File:X-ray manual - U.S. Army (1917) (14756966352).jpg

Identifier: xraymanualusarmy00unit (find matches)
Title: X-ray manual : U.S. Army
Year: 1917 (1910s)
Authors: United States. Surgeon-General's Office American Roentgen Ray Society
Subjects: X-rays Fractures Teeth Chest Heart Radiography
Publisher: New York : Middleditch
Contributing Library: Francis A. Countway Library of Medicine
Digitizing Sponsor: Open Knowledge Commons and Harvard Medical School

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ot only wasthe greatest care required in pumping, but the metalparts had to be freed from occluded gas by heating in avacuum nearly to their melting point. In this tube thereis no source of electrons except from the hot filament,and as this supply depends only on the temperature ofthe filament, the operator has perfect control of the num-ber of available electrons by simply changing the res-sistance in the auxiliary circuit, Fig. 7. T—Tube. S—Shunt spark gap. SB—Storage battery. A—Ammeter. R—Resistance in battery cathode circuit. MA—Milliammeter. The current through the tube cannot be increased afterthe supply of electrons is entirely utilized, no matter howmuch the voltage is raised. This maximum current foreach particular filament temperature is named the satu-ration current, and until this is reached the voltage main-tained between cathode and target may be too low foruse. (Note: So long as the current reaching the tubedoes not exceed the number of electrons emitted per
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Fig. 7. Coolidge set up with storage battery(for lighting: filament.

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