CA1249076A - Method and apparatus for indicating quench of a liquid scintillation solution - Google Patents
Method and apparatus for indicating quench of a liquid scintillation solutionInfo
- Publication number
- CA1249076A CA1249076A CA000483557A CA483557A CA1249076A CA 1249076 A CA1249076 A CA 1249076A CA 000483557 A CA000483557 A CA 000483557A CA 483557 A CA483557 A CA 483557A CA 1249076 A CA1249076 A CA 1249076A
- Authority
- CA
- Canada
- Prior art keywords
- pulse height
- solution
- light flashes
- quench
- sample
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Measurement Of Radiation (AREA)
Abstract
METHOD AND APPARATUS FOR INDICATING QUENCH
OF A LIQUID SCINTILLATION SOLUTION
Abstract of the Disclosure A method and apparatus for indicating quench associa-ted with a liquid scintillation solution wherein the solu-tion includes a sample, a solvent and a solute. The method includes exposing the solution to flashes of light, detecting a pulse height spectrum for scintillations pro-duced in the solution in response to the light flashes, determining a unique point on such pulse height spectrum, and relating the unique point to a corresponding pulse height value, such pulse height value providing an indica-tion of quench associated with the solution. The wave-length of light preferably excites essentially only the solvent and the light flash intensity and duration is such that the pulse height spectrum produced in response to the light flashes does not overlap a pulse height spectrum for the sample in the solution. An attribute of the shape of the light pulse height spectrum may be examined to provide an indication of the homogeneous or non-homogeneous nature of the quench present in the solution.
OF A LIQUID SCINTILLATION SOLUTION
Abstract of the Disclosure A method and apparatus for indicating quench associa-ted with a liquid scintillation solution wherein the solu-tion includes a sample, a solvent and a solute. The method includes exposing the solution to flashes of light, detecting a pulse height spectrum for scintillations pro-duced in the solution in response to the light flashes, determining a unique point on such pulse height spectrum, and relating the unique point to a corresponding pulse height value, such pulse height value providing an indica-tion of quench associated with the solution. The wave-length of light preferably excites essentially only the solvent and the light flash intensity and duration is such that the pulse height spectrum produced in response to the light flashes does not overlap a pulse height spectrum for the sample in the solution. An attribute of the shape of the light pulse height spectrum may be examined to provide an indication of the homogeneous or non-homogeneous nature of the quench present in the solution.
Description
~2~
97D-138 ~anada -1-METHOD AND APPARATUS FOR INDICATING QUENC~
OF A LIpUID SCINTILLATION SOLUTION
.
_ackground of the Invention The present invention relates generally to the field of liquid scintillation counting and in particular to an improved method and apparatus for indicating quench of a liquid scintillation solution.
Liquid scinti11atiOn counting techniques are well known for measuring the activity of samples containing radionuclides~ Such a radioactive sample, typically a beta emitterr is dissolved or suspended in a liquid scin-tillation medium. The liquid scintillation medium in turn comprises a solvent or solvents, typically methyl-benzene derivatives, and a solute or solutes present in a few percent by weight of the liquid scintillation medium. It is theorized that most o~ the kinetic energy from the nuclear disintegrations of the radioactive sample is ab-sorbed by the solvent and then transferred to the solute which emits photons as visible light ~lashes or scintilla-tions. The amount of light emitted from a scintillation is proportional to the energy of the corresponding nuclear disintegration.
A liquid scintillation counter measures the relative intensities of scintillations occurring within a liquid scintillation solution. As used herein, a liquid scin-tillation solution means a solution comprising the sample dissolved or suspended within the liquid scintillation medium. Typically, scintillations occurring within the liquid scintillation solution are detected by a suitable photodetector ~hich produces output pulses having pulse heights proportional to the number o~ photons by the cor-responding scintillatlons. The liquid scintillation coun ter counts the pulses in a plurality of pulse hei~ht chan-97D-138 Canada -2-nels or "windows" having upper and lower pulse height limits that together span a predetermined range of pulse heights. The counts accumulated in the windows may be plotted with respect to corresponding pulse heights to provide a pulse height spectrum represen-ting the energy spectrum of the nuclear radiation emitted by the radio-active sample.
It is well known in the liquid scintillation counting art that materials present in the liquid scintillation solution can decrease the number of photons reaching the photodetector for a given nuclear disintegration. For example, the production of photons in the solution may be decreased or emitted photons can be absorbed. Such effects are commonly referred to as "quenching" and in each case result in the reduction in the number of photons detectable by the photodetector. ~ecause quenching de~
creases the number of photons applied to the photodetec-tor, some scintillation events which would be detected in an unquenched sample are below the photodetector detection threshold in a quenched sample. The result is that the number of counts per unit time detected by the photodetec-tor for a quenched sample is decreased as compared with an otherwise identica] unquenched sample. The scintillation count rate detected in a quenched sample as compared with the disinteg~ation rate occurring within the sample is commonly referred to as "counting efficiency".
Quenching acts equally on all events produced by the same type of excitation particle, for example, electron ~beta), alpha, proton, and so on. Thusj if quenching is sufficient to reduce the measured response for one disin-tegration by a given percentage, it will reduce all res-ponses by the same percentage. In a liquid scintillation counter~ quenching results in a shift of the pulse height spectrum detected by the counter to lower pulse height ~ 1 2~D76 97D-138 Canada -3-values, which is commonly referred to as "pulse heightshift".
Continuing efforts in the liquid scintillation art have been directed to measuring quench. Many prior quench determination methods employ an external radiation source, such as a gamma source, which may be positioned so as to irradiate the liquid scintillation solution. A pulse height spectrum of the solution in response to the exter-nal source is used to provide an indication of quench.
Several quench determination methods using an external source are discussed, for example, in U.S. Patent 4,075,480.
When using an external source to determine quench the solution pulse height spectrum in response to the external source radiation obscures or interferes with the pulse height spectrum produced by the sample in the solu-tion. Consequently, it is not possible to simultaneously count sample activity and perform a quench determina-tion. Typically, sample activity is counted during one time period and quench determination is performed during a different time period. In a static liquid scintillation counting system, that is, one where a static or stationary sample is counted, the use of an external standard to determine quench lengthens the amount of time required to measure sample activity corrected for quench.
External standard quench determination me-thods are even less desirable in flow liquid scintillation s~rs-tems. In such systems, a sample in a liquid scintillation medium is flowed through a flow detector. Thus, the quench of the solution may change from the time that sam-ple activity is measured to the time that a quench deter-mlnation is performed, resultin~ in an inaccurate deter-mination of quench. Moreover, sample activit~r data is 9 7 D- 138 Canada -4-lost during the time that quench determination is being performed, a distinct disadvantage where the liquid scin-tillakion solution, including the sample, is continuously flowing through the Elow detector.
Summary of the Inven~ion A method and apparatus in accordance with the present invention overcomes the difficulties and limitations des-cribed above. Such a method and apparatus uniquely and inventively enables the determination of quench at the same time that sample count data is being gathered. Thus, sample activity and quench may be simultaneously deter-mined, an advantage in both static and flowing liquid scintillation counting systems. Moreover, the method and apparatus of the present invention does not require the use of an external radioactive source, thereb~ eliminating structure in liquid scintillation counting systems Eor safely handling such a source.
