EP0467044A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Hole-trap-compensated scintillator material
Assignee: General Electric Co
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Filing: 1991-05-24
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Granted: —
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Expires: 2011-05-24
Abstract
Abstract Afterglow in a luminescent material in which a significant factor in afterglow is the release of holes from hole traps in the scintillator material is substantially reduced by adding a hole-trapping species to the scintillator composition which successfully competes with the hole traps in the basic scintillator composition. In gadolinium gallium garnet activated with chromium, the addition of cerium, terbium or praseodymium reduces afterglow in this manner.
Inventors
- 👤 Veneta George Tsoukala
- 👤 Charles David Greskovich
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-25 00:44
CPC Classifications
G; G01; G01T; G01T1/00; G01T1/16; G01T1/20; G01T1/202; G01T1/2023; C; C04; C04B; C04B35/00; C04B35/01; C04B35/622; C04B35/64; C04B35/645; C04B35/6455; C09; C09K; C09K11/00; C09K11/08; C09K11/77; C09K11/7766; C09K11/7776; C04B2235/00; C04B2235/02; C04B2235/30; C04B2235/32; C04B2235/3224; C04B2235/3229; C04B2235/3231; C04B2235/3241; C04B2235/3286; C04B2235/60; C04B2235/604; C04B2235/65; C04B2235/656; C04B2235/6562; C04B2235/658; C04B2235/6583; C04B2235/6585; C04B2235/6587; C04B2235/66; C04B2235/661; C04B2235/662; C04B2235/663; C04B2235/70; C04B2235/74; C04B2235/76; C04B2235/762; C04B2235/764; C04B2235/96; C04B2235/9646; C04B2235/9653
Claims Analysis
Total Claims: 63
Claim 1
Independent Claim
155 words
An enhanced crystalline garnet scintillator having significantly reduced luminescent afterglow comprising: a basic, crystalline, garnet-structure scintillator composition which luminesces with a basic scintillator light output intensity in response to a given intensity of stimulating radiation and exhibits afterglow which is a reference percentage of said basic scintillator light output intensity at a given time after the cessation of said stimulation, said afterglow being at least partially a result of radiative recombination of holes released from traps after said cessation of said stimulation; and a hole trapping species distributed in said basic scintillator composition in a concentration which is effective to cause said enhanced scintillator to exhibit afterglow which, at said given time after cessation of stimulation by said given intensity of said stimulating radiation, is less than one half of said reference percentage of the light output intensity produced by said enhanced scintillator in response to stimulation by said given intensity of said stimulating radiation.
Claim 2
Dependent Claim
155 words
An enhanced crystalline garnet scintillator having significantly reduced luminescent afterglow comprising: a basic, crystalline, garnet-structure scintillator composition which luminesces with a basic scintillator light output intensity in response to a given intensity of stimulating radiation and exhibits afterglow which is a reference percentage of said basic scintillator light output intensity at a given time after the cessation of said stimulation, said afterglow being at least partially a result of radiative recombination of holes released from traps after said cessation of said stimulation; and a hole trapping species distributed in said basic scintillator composition in a concentration which is effective to cause said enhanced scintillator to exhibit afterglow which, at said given time after cessation of stimulation by said given intensity of said stimulating radiation, is less than one half of said reference percentage of the light output intensity produced by said enhanced scintillator in response to stimulation by said given intensity of said stimulating radiation.
Claim 3
Dependent Claim
25 words
The enhanced scintillator recited in claim 1 wherein: said hole trapping species exhibits a faster thermallization rate than hole traps of said basic scintillator composition.
Claim 4
Dependent Claim
37 words
The enhanced scintillator recited in claim 1 wherein: said basic scintillator composition comprises a host composition to which an activator species is added to provide efficient luminescence; and said activator and said hole trapping species are different.
Claim 5
Dependent Claim
20 words
The enhanced scintillator recited in claim 3 wherein: said host composition in its pure form is at most weakly luminescent.
Claim 6
Dependent Claim
24 words
The enhanced scintillator recited in claim 4 wherein: said hole trapping species is capable of functioning as a luminescent activator in said host composition.
Claim 7
Dependent Claim
34 words
The enhanced scintillator recited in claim 5 wherein: said enhanced scintillator does not emit significant luminescent light at the frequency at which said host composition luminesces when activated by said hole trapping species alone.
