Abstract: A low-level liquid scintillation measurement system for counting sample optical events resulting from the radioactive decay of a constituent of a sample to be measured while reducing the counting of background optical events which are optical events produced by background radiation and which create electrical pulses other than pulses representing a sample optical event.

Abstract: Apparatus and a method useful for identifying and verifying which radionuclide is present in a test sample for use in a liquid scintillation counter is disclosed. The invention is directed to measuring a quench-indicating parameter of the sample and an external source quench-indicating parameter. The measured values are compared to known radionuclide equations to determine if an identifying fit exists. If the measured values are determined to satisfy, one of the known radionuclide equations, then the identity of a radionuclide is established. In a multilabel sample the measured values may be used to identify the radionuclide having the highest end point maximum energy.

Abstract: A method and apparatus for separating background events from valid sample events in a liquid scintillation counter are disclosed. Upon the detection of a coincident event pulse the number of pulses detected during a short time interval immediately thereafter together with the energy level of the event pulse is utilized to determine the probability that the event pulse is a valid sample pulse as opposed to an invalid background pulse. The total count rate is determined by summing pulses over the appropriate energy range where each pulse is counted as one multiplied by the above probability that the pulse is a valid sample pulse.

Abstract: Apparatus and a regionless method of ascertaining the activity of each radionuclide in a dual-label sample. A set of correlation curves is generated utilizing quench standards for both a low energy radionuclide and a high energy radionuclide. A test sample was then counted and the quench-indicating parameters for the test sample are compared with the quench-indicating parameters of the correlation curves to determine the appropriate contribution of each radionuclide to the overall energy spectra of the test sample. From this comparison the overall count rate for the test sample may be allocated between a low energy radionuclide and a high energy radionuclide. By dividing the count rates by efficiencies determined from another set of correlation curves the actual disintegration per minute (DPM) rate for each radionuclide may be ascertained.

Abstract: A method for ascertaining radiochemical homogeneity in a liquid scintillation sample reliably identifies inaccurate geometries is disclosed so that meaningful activity counts can be determined. The novel method involves measuring the activity level of a set of homogeneous quench standard to obtain quench indicating parameter, or the Spectral Index of the External standard (SIE). The endpoint of each standard sample is computed allowing the formation of a table so that a calibration curve for each radionuclide of interest can be computed. The activity level of the unknown sample is then measured and the SIE determined so that an endpoint can be calculated. Finally, the theoretical endpoint obtained from a calibration curve is compared to the computed endpoint; if the computed endpoint of the sample deviates by more than 4% for tritium and 5% for higher energy radionuclides from the theoretical endpoint, the sample is considered to be nonhomogeneous or heterogeneous.

Abstract: Method and apparatus for counting nuclear scintillations of a specimen containing tritium. A simple system using a single photomultiplier tube and suitable circuitry segregates the pulses which are emitted from a scintillator due on interaction with a nuclear particle from the pulses attributable to random noise. The system is operable with many scintillation materials as long as the characteristic output from the scintillator is long relative to the duration of a random noise pulse. The preferred embodiment of this radiation assay instrument includes a solid scintillator, a photomultiplier tube whose output is split among a two-path circuit containing a first path for providing an integrated pulse signal as input to a pulse height analyzer and a second path which discriminates based on the number of component pulses in the signal to provide an enable signal to the pulse height analyzer.

Abstract: A fluid flow control device includes a thermally conductive conduit section having both interior and exterior heat exchange surfaces, with the interior surface being adapted to contact fluid flowing thereover. A controllable heat transfer means coupled to the conduit section has a first operative state for removing heat from the exterior heat exchange surface to reduce the temperature of the conduit section sufficiently to freeze liquid adjacent the interior heat exchange surface and thereby at least partially restrict the flow of fluid thereover. In a second operative state, the heat transfer means supplies heat to the interior heat exchange surface to melt at least a portion of any frozen liquid adjacent the interior heat exchange surface and thereby permit the flow of fluid thereover.

