Hi -
There's something that's always puzzled me about explanations of how a crt works.
As I understand it, an electron comes off the heater filament and heads towards the first anode, which accelerates it...

How does the acceleration happen?

You'd think the acceleration of the approaching electron due to its attraction by the anode would be cancelled out by an equal deceleration of the electron after it has passed.

Could someone clarify for me, please? Thank-you,
Graham
(London UK)

 

Hi -
There's something that's always puzzled me about explanations of how a crt works.
As I understand it, an electron comes off the heater filament and heads towards the first anode, which accelerates it...

How does the acceleration happen?

You'd think the acceleration of the approaching electron due to its attraction by the anode would be cancelled out by an equal deceleration of the electron after it has passed.

Could someone clarify for me, please? Thank-you,
Graham
(London UK)

The electron continues to be accelerated by the SECOND anode. which has a much higher potential. The fact is that a CRT is a rather unusual tube arrangement.

 

In case you missed it, after Grid 2 that "pulls" the electrons off the cathode, there is a series of grids that keep accelerating the beam toward the faceplate, which might nearly reach 30 KV in direct view color tubes. The voltages on the grids between G2 and the screen (the highest voltage anode) keep accelerating the electrons away from the gun, and the voltage applied controls the focus of the beam where it meets the faceplate.

 

Hi -
There's something that's always puzzled me about explanations of how a crt works.
As I understand it, an electron comes off the heater filament and heads towards the first anode, which accelerates it...

How does the acceleration happen?

You'd think the acceleration of the approaching electron due to its attraction by the anode would be cancelled out by an equal deceleration of the electron after it has passed.

Could someone clarify for me, please? Thank-you,
Graham
(London UK)

The acceleration field is a gradient of the electric acceleration field between apertures (cathode, control-grids, focus anode, accel anode, etc ...) in the electron gun. Once the accelerated electron passes the aperture the physical conductor of the electrode body quickly shields the previous acceleration field from the electron so there is little or no change in electron velocity after the aperture.

 

There is also that second anode, which is connected at that spot on the side of the CRT where the horizontal output HIGH voltage comes from. Not sure exactly where it is, but there was always a static feel on the face f the tube.

 

There is also that second anode, which is connected at that spot on the side of the CRT where the horizontal output HIGH voltage comes from. Not sure exactly where it is, but there was always a static feel on the face f the tube.

https://en.wikipedia.org/wiki/Aquadag

 

Somewhat tangentially related, this question reminded me of this excellent video:

 

What a hoot! Thanks for the trip down memory lane!