I think Tubesrule gave the right answer for the electrostatic tubes.

As far as HV effect...

I tried to do a literature search, I found some information but I have to jump through too many hoops to access the articles from home. So, I think that what I am going to say is accurate, but also incomplete as an answer.

I suspect that the major ions species are nitrogen and hydrogen since they are not so easy to getter out. There may be some CO2, which the beam would dissociate.

I did a damage simulation using SRIM for 5 and 10 KeV for hydrogen ions and nitrogen ions on Zinc Sulfide. The types of damage that they would cause are lattice dislocations, vacancies and displacements. Zinc sulfide would get broken into the metal zinc and elemental sulphur. Oxygen would also make zinc oxide and volatile sulfates. None of these would scintillate.

Average grains sizes for ZnS are between 1-10 microns. You'll notice that the damage is from a few hundredths of a micron to a few tenths of a micron in depth. Small compared to the grain size.

The emission of light by excited ZnS and the effect of dopants is complicated. ZnS is a semiconductor and much of the light is from recombination of electrons and holes. Impurities, such as iron, not only have an overlapping absorption band, but cause deep wells that can cause a non-radiative recombination of the electrons and holes (no light...)

If you look at the damage it seems to be on the surface of the ZnS grains. The metal zinc and elemental sulphur would be randomly distributed in that surface and would easily capture light before it managed to escape the crystal. They, and sulfates from oxygen could also cause non-radiative recombinations.

What I'm leading up to is that I don't think there's a big difference between 5KV CRTs and 10KV CRTs. At least not more than a factor of 2 in aging rates.

The first two plots are 5 & 10KeV nitrogen on ZnS and the next two are 5 & 10 KeV hydrogen on ZnS. Oxygen would look similar to nitrogen.

The plots show the damage per ion per angstrom of travel versus depth. The peak damage along a track is about the same for 5KV and 10KV. The biggest difference is the depth of the damage. There is a much bigger difference between hydrogen and nitrogen. Hydrogen causes damage deeper into the grain but nitrogen causes much more total damage.

If the explanations I gave for the quenching or capture of the photon emission is correct, then the difference in depth of the damage isn't going to have a big effect. It's just the total amount of damage that matters and it appears that 5KV might last about twice as long as a 10KV CRT assuming that it has the same amount of residual gas to start with.

But, all this hand-waving might be nothing more than hand-waving.

John

Ion Trap Magnets
 

Since this thread contain some discussion of ion trap magnets I thought I'd mention this.

The RCA Sept 15, 1949 datasheet for the 12LP4 says that the main pole pieces of the magnet should be longitudinally opposite the internal pole pieces of the gun. Also, the orientation should be such that the north pole is adjacent to pin 6 and the south pole to pin 12.

I set the ion trap magnet that way when I installed the 12LP4 that Scotty rebuilt with a rebuilt gun. It required almost no re-adjustment of the ion trap. It was very close to the proper position to begin with. This seems like a way to minimize any damage that might occur by having a badly adjusted magnet when you do an initial adjustment.

John

I can distinctly remember in the 1950's as a toddler when my Mom told my brother and I that we shouldn't go out in the living room in our underwear because the people on TV can see you. I remember peeking in the room behind a door so I would not be seen.

I had forgotten about that memory until this post. Must be my earliest recollection:-)

Greetings from FixitLand!

The 17LP4 CRTs in the Motorola 17F13 combo set I had some 35 years ago, and in the Zenith K1846R I have now, both have (had) brownish, roundish patches at screen center. Is this not the ion burn we're discussing?

Take care,
--
J. E. Knox 'The Victor Freak'

if the patch has a non-distinct very gradual edge, it is surely ion burn, since the ions are not focussed like the electron beam.

Good day Gentlemen,

2 pictures of a pre-war TV with severe ion burn. Since, the CRT has been rebuilt by RACS.

Photo credit: courtesy Eckhard, Thanks!

Best Regards

jhalphen
Paris/France

To me, it sounds like this tube has 'gone to air' or lost its vacuum. Many times when this happens the white phosphur on the screen begins to peel or flake away. Naturally there will be zero emission.

It would show an image, if I zapped it with a rejuvanator and viewed in a dark room. All used up.

Hello Bryan, I didn't even realize who I was quoting until I saw this. I know I wasn't telling you anything that you don't already know! It's been a wonderful winter for electronics projects, but the money just isn't there... I wanna recap something SO bad!! LOL

Been tight here...though time has been tighter than cash. Getting to be a long time since I have brought one back from the dead.

Wow and I thought it was just me who was having a hard time finding funding for projects. Work is slow during the winter months. During my flight training I was told that flight instruction is the best part time job, and the worst full time job.

Maybe this summer I'll finally get a new project and become more active again in the Vk forums! I miss it sooo much.

See ya,
Matt Davala

I didn't realize it was possible to completely "use up" the cathode in a television CRT unless the set was used 24 hours a day at nearly maximum brightness for years on end, and never shut off. I've heard of tubes with very low emission after years or decades of use, but this is the first time I've ever heard of one with absolutely zero cathode emission. The only other way this can happen, that I can think of anyway, is if someone tried to rejuvenate the tube and had the rejuvenator set so high it stripped the barium oxide coating right off the cathode.