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Coolidge uses 200kV Lenard Rays to Punch Holes in Rabbits Ears

Lenard's Tube

P.Lenard in 1892, managed to bring Cathode Rays out from the Vacuum Tube, and into the atmosphere using the above apparatus. A thin aluminium foil window "D" is held by the brass cap "B". A metal cylinder "A" serves as an anode. The cathode is "C".

No more information was given with this diagram, and it is assumed that the major accelerating potential is between "C" and "B", with "A" perhaps used for beam shaping?

In the 1920`s W.D.Coolidge was producing excellent X-Ray tubes, he used the same innovations to produce a Lenard Tube with an accelerating potential of 200kV. Lenard`s original tube used only 30kV and the resultant Lenard rays had only centimeter range, and had to be detected using a barium platinocyanide screen.

The Coolidge Tube used a hot wire cathode in a hemispherical focussing cup, with the rays issuing from a thin nickel foil window (the anode), reinforced with a molybdenum wire grid. An account from 1929, concerning the power of the Coolidge produced Lenard Rays -

"Potentials as high as 200,000 volts have been used by Coolidge. With such a voltage the cathode rays can be detected at a distance of 40cms. from the window in atmospheric air. Such rays are far inferior in speed than beta-rays of radium, but are produced by the tube in quantities far exceeding anything remotely possible with the quantities of radioactive substances available.

The effects of this intense high speed cathode radiation are very remarkable. The rays produce a purple glow in the air around the window; they produce in calcite a phosphorescent glow which remains visible for hours after the exposure.

The action on organic tissue of all kinds is very striking. Plant leaves after exposure dry up. The effects on animal tissue, as exemplified by a rabbit`s ear, vary with the length of exposure. A very short exposure produces a tanning of the skin; an exposure of one second leads to the formation of a scab, which afterwards falls off with the hair, and is followed by a profuse growth of new hair which is, however, snow-white; an exposure of 50 seconds leads to scabs in the rayed area which leave a hole right through the ear when they fall."

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