This is one of a set of very similar soft x-ray detectors in the collection. These photoionization chambers, manufactured in the early 1960's, are based on an original design by H. Friedman at the Naval Research Laboratory. They are representative of some of the detectors flown on early satellites used in studies of the sun. These x-ray detectors comprise a ceramic shell equipped at one end with a window that in most cases consists of beryllium. Electrons released by a strike of an impinging x-ray on the filling gas are drawn to an anode in the chamber by the electrical potential imposed between the ends of the shell. Collision of the initially released charges with gas molecules results in the release of further electrons. Repetition of the process leads to a cascade of charge and significant amplification of the electrical signal generated by the initial x-ray.

The detectors were transferred to NASM by NASA (GSFC) in 1988 and are currently stored at the Garber facility.