The “Pedoscope” Coolidge Tube





            Dating probably to the thirties, this Coolidge type line focus tube is 10” (25cms) long with a 4” (10cms) bulb. It is fitted externally with a black-painted spool-like aluminium heat sink fixed on the protruding anode shaft. A voltage adjusting rheostat is visible on the cathode end of the tube, fitted to the two-prong connection of the filament.


                    Note the slightly conical shape of the copper anode, and the unusual 30 degree angle of the target surface. This angle falls half way between the 45 degree   target angle in gas discharge tubes and in early Coolidge type tubes, and the usually low, 10-15 degree angle, in the line focus tubes introduced in the Twenties.


                    This tube bears an etching “Made in Holland” on the anode stem,   without any maker’s name. It could have been made by Philips.


                     It comes most probably from the English made “Pedoscope” shoe-fitting fluoroscopy device. Such devices came in use in the twenties, and were still in frequent use in the fifties. But, owing to the high risk of radiation, they were gradually banned in the sixties, and practically disappeared in the early seventies.



(Science Museum, London)

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