Abstract: A fluid flow control device includes a thermally conductive conduit section having both interior and exterior heat exchange surfaces, with the interior surface being adapted to contact fluid flowing thereover. A controllable heat transfer means coupled to the conduit section has a first operative state for removing heat from the exterior heat exchange surface to reduce the temperature of the conduit section sufficiently to freeze liquid adjacent the interior heat exchange surface and thereby at least partially restrict the flow of fluid thereover. In a second operative state, the heat transfer means supplies heat to the interior heat exchange surface to melt at least a portion of any frozen liquid adjacent the interior heat exchange surface and thereby permit the flow of fluid thereover.

Abstract: Method and apparatus for the processing of fluid materials, particularly in the preparation of samples for radioactive isotope tracer studies by combustion of starting materials containing such isotope tracers. The sample is burned in a combustion chamber which tapers upwardly and inwardly above the sample receptacle so as to approximate the shape of the flame of a burning sample, and the combustion products are continuously exhausted from the combustion chamber and passed through a heat exchanger which condenses the condensable vapors in the combustion products. The condensed vapors are then separated from the gases, and the gases are passed into a reaction column if there is a radioactive isotope tracer remaining in gas form.

Abstract: A light seal for the counting chamber of a scintillation counter comprises a ring shutter mounted in the shielded housing which forms the counting chamber. The ring shutter is mounted for rotation between an open position where an aperture in the ring shutter is aligned with an opening into the shielding housing to permit transfer of sample vials in and out of the counting chamber, and a closed position where a shroud portion of the shutter covers the opening in the housing to block the entry of light. The ring shutter closely surrounds the sample vial in the counting chamber and is preferably formed of a radiation shielding material. The shroud portion of the ring shutter includes a cam for engaging a sample vial disposed within the shutter aperture when the shutter rotates from the open position to the closed position, for lifting the sample vial to a predetermined elevation within the counting chamber.

Abstract: A pipetting system for dispensing multiple liquids into a single receptacle includes a plurality of liquid reservoirs, a plurality of syringes for aspirating preselected quantities of liquids from the reservoirs, and a common dispensing head connected to all the syringes for simultaneously receiving the preselected quantities of liquids from a plurality of the syringes and simultaneously dispensing the liquids into the reservoir. The system also includes means for simultaneously aspirating the preselected quantities of liquids from the reservoirs into the syringes. In addition, the system includes aspirating means for withdrawing a liquid sample from a container into the dispensing head at an aspirating position, means for storing the aspirated sample while the dispensing head is moved from the aspirating position to a dispensing position, and means for dispensing the aspirated sample to the dispensing head simultaneously with the dispensing of the preselected quantities of other liquids.

Abstract: Method and apparatus for the processing of fluid materials, particularly in the preparation of samples for radioactive isotope tracer studies by combustion of starting materials containing such isotope tracers. The sample is burned in a combustion chamber which tapers upwardly and inwardly above the sample receptacle so as to approximate the shape of the flame of a burning sample, and the combustion products are continuously exhausted from the combustion chamber and passed through a heat exchanger which condenses the condensable vapors in the combustion products. The condensed vapors are then separated from the gases, and the gases are passed into a reaction column if there is a radioactive isotope tracer remaining in gas form.

Abstract: A storage and indexing mechanism for a plurality of sample containers includes a portable tray for supporting and guiding the sample containers along preselected indexing paths on the tray. The sample containers can be pre-loaded on the tray with the tray being used for storage and transport of the sample containers. When it is desired to process the sample containers, as in a scintillator counter or other analytical instrument, the portable tray containing the sample containers is placed on a stationary stage for receiving and holding the tray on the analytical instruments. The stage includes means cooperating with the tray for indexing the sample containers along the indexing paths on the tray when the tray is mounted on the stage, and means for registering the tray and the sample containers thereon with the indexing means when the tray is mounted on the stage.