Claim 8
Dependent Claim
26 words
The enhanced scintillator recited in claim 6 wherein: the output spectrum of said enhanced scintillator is free of emission lines associated with said hole trapping species.
Claim 9
Dependent Claim
13 words
The enhanced scintillator recited in claim 3 wherein: said enhanced scintillator is polycrystalline.
Claim 10
Dependent Claim
13 words
The enhanced scintillator recited in claim 8 wherein: said enhanced scintillator is transparent.
Claim 11
Dependent Claim
24 words
The enhanced scintillator recited in claim 3 wherein: said host composition comprises a garnet crystal structure solid solution and said activator species comprises chromium.
Claim 12
Dependent Claim
26 words
The enhanced scintillator recited in claim 10 wherein: said hole trapping species is selected from the group consisting of cerium, terbium and praseodymium and mixtures thereof.
Claim 13
Dependent Claim
14 words
The enhanced scintillator recited in claim 11 wherein: said hole trapping species is cerium.
Claim 14
Dependent Claim
54 words
The enhanced scintillator recited in claim 3 wherein: said host composition is a garnet-crystal-structure solid solution selected from the group consisting of gadolinium gallium garnet, gadolinium scandium gallium garnet, gadolinium scandium aluminum garnet and yttrium aluminum garnet and mixtures thereof; and said activator species is selected from the group consisting of chromium, cerium, neodymium.
Claim 15
Dependent Claim
26 words
The enhanced scintillator recited in claim 13 wherein: said hole trapping species is selected from the group consisting of cerium, terbium and praseodymium and mixtures thereof.
Claim 16
Dependent Claim
14 words
The enhanced scintillator recited in claim 14 wherein: said hole trapping species is cerium.
Claim 17
Dependent Claim
12 words
The enhanced scintillator recited in claim 15 wherein: said activator is chromium.
Claim 18
Dependent Claim
13 words
The enhanced scintillator recited in claim 16 wherein: said enhanced scintillator is polycrystalline.
Claim 19
Dependent Claim
13 words
The enhanced scintillator recited in claim 17 wherein: said enhanced scintillator is transparent.
Claim 20
Dependent Claim
12 words
The enhanced scintillator recited in claim 14 wherein: said activator is chromium.
Claim 21
Dependent Claim
86 words
A enhanced scintillator comprising: a basic garnet solid solution scintillator composition which exhibits relatively high afterglow as a result of the emptying of hole traps in the basic scintillator composition following a cessation of stimulation; a hole trapping species present in a concentration which is effective to reduce the afterglow-inducing effect of emptying of hole traps in said enhanced scintillator composition after the cessation of stimulation by at least 50% from the afterglow level of said basic scintillator composition; and said scintillator being crystalline in structure.
Claim 22
Dependent Claim
86 words
A enhanced scintillator comprising: a basic garnet solid solution scintillator composition which exhibits relatively high afterglow as a result of the emptying of hole traps in the basic scintillator composition following a cessation of stimulation; a hole trapping species present in a concentration which is effective to reduce the afterglow-inducing effect of emptying of hole traps in said enhanced scintillator composition after the cessation of stimulation by at least 50% from the afterglow level of said basic scintillator composition; and said scintillator being crystalline in structure.
Claim 23
Dependent Claim
27 words
The enhanced scintillator recited in claim 20 wherein: said hole-trapping species exhibits a faster trap thermallization rate than the trap thermallization rate of the basic scintillator composition
Claim 24
Dependent Claim
36 words
The enhanced scintillator recited in claim 20 wherein: said basic scintillator composition comprises a host composition to which an activator species is added to provide luminescence; and said activator and said hole trapping species are different.
Claim 25
Dependent Claim
20 words
The enhanced scintillator recited in claim 22 wherein: said host composition in its pure form is, at most, weakly luminescent.
Claim 26
Dependent Claim
24 words
The enhanced scintillator recited in claim 23 wherein: said hole trapping species is capable of functioning as a luminescent activator in said host composition.
Claim 27
Dependent Claim
13 words
The enhanced scintillator recited in claim 20 wherein: said enhanced scintillator is polycrystalline.
