[ohohyodafarted]

You're right Eric,

the problem is between the thick metal ring and the thin metal ring which are fused together in some sort of fusion welding process.

Yes, we have taken advantage of the fact that you can "flow" a sealant into the area where the thick and thin metal meet. Vac seal is not the material of choice. Too thin to fill the voids between the metal layers. It does however seem to endure the heat of the evacuation oven very well. In our first trial, we used vacseal. When we took the crt out of the oven the Vacseal had left a very nice glassy coating on the surfaces that we applied it to. That tube was however not a leaker.

I also used Vacseal to seal some vacuum pumping lines that I was experimenting with and it did not seal the leaks.

Also, I spoke to a fellow in the business of working on UHV eqipment. He rapairs and services HE leak detectors. He had nothing good to say about Vacseal. He did however say that the material we are now using was very much favored by him for sealing leaks.

Oh yes, I almost forgot, one of the reasons that Vacseal is not the first choice, is that it is a solvent base material and it's curing hinges on the depletion of the solvent. This is a very big problem for sealing a CRT. The issue is that as we pull a vacuum on the crt, the Vacseal will have a tendency to outgas it's solvent into the crt. That could potentially contaminate the crt after pumpdown. The sealant we use is not solvent based.