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Those damn 'X' Rays, from Tubes etc..

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TimFox:

--- Quote from: jmelson on April 12, 2020, 04:16:54 pm ---
--- Quote from: pwlps on April 12, 2020, 03:44:58 pm ---Without a heated cathode the current would be much smaller. Yet, as far as I understand X-rays were discovered by Roentgen without a heated cathode ?  I wonder how big was the intensity by today's standards.

--- End quote ---
Roght, but I guess Roentgen's tubes had a little bit of gas in them, which ionized and provided electrons to get a discharge started.

Jon

--- End quote ---
The original x-ray generating tubes used by Roentgen were actually glow-discharge tubes filled with low-pressure gas ("Crookes Tubes", q.v.), and were common until roughly 1920 (see Wikipedia).  As in VR tubes, the anode-cathode voltage in such a tube is roughly constant, determined by the anode-cathode distance and gas pressure.  Electrons hitting the anode produce x-rays by Bremsstrahlung, as in a hot-cathode high-vacuum device.  I believe that this is where the term "hardness" for x-ray spectra originates, since a "harder vacuum" operated at higher voltage.

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