Direct Measurement of the Quantum Counting Efficiency of RCA C31000E/F Photomultipliers at 6328 A

Method for the determination of photomultiplier collection efficiency, F

Photomultiplier collection efficiency, F, is a fundamental, but difficult, parameter to measure with certainty. A method for its determination, based on the gain of the first dynode, has been devised and applied to two different types of photomultiplier. The measurements are substantially free from the sources of error, which have compromised previously reported results by other authors. F may be determined by the proposed method with an accuracy of better than +/-3% for any photomultiplier tube with sufficient gain to uncover its single electron response.

Stray-light suppression with high-collection efficiency in laser light-scattering experiments

We describe an optical system that we constructed to collect a large fraction of fluorescent light emitted isotropically from a cylindrical interaction region. While maintaining an overall detection efficiency of 9%, the system rejects, by more than 12 orders of magnitude, incident laser light along a single axis that intersects the interaction region. Such a system is useful for a wide variety of light-scattering experiments in which high-collection efficiency is desirable, but in which light from an incident laser beam must be rejected without resorting to spectral filters.

High resolution luminescence spectrometer. 1: simultaneous recording of total luminescence and phosphorescence

A luminescence spectrometer is described that has the particular advantage of allowing the simultaneous recording of total luminescence and phosphorescence spectra. The basic design is straightforward and uses commercially available components. The measuring and recording system is completely digital. The technique of single-photon counting is employed, and the data are recorded digitally in the form of listings and punched paper tapes. This output is suitable for further data analysis on a computer. An additional analog recording system allows an instant examination of the quality of the incoming data.

Photomultiplier single photon counting efficiency

An RCA C31000F (8853) photomultiplier with a cathode quantum efficiency of 5.5% (for 633-nm light) was found to have a single photon counting efficiency of only 3.3%. The difference is shown to be due to small pulses well below the single electron peak in the output pulse height spectrum. These pulses are usually below the discriminator threshold level and are not counted. The reason for the small pulses is not understood.