.
Claim 5
Dependent Claim 25 words
A method according to claim 3, wherein: the crystal is grown such that it contains a cobalt concentration of less than about to 5 ppm.
Claim 6
Dependent Claim 27 words
A method according to claim 5, wherein: the crystal is grown such that it contains a cobalt concentration of between about 1 ppm and about 5 ppm.
Claim 7
Dependent Claim 12 words
A method according to claim 1, wherein: the crystal is cadmium tungstate.
Claim 8
Dependent Claim 24 words
A method according to claim 7, wherein: the afterglow-reducing dopant is selected from the group consisting of calcium, cobalt, germanium, niobium, sodium, and chromium.
Claim 9
Dependent Claim 27 words
A method according to claim 8, wherein: the afterglow-reducing dopant is cobalt which is added to the melt at a concentration of less than about 50 ppm.
Claim 10
Dependent Claim 24 words
A method according to claim 9, wherein: the crystal is grown such that it contains a cobalt concentration of less than about 5 ppm.
Claim 11
Dependent Claim 18 words
A method according to claim 1, wherein: said preparing a crystal melt is according to the Czochralsky technique.
Claim 12
Dependent Claim 13 words
A scintillation crystal comprising: a scintillator crystal lattice doped with an afterglow-reducing dopant.
Claim 13
Dependent Claim 25 words
A scintillation crystal according to claim 12, wherein: said afterglow-reducing dopant is selected from the group consisting of calcium, cobalt, germanium, niobium, sodium, and chromium.
Claim 14
Dependent Claim 22 words
A scintillation crystal according to claim 13, wherein: said afterglow-reducing dopant is cobalt in a concentration of less than about 5 ppm.
Claim 15
Dependent Claim 25 words
A scintillation crystal according to claim 14, wherein: said afterglow-reducing dopant is cobalt in a concentration of between about 1 ppm and about 5 ppm.
Claim 16
Dependent Claim 15 words
A scintillation crystal according to claim 15, wherein: said scintillator crystal lattice is cadmium tungstate.
Claim 17
Dependent Claim 25 words
A scintillation crystal according to claim 16, wherein: said afterglow-reducing dopant is selected from the group consisting of calcium, cobalt, germanium, niobium, sodium, and chromium.
Claim 18
Dependent Claim 21 words
A scintillation crystal according to claim 17, wherein: said afterglow-reducing dopant is cobalt in a concentration of less than about 5ppm.

References Cited (Backward Citations)

DE1544239A1 Cited
GB2045795A Cited
US4725734A Cited
US4694177A Cited
EP0467044A2 Cited

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