Toward the foregoing ends, the present invention is directed to generating light 1ashes wherein the light includes a predetermined wavelength selected to excite essentially only the solvent within a liquid scintillation solution, exposing the liquid scintillation solution to such light flashes, detecting a pulse height spectrum for scintillations produced in the solution in response to the light flashes, determining a unique point on the pulse height spectrum, and relating the unique point to a corre-sponding pulse height value, such pulse height value pro-viding a value related to the degree of quench associated with the solution.
In a preferred embodiment disclosed herein, the light is in an ultraviolet wavelength range and the intensity of the light flashes is such that the pulse height spectrum produced in response to the light does not overlap a spec-97D-138 Canada -5-trum produced by the sample in the solution. Thus, sample activity and quench may be simul~aneously determined.
Description of the Drawings Fig. l is a block diagram of an apparatus in accord-ance with the present invention.
Fig. 2 depicts pulse height spectra obtained with the apparatus of Fig. l for varying degrees and types of quench~
Detailed Description of Preferred Embodiment ~ ith reference to Fig. l, an apparatus in accordance with the present invention is shown therein in fùnctional block diagram form. The apparatus of Fig. 1 is adapted to receive a vial 10 within a shielded counting chamber. The vial 10 holds a liquid scintillation solution ll compris-ing a radioactive sample and a conventional liquid scin-tillation medium. A pair of photomultiplier tubes (PMTs) 12 and 14 are arranged to detect and convert scintilla-tions in the solution ll into output voltage pulses, each such pulse having an amplitude proportional to the number of photons produced by the corresponding detected scin-tillation.
In accordance with the present inventionl a flashed or pulsed light source 16 is disposed within the counting chamber. The source 16 is arranged such that light flashes emitted therefrom are directed to and fall upon the solution 11. In the embodiment disclosed herein, the flashed light source emits li~h~ in the ultraviolet wave-length range including, for example~ at 260nm. The wave-length of the light is selected to include 260nm because the solvents in most liquid scintillation mediums absorb light~at 260nm. Thus, the light absorbed by the solvent simulates the start of the same energy transfer mechanism ,~
, 97D-138 Canada -6~
as stimulated by nuclear disintegrations within the sam-ple. sriefly, such mechanism begins either by a beta particle or photons oE light in the flash of light stimu~
lating atoms of the solvent into an excited state. The excited solvent molecules in turn excite the molecules of the solute within the medium and as such solute molecules decay, emit photons. As will be appreciated, the wave-length of the light may be varied according to the absorp-tion characteristi~s of the solvent~
As noted~ most solvents absorb light at 260nm The solute within the medium, however, must not absorb light at the same wavelength as the solvent or absorb light at other wavelengths that may be emitted by the source 16.
Thus, both the light wavelength or range of wavelengths and the medium itself are selected such that essentially only the solvent within the medium, and not the solute, is excited. The light wavelength may be controlled by selec-ting a suitable source having an emission spectrum that excludes wavelengths that would excite the solute or the source 16 may be filtered to obtain the same result. By way of nonlimiting example only, a medium having a solvent that absorbs light at a wavelength of 26~ nm and a solute that does not absorb light of such wavelength may be the solvent 1,2,4-trimethyl benzene and the solutes PPO and M2 -POPOP ~
A flashed light source power supply 18 powers the source 16 and, by adjusting the supply 18, adjusts the duration, intensity and repetition rate of the flashes from the source 16. The duration is limited in minimum length or on time by the intensity of the source 16 and the number of photons emitted by the source 16 per unit time. As will be described further hereinbelow, the mini-mum duration and intensity are selected such that a pulse hei~ht spectrum developed in response to the flashes oE
97D~138 Canada -7-light from the source 16 does not overlap a pulse height spectrum developed for a sample suspended in the medium.
The maximum flash duration is limited such that the inten-sity of a scintillation produced in the medium in response to a 1ash does not exceed the detection capabilities of the liquid scintillation counting apparatus.
Lastly, the repetition rate of the light flashes is de-termined by the number of counts required to adequately define a pulse height spectrum developed in response to the light flashes and may depend on such factors as the len~th of time during which counting takes place and the detected count rate of the radionuclide in the sample.
In the embodiment disclosed herein and by way of nonlimiting example only, the light flash duration may be in a range of about one to ten nanoseconds at a repeti-tion rate of about 1000 flashes per minute. The flashed light source 16 and the flashed light source power supply 18 may be, for example, a Model 510C nanosecond excitation lampl available from Photochemical Research Associates, Inc., of London, Ontario, Canada, and as described in a publication entitled "Fluorescence Lifetime Instrumen-tation" and appearing in a Photochemical Research Associates, Inc.
price list dated January 1, 1981.
It will be recognized that other suitable flashed light sources may be adapted for use with the present invention. For example, a continuous ult~aviolet source may be used with a shutter to provide the required flash duration and repetition rateO Those skilled in the art will readily recognize other forms of flashed light sources which may ~e adapted for use with the apparatus of Fig. 1 97D-138 Canada -8-In the embodimenk disclosed herein, the vial 10 is of quartz glass so as to not absorb the ultraviolet light emitted by the source 16. To shield the PMTs 12 and 14 from such ultraviolet light, the PklTs 12 and 14 are each fitted with a suitable ultraviolet absorbing lens 20 and 22, such as, Pyrex brand ~lass.
The output of each PMT 12 and 14 is applied to a pulse summation and amplifier 24. The pulse summation and amplifier 24 sums the pulses from the PMTs 12 and 14 and ampliEies the sumrned result producing an analog pulse output.
The output of each P~T 12 and 14 is also coupled as an input to a coincidence circuit 26 which produces an output pulse upon receipt of essentially coincident input pulses~ The outputs from the pulse summation and ampli-fier 16 and the coincidence circuit 18 are both applied to an analog gate 28 which passes the analog output from the pulse summation and amplifier 2~ when the output pulse from the coincidence circuit 26 is also received by the gate 28. Thus, when a scintillation event within the solution 11 is detected by the PMTs 12 and 14, the coinci-dent pulses from such PMTs 12 and 14 are summed by the pulse summation and amplifier 24 and are applied to the gate 28. The coincident pulses from the PMTs 12 and 14 are also detected by the coincidence circuit 26 which applies a pulse to the gate 28. In the presence of the output pulse from the coincidence cirtuit 26r the analog output pulse from the pulse summation and amplifier 24 is passed by the gate 2~.
The output of the gate 28 is applied to an analog~to-digital (ADC) logarithmic pulse hei~ht converter 30 which provides a digital output logarithmically proportional to the height of the analog pulse applied thereto. The digi-97D-138 Canada -9 tal output of the ADC pulse height converter 30 is applied to a microprocessor-based control unit 32. The control unit 32 is o~ conventional design and includes a micro-processor and related memory and input-output interface units, all well known in the art, The control unit 3 compares the value of the digital output from the ADC
pulse height converter 30 to a plurality of predetermined values which define a plurality of energy ranges or win-dows together spanning a predetermined energy or pulse height range. According to the value represented by the digital output from the ADC pulse height converter 30, the control unit 32 determines which window the digital value falls within and accordingly increments one storage loca-tion within a pulse height distribution storage area 34.
