Detectors for the Extreme Ultraviolet I: Photomultipliers Used in the dc Output Current Mode

An investigation has been made of voltage-sensitivity characteristics, absolute spectral response, dark current and output current limitations of seven photomultipliers suitable for detection of extreme uv radiation. These photomultipliers are windowless types, utilizing cathode surfaces blind to visible and near uv radiation; they include a microminiature continuous channel multiplier. For measurements of absolute spectral sensitivity, they were compared to a conventional 1P21, coated with sodium salicylate which, in turn, had been calibrated at 1216 A with a nitric oxide ionization chamber. The spectral response measurements cover the spectral region from 1500 A to 584 A. The photomultipliers were used in a dc output currrent mode and were excited with radiation from both pulsed and dc gas discharge sources. A discussion of the suitability of the detectors for use with each type of source is given.