The 15R is a matching rectifier for the 15E UHF pulse Radar triode. Eimac designed the valves in 1940 for the first American airborne Radar.
The peak current required by the triodes could reach 20 Amps and the figure of 30 mA is the average value. The peak pulse power was 5 kW at a repetition rate of 400 Hz and a duration of 2 μS The Va figure above is the PIV rating.
The manufacture of the rectifier is the same as the triode but without the grid cage.
The box is marked US Army & US Navy and the valve was accepted on December 10, 1943. The box measures 76 mm square and 85 mm tall.
The evacuation pip is on the side of the envelope.
The filament is a helix of bright thoriated tungsten running vertically within the cylindrical anode.
The wide glass tube envelope is 36 mm in diameter and, is 69 mm tip-to-tip.
Reference: Private communication. Type 15R was first introduced in 1940.