Multiplier Phototubes for the Far Ultraviolet

A new group of extreme solar-blind multiplier phototubes with cleaved lithium fluoride windows consisting of: end-on tubes with 28 mm active diameter cesium iodide (542G-08) and potassium bromide (542J-08) photocathode; 10 mm active diameter cesium iodide (541G-08) and copper iodide (541H-08) photocathodes; and a side-window tube with a cesium iodide reflective photocathode (641G-08), are described. The spectral responses have characteristic long wavelength cut-offs which serve as an efficient means of rejecting the scattered long-wavelength radiation in dispersive systems. The tubes have anode dark currents at room temperature equivalent to approximately one photoelectron per second. The count rate in the dark of cathode-originating electrons is 10-20 counts per minute. The pulse height distribution from a 541G-08 illuminated with low-level ultraviolet shows an exponential form down to a small fraction (1/25) of the average single electron pulse height. The highly ruggedized tubes are designed for the rigors of space applications.