X-rays and bulbs.... final thoughts

Hello all,

Just some final comments on incandescent bulbs and x-rays.  I was reading
through the posts and most of you seem to have the right idea.... the amount
of vacuum within the bulb is the key.  In a nutshell, when the bulb is
sufficiently vacuumed of air and not backfilled with noble gases, it will
produce x-rays when energized by the high voltages from Tesla and similar
coils.  The vacuumed incandescents are like Crookes and x-ray tubes of the
"cold cathode" type, where the degree of vacuum is not especially hard but
enough to produce softer x-rays (I believe the vacuum level between 10 and
40 milliTorr).    This clearly differs from the Coolidge tubes whose vacuum
is at least 0.1 mT.

Upon energizing a candidate bulb with a Tesla coil, the tell tale sign of
x-ray production will be a lack of blue corona around the filament, but a
greenish fluorescence, along with white and yellow perhaps but primarily
green, present on the inside walls of the glass envelope.  Use a Geiger
counter for confirmation if unsure, with the probe placed at a discreet

Be mindful of x-ray exposure!  Although the currents are less with smaller
Tesla coils, the voltages are still high enough to cause possible damage to
biological organisms (you!).  At 50 Kv, the x-rays are strong enough to
penetrate a coffee can as I pointed out in an earlier post.  If they can go
through the can, you are a good target too!  The higher the voltage, the
greater the penetrating amount of the x-rays.  For shielding, use either
distance (my favorite as long as no one is within the exposure range) or

Watch out for some of the smaller incandescent bulbs on the market today!
There are still some 25 watt varities I know of that will produce x-rays
upon application of sufficient voltage.

Hope this has helped clear up any uncertainty.

John Bowers