How Come Early CRTs contained more Ions?

[jeyurkon]

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