US3790784A
Expired / Lapsed
US
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Method and apparatus for treating thermoluminescent dosimeters during read-out to enable their immediate reuse
Assignee: Isotopes Inc
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Filing: 1972-06-06
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Granted: 1974-02-05
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Expires: 1992-06-06
Abstract
Abstract A method and apparatus for treating thermoluminescent dosimeters to enable read-out of the dosimeters and to permit their prompt reuse by eliminating the conventional annealing cycle. The dosimeter is initially preheated to a first temperature and is maintained at that temperature for a predetermined time. The dosimeter is then heated to a second read-out temperature and is maintained at the read-out temperature for a selected time interval. The dosimeter is then immediately heated further to an annealing temperature which is maintained for a selected interval, followed by cooling of the dosimeter whereby the dosimeter can again be promptly reused for accurately determining radiation dosage without the necessity of subjecting the dosimeter to the conventional and lengthy annealing cycle.
Inventors
- 👤 G Webb
- 👤 H Phykitt
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 07:43
CPC Classifications
G; G01; G01T; G01T1/00; G01T1/02; G01T1/10; G01T1/11; G01T1/115
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
127 words
A method of treating thermoluminescent dosimeters to enable reading of the dosimeters and to permit prompt reuse of the dosimeters, comprising the steps of: heating a dosimeter to a predetermined first temperature; maintaining the dosimeter at said first temperature for a predetermined first time interval; heating the dosimeter to a predetermined second temperature; maintaining the dosimeter at said second temperature for a predetermined second time interval; immediately increasing the temperature of the dosimeter from said second temperature to a predetermined third temperature after said second time interval to anneal the dosimeter; maintaining the dosimeter at said third annealing temperature for a predetermined third time interval; and cooling the dosimeter to a predetermined fourth temperature whereby the dosimeter can again be promptly reused for accurately determining radiation dosage.
Claim 2
Independent Claim
127 words
A method of treating thermoluminescent dosimeters to enable reading of the dosimeters and to permit prompt reuse of the dosimeters, comprising the steps of: heating a dosimeter to a predetermined first temperature; maintaining the dosimeter at said first temperature for a predetermined first time interval; heating the dosimeter to a predetermined second temperature; maintaining the dosimeter at said second temperature for a predetermined second time interval; immediately increasing the temperature of the dosimeter from said second temperature to a predetermined third temperature after said second time interval to anneal the dosimeter; maintaining the dosimeter at said third annealing temperature for a predetermined third time interval; and cooling the dosimeter to a predetermined fourth temperature whereby the dosimeter can again be promptly reused for accurately determining radiation dosage.
Claim 3
Dependent Claim
42 words
A method as in claim 1 further including the step of measuring the light emissions of the dosimeter during the temperature rise of the dosimeter from the first to the second temperature and while the dosimeter is maintained at said second temperature.
Claim 4
Dependent Claim
38 words
A method as in claim 1 wherein the dosimeter is heated to said first temperature at a predetermined first heating rate and wherein the dosimeter is also heated to said second temperature at a predetermined second heating rate.
Claim 5
Dependent Claim
21 words
A method as in claim 3 wherein the dosimeter is heated to said annealing temperature at a predetermined third heating rate.
Claim 6
Dependent Claim
20 words
A method as in claim 4 wherein the dosimeter is cooled to said fourth temperature at a predetermined cooling rate.
Claim 7
Dependent Claim
33 words
A method as in claim 5 for treating lithium fluoride, lithium borate (manganese) or calcium sulphate (dysprosium) wherein the first tempErature is within the range of about 120* C to about 150* C.
Claim 8
Dependent Claim
18 words
A method as in claim 6 wherein the dosimeter is maintained at said first temperature for 8 seconds.
Claim 9
Independent Claim
33 words
A method as in cliam 5 for treating lithium fluoride, lithium borate (manganese) or calcium sulphate (dysprosium) wherein the second temperature is within the range of about 265* C to about 275* C.
Claim 10
Independent Claim
33 words
A method as in cliam 5 for treating lithium fluoride, lithium borate (manganese) or calcium sulphate (dysprosium) wherein the second temperature is within the range of about 265* C to about 275* C.