The pulse height distributin storage area 34 includes a plurality of storage locations corresponding to the win-dows established by the control unit 32. As the liquid scintillation counting process is per-Eormed, the values stored in the various storage locations within the s-torage area 34 together represent a pulse height distribution curveO The storage area 34 may comprise, for example, a portion of the memory accessible to and controlled by the microprocessor within the control unit 32, each storage location within such storage area 34 being cleared or reset prior to the start of a liquid scintillation count-ing procedures.
The liquid scintillation counting system of Fig. 1 further includes a conventional display unit 36 such as a cathode ray tube ~C~T) and a suitable input device such as a keyboard 38. The display unit 36 can display the count rate derived in a particular window or may display a curve graphically showing the pulse height distribution spec-trum.
"~
97D-138 Canada -10-It will be recognized that the PMTs 12 and 14, pulse summation and amplifier 24, coincidence circuit 26, gate 28/ ADC lo~arithmic pulse height converter 30, control unit 32, pulse height distribution storage area 3~, dis play unit 36 and input device 38 are of conventional de~
sign and instruments employing such elements are ~ell known in the liquid scintillation art. Such instru~ents include the Series 5800 and 9800 liquid scintillation counters available from Beckman Instruments, Inc., al~
though those s~illed in the art will recognize other suit-able instruments which may be adapted in accordance with the inventive concepts taught herein.
Turning now to a description of the operation of the apparatus of Fig. 1 and a preferred embodiment of the method of the present invention, the vial 10 is placed into the counting chamber of the apparatus. The flashed light source power supply 18 is activated so as to cause the light source 16 to emit ultraviolet light flashes as described above. The intensity of such light flashes, also controlled by the flashed light power supply 18, is adjusted as described hereinbelow.
With the flashed light source 16 applying light flashes to the solution ll, the apparatus of Fig. 1 begins counting so as to determine pulse height spectra for the solution 11. Each scintillation occurring within the solution ll is detected by the PM~s 12 and 14 which pro-vide coincident pulses to the pulse summation and ampli-fier 24 and the coincidence circuit 26. The pulses are summed and amplified and are applied to the gate 28.
Because the pulses from the P~Ts 12 and 14 are coincident, the gate 28 passes the analog pulse output of the pulse summation and amplifier 24 to the A~C logarithmic pulse height converter 30. The converter 30 converts the analog pulse to a digital representation logarithmically propor-97D-138 Canada tional to the analog pulseO The digital representation is applied to the control unit 32 which compares the digital representation to the pulse height windows. A storage location in the storage area 34 corresponding to the win-dow within which the digital representation falls is then incremented by the control unit 32.
At the end of sorne predetermined counting period, the collected counts in the storage locations may be read by the control unit 32 and displayed as a pulse height spec-trum on the display unit 36.
Pulse height spectra for a typical solution 11 are shown in Fig. 2. A first spectrum 50 illustrates a pulse height spectrum for, for example, a carbon 14 sample in the solution ll. In accordance with the present inven--tion, a second spectrum 52 represents the pulse height spectrum for scintlllations occurring in the solution 11 in response to the flashed light source 16. The number of photons generated by the source 16 during each flash is adjusted by adjusting the supply 1~ such that the spectrum 52 does not overlap the spectrum 5~. In particular, the electrical energy delivered by the power supply 18 during each flash is controlled by means of suitable controls on the power supply 18, all in a conventional fashion, there-by controlling the intensity of the flash and thus the number of photons delivered to the solution ll with each ~lash. The position of the spectrum 52 along the pulse height axis depends upon the number of photons delivered to the solution 11 with each flash. Thus, by selecting an appropriate flash intensity and duration, the spectrum 52 is placed on a portion o~ the pulse height axis such that the spectrum 52 does not overlap the spectrum 50. Because the spectra 50 and 52 do not overlap, both spectra may be simultaneously determined, and, as described more fully ~ ~g~
97D-138 Canada -12-below, both sample activity and quench may be measured simultaneously.
With continued reference to Fig. 2, dashed spectra 5 and 56 represent pulse height shift which occurs in the solution 11 when the solution 11 is quenched~ Although the radioactivity of the sample remains the same and the source 16 con-tinues to generate light flashes as described above, quench in the solution 11 effectively shifts the spectra 50 and 52 to the left, that is, to lower pulse height values as seen by spectra 54 and 56, respectively.
In accordance with the present invention, quench in the solution 11 is advantangeously and uniquely indicated by the shift of the pulse height spectrum generated in response to the light flashes from the source 16. By detecting a unique point on such spectrum and determining a corresponding pulse height value for such point, a value related to the degree of quench in the solution 11 is obtained and such value may be used to provide an indica-tion of the degree of quench. In the embodiment disclosed herein, the unique point on the light pulse height spec-trum is the peak thereof, although other unique points, such as inflection points on the leading or trailing edge of such spectrum, could also be used.
Such inventive concepts are illustrated with refer-ence to Fig. 2. With the solution 11 at a first level or degree of quench, the spectra 50 and 52 are developed.
peak point Pl of the spectrum 52 corresponds to a pulse height value PHa on the pulse height (log energy) axis.
It will be recognized by those skilled in the art that the system of Fig. 1 may automatically select the peak point Pl and the corresponding pulse height value PHa using, for example, the microprocessor within the control unit 32, 97D-13~ Canada 13~
using programming techniques and algorithms that are well known in computer art.
With the degree of quench in the solution 11 increas-ed, the pulse height spectra shift as indicated by spectra 54 and 56. Accordingly, a peak point P2 on the spectrum 56 corresponds to a second pulse height va]ue P~b on the pulse height axis. Both Gf the pulse height values PHa and PHb provide values that are related to the degree of quench present in the solution 11. Moreover, the differ-ence between the pulse height values PHa and PHb provides a quench number which indicates the degree of quench pres-ent in the solution 11 when the spectra 54 and 56 were developed with respect to the degree of quench present in the solution when the spectra 50 and 52 were developed.
Such a quench number may be obtained automatically using, for example, the microprocessor within the control unit 32 and programming techniques well known in the art.
Such a quench number may be used to determine the degree of quench in various solutions with respect to a standard or calibration solution by comparing the pulse height values for the various solutions to a pulse height value obtained for the standard solution. For example, such a standard solution may be essentially unquenched to thus provide quench numbers which relate de~rees of quench in solutions to the essentially unquenched standard solu-tion. Such a quench number may further be used to imple-ment automatic quench compensation in the liquid scintill-ation countin~ system using methods known in the art, such as that disclosed in U.S. Pat. 4,~2~,401~
In accordance with a further aspect of the present invention, an attribute of the shape of the pulse height spectrum ~enerated in response to the flashed li~ht source 16 further provides an indication o~ the nature of ~uench 97D-138 Canada -14-occurring in the solution 11. With continued reference to Fig. 2, the spectrum 56 represents a particular resolu-tion defined as the result obtained by dividing a first value equal to the width of the spectrum 56 expressed in pulse height units by a second value equal to the pulse height value at the maximum point or peak height of the spectrum 56, the width being taken at some predetermined height along the spectrum 56 with respect to the maximum peak height. For example, the resolution of the spectrum 56 at one-half peak height ls the width of the spectrum 56 expressed in pulse height units at one-half of its height, divided by the pulse height value corresponding to the maximum point of the spectrum 56. With reference to Fig.