Claim 28
Dependent Claim
13 words
The enhanced scintillator recited in claim 25 wherein: said enhanced scintillator is transparent.
Claim 29
Dependent Claim
63 words
A enhanced scintillator comprising: gadolinium oxide; gallium oxide; chromium oxide in a concentration which is effective to render said enhanced scintillator luminescent in response to stimulating radiation; and cerium oxide in a concentration which is effective to reduce the afterglow level of said enhanced scintillator relative to the afterglow level in the absence of cerium; said enhanced scintillator having a garnet crystal structure.
Claim 30
Dependent Claim
63 words
A enhanced scintillator comprising: gadolinium oxide; gallium oxide; chromium oxide in a concentration which is effective to render said enhanced scintillator luminescent in response to stimulating radiation; and cerium oxide in a concentration which is effective to reduce the afterglow level of said enhanced scintillator relative to the afterglow level in the absence of cerium; said enhanced scintillator having a garnet crystal structure.
Claim 31
Dependent Claim
13 words
The enhanced scintillator recited in claim 27 wherein: said enhanced scintillator is polycrystalline.
Claim 32
Dependent Claim
13 words
The enhanced scintillator recited in claim 28 wherein: said enhanced scintillator is transparent.
Claim 33
Dependent Claim
66 words
A enhanced scintillator comprising: gadolinium gallium garnet; chromium in a concentration in said garnet which is effective to render said enhanced scintillator luminescent in response to stimulating radiation; and one or more hole trapping species in a concentration in said garnet which is effective to reduce the afterglow level relative to the afterglow level of said enhanced scintillator in the absence of said hole trapping species.
Claim 34
Dependent Claim
66 words
A enhanced scintillator comprising: gadolinium gallium garnet; chromium in a concentration in said garnet which is effective to render said enhanced scintillator luminescent in response to stimulating radiation; and one or more hole trapping species in a concentration in said garnet which is effective to reduce the afterglow level relative to the afterglow level of said enhanced scintillator in the absence of said hole trapping species.
Claim 35
Dependent Claim
26 words
The enhanced scintillator recited in claim 30 wherein: said hole trapping species is selected from the group consisting of cerium, terbium and praseodymium and mixtures thereof.
Claim 36
Dependent Claim
14 words
The enhanced scintillator recited in claim 31 wherein: said hole trapping species comprises cerium.
Claim 37
Dependent Claim
15 words
The enhanced scintillator recited in claim 32 wherein: said hole trapping species consists of cerium.
Claim 38
Dependent Claim
37 words
The enhanced scintillator recited in claim 30 wherein: said chromium is present in said gadolinium gallium garnet in a concentration equivalent to chromium oxide being between 0.05 and 1.0 weight percent of the overall enhanced scintillator composition.
Claim 39
Dependent Claim
16 words
The enhanced scintillator recited in claim 34 wherein: said weight percent is between 0.1 and 0.6.
Claim 40
Dependent Claim
14 words
The enhanced scintillator recited in claim 35 wherein: said hole trapping species comprises cerium.
Claim 41
Dependent Claim
25 words
The enhanced scintillator recited in claim 36 wherein said cerium is present in said gadolinium gallium garnet in a concentration of less than 0.2 wt%.
Claim 42
Dependent Claim
28 words
The enhanced scintillator recited in claim 37 wherein: said cerium is present at a concentration of between 0.005 and 0.15 weight percent of the overall enhanced scintillator composition.
Claim 43
Dependent Claim
18 words
The enhanced scintillator recited in claim 36 wherein: said weight percent of cerium is between 0.01 and 0.15.
Claim 44
Dependent Claim
18 words
The enhanced scintillator recited in claim 34 wherein: said chromium oxide weight percent is between 0.1 and 0.6.
Claim 45
Dependent Claim
39 words
The enhanced scintillator recited in claim 40 wherein: said hole trapping species comprises cerium present in said gadolinium gallium garnet in a concentration equivalent to cerium being between 0.005 and 0.2 weight percent of the overall enhanced scintillator composition.
Claim 46
Dependent Claim
18 words
The enhanced scintillator recited in claim 41 wherein: said weight percent of cerium is between 0.01 and 0.1.
