Abstract: A 360.degree. surround photon detector/electron multiplier having: i) a continuous annular inner wall formed of thin light-transmissive material defining an internal coaxial detection chamber; ii) an annular enclosed evacuated envelope integral with the inner wall; iii) a cylindrical photocathode positioned adjacent the vacuum side of the inner wall; and iv), an electron multiplier assembly housed within the envelope for multiplying photoelectrons emitted from the photocathode and operable as a plurality of adjacent, circumferentially arrayed electron multipliers, each including an output terminal. The outputs originating from various segments of the photocathode may be utilized with coincidence circuitry requiring simultaneous detection of light events in at least two different sections of the photocathode in order to eliminate spurious signals such as result from thermal electron emissions from the photocathode.

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).