97D-138 ~anada -1-METHOD AND APPARATUS FOR INDICATING QUENC~
OF A LIpUID SCINTILLATION SOLUTION
.
_ackground of the Invention The present invention relates generally to the field of liquid scintillation counting and in particular to an improved method and apparatus for indicating quench of a liquid scintillation solution.
Liquid scinti11atiOn counting techniques are well known for measuring the activity of samples containing radionuclides~ Such a radioactive sample, typically a beta emitterr is dissolved or suspended in a liquid scin-tillation medium. The liquid scintillation medium in turn comprises a solvent or solvents, typically methyl-benzene derivatives, and a solute or solutes present in a few percent by weight of the liquid scintillation medium. It is theorized that most o~ the kinetic energy from the nuclear disintegrations of the radioactive sample is ab-sorbed by the solvent and then transferred to the solute which emits photons as visible light ~lashes or scintilla-tions. The amount of light emitted from a scintillation is proportional to the energy of the corresponding nuclear disintegration.
A liquid scintillation counter measures the relative intensities of scintillations occurring within a liquid scintillation solution. As used herein, a liquid scin-tillation solution means a solution comprising the sample dissolved or suspended within the liquid scintillation medium. Typically, scintillations occurring within the liquid scintillation solution are detected by a suitable photodetector ~hich produces output pulses having pulse heights proportional to the number o~ photons by the cor-responding scintillatlons. The liquid scintillation coun ter counts the pulses in a plurality of pulse hei~ht chan-97D-138 Canada -2-nels or "windows" having upper and lower pulse height limits that together span a predetermined range of pulse heights. The counts accumulated in the windows may be plotted with respect to corresponding pulse heights to provide a pulse height spectrum represen-ting the energy spectrum of the nuclear radiation emitted by the radio-active sample.
It is well known in the liquid scintillation counting art that materials present in the liquid scintillation solution can decrease the number of photons reaching the photodetector for a given nuclear disintegration. For example, the production of photons in the solution may be decreased or emitted photons can be absorbed. Such effects are commonly referred to as "quenching" and in each case result in the reduction in the number of photons detectable by the photodetector. ~ecause quenching de~
creases the number of photons applied to the photodetec-tor, some scintillation events which would be detected in an unquenched sample are below the photodetector detection threshold in a quenched sample. The result is that the number of counts per unit time detected by the photodetec-tor for a quenched sample is decreased as compared with an otherwise identica] unquenched sample. The scintillation count rate detected in a quenched sample as compared with the disinteg~ation rate occurring within the sample is commonly referred to as "counting efficiency".
Quenching acts equally on all events produced by the same type of excitation particle, for example, electron ~beta), alpha, proton, and so on. Thusj if quenching is sufficient to reduce the measured response for one disin-tegration by a given percentage, it will reduce all res-ponses by the same percentage. In a liquid scintillation counter~ quenching results in a shift of the pulse height spectrum detected by the counter to lower pulse height ~ 1 2~D76 97D-138 Canada -3-values, which is commonly referred to as "pulse heightshift".
Continuing efforts in the liquid scintillation art have been directed to measuring quench. Many prior quench determination methods employ an external radiation source, such as a gamma source, which may be positioned so as to irradiate the liquid scintillation solution. A pulse height spectrum of the solution in response to the exter-nal source is used to provide an indication of quench.
Several quench determination methods using an external source are discussed, for example, in U.S. Patent 4,075,480.
When using an external source to determine quench the solution pulse height spectrum in response to the external source radiation obscures or interferes with the pulse height spectrum produced by the sample in the solu-tion. Consequently, it is not possible to simultaneously count sample activity and perform a quench determina-tion. Typically, sample activity is counted during one time period and quench determination is performed during a different time period. In a static liquid scintillation counting system, that is, one where a static or stationary sample is counted, the use of an external standard to determine quench lengthens the amount of time required to measure sample activity corrected for quench.
External standard quench determination me-thods are even less desirable in flow liquid scintillation s~rs-tems. In such systems, a sample in a liquid scintillation medium is flowed through a flow detector. Thus, the quench of the solution may change from the time that sam-ple activity is measured to the time that a quench deter-mlnation is performed, resultin~ in an inaccurate deter-mination of quench. Moreover, sample activit~r data is 9 7 D- 138 Canada -4-lost during the time that quench determination is being performed, a distinct disadvantage where the liquid scin-tillakion solution, including the sample, is continuously flowing through the Elow detector.
Summary of the Inven~ion A method and apparatus in accordance with the present invention overcomes the difficulties and limitations des-cribed above. Such a method and apparatus uniquely and inventively enables the determination of quench at the same time that sample count data is being gathered. Thus, sample activity and quench may be simultaneously deter-mined, an advantage in both static and flowing liquid scintillation counting systems. Moreover, the method and apparatus of the present invention does not require the use of an external radioactive source, thereb~ eliminating structure in liquid scintillation counting systems Eor safely handling such a source.
Toward the foregoing ends, the present invention is directed to generating light 1ashes wherein the light includes a predetermined wavelength selected to excite essentially only the solvent within a liquid scintillation solution, exposing the liquid scintillation solution to such light flashes, detecting a pulse height spectrum for scintillations produced in the solution in response to the light flashes, determining a unique point on the pulse height spectrum, and relating the unique point to a corre-sponding pulse height value, such pulse height value pro-viding a value related to the degree of quench associated with the solution.
In a preferred embodiment disclosed herein, the light is in an ultraviolet wavelength range and the intensity of the light flashes is such that the pulse height spectrum produced in response to the light does not overlap a spec-97D-138 Canada -5-trum produced by the sample in the solution. Thus, sample activity and quench may be simul~aneously determined.
Description of the Drawings Fig. l is a block diagram of an apparatus in accord-ance with the present invention.
Fig. 2 depicts pulse height spectra obtained with the apparatus of Fig. l for varying degrees and types of quench~
Detailed Description of Preferred Embodiment ~ ith reference to Fig. l, an apparatus in accordance with the present invention is shown therein in fùnctional block diagram form. The apparatus of Fig. 1 is adapted to receive a vial 10 within a shielded counting chamber. The vial 10 holds a liquid scintillation solution ll compris-ing a radioactive sample and a conventional liquid scin-tillation medium. A pair of photomultiplier tubes (PMTs) 12 and 14 are arranged to detect and convert scintilla-tions in the solution ll into output voltage pulses, each such pulse having an amplitude proportional to the number of photons produced by the corresponding detected scin-tillation.
In accordance with the present inventionl a flashed or pulsed light source 16 is disposed within the counting chamber. The source 16 is arranged such that light flashes emitted therefrom are directed to and fall upon the solution 11. In the embodiment disclosed herein, the flashed light source emits li~h~ in the ultraviolet wave-length range including, for example~ at 260nm. The wave-length of the light is selected to include 260nm because the solvents in most liquid scintillation mediums absorb light~at 260nm. Thus, the light absorbed by the solvent simulates the start of the same energy transfer mechanism ,~
, 97D-138 Canada -6~
as stimulated by nuclear disintegrations within the sam-ple. sriefly, such mechanism begins either by a beta particle or photons oE light in the flash of light stimu~
lating atoms of the solvent into an excited state. The excited solvent molecules in turn excite the molecules of the solute within the medium and as such solute molecules decay, emit photons. As will be appreciated, the wave-length of the light may be varied according to the absorp-tion characteristi~s of the solvent~
As noted~ most solvents absorb light at 260nm The solute within the medium, however, must not absorb light at the same wavelength as the solvent or absorb light at other wavelengths that may be emitted by the source 16.
