[en] The forty papers presented at this conference covered the use of liquid and solid scintillation counting in nuclear physics, biology and medicine, as well as various counting techniques, data processing methods, novel scintillators, and other topics of current interest

[en] Low level liquid scintillation counting is reviewed in terms of its present use and capabilities for measuring low activity samples. New areas of application of the method are discussed with special interest directed to the food industry and environmental monitoring. Advantages offered in the use of a low background liquid scintillation counter for the nuclear power industry and nuclear navy are discussed. Attention is drawn to the need for commercial development of such instrumentation to enable wider use of the method. A user clientele is suggested as is the required technology to create such a counter

[en] The difficulties inherent in the disposal and handling of the radionuclides used in radioimmunoassay are prompting users to seek other methods of analysis such as bio- and chemiluminescent techniques for immunoassay. Specifications for optimizing automatic luminescence instrumentation are given for the various components of the system. The author predicts that flexible luminometers will eventually outperform the liquid scintillation counters currently in use

[en] In this experiment, an attempt was made to raise the average Z of a scintillation solution with as little attendant quenching as possible. Since high-Z atoms quench by means of a close encounter, as stated above, such encounters are minimized by the use of alkyl groups substituted on the solvent, solute, and heavy atoms. The aromatic compound 1,2,4-trimethylbenzene (pseudocumene) was used as the solvent; 4,4''-di(5-tridecyl)-p-terphenyl as the solute; and tetrabutyltin as the high-Z material. Various experiments were performed with less protected solvents and heavy atoms. These include benzene, toluene, p-terphenyl, bromobutane, and bromobenzene

[en] Recent advances in microchannel plate (MCP) photomultiplier technology has prompted a study to evaluate the use of this photon detector for liquid scintillation counting. The advantages offered by an MCP photomultiplier over a conventional photomultiplier are: better time resolution, low background noise and small physical size resulting in reduced shielding requirements. A comparison between the MCP and conventional photomultipliers is made when measuring ³H (18.6 keV βmax) and ¹⁴C (156 keV βmax) in a coincidence liquid scintillation mode of counting

[en] The Dominant-Phase Theory of Microemulsions (DPTM) shows that gels can be transformed into microemulsions by the addition of suitable cosurfactants and indicates the chemical form that these cosurfactants should have. This is possible because, according to the DPTM, the most important factor determining the physical state of the mixture is the stretching force acting on the emulsifier molecules. The DPTM postulates that in a microemulsion this stretching force is small and as a result the emulsifier molecules are subject to little restraint, giving a mixture of low viscosity, whereas in a gel the stretching force is large, resulting in a mixture of high viscosity because the motion of the emulsifier molecules is restricted. For high efficiency counting, the oil and all cosurfactants and emulsifiers in the mixture must contain a benzene ring in their molecular structure. The application of these ideas is illustrated by a description of the development of an emulsion liquid scintillation counting mixture for the high efficiency, high merit value and stable counting of up to 30 percent sodium hydroxide aqueous solutions using toluene as the oil and Triton X-100 as the emulsifier, with 2-phenylethanol and DL-2-hydroxy-2-phenyl acetic acid (mandelic acid) as cosurfactants

[en] Multichannel analyser (MCA) relative pulse height spectra were used to monitor linear and logarithmic output liquid scintillation counters. Spectra for radiocarbon dating reference standards, known age samples and background were recorded. The counters tested were optimized for low-level sup(14)C counting. Their high voltage (EHT) was reduced, the phototubes were masked and the limited counting efficiency windows (65-80 percent) were set at balance point. The total count from the conventionally set window as well as the 1000 (0-250 KeV) channel relative pulse height spectrum was recorded. Spectral analysis could be carried out for the total 0-1 MeV energy range or within the counter set lower and upper limit window discriminators. This enables (i) MCA and set window computations to be compared, (ii) counter windows to be checked or optimized, (iii) merit of computations based on total spectral information to be evaluated and (iv) merit of linear or logarithmic data presentation to be evaluted. It will be shown that pulse height spectra analysis based on WINDOWLESS data acquisition is superior in all aspects to the conventional set window mode of data analysis. Full energy spectra information allows speedy recognition of: non-Poisson (non-random) events, quenching, radioactive impurities, counter instability and, especially for low-level counting, evaluation of long term spectral stability. Applied to radiocarbon dating it allows computations of minimal errors

[en] The pulse height spectrum was measured for the minimum detectable event of a coincidence liquid scintillation counter - the two photoelectron event. Using a chemiluminescence source of single photons the chance coincidence events for one photoelectron produced in each multiplier phototube within the coincidence resolving time would represent the two photoelectron spectrums. The peak of this spectrum gave the average pulse height of the two photoelectron event. Using different radionuclides which decay by emission of discrete energy events; conversion electrons, X-rays and/or gamma rays; the pulse height spectra produced by given energy electrons were measured. From these the average number of photoelectrons corresponding to the pulse height was calculated. The energy divided by the number of photoelectrons was measured over the electron energy range 3.4 to 1067 keV. The average energy per photoelectron was approximately constant at 0.68 keV/photoelectron for electron energies greater than 200 keV. Below 200 keV the values increased to about 0.95 keV/photoelectrons at 5.9 keV. These data are compared to data for a non-coincidence, single multiplier phototube counter

[en] The Radioactive Sample Processor, RSP-β400, has been designed to substantially reduce the three aspects (time, cost and effort) of sample handling and counting of beta-emitting radioisotopes using the technique of liquid scintillation counting. This is accomplished through a combination of two previously available technologies. First, a sample processor is utilized for the accurate removal of a specific variable (0.1-1.0 ml) sample volume from a disposable sample tray and the subsequent mixing of this sample with a liquid scintillation solution (4.0 ml total volume). Second, a dual counting chamber (double sample throughput) is incorporated for the accurate quantitation of the radioactivity in two samples simultaneously. The reliability, reproducibility, linearity of detector response, data handling capacities and various counting parameters are discussed in regard to the performance of the RSP-β400 instrument. Several applications for the utilization of the RSP-β400 Sample Processor in both the basic research and clinical research areas are explored

[en] Transmission of light from the scintillating liquid to the photomultiplier tubes (PMT's) is a fundamental part of liquid scintillation counting. This paper examines the various pathways along which photons must travel to reach the PMT's. Long exposure 'autofluorographs' were taken of vials containing scintillating liquids