Plasma!

[Dennis P Brown]

Sorry, been busy so not keeping up of late (had been on travel some time and just now catching up on all the things that fell by the way side - lol.) Your results are fairly good and that isn't too bad a vacuum that has been open to the air. I saw that your system is large so out gassing and getting it very clean takes time - frankly, that will always be an issue for your system that you will need to live with. The key is not opening it to air for long periods of time. However, burning a deuterium plasma in it for a short time at a significant fraction of a torr would likely do wonders after opening and might be worth trying if your deuterium supply isn't too limited - this is ideally done below 15 kV so x-ray isn't an issue.

[Anze A Ursic]

Dennis, thanks for the idea, however, because of the nature of our DF3 supply, nothing below 15-16kV is possible. the power supply just shuts off lol.

But, we're doing a preliminary test on wednesday and burning some deuterium at 16kV more so to check everything including the HV setup, the ballast, the pressure control, my LabView remote control gui, etc,...

I did hit 3.3E-5 Torr yesterday and the vacuum expert was right, the chamber and specifically the turbo were dirty and we had a lot of outgassing. I plotted the pressure vs time again and you can see drastic improvements day by day, to a point where we're getting below E-4 torr in fractions of the time. Our fusion run date is scheduled for 5/16/2022 so if we continue pumping and purging the system, I wouldn't be surprised if we hit E-6 Torr.

Anze

[Anze A Ursic]

Since the viton gasket was mentioned a few times, is that an X-ray hazard? Meaning, is it a dangerous source of X-rays since it attenuates X-rays worse than steel?

Anze

[Dennis P Brown]

Plastics are not an x-ray hazard - they absorb but don't emit x-rays. Steel attenuates x-rays as well as produces them (when bombarded by energetic enough electrons, of course.) It has to do with the inner electrons being knocked off the Iron (Fe) atoms by high energy electrons. Iron has many bound electrons so the binding energy of its inner electrons is huge. So when an inner electron is knocked off, an outer electron drops into that inner, "empty" orbit. This is done by the outer electron emitting a photon with a large energy - i.e. an x-ray. However, the Fe in this process also reduces the energy; so by a series of such absorptions this can significantly reduce the x-rays via that process (also, simple scatter/recoil during the process.)

Carbon based compounds have far fewer electrons so the binding energy of the inner electrons isn't very large. As such, they cannot produce x-rays under any circumstances by having an inner electron knocked off.

At high photon energies the specific process defines the difference between whether such a photon is an x-ray photon or a gamma ray photon - even for photons of identical energy. The process defines which name is used - an inner electron photon process is always an x-ray and any nuclear process that produces a high energy photon is a gamma ray photon.