Hi,

so, now I can give back something for your good advice on ECR ;)

if you want to do VUV you can use, for example, such a glass:

https://accuglassproducts.com/product.php?productid=17741&cat=603&page=1

If you have really self sputtering, then it should be possible to go down with your gas pressure without any real influence on the dense plasma above your cathode. This would be a simple way to test your hypothesis in addition to OES.

arrigato,

I would create enough ions and radicals from sputtering to replace the Argon gas? i close slowly my Argon supply, and despite the pressure drop it would continue, well the drop can not be that big.. or do the energetic particles give less pressure to a baratron? ( they are not thermalised)

for now this intense green copper plasma is not stable, in minute periodicity it is oscillating between a 'normal' state (the copper surface is more white/rosa) and a high current real intense green state. I suspect the Oxygen contamination changing my secondary electron rates. So I oscillate between contaminated target to clean one.

Have you ever seen burning anodes?

The high ion currents must have their counterpart current on the anode. Mine is small a looks like burning.. (like flames dancing around it)

any place on RG to put videos?

mit freundlichen Guressen aus Nagoya

Hallo :)

If it is really self sputtering, then the ions emerging from your cathode should be sufficient to maintain the sputtering process - at least with very little working gas inside. The drop in your pressure will depend solely on your pump when you shut off the Ar supply (which pump do you have in your experiment?).

The pressure on your Baratron gauge should be independent on the gas sort, so if your temperature is not rising in your experiment (which is not the case, if you have no real thermalisation), you should be fine.

Regarding your "flames" on the anode - it might be that you have some anode spots (or fireballs). These are things I am dealing with in my research - but that is now just an educated guess - maybe you can link a picture here - or put some movie in a dropbox and send me the link then I can tell you more.

Anode spots can arise when you get a lot of energetic electrons in front of your electrode (with energies > ionisation potential) which will create additional ions in the sheath around your anode. This causes expansion of the sheath into a 3-D object, a fireball.

You can also check this by altering the pressure: fireballs are sensitive to the neutral mean free path. Hence if you reduce the pressure, the FBs (if this is what your "flames" are) will grow larger.

beste Grüße aus Graz

Hi, to answer rapidly to your question, I would say never ! The desexcitation of atoms can "mask" Ar* and Ar+* emissions to your eyes but Visible OES could give you much more information. Experiment proposed by Johannes would be better than OES to confirm self-sputtering.

Well, we saw also short of firewalls in our anode in a Simple DG GC when pressure is quite high (>1torr?) We found a very simple way to check wether they were due to charged particles by making the balls spin around the anode bar with a magnet!

Hello Francisco,

Yes, it is quite possible that you get fireballs also above p > 1mtorr (in fact, you will see them up to atmospheric pressure, but they tend to split up. So their size decreases while their number increases).

They are for sure due to an additional production of charged particles (that is, of course, if they are fireballs).

https://www.youtube.com/channel/UCSDkhk2mh9p4HbUy7UWq7KA

there hould be a video of the breathing plasma.

the quality is not perfect..sorry

I wrote some more into the abstract of the video available in my contributions. (breathing-plasma)

No post-doc position in Limoges?