Thus, both the light wavelength or range of wavelengths and the medium itself are selected such that essentially only the solvent within the medium, and not the solute, is excited. The light wavelength may be controlled by selec-ting a suitable source having an emission spectrum that excludes wavelengths that would excite the solute or the source 16 may be filtered to obtain the same result. By way of nonlimiting example only, a medium having a solvent that absorbs light at a wavelength of 26~ nm and a solute that does not absorb light of such wavelength may be the solvent 1,2,4-trimethyl benzene and the solutes PPO and M2 -POPOP ~
A flashed light source power supply 18 powers the source 16 and, by adjusting the supply 18, adjusts the duration, intensity and repetition rate of the flashes from the source 16. The duration is limited in minimum length or on time by the intensity of the source 16 and the number of photons emitted by the source 16 per unit time. As will be described further hereinbelow, the mini-mum duration and intensity are selected such that a pulse hei~ht spectrum developed in response to the flashes oE
97D~138 Canada -7-light from the source 16 does not overlap a pulse height spectrum developed for a sample suspended in the medium.
The maximum flash duration is limited such that the inten-sity of a scintillation produced in the medium in response to a 1ash does not exceed the detection capabilities of the liquid scintillation counting apparatus.
Lastly, the repetition rate of the light flashes is de-termined by the number of counts required to adequately define a pulse height spectrum developed in response to the light flashes and may depend on such factors as the len~th of time during which counting takes place and the detected count rate of the radionuclide in the sample.
In the embodiment disclosed herein and by way of nonlimiting example only, the light flash duration may be in a range of about one to ten nanoseconds at a repeti-tion rate of about 1000 flashes per minute. The flashed light source 16 and the flashed light source power supply 18 may be, for example, a Model 510C nanosecond excitation lampl available from Photochemical Research Associates, Inc., of London, Ontario, Canada, and as described in a publication entitled "Fluorescence Lifetime Instrumen-tation" and appearing in a Photochemical Research Associates, Inc.
price list dated January 1, 1981.
It will be recognized that other suitable flashed light sources may be adapted for use with the present invention. For example, a continuous ult~aviolet source may be used with a shutter to provide the required flash duration and repetition rateO Those skilled in the art will readily recognize other forms of flashed light sources which may ~e adapted for use with the apparatus of Fig. 1 97D-138 Canada -8-In the embodimenk disclosed herein, the vial 10 is of quartz glass so as to not absorb the ultraviolet light emitted by the source 16. To shield the PMTs 12 and 14 from such ultraviolet light, the PklTs 12 and 14 are each fitted with a suitable ultraviolet absorbing lens 20 and 22, such as, Pyrex brand ~lass.
The output of each PMT 12 and 14 is applied to a pulse summation and amplifier 24. The pulse summation and amplifier 24 sums the pulses from the PMTs 12 and 14 and ampliEies the sumrned result producing an analog pulse output.
The output of each P~T 12 and 14 is also coupled as an input to a coincidence circuit 26 which produces an output pulse upon receipt of essentially coincident input pulses~ The outputs from the pulse summation and ampli-fier 16 and the coincidence circuit 18 are both applied to an analog gate 28 which passes the analog output from the pulse summation and amplifier 2~ when the output pulse from the coincidence circuit 26 is also received by the gate 28. Thus, when a scintillation event within the solution 11 is detected by the PMTs 12 and 14, the coinci-dent pulses from such PMTs 12 and 14 are summed by the pulse summation and amplifier 24 and are applied to the gate 28. The coincident pulses from the PMTs 12 and 14 are also detected by the coincidence circuit 26 which applies a pulse to the gate 28. In the presence of the output pulse from the coincidence cirtuit 26r the analog output pulse from the pulse summation and amplifier 24 is passed by the gate 2~.
The output of the gate 28 is applied to an analog~to-digital (ADC) logarithmic pulse hei~ht converter 30 which provides a digital output logarithmically proportional to the height of the analog pulse applied thereto. The digi-97D-138 Canada -9 tal output of the ADC pulse height converter 30 is applied to a microprocessor-based control unit 32. The control unit 32 is o~ conventional design and includes a micro-processor and related memory and input-output interface units, all well known in the art, The control unit 3 compares the value of the digital output from the ADC
pulse height converter 30 to a plurality of predetermined values which define a plurality of energy ranges or win-dows together spanning a predetermined energy or pulse height range. According to the value represented by the digital output from the ADC pulse height converter 30, the control unit 32 determines which window the digital value falls within and accordingly increments one storage loca-tion within a pulse height distribution storage area 34.
The pulse height distributin storage area 34 includes a plurality of storage locations corresponding to the win-dows established by the control unit 32. As the liquid scintillation counting process is per-Eormed, the values stored in the various storage locations within the s-torage area 34 together represent a pulse height distribution curveO The storage area 34 may comprise, for example, a portion of the memory accessible to and controlled by the microprocessor within the control unit 32, each storage location within such storage area 34 being cleared or reset prior to the start of a liquid scintillation count-ing procedures.
The liquid scintillation counting system of Fig. 1 further includes a conventional display unit 36 such as a cathode ray tube ~C~T) and a suitable input device such as a keyboard 38. The display unit 36 can display the count rate derived in a particular window or may display a curve graphically showing the pulse height distribution spec-trum.
"~
97D-138 Canada -10-It will be recognized that the PMTs 12 and 14, pulse summation and amplifier 24, coincidence circuit 26, gate 28/ ADC lo~arithmic pulse height converter 30, control unit 32, pulse height distribution storage area 3~, dis play unit 36 and input device 38 are of conventional de~
sign and instruments employing such elements are ~ell known in the liquid scintillation art. Such instru~ents include the Series 5800 and 9800 liquid scintillation counters available from Beckman Instruments, Inc., al~
though those s~illed in the art will recognize other suit-able instruments which may be adapted in accordance with the inventive concepts taught herein.
Turning now to a description of the operation of the apparatus of Fig. 1 and a preferred embodiment of the method of the present invention, the vial 10 is placed into the counting chamber of the apparatus. The flashed light source power supply 18 is activated so as to cause the light source 16 to emit ultraviolet light flashes as described above. The intensity of such light flashes, also controlled by the flashed light power supply 18, is adjusted as described hereinbelow.
With the flashed light source 16 applying light flashes to the solution ll, the apparatus of Fig. 1 begins counting so as to determine pulse height spectra for the solution 11. Each scintillation occurring within the solution ll is detected by the PM~s 12 and 14 which pro-vide coincident pulses to the pulse summation and ampli-fier 24 and the coincidence circuit 26. The pulses are summed and amplified and are applied to the gate 28.
