Air-stable solid photocathodes with good ageing properties for fast gaseous detectors

Fourteen organometallic materials have been investigated as potential photocathodes for the ultraviolet. Several air-stable photocathodes have been found, each with a quantum efficiency of about 1% at 200 nm. These materials, covered with adsorbed layers of tetrakis[dimethylamine]ethylene or ethylferrocene, can have quantum efficiencies up to 5% at 200 nm, and can tolerate contact with air for periods of up to an hour. The quantum efficiencies are several times smaller than the ones that can be achieved with CsI, but the fabrication procedure is simple, and the materials have superior ageing properties. Gaseous detectors combined with these photocathodes can operate at gains up to 10 7 without photon feedback, allowing spatial resolutions of 2–3 mm to be achieved. Such detectors may find a wide range of application in the future.