[TCML] apple green glow

[Frank]

Generally speaking, X ray production is considered to possibly occur 
above 15KV.

X rays do not need to strike an anode to be generated.
The first Xray tube was a Crookes Maltese cross tube, the anode and 
cathode were perpendicular to each other with the cathode actually 
recessed in a glass stem.
The tube was originally built to demonstrate that cathode rays travel 
in a straight line in high vacuums.
It made X ray pictures and could cause burns if exposed to it long enough.
Roentgen discovered this by a glowing screen some few feet away from 
such a tube in operation.

Similar tubes, such as the Crookes focus tube, the high pressure tube 
and a high pressure Geissler tube generate X rays just to name a few.

Perhaps one of the most famous X ray tubes was the Lenard's tube. 
Again, there was no collision of electrons against a target to produce X rays.
You can build an X ray tube just by exciting a radio tube with a 
Tesla coil and it will produce enough X rays to make X ray photographs.

There is a modern X ray machine for NDT testing that used about 100KV 
and a modern cold cathode Lenard's tube for weld inspections.
I have such a machine as well as a single element reproduction of a 
Tesla X ray tube.

The green glow is the glass fluorescing by bombardment with X rays.

Brian, no, regular soft or hard glass will not block the X rays. If 
this were the case, there would be no X rays created by a regular X ray tube.

The X ray produced by such a tube as the one Kurt has or what you 
might expect with an "unfocused" tube one might find today are no 
threat if you see that green glow.
Yes, there is radiation produced but it is so diffused and weak, 
exposure would have to in terms of days and days before any harm could start.
If you still had a radium hand watch, you would be more at risk.

The first color televisions used around 25-35KV and X rays were 
observed in the flyback/ HV rectifier section of the set. Hence the 
warning on some of the later tube sets in the flyback section.
The actual CRT posed no danger and I am unaware of the face ever 
being leaded glass. Yes it was thick but this was to protect from 
implosion and glass dangers.

Frank

At 11:07 PM 9/1/2008 +0400, you wrote:
>As far as I understand that, the green glow of a glass tube indicates the
>presence of cathode rays. As a proof, this effect may be obtained in
>vacuum tubes with high voltage pulses supplied to a single electrode (the
>most simple setup is a small unfilled bulb put on a tesla coil or any
>other hv source). As there is no anode, no xrays can be formed by the
>electrons colliding with it (also the energy levels required for a glass
>to start glowing from xrays are long way higher), the effect is definitely
>a result of a cathode ray hitting a glass surface. On the other hand, I'm
>unsure if xrays are not produced in that process as well (however I doubt
>their power is enough to do any harm).
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