Claim 47
Dependent Claim
15 words
The enhanced scintillator recited in claim 31 wherein: said enhanced scintillator is crystalline in structure.
Claim 48
Dependent Claim
13 words
The enhanced scintillator recited in claim 43 wherein: said enhanced scintillator is polycrystalline.
Claim 49
Dependent Claim
13 words
The enhanced scintillator recited in claim 44 wherein: said enhanced scintillator is transparent.
Claim 50
Dependent Claim
63 words
A enhanced scintillator comprising: gadolinium gallium garnet; chromium in a concentration equivalent to chromium oxide being between 0.05 and 1.0 weight percent of the overall enhanced scintillator composition; and a hole trapping species present in said gadolinium gallium garnet in a concentration equivalent to an of said hole trapping species being between 0.005 and 0.15 weight percent of the overall enhanced scintillator composition.
Claim 51
Dependent Claim
63 words
A enhanced scintillator comprising: gadolinium gallium garnet; chromium in a concentration equivalent to chromium oxide being between 0.05 and 1.0 weight percent of the overall enhanced scintillator composition; and a hole trapping species present in said gadolinium gallium garnet in a concentration equivalent to an of said hole trapping species being between 0.005 and 0.15 weight percent of the overall enhanced scintillator composition.
Claim 52
Dependent Claim
33 words
The enhanced scintillator recited in claim 46 wherein: said hole trapping species is cerium in a concentration equivalent to cerium being between 0.01 and 0.1 weight percent of the overall enhanced scintillator composition.
Claim 53
Dependent Claim
61 words
A enhanced scintillator consisting substantially of: a gadolinium gallium garnet solid solution having a garnet crystal structure; chromium in a concentration equivalent to chromium oxide being between 0.05 and 0.1 weight percent of the overall enhanced scintillator composition; and cerium present in said gadolinium gallium garnet in a concentration between 0.005 and 0.15 weight percent of the overall enhanced scintillator composition.
Claim 54
Dependent Claim
61 words
A enhanced scintillator consisting substantially of: a gadolinium gallium garnet solid solution having a garnet crystal structure; chromium in a concentration equivalent to chromium oxide being between 0.05 and 0.1 weight percent of the overall enhanced scintillator composition; and cerium present in said gadolinium gallium garnet in a concentration between 0.005 and 0.15 weight percent of the overall enhanced scintillator composition.
Claim 55
Dependent Claim
13 words
The enhanced scintillator recited in claim 48 wherein: said enhanced scintillator is polycrystalline.
Claim 56
Dependent Claim
13 words
The enhanced scintillator recited in claim 49 wherein: said enhanced scintillator is transparent.
Claim 57
Dependent Claim
46 words
A enhanced scintillator whose luminescent properties are provided by the presence therein of a chromium and cerium containing, gadolinium and gallium based solid solution having a garnet crystal structure; said chromium and cerium being present in a chromium to cerium weight ratio between 0.7 and 31.
Claim 58
Dependent Claim
46 words
A enhanced scintillator whose luminescent properties are provided by the presence therein of a chromium and cerium containing, gadolinium and gallium based solid solution having a garnet crystal structure; said chromium and cerium being present in a chromium to cerium weight ratio between 0.7 and 31.
Claim 59
Dependent Claim
13 words
The enhanced scintillator recited in claim 51 wherein: said enhanced scintillator is polycrystalline.
Claim 60
Dependent Claim
13 words
The enhanced scintillator recited in claim 52 wherein: said enhanced scintillator is transparent.
Claim 61
Dependent Claim
34 words
In a computed tomography machine of the type having a solid state scintillator, the improvement comprising: said solid state scintillator being a garnet crystal structure solid solution comprising gadolinium, gallium, chromium, cerium and oxygen.
Claim 62
Dependent Claim
34 words
In a computed tomography machine of the type having a solid state scintillator, the improvement comprising: said solid state scintillator being a garnet crystal structure solid solution comprising gadolinium, gallium, chromium, cerium and oxygen.
Claim 63
Dependent Claim
28 words
The improvement recited in claim 54 wherein: said solid solution is a doped gadolinium gallium garnet including one of more of aluminum, yttrium, zirconium, hafnium, praseodymium and ytterbium.
References Cited (Backward Citations)
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