Very cool to see, I didn't think a CRT could even work with that much gas inside it. You can see the red glowing electron beam emerging from the very primitive electron gun, and it seems to visibly reach it's focal point before it reaches the phosphor screen (unsurprising as it has no focus electrode).

https://www.youtube.com/watch?v=mOAEv-jZarM

Very cool indeed! Imagine if someone put deflection coils, and did some slow scan vector images. That neon beam moving around would bw so cool.

@LightsAreBright27
Omg yes! The effect would be enhanced with some longer persistence phosphor (and a focusing setup with either a coil permanent magnets), but yes that would look very very cool

I would like to see that displaying not only vector, but raster graphics. The glow filling the tube would look cool.

@lightsofpahrump raster would be cool, but it doesn't work well on slow scan CRTs. If you want to make the scanning rate faster, the neon beam would be moving too quick so it will become too faint to see

Then how about running a low resolution like the 30 lines of Baird's mechanical televisor? That could scan slowly enough to have the beam be seen, remember that 30 non-interlaced was chosen as a compromise between detail and flicker on the rather slow mechanical system/

One can coat the screen with modern long-persistent strontium aluminate phosphor. It is vacuum compatible. I bet educational effect will be even better with phosphorescent image gradually disappearing and refreshing with slow scan!

Then how about running a low resolution like the 30 lines of Baird's mechanical televisor? That could scan slowly enough to have the beam be seen, remember that 30 non-interlaced was chosen as a compromise between detail and flicker on the rather slow mechanical system/

Think about it this way: The faint light of the electron beam through the gas is already faint as a single beam.
Now you are going to spread the same amount of light energy over a larger area as you pass the deflection coils. The same amount of photons divided by a larger area, makes the brightness incredibly low.

If you increase the beam current, you'll be able to see it. That might actually be necessary to make the image on screen bright enough, because the dot of light will also be spread over a larger area. If you adjust the dot of light on an XY scope with no signal to normal brightness and then apply signal, the trace will be very faint.