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US 4,029,401 AGranted
Automatic quench compensation for liquid scintillation counting system
AssigneeBeckman Instruments, Inc.
InventorRoy E. Nather
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AssigneeBeckman Instruments, Inc.
InventorRoy E. Nather
Estimating the term…
A method is provided for automatically compensating liquid scintillation systems for efficiently counting samples of varying quench by establishing the amount of change of a system parameter such as gain required to restore the sample spectrum to be counted in at least one counting window to the proper counting window discriminator levels as a non-linear function of the change in a measure of quench. The degree of quench may be measured on each of the samples prior to counting, for instance by the external-standard channels-ratio method, and the system parameter automatically adjusted to restore the spectrum to the proper window or windows. Implementing circuitry shown includes a digital-to-analog converter and non-linear network which can be calibrated by using the endpoint of a known least quenched sample to establish the base gain and a reference standard and using a known, highly quenched sample to establish another point on the gain vs. external-standard curve to establish the slope, so that when the external-standard ratio is set into it the amount of gain restoration required appears as an output.
A method of automatically compensating for spectral shift due to quench in a liquid scintillation nuclear counter having an adjustable and voltage-controllable parameter to which the alignment of the spectral energy end-point of an isotope with a selected discriminator level is responsive, wherein the counter has at least one energy level counting window, a computer, and a digital-to-analog converter for producing an output voltage proportional to the difference between a reference input and a sample input thereto, said method comprising the steps of:
Apparatus for optimizing counting conditions in test samples containing n radioactive isotopes disposed in a liquid scintillator with each isotope being of the type that produces an observable energy spectrum, said apparatus comprising a light transducer, means for positioning a sample adjacent said transducer in light transmissive relationship therewith, means for measuring a selected quench indicating parameter indicative of the quench level of the sample, n pulse height analyzers for analyzing pulses emanating from said transducer, said n pulse height analyzers each including means for discriminating pulses on the basis of pulse heights, and means responsive to said measured quench indicating parameter for automatically adjusting the operating level of said discriminating means according to the value of said measured parameter.
A method of optimizing counting conditions in test samples containing n radioactive isotopes disposed in a liquid scintillator with each isotope being of the type that produces an observable energy spectrum, said method comprising the steps of positioning a sample adjacent a light transducer in light transmissive relationship therewith, measuring a selected quench indicating parameter indicative of the quench level of the sample, analyzing pulses emanating from said transducer by n pulse height analyzers each including means for discriminating pulses on the basis of pulse heights, and automatically adjusting the operating level of said discriminating means in response to said measured quench indicating parameter and according to the value of said measured parameter.
Apparatus for optimizing counting conditions in test samples containing n radioactive isotopes disposed in a liquid scintillator with each isotope being of the type that produces an observable energy spectrum, said apparatus comprising a light transducer, means for positioning a sample adjacent said transducer in light transmissive relationship therewith, means for measuring a selected quench indicating parameter indicative of the quench level of the sample, n pulse height analyzers for analyzing pulses emanating from said transducer, said n pulse height analyzers each including means for discriminating pulses on the basis of pulse heights, and means for compensating for quench induced shifts in the energy spectrums of the isotopes relative to operating levels of said discriminating means including voltage controllable means for controlling the relationship between an endpoint of the energy spectrum of one or more of the isotopes and the operating level of one or more of the discriminating means and precalibrated means responsive to said measured quench indicating parameter of applying a voltage to said voltage controllable means to automatically restore the relationship of the endpoints of the shifted energy spectrums to the operating levels of the discriminating means.
A method of optimizing counting conditions in test samples containing n radioactive isotopes disposed in a liquid scintillator with each isotope being of the type that produces an observable energy spectrum, said method comprising the steps of positioning a sample adjacent a light transducer in light transmissive relationship therewith, measuring a selected quench indicating parameter indicative of the quench level of the sample, analyzing pulses emanating from said transducer by n pulse height analyzers each including means for discriminating pulses on the basis of pulse heights, and automatically adjusting an endpoint of the energy spectrum of one or more of the isotopes relative to an operating level of one or more of the discriminating means in response to said measured quench indicating parameter and according to the value of said measured parameter.
A method of automatically compensating for spectral shift due to quench in a liquid scintillation nuclear counter having an adjustable and voltage controllable parameter for controlling the relationship between an endpoint of an energy spectrum of an isotope and an operating level of a discriminator defining a counting window for the counter, a comparator for producing an output voltage proportional to a difference between a reference input and a sample input thereto, and a variable gain device coupling the output of said comparator to said voltage controllable parameter, said method comprising:
Dependencies are inferred from the claim text.