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EFP60 - Secondary Emission Amplifier
Almost certainly Philips EFP60 was the first high-frequency amplifier based upon the secondary emission effect. This article, dated August 1939, with the contribution of British Mullard on the Journal of Scientific Instruments allows to date the announcement of the tube just few days before WWII began in Europe. It was probably intended for applications as VHF amplifier in then promising television field. All the available resources were moved to military productions and both television and EFP60 had to wait until the end of the war. In the meantime the secondary emission effect was exploited in America by RCA to design the giant acorn tubes, 1630 and its prototype R-1790, as RF front-end in early SCR-270 VHF radar sets.
EFP60 Datasheet