Because the pulses from the P~Ts 12 and 14 are coincident, the gate 28 passes the analog pulse output of the pulse summation and amplifier 24 to the A~C logarithmic pulse height converter 30. The converter 30 converts the analog pulse to a digital representation logarithmically propor-97D-138 Canada tional to the analog pulseO The digital representation is applied to the control unit 32 which compares the digital representation to the pulse height windows. A storage location in the storage area 34 corresponding to the win-dow within which the digital representation falls is then incremented by the control unit 32.
At the end of sorne predetermined counting period, the collected counts in the storage locations may be read by the control unit 32 and displayed as a pulse height spec-trum on the display unit 36.
Pulse height spectra for a typical solution 11 are shown in Fig. 2. A first spectrum 50 illustrates a pulse height spectrum for, for example, a carbon 14 sample in the solution ll. In accordance with the present inven--tion, a second spectrum 52 represents the pulse height spectrum for scintlllations occurring in the solution 11 in response to the flashed light source 16. The number of photons generated by the source 16 during each flash is adjusted by adjusting the supply 1~ such that the spectrum 52 does not overlap the spectrum 5~. In particular, the electrical energy delivered by the power supply 18 during each flash is controlled by means of suitable controls on the power supply 18, all in a conventional fashion, there-by controlling the intensity of the flash and thus the number of photons delivered to the solution ll with each ~lash. The position of the spectrum 52 along the pulse height axis depends upon the number of photons delivered to the solution 11 with each flash. Thus, by selecting an appropriate flash intensity and duration, the spectrum 52 is placed on a portion o~ the pulse height axis such that the spectrum 52 does not overlap the spectrum 50. Because the spectra 50 and 52 do not overlap, both spectra may be simultaneously determined, and, as described more fully ~ ~g~
97D-138 Canada -12-below, both sample activity and quench may be measured simultaneously.
With continued reference to Fig. 2, dashed spectra 5 and 56 represent pulse height shift which occurs in the solution 11 when the solution 11 is quenched~ Although the radioactivity of the sample remains the same and the source 16 con-tinues to generate light flashes as described above, quench in the solution 11 effectively shifts the spectra 50 and 52 to the left, that is, to lower pulse height values as seen by spectra 54 and 56, respectively.
In accordance with the present invention, quench in the solution 11 is advantangeously and uniquely indicated by the shift of the pulse height spectrum generated in response to the light flashes from the source 16. By detecting a unique point on such spectrum and determining a corresponding pulse height value for such point, a value related to the degree of quench in the solution 11 is obtained and such value may be used to provide an indica-tion of the degree of quench. In the embodiment disclosed herein, the unique point on the light pulse height spec-trum is the peak thereof, although other unique points, such as inflection points on the leading or trailing edge of such spectrum, could also be used.
Such inventive concepts are illustrated with refer-ence to Fig. 2. With the solution 11 at a first level or degree of quench, the spectra 50 and 52 are developed.
peak point Pl of the spectrum 52 corresponds to a pulse height value PHa on the pulse height (log energy) axis.
It will be recognized by those skilled in the art that the system of Fig. 1 may automatically select the peak point Pl and the corresponding pulse height value PHa using, for example, the microprocessor within the control unit 32, 97D-13~ Canada 13~
using programming techniques and algorithms that are well known in computer art.
With the degree of quench in the solution 11 increas-ed, the pulse height spectra shift as indicated by spectra 54 and 56. Accordingly, a peak point P2 on the spectrum 56 corresponds to a second pulse height va]ue P~b on the pulse height axis. Both Gf the pulse height values PHa and PHb provide values that are related to the degree of quench present in the solution 11. Moreover, the differ-ence between the pulse height values PHa and PHb provides a quench number which indicates the degree of quench pres-ent in the solution 11 when the spectra 54 and 56 were developed with respect to the degree of quench present in the solution when the spectra 50 and 52 were developed.
Such a quench number may be obtained automatically using, for example, the microprocessor within the control unit 32 and programming techniques well known in the art.
Such a quench number may be used to determine the degree of quench in various solutions with respect to a standard or calibration solution by comparing the pulse height values for the various solutions to a pulse height value obtained for the standard solution. For example, such a standard solution may be essentially unquenched to thus provide quench numbers which relate de~rees of quench in solutions to the essentially unquenched standard solu-tion. Such a quench number may further be used to imple-ment automatic quench compensation in the liquid scintill-ation countin~ system using methods known in the art, such as that disclosed in U.S. Pat. 4,~2~,401~
In accordance with a further aspect of the present invention, an attribute of the shape of the pulse height spectrum ~enerated in response to the flashed li~ht source 16 further provides an indication o~ the nature of ~uench 97D-138 Canada -14-occurring in the solution 11. With continued reference to Fig. 2, the spectrum 56 represents a particular resolu-tion defined as the result obtained by dividing a first value equal to the width of the spectrum 56 expressed in pulse height units by a second value equal to the pulse height value at the maximum point or peak height of the spectrum 56, the width being taken at some predetermined height along the spectrum 56 with respect to the maximum peak height. For example, the resolution of the spectrum 56 at one-half peak height ls the width of the spectrum 56 expressed in pulse height units at one-half of its height, divided by the pulse height value corresponding to the maximum point of the spectrum 56. With reference to Fig.
2, the resolution of spectrum 56 may be determined at its one-half height where the width is shown by a dashed line segment 58. Such width, projected down to the pulse height axis, represents a width of PWl - PW2 pulse height units. To find resolution, the difference P~l - PW2 is divided by the pulse height value at the maximum point of the spectrum 56, or PHb.
By comparing the resolution of various spectra, a qualitative determination of the nature of quench within the solution may be obtained. More particularly, a third spectra 56a shown by a dotted line in Fig. 2, may be ob-tained having the same maximum peak value PHb as spectrum 56. The half height resolution of the spectrum 56a is obtained by dividing the width of the peak 56a at its half height, shown by a dashed line segment 60 having a value of PW3 - PW4 pulse height units, by PHb, the pulse height value corresponding to a peak P3 on the spectrum 56a. By inspection, it is apparent that the resolution value of the spectrum 56 is smaller than the resolution value of the spectrum 56aO
,...
97D-138 Canada -15-The resolution of a spectrum is affected by the nature of the quench occurring within the solutlon 11.
More par-ticularly, the resolution represented by the spec-trum 56 represents predominantly homogeneous chemical quench in the solution 11. As is well ~nown by those skilled in the art, chemical quench involves the reduction of the number of photons emitted by the solute within the liquid scintillation medium.
However, color quench may also be present in the solution 11 to varying degrees. Color quench may be des~
cribed as the absorption of photons emitted by the solute. The presence of color quench results in the change in resoluion of the spectrum 56 to the resolution illustated by the spectrum 56a. The resolution of spec-trum 56 represents predominantly homogeneous quench pro-duced by chemical quench, while the resolution o~ the spectrum 56a represents a non-homogeneous quench provided both by chemical and color quench. It should be noted that although the resolution of the spectra 56 and 56a differ, the peak P3 on the spectrum 56 corresponds to the same pulse height value as the peak P2, namely, PHb~
Thus, the spectra 56 and 56a continue to represent the same degree o~ quench present in the solution 11 as well as indicating the type of quench occurring therein.
