80W laser tube negative pole has a ring

I have built an 80 watt CO2 laser and have been working on it for over 3 months, the last two weeks the laser tube on the negative pole has a ring. I can cut. I put in deionized water but it continues. Does anyone know how I can solve my problem?
Thanks.

Can you tell where it’s arcing to?

This really doesn’t look like arching, which is generally limited to the anode (hv) end of the tube.

Any chance for a better (closer) look…?

:smile_cat:

Is this a better?

The problem starts from the beginning of the work.

Better…

Do you have a mA meter so you can watch the current use? Is it a reasonable value?

I don’t know if you can really do much, pretty clear it’s within an area that you can’t ‘get to’.

The only ‘input’ to the tube is from the lps, doesn’t look like that’s an issue… but visually you can’t really tell much except it’s lasing.

Ensure it’s not drawing too much current and that the output beam is in TEM0 state.

Good luck, let us know what’s up…

:smile_cat: