Question about electron gun design

[bandersen]

It would be a much higher potential to accelerate the electrons.
I just remembered I have a 12FP7 radar CRT like this. Here's a picture of it next to a 7JP4 for scale. It has external 3rd anode connection, but it's not visible in this photo.
Yes, that huge 12" CRT uses electrostatic deflection.

[jr_tech]

Nice Pix! Some that I have seen use 3-5 "wall bands" that are operated at ever increasing potential as the screen is approached. The idea here is to deflect electrons as they are moving slowly (for high deflection sensitivity) then accelerate the electrons as they approach the screen (for high brightness). The trick is to do this without loosing too much of the deflection sensitivity or producing distortions as the beam is accelerated. The "scan expansion mesh" was one of the better solutions.
I have attached a Pix of another early scheme that worked fairly well...a resistive spiral is deposited on the inside of the bottle. At the end near the deflection plates the spiral is connected to a low voltage (similar to that on the deflection plates)... the other end, to 10kV or so, to produce a nice bright image.

jr

[ppppenguin]

Don't forget the fundamental properties of electrostatic CRTs: deflection sensitivity is inversely proportional to EHT voltage. In magnetic CRTs there's a square root law so the deflection power doesn't increase as fast with higher EHT.

PDA overcomes this inherent problem with electrostatic CRTs. I suspect it only really works with narrow deflection angles, possibly due to geometry problems and the usual trouble of the beam hitting the deflector plates.