Question regarding VTTC flashover (resolved)

[V-Troxi]

Hello everyone!

Two years ago, built a big VTTC with a GU-5B triode, which was a successful project.
Over the last weeks I have frequently thought about the first tests that I did with this coil and now I am quite worried about the possibility that I produced x-rays.
In a triode, as in any vacuum tube, bremsstrahlung can occur if the applied voltage is high enough.
My coil was initially operated with two MOTs in series, resulting in an anode voltage of 8kV (12kVpk) after the voltage doubler.
According to my calculations, the normal operation of the coil at this voltage is safe because the glass of the tube should shield almost all radiation, since the photon energies are still quite low.

But during multiple of these initial tests, I had some flashovers of two types:
1. A big secondary to primary flashover which immediately tripped my breaker.
This only happened once and I considered the energy in the secondary circuit to not be high enough to be of concern.

2. Primary racing arcs that burned the underlying PVC pipe. These happened quite frequently and are the main concern for me.

What I am wondering now: are these primary racing arcs concerning when it comes to to x-ray production?
Can they increase the anode voltage to such an extent that high amounts of radiation are produced, or am I worried for no reason?
I have also tried to calculate this, but I have no idea how much energy each of these flashovers had and therefore an approximation of a maximum dosis is quite hard.

I would really appreciate any help and estimates on this topic since I am out of ideas and this is not really in my area of expertise.

Maybe someone has experienced similar flashovers with a VTTC and can give me an assessment me or someone who knows more about physics can help me out.

EDIT: This has now been resolved. The duration of the flashovers was very short and therefore the max. dissipated energy in the time-frames is quite limited (even when considering the doubler-caps). Calculations show that even in a worst case, the resulting dose would be negligible.

Best regards,
V-Troxi

[klugesmith]

Someone else can talk about possibility of very high anode voltages in your VTTC fault case.

You might get some comfort if you had a dosimeter than can indicate exposure to ionizing radiation.
The 1950's era CD V-138, with full scale range of 200 milliroentgens, is easy to buy online.
https://www.orau.org/health-physics-museum/collection/civil-defense/cdv-instruments/cdv-138.html

Here is video of one specimen getting zapped by a dental x-ray generator.

[V-Troxi]

Thanks for the idea.
I've thought about using a dosimeter as well. Unfortunately the setup has changed quite a bit so I can't really replicate this fault anymore.

I'm still eager to hear any ideas regarding this concern.
And has anyone experienced similar flashovers?

Best regards,
V-Troxi

[MechatEng2023]

The glass will block X-rays under 20 keV energy.  If any X-rays are produces, the glass wall of the vacuum tube will fluoresce in blue or green.
You can try it with small incandescent lamps which are evacuated, not inert gas filled.

/>The peak voltage should be kept under 20 kV.
Geiger counters have a low sensitivty to X-rays. You can also detect X-rays by placing a camera close to the vacuum tube. If significant amount of X-rays are emitted, dots will appear in the video.

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