Gundelach Hooded Anti-Cathode Ion Tube

Hooded anode as illustrated page 11 “Atlas Typischer Röntgenbilder, by Rudolf Grashey, 1912, J.F.Lehmann’s Verlag”

This early cold cathode x-ray tube, bears no maker’s name, but figures in an advertisement by Emil Gundelach, dating to 1910 (E.R.N. Grigg : The Trail of the Invisible Light, p 479, Charles C. Thomas, 1965). The tube is 23” (58cms) long with a 7” (18cms) bulb. The regeneration device is in the small secondary chamber, consisting of concentric semiconductor cylinders, separated by a dielectric material (see x-ray picture), and respectively connectable, at will, to the cathode and anti-cathode of the tube. This type of regeneration is usually described as the “condenser type”, introduced by Gundelach.

The anode is a small aluminium rod, and the aluminium cathode is of the typical concave type. But the rare and most interesting feature of this tube is the anti-cathode of the heavy type where the target, probably of platinum foil, is of large size, slightly convex, and enclosed inside a large aluminium hood fixed to a ferrous-looking, tube-like and slightly rusty stem. This “hood” was probably intended for a better concentration on the centre of the target of the electron flow coming from the cathode, while providing protection from off-focal radiation. However, this hooded anti-cathode fits perfectly the description of what came to be known a few years later as the “hooded anode”.

With the exception of the Chabaud Tube (1905-1906) which had a hooded anode (anti-cathode), and probably some rare other tubes, as the one shown above, the “hooded anode” stayed practically unknown until it was introduced (or re-invented) by W.D.Coolidge in 1915 after the introduction of the Coolidge type tubes. (Grigg : The Trail of the Invisible Light, pp 79 and 129, Charles C. Thomas, 1965). It was not commonly adopted by the tube industry before the thirties.

	Go to Category Index
	Go to Main Page