Claim 11
Dependent Claim
18 words
A method as in claim 8 wherein the dosimeter is maintained at said second temperature for 8 seconds.
Claim 12
Dependent Claim
33 words
A method as in claim 5 for treating lithium fluoride, lithium borate (manganese) or calcium sulphate (dysprosium) wherein the annealing temperature is within the range of about 300* C to about 310* C.
Claim 13
Dependent Claim
20 words
A method as in claim 10 wherein the dosimeter is maintained at said annealing temperature for 18 to 20 seconds.
Claim 14
Dependent Claim
33 words
A method as in claim 5 for treating lithium fluoride, lithium borate (manganese) or calcium sulphate (dysprosium) wherein the fourth temperature is within the range of about 100* C to about 120* C.
Claim 15
Dependent Claim
17 words
A method as in claim 5 wherein said first heating rate is about 30* C per second.
Claim 16
Dependent Claim
17 words
A method as in claim 5 wherein said second heating rate is about 30* C per second.
Claim 17
Dependent Claim
17 words
A method as in claim 5 wherein said third heating rate is about 30* C per second.
Claim 18
Dependent Claim
36 words
A method as in claim 5 wherein the mean of said cooling rate is about 10* C per second with a maximum cooling rate of about 25* C per second from 300* C to 200* C.
Claim 19
Dependent Claim
23 words
A method as in claim 1 wherein said cooling step includes passing nitrogen gas over the dosimeter to aid cooling of the dosimeter.
Claim 20
Dependent Claim
21 words
A method as in claim 17 wherein the nitrogen is passed over the dosimeter at a flow rate of 7 S.C.F.H.
Claim 21
Dependent Claim
134 words
Apparatus for treating thermoluminescent dosimeters to enable reading of the dosimeters and to permit prompt reuse of the dosimeters, comprising: a dosimeter heating element for receiving and heating the dosimeters; a heat detector remotely positioned with respect to said heating element for sensing the temperature of said element; feedback and comparator means in circuit with said heating element and said heat detector for enabling accurate control of the temperature of said heating element; sequencer and reference program means in circuit with said feedback and comparator means for sequentially controlling the temperature of said heating element in accordance with a predetermined program; and means in operative relationship with said heating element for receiving light energy from a dosimeter heated by said element and for displaying information with respect to the irradiated condition of said dosimeter.
Claim 22
Dependent Claim
134 words
Apparatus for treating thermoluminescent dosimeters to enable reading of the dosimeters and to permit prompt reuse of the dosimeters, comprising: a dosimeter heating element for receiving and heating the dosimeters; a heat detector remotely positioned with respect to said heating element for sensing the temperature of said element; feedback and comparator means in circuit with said heating element and said heat detector for enabling accurate control of the temperature of said heating element; sequencer and reference program means in circuit with said feedback and comparator means for sequentially controlling the temperature of said heating element in accordance with a predetermined program; and means in operative relationship with said heating element for receiving light energy from a dosimeter heated by said element and for displaying information with respect to the irradiated condition of said dosimeter.
Claim 23
Dependent Claim
29 words
Apparatus as in claim 19 wherein said heating element is covered over a predetermined area thereof with a black coating and wherein said heat detector is an infra-red detector.
Claim 24
Dependent Claim
37 words
Apparatus as in claim 20 further including a second infra-red detector positioned to sense the ambient temperature adjacent said first detector and compensating means in circuit with said second detector for compensating for changes in ambient temperature.
Claim 25
Dependent Claim
57 words
Apparatus as in claim 19 wherein said display means include: a photomultiplier positioned to receive light energy from a dosimeter positioned on said heating element; converter means in circuit with said photomultiplier to convert an output signal from said photomultiplier to a pulse-train signal; and a display element coupled to said converter means for displaying said information.
Claim 26
Dependent Claim
42 words
Apparatus as in claim 19 further including a light source positioned to direct light onto said light receiving means and means in circuit with said light source for selectively illuminating said light source and for selectively enabling calibration of said display means.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-02-04 | 1977-08-06 | 1978-02-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-02-04 | 1981-08-06 | 1982-02-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-02-04 | 1985-08-06 | 1986-02-05 | $7700.00 | Window Closed / Lapsed |