Abstract: A mechanism for centering a movable member within an elongated passageway of variable width, such as for use in an article transport system of a benchtop scintillation detector or other laboratory sample processor. The centering is performed by a plurality of outwardly bowed guide elements attached to the movable member, arranged around the periphery of the movable member, and oriented generally along the axis of travel of the movable member. In the particular embodiment herein, the guide elements are maintained in bowed position by one or more biasing means housed within the movable member. The bowing of the guide elements urges the movable member toward the center of the passageway at all times, regardless of the transverse dimension of the passageway, and regardless of the presence of gaps in the passageway.

Abstract: A system for combusting materials containing radioactive nuclides to permit recovery of the radioactive nuclides includes a combustion zone for combusting a sample material containing at least one radioactive nuclide. The combustion products are continuously exhausted from one end of the combustion zone, and a continuous pressurized stream of oxygen-containing gas is introduced into the combustion zone between the exhaust end of the zone and the sample during the combustion thereof. At least a portion of the pressurized oxygen-containing gas stream is directed through the combustion zone in a spiral path toward the sample to circulate at least a portion of the combustion products around the combustion zone as they flow toward the exhaust end of the zone counter to the flow of the spiraling stream of oxygen-containing gas, thereby intimately mixing the combustion products with the oxygen-containing gas in the combustion zone.

Abstract: A data analyzing system for scintillation spectrometers of the type for measuring activity levels of samples containing radioactive isotopes and subjected to varying degrees of quench, including methods and apparatus for optimizing counting conditions and thereby improving statistical counting validity irrespective of the degree of quenching present in any given sample, and wherein a measured parameter indicative of the effective quench condition of each sample is utilized to automatically adjust, by preselected preset amounts, the counting window for any given isotope relative to the observed energy spectrum for that isotope. Various methods and apparatus are described which, although suitable for optimizing counting conditions for both multiple-labeled and single-labeled test samples, are particularly effective in creating significantly improved isotope separations when dealing with multiple-labeled samples -- for example, a double-labeled sample containing tritium (.sup.3 H) and carbon-14 (.sup.14 C).

Abstract: A liquid scintillation counting composition of the type comprising ar aromatic hydrocarbon solvent, an ethoxylated alkyl phenol surfactant, and a scintillation solute, contains a small amount of a substituted ethoxylated carboxylate acid and/or a tertiary amine salt or a quaternary ammonium salt of such acid. The free acid reduces chemiluminescence upon the addition of an alkaline sample to the composition, while the tertiary amine or quaternary ammonium salt enhances the water miscibility of the composition.

Abstract: Method and apparatus for the processing of fluid materials, particularly in the preparation of samples for radioactive isotope tracer studies by combustion of starting materials containing such isotope tracers. The sample is burned in a combustion chamber which tapers upwardly and inwardly above the sample receptacle so as to approximate the shape of the flame of a burning sample, and the combustion products are continuously exhausted from the combustion chamber and passed through a heat exchanger which condenses the condensable vapors in the combustion products. The condensed vapors are then separated from the gases, and the gases are passed into a reaction column if there is a radioactive isotope tracer remaining in gas form.

Abstract: A liquid scintillation counting composition of the type comprising an aromatic hydrocarbon solvent, an ethoxylated alkyl phenol surfactant, and a scintillation solute, contains a small amount of a substituted ethoxylated carboxylate acid and/or a tertiary amine salt or a quaternary ammonium salt of such acid. The free acid reduces chemiluminescence upon the addition of an alkaline sample to the composition, while the tertiary amine or quaternary ammonium salt enhances the water miscibility of the composition.

Abstract: A combustion system for combusting materials containing radioactive nuclides to permit recovery of the radioactive nuclides. The system comprises a primary combustion zone in which the sample material is initially combusted and from which the combustion products are continuously exhausted. The exhaust products from this primary combustion zone are passed through a secondary combustion zone in which uncombusted materials in the exhaust products are combusted. In the secondary combustion zone, the exhaust products from the primary zone are directed in a helical path so that centrifugal forces drive the gases and any particulate matter entrained therein toward the walls of the secondary zone while intimately mixing the materials with each other to achieve rapid and complete combustion. The secondary combustion zone preferably comprises a helical tube which is heated by passing an electric current through the walls thereof. The helical path preferably has a radius of curvature of less than about 1.