H.G.Fischer Discharge Tube

Ref. B20

With a 20” (50 cm) long tube with a 7” (17.5 cm) bulb, this discharge tube bears great similarities to the Macalaster & Wiggin Transformer Tube, having the same type of ring attachment to the anode. Presumably this attachment improves the efficiency of the electron beam emitted by the cathode, insuring it strikes the center of the target on the anti-cathode.

This tube, made by H.G.Fischer, Chicago, bears the serial number 86325. It probably dates to the last years of the second decade: On the back of the copper head of the anti-cathode are stamped four patent dates: Sept 1911, Dec.1913, June 1914, and Nov. 1916.

The regeneration device in the auxiliary chamber contains grayish fibrous material, probably asbestos.

In early X-ray literature, in accordance with the belief that they were particularly efficient, tubes with a ring attachment were sometimes called “Penetrator Tubes”. They appeared before the turn of the century, and in the book “Practical Radiography”, by A.W. Isenthal and H. Snowden Ward, printed in 1898, a Penetrator tube is already illustrated (p.63).