How Come Early CRTs contained more Ions?

[jr_tech]

Originally Posted by cwmoser

I've understand that the ION Magnet should be adjusted to the brightest image. I backed mine off slightly from maximum brightness to eliminate shadows on the edge of the picture tube. I assume this is OK considering that the ions still will not hit the phosphorous because the electron gun shoots out deflected?

Then I have heard that if you don't adjust the ION magnet just right, it will mark the center of the picture tube.

Comments?

Possibly you could re-position the yoke slightly to obtain reduce the "neck shadow" and then obtain a brighter picture by re-adjusting the ion trap to its optimum position, but I don't think that a slight mis-adjustment of the trap magnet will allow ions to strike the screen. A VERY MUCH stronger magnet would be required to bend the ion beam enough to travel straight down the gun.
BTW The screen is coated with "phosphor*" not the element phosphorous, many confuse the two terms.

*For example, "white" P4 Phosphor is actually a mix of "blue" Zinc Sulfide (silver and zinc doped) and "Yellow" Cadmium Sulfide (silver doped).

jr