In an automatic system, the resolutions of the spec-tra 56 and 56a may be automatically calculated by the microprocessor within the control unit 32 using conven-tional programming techniques. For example, for the spec-trum 56, the microprocessor detects the peak P2, deter-mines the height of such peak, divides the height by two, determines the width of the spectrum 56 at such half height in pulse height units, and divides such width by the pulse height value at PHb. All such steps involve conventional programming techniques known in the computer 97D-138 Canada 16~
and/or liquid scintillation art. Furthermore, the micro-processor may compare the resolution so obtained to a resolution obtained in a similar manner for a standard solution or for the solution which yielded the spectrum 56a. The result which may be displayed on the display unit 36 prov des an indication of the homogeneous or non-homogeneous nature of the solution.
Those skilled in the art will appreciate that various modifications may be made in the apparatus and method of the present invention without departing from the scope of the appended claims. For example, although the above description has been set forth with respect to log energy along the pulse height axis, a pulse height axis linearly related to energy may also be used.
Moreover, the apparatus and method of the present invention may be adapted for use with a flow liquid scin-tillation system. In such a system, the flow cell is constructed of quartz as is the vial 10 as described above. As a particular advantage in a flow system, the present invention enables simultaneous determination of sample activity and quench.
lP
By comparing the resolution of various spectra, a qualitative determination of the nature of quench within the solution may be obtained. More particularly, a third spectra 56a shown by a dotted line in Fig. 2, may be ob-tained having the same maximum peak value PHb as spectrum 56. The half height resolution of the spectrum 56a is obtained by dividing the width of the peak 56a at its half height, shown by a dashed line segment 60 having a value of PW3 - PW4 pulse height units, by PHb, the pulse height value corresponding to a peak P3 on the spectrum 56a. By inspection, it is apparent that the resolution value of the spectrum 56 is smaller than the resolution value of the spectrum 56aO
,...
97D-138 Canada -15-The resolution of a spectrum is affected by the nature of the quench occurring within the solutlon 11.
More par-ticularly, the resolution represented by the spec-trum 56 represents predominantly homogeneous chemical quench in the solution 11. As is well ~nown by those skilled in the art, chemical quench involves the reduction of the number of photons emitted by the solute within the liquid scintillation medium.
However, color quench may also be present in the solution 11 to varying degrees. Color quench may be des~
cribed as the absorption of photons emitted by the solute. The presence of color quench results in the change in resoluion of the spectrum 56 to the resolution illustated by the spectrum 56a. The resolution of spec-trum 56 represents predominantly homogeneous quench pro-duced by chemical quench, while the resolution o~ the spectrum 56a represents a non-homogeneous quench provided both by chemical and color quench. It should be noted that although the resolution of the spectra 56 and 56a differ, the peak P3 on the spectrum 56 corresponds to the same pulse height value as the peak P2, namely, PHb~
Thus, the spectra 56 and 56a continue to represent the same degree o~ quench present in the solution 11 as well as indicating the type of quench occurring therein.
In an automatic system, the resolutions of the spec-tra 56 and 56a may be automatically calculated by the microprocessor within the control unit 32 using conven-tional programming techniques. For example, for the spec-trum 56, the microprocessor detects the peak P2, deter-mines the height of such peak, divides the height by two, determines the width of the spectrum 56 at such half height in pulse height units, and divides such width by the pulse height value at PHb. All such steps involve conventional programming techniques known in the computer 97D-138 Canada 16~
and/or liquid scintillation art. Furthermore, the micro-processor may compare the resolution so obtained to a resolution obtained in a similar manner for a standard solution or for the solution which yielded the spectrum 56a. The result which may be displayed on the display unit 36 prov des an indication of the homogeneous or non-homogeneous nature of the solution.
Those skilled in the art will appreciate that various modifications may be made in the apparatus and method of the present invention without departing from the scope of the appended claims. For example, although the above description has been set forth with respect to log energy along the pulse height axis, a pulse height axis linearly related to energy may also be used.
Moreover, the apparatus and method of the present invention may be adapted for use with a flow liquid scin-tillation system. In such a system, the flow cell is constructed of quartz as is the vial 10 as described above. As a particular advantage in a flow system, the present invention enables simultaneous determination of sample activity and quench.
lP
Claims (13)
1. A method for measuring a value related to quench associated with a liquid scintillation solution wherein the solution includes a sample, a solvent and a solute, the method including the steps of:
generating light flashes wherein the light includes a predetermined wavelength for exciting essentially only the solvent;
exposing the solution to the light flashes;
detecting a pulse height spectrum for scintillations produced in the solution in response to the light flashes;
determining a unique point on the pulse height spec-trum; and relating the unique point to a corresponding pulse height value, such pulse height value providing a value related to quench associated with the solution.
generating light flashes wherein the light includes a predetermined wavelength for exciting essentially only the solvent;
exposing the solution to the light flashes;
detecting a pulse height spectrum for scintillations produced in the solution in response to the light flashes;
determining a unique point on the pulse height spec-trum; and relating the unique point to a corresponding pulse height value, such pulse height value providing a value related to quench associated with the solution.
2. A method as in claim 1, wherein the method fur-ther includes detecting a pulse height spectrum for the sample and the exposing step includes exposing the solu-tion to the light flashes wherein the light flashes have an intensity and duration such that the pulse height spec-trum produced in response to the light flashes does not overlap the sample pulse height spectrum.
3. A method as in claim 1, wherein the method fur-ther includes detecting an attribute related to the shape of the pulse height spectrum representing solution res-ponse to the light flashes to thereby provide a value related to the homogeneous or non-homogeneous nature of the quench present in the solution.
4. A method as in claim 1, wherein the method fur-ther includes comparing the pulse height value correspond-ing to the unique point to a pulse height value determined in a similar manner for a standard solution to provide an indication of the degree of quench present in the liquid scintillation solution with respect to the standard solu-tion.
5. A method for indicating quench associated with a liquid scintillation solution wherein the solution in-cludes a sample, a solvent and a solute, the method inclu-ding the steps of:
generating light flashes wherein the light has a predetermined wavelength for exciting essentially only the solvent;
exposing the solution to the light flashes;
detecting pulse height spectra for scintillations produced in the solution in response to the light flashes and in response to the sample, the light flashes having an intensity and duration such that the pulse height spectrum produced in response to the light flashes does not overlap the sample pulse height spectrum;
detecting a unique point on the pulse height spectrum detected in response to the light flashes;
relating the unique point to a corresponding pulse height value; and comparing the pulse height value corresponding to the unique point to a pulse height value determined in a simi-lar manner for a standard solution to provide an indica-tion of the degree of quench present in the solution with respect to the standard solution.
generating light flashes wherein the light has a predetermined wavelength for exciting essentially only the solvent;
exposing the solution to the light flashes;
detecting pulse height spectra for scintillations produced in the solution in response to the light flashes and in response to the sample, the light flashes having an intensity and duration such that the pulse height spectrum produced in response to the light flashes does not overlap the sample pulse height spectrum;
detecting a unique point on the pulse height spectrum detected in response to the light flashes;
relating the unique point to a corresponding pulse height value; and comparing the pulse height value corresponding to the unique point to a pulse height value determined in a simi-lar manner for a standard solution to provide an indica-tion of the degree of quench present in the solution with respect to the standard solution.
