Patent US3609362A successfully refreshed from Google Patents.
US3609362A
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US
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Error correction in radioactive sample measurements
Assignee: Nuclear Chicago Corp
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Filing: 1968-02-08
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Granted: 1971-09-28
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Expires: 1988-02-08
Abstract
Abstract A liquid scintillation counting system with provision for measuring the efficiency correction of each primary sample measurement without intervening change of transducer gain is also provided with frequent standardization of transducer gain to eliminate efficiency change due to gain change from both the primary measurement and the efficiency correction measurement. Gain measurement and correction are made by circuits comparing the cumulative differential count on opposite sides of a standard alpha-particle spectrum peak with limit values numerically increased in successively longer portions of the counting interval. Gain correction is made in accordance with statistically probable gain error, and the counting interval is reinitiated. Particular circuits are described.
Inventors
- 👤 Barton H Laney
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 11:41
CPC Classifications
G; G01; G01T; G01T1/00; G01T1/16; G01T1/20; G01T1/204
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
284 words
In an automatic liquid scintillation counting system having: a. a chamber containing a photomultiplier transducer adapted to produce electrical pulses of an amplitude spectrum corresponding to scintillation intensities, such correspondence shifting with slow drifts in gain of the transducer, b. means to insert and remove samples to be measured, the samples comprising bodies of liquid scintillator of varying quench with radioactive material therein, c. means to count transducer output pulses of at least one selected amplitude range corresponding to a portion of the energy spectrum To measure the activity in each sample, and d. means to produce an efficiency correction count of at least one selected amplitude range of transducer output produced with the sample in the chamber and indicative of efficiency of the measurement count, each correction count and the corresponding measurement count being produced in sufficient time contiguity to assure the same transducer gain, the improved construction comprising: e. a standard source of light scintillations, f. means for interrupting the measurement and correction of samples and inserting only the standard source into the chamber at intervals substantially shorter than the time required for gain drift substantially affecting the efficiency of counting of unquenched samples, g. means for detecting shifts of the spectrum of transducer output pulses produced in response to the standard source from a standard spectrum, of a magnitude too small to substantially affect the efficiency of counting of unquenched samples, and h. means responsive to the detection of such shift to alter the transducer gain to restore the standard spectrum, and thereupon to resume the measurement and efficiency correction of samples, so that efficiency changes due to gain changes are substantially entirely eliminated from the correction indication on quenched samples.
Claim 2
Dependent Claim
284 words
In an automatic liquid scintillation counting system having: a. a chamber containing a photomultiplier transducer adapted to produce electrical pulses of an amplitude spectrum corresponding to scintillation intensities, such correspondence shifting with slow drifts in gain of the transducer, b. means to insert and remove samples to be measured, the samples comprising bodies of liquid scintillator of varying quench with radioactive material therein, c. means to count transducer output pulses of at least one selected amplitude range corresponding to a portion of the energy spectrum To measure the activity in each sample, and d. means to produce an efficiency correction count of at least one selected amplitude range of transducer output produced with the sample in the chamber and indicative of efficiency of the measurement count, each correction count and the corresponding measurement count being produced in sufficient time contiguity to assure the same transducer gain, the improved construction comprising: e. a standard source of light scintillations, f. means for interrupting the measurement and correction of samples and inserting only the standard source into the chamber at intervals substantially shorter than the time required for gain drift substantially affecting the efficiency of counting of unquenched samples, g. means for detecting shifts of the spectrum of transducer output pulses produced in response to the standard source from a standard spectrum, of a magnitude too small to substantially affect the efficiency of counting of unquenched samples, and h. means responsive to the detection of such shift to alter the transducer gain to restore the standard spectrum, and thereupon to resume the measurement and efficiency correction of samples, so that efficiency changes due to gain changes are substantially entirely eliminated from the correction indication on quenched samples.
Claim 3
Dependent Claim
95 words
The system of claim 1 characterized by the means for detecting shifts of the spectrum comprising: j. means for initiating and registering a differential count from the time of initiation of two portions of the spectrum of the standard source which are of equal average rate in the standard spectrum, k. means for comparing the registered value at least once in each of a plurality of successively longer stages of counting with limiting values increasing in absolute value with lapse of time in approximate proportion to the standard deviation of an average zero differential count,
Claim 4
Dependent Claim
28 words
The system of claim 2 characterized by: n. the amount of each gain alteration decreasing with advancement of the stage of counting at which the detection is made.
Claim 5
Dependent Claim
140 words
A comparator for comparing average rates of occurrence in two pulse train signals at least one of which is of statistically random interval distribution, comprising: a. means for initiating a predetermined counting interval and continuously registering the differential count from the time of initiation thereof, b. means for comparing the registered value, at least at a plurality of intervals as the count proceeds, with limiting values increasing in absolute value, but at a rate substantially less than proportional to the lapse of time, c. means for producing a first output indication signalling inequality of average rates upon reaching by the registered value of a limiting value with which comparison is then made, and d. means for producing a second output indication signalling substantial equality of average rates upon completion of the counting interval without production of the first output indication.
Claim 6
Dependent Claim
140 words
A comparator for comparing average rates of occurrence in two pulse train signals at least one of which is of statistically random interval distribution, comprising: a. means for initiating a predetermined counting interval and continuously registering the differential count from the time of initiation thereof, b. means for comparing the registered value, at least at a plurality of intervals as the count proceeds, with limiting values increasing in absolute value, but at a rate substantially less than proportional to the lapse of time, c. means for producing a first output indication signalling inequality of average rates upon reaching by the registered value of a limiting value with which comparison is then made, and d. means for producing a second output indication signalling substantial equality of average rates upon completion of the counting interval without production of the first output indication.
Claim 7
Dependent Claim
26 words
The comparator of claim 4 wherein the limiting values increase in approximate proportion to the square root of the time from initiation of the differential count.
Claim 8
Dependent Claim
14 words
The comparator of claim 5 having means to indicate the sign of the differential.
Claim 9
Dependent Claim
31 words
The comparator of claim 6 wherein the first output indication means indicates the portion of the counting interval wherein the limit was reached, whereby the probable magnitude of inequality is indicated.
Claim 10
Dependent Claim
131 words
Apparatus for standardizing a control variable of radioactivity measuring systems anD the like comprising, in combination with the comparator of claim 7: e. means for producing and feeding to the comparator pulse trains having equal average rates of occurrence in a standard condition of the variable to be controlled, at least one being of random time distribution, and at least one being of average rate responsive to the variable to be controlled, f. and means responsive to each operation of said first output indication means to adjust the variable in the direction to eliminate the differential, by an amount responsive to the portion of the interval wherein the limit is reached, and to reset the registering means and thereupon commence a new counting interval, until the second output indication is produced.
Claim 11
Dependent Claim
30 words
The control system of claim 8 wherein the amount of the adjustment approximately corresponds to the probable error of the variable indicated by the portion wherein the limit is reached.
Claim 12
Dependent Claim
150 words
The control system of claim 8 wherein the means to adjust the variable comprises a plural stage binary pulse register having each binary stage coupled to the variable to produce, in corresponding states, increments of the variable each of a magnitude approximately twice that of the preceding stage, means responsive to the first output indication to transmit a pulse to one of the binary register stages selected in response to the indication of the portion of the counting interval wherein the limit was so reached, being a highest order stage when the output indication is received in the first portion of the interval and a lowest order stage when the output indication is received in the last portion of the interval, and means responsive to the direction in which the differential count exceeds the limit to selectively condition the binary register for addition or subtraction of the pulse so transmitted.
Claim 13
Dependent Claim
42 words
The control system of claim 10 wherein the limits established in successive portions of the interval, together with the lengths thereof, produce probable magnitudes of inequality of average rates corresponding to probable errors of the variable varying by successive factors of one-half.
Claim 14
Dependent Claim
83 words
Apparatus including the comparator of claim 4 for standardizing the response of a radioactivity transducer system comprising: a. a source of radioactive disintegration events to which the transducer is responsive, b. means including said comparator for detecting deviation of the response of the transducer system from a standard response, and c. means responsive to each output indication signalling inequality to alter the transducer response in the direction to restore the standard output and to reset the registering means and reinitiate the counting interval.
Claim 15
Dependent Claim
57 words
The apparatus of claim 12 wherein the limiting values with which comparison is made are, at least once in each of a plurality of subintervals of successively greater length, of a numerical value between 2.0 sigma and 3.0 sigma , where sigma is the standard deviation of an average zero differential count at the time of comparison.
Claim 16
Dependent Claim
46 words
The apparatus of claim 13 wherein comparison is made with limits substantially less than 3.0 sigma only during a small fraction of each such subinterval, so that early sensitivity to true inequality is obtained without great increase in the cumulative probability of spurious signalling of inequality.
Claim 17
Dependent Claim
35 words
The apparatus of claim 14 wherein the comparison is made continuously and the numerical limits are changed stepwise to make the limits less than 3.0 sigma only for a short time prior to each change.
Claim 18
Dependent Claim
18 words
The apparatus of claim 15 wherein each stepwise change in limits is by a factor greater than 1.5.
Claim 19
Dependent Claim
34 words
The control system of claim 9 wherein the adjustment corresponds to the error of the variable producing a mean differential counting rate reaching the limit at the end of said portion of the interval.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-09-27 | 1975-03-29 | 1975-09-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-09-27 | 1979-03-29 | 1979-09-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-09-27 | 1983-03-29 | 1983-09-28 | $7700.00 | Window Closed / Lapsed |