6. A method as in claim 5, wherein the method fur-ther includes comparing an attribute related to the shape of the pulse height spectrum developed in response to the light flashes to an attribute related to the shape of a pulse height spectrum obtained in a similar manner for another sample to provide an indication of the homogeneous or non-homogeneous nature of the quench present in the solution.
7. An apparatus for indicating quench associated with a liquid scintillation solution wherein the solution includes a sample, a solvent and a solute, the apparatus including:
means for generating light flashes wherein the light has a predetermined wavelength for exciting essentially only the solvent;
means for exposing the solution to the light flashes;
means for detecting a pulse height spectrum for scin-tillations produced in the solution in response to the light flashes;
means for determining a unique point on the pulse height spectrum; and means for relating the unique point to a correspond-ing pulse height, such pulse height providing a value related to quench associated with the solution.
means for generating light flashes wherein the light has a predetermined wavelength for exciting essentially only the solvent;
means for exposing the solution to the light flashes;
means for detecting a pulse height spectrum for scin-tillations produced in the solution in response to the light flashes;
means for determining a unique point on the pulse height spectrum; and means for relating the unique point to a correspond-ing pulse height, such pulse height providing a value related to quench associated with the solution.
8. An apparatus as in claim 7, wherein the apparatus further includes means for detecting a pulse height spec-trum for the sample and the means for exposing further includes means for exposing the solution to the light flashes wherein the light flashes have an intensity and duration such that the pulse height spectrum produced in response to the light flashes does not overlap the sample pulse height spectrum.
9. An apparatus as in claim 7, wherein the apparatus further includes means for detecting an attribute related to the shape of the pulse height spectrum representing solution response to the light flashes to thereby provide a value related to the homogeneous or non-homogeneous nature of the quench present in the solution.
10. An apparatus as in claim 7, wherein the appara-tus further includes means for comparing the pulse height corresponding to the unique point to a pulse height deter-mined in a similar manner for a standard solution to pro-vide an indication of the degree of quench present in the liquid scintillation solution with respect to the standard solution .
11. An apparatus for indicating quench associated with a liquid scintillation solution wherein the solution includes a sample, a solvent and a solute, the apparatus including:
means for generating light flashes wherein the light has a predetermined wavelength for exciting essentially only the solvent;
means for exposing the solution to the light flashes;
means for detecting pulse height spectra for scintil-lations produced in the solution in response to the light flashes and in response to the sample, the light flashes having an intensity and duration such that the pulse height spectrum produced in response to the light flashes does not overlap the sample pulse height spectrum;
means for detecting a unique point on the pulse height spectrum detected in response to the light flashes;
and means for relating the unique point to a correspond-ing pulse height value, such pulse height value providing a value related to quench associated with the solution.
means for generating light flashes wherein the light has a predetermined wavelength for exciting essentially only the solvent;
means for exposing the solution to the light flashes;
means for detecting pulse height spectra for scintil-lations produced in the solution in response to the light flashes and in response to the sample, the light flashes having an intensity and duration such that the pulse height spectrum produced in response to the light flashes does not overlap the sample pulse height spectrum;
means for detecting a unique point on the pulse height spectrum detected in response to the light flashes;
and means for relating the unique point to a correspond-ing pulse height value, such pulse height value providing a value related to quench associated with the solution.
12. An apparatus as in claim 11, wherein the appara-tus further includes means for comparing the pulse height corresponding to the unique point to a pulse height deter-mined in a similar manner for a standard solution to pro-vide an indication of the degree of quench present in the solution with respect to the standard solution.
13. An apparatus as in claim 12, wherein the appara-tus further includes means for comparing an attribute related to the shape of the pulse height spectrum develop-ed in response to the light flashes to an attribute rela-ted to the shape of a pulse height spectrum obtained in a similar manner for another sample to provide an indication of the homogeneous or non-homogeneous nature of the quench present in the solution.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000483557A CA1249076A (en) | 1985-06-10 | 1985-06-10 | Method and apparatus for indicating quench of a liquid scintillation solution |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000483557A CA1249076A (en) | 1985-06-10 | 1985-06-10 | Method and apparatus for indicating quench of a liquid scintillation solution |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1249076A true CA1249076A (en) | 1989-01-17 |
Family
ID=4130679
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000483557A Expired CA1249076A (en) | 1985-06-10 | 1985-06-10 | Method and apparatus for indicating quench of a liquid scintillation solution |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1249076A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109814149A (en) * | 2019-01-01 | 2019-05-28 | 中国人民解放军63653部队 | The quick low interference measurement techniques of Strontium-90 based on screened film |
-
1985
- 1985-06-10 CA CA000483557A patent/CA1249076A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109814149A (en) * | 2019-01-01 | 2019-05-28 | 中国人民解放军63653部队 | The quick low interference measurement techniques of Strontium-90 based on screened film |
| CN109814149B (en) * | 2019-01-01 | 2023-05-05 | 中国人民解放军63653部队 | Method for directly measuring strontium-90 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Clift et al. | A temporal method of avoiding the Cerenkov radiation generated in organic scintillator dosimeters by pulsed mega-voltage electron and photon beams | |
| Moses et al. | Cerium fluoride, a new fast, heavy scintillator | |
| Yguerabide | Fast and accurate method for measuring photon flux in the range 2500–6000 Å | |
| US4075480A (en) | Quench determination in liquid scintillation counting systems | |
| US4694176A (en) | Method and apparatus for indicating quench of a liquid scintillation solution | |
| Levita et al. | LiF dosimetry based on radiophotoluminescence (RPL) | |
| EP0221626B1 (en) | Radionuclide indentification in liquid scintillation counting | |
| CA1249076A (en) | Method and apparatus for indicating quench of a liquid scintillation solution | |
| JPH0512676B2 (en) | ||
| EP0181922B1 (en) | Method and apparatus for indicating quench of a liquid scintillation solution | |
| US4060728A (en) | Method of measuring the disintegration rate of beta-emitting radionuclide in a liquid sample | |
| JP2972936B2 (en) | Method and apparatus for combining scintillation pulse wave height data | |
| JP2609942B2 (en) | Apparatus and method for determining single-phase or multi-phase for liquid scintillation samples | |
| EP0199665B1 (en) | Reverse sum quench measurement using a liquid scintillation counter | |
| EP0181923B1 (en) | Quench, volume and activity determinations in a liquid scintillation flow system | |
| RU2150693C1 (en) | Method for certifying fissionable material parts and checking them for safety | |
| Hsu et al. | Skin dose measurement with microspec-2TM | |
| Benoit et al. | Feasibility of fibered monitoring system for pulsed dose-rate facilities based on radioluminescence of SrS: Ce, Sm phosphor | |
| Piesch | The Indication of Adsorbed Dose in Critical Organs by Energy Independent Personnel Dosimeters | |
| JPH05209965A (en) | Measurement device for beta ray nuclide density | |
| Kossert et al. | Primary activity standardization of 134 Cs | |
| McMillan et al. | The measurement of scintillation emission spectra by a coincident photon counting technique | |
| CA1249077A (en) | Quench, volume and activity determinations in a liquid scintillation flow system | |
| Knoetze | Hardware Tests for Proton Beam Therapy Calorimetry Research and Development Project Report | |
| Henshaw et al. | The use of a scintillation counter to measure diagnostic X-ray tube kilovoltage, radiation exposure rates and contamination by low energy gamma emitters |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |