What Voltages Should Be Used for Focus and Deflection Plates in an Electron Gun?

[india]

Hi all, I am making electron gun. I have several High voltage power supply to provide enough voltages to Filament, Anode, Grid, Focus and deflection plates. I want to make electron gun of acclerationg potential of 5-8 KeV. I know I have to give negative supply to cathode or filament. and then put positive voltage to anode plate. But I don't know, the values of voltages that can be given to focus and deflection plate. Is there any method to calculate specific voltages ?

 

[voko]

There are books written on the subject. Here is one: http://www.fieldp.com/freeware/charged_particle.pdf

 

[davenn]

Hi all, I am making electron gun. I have several High voltage power supply to provide enough voltages to Filament, Anode, Grid, Focus and deflection plates. I want to make electron gun of accelerating potential of 5-8 KeV. I know I have to give negative supply to cathode or filament. and then put positive voltage to anode plate. But I don't know, the values of voltages that can be given to focus and deflection plate. Is there any method to calculate specific voltages ?

Hi india
welcome to PF :)

well there's no negative voltage on the filament as such. take a TV CRT tube electron gun for example ... they are usually fed with ~ 12VAC. The Anode at the front end of the tube has anywhere from 20 - 28 kV on it.

why would you try and build one when you could experiment with an old TV/monitor CRT ?

Dave

 

[india]

Thanks Dave, Yes I know, I written wrong. I have 14VAC for filament and 20KV supply for the anode. I have already built gun, just amazed to give power supply for focus electrode and deflection plate. So I want to know, what type of power, and how much power I have to give the focus electrode and deflection plate. is there any relationship between them. or any voltage like 150-200V can be given to deflection plate.

Hi india
welcome to PF :)

well there's no negative voltage on the filament as such. take a TV CRT tube electron gun for example ... they are usually fed with ~ 12VAC. The Anode at the front end of the tube has anywhere from 20 - 28 kV on it.

why would you try and build one when you could experiment with an old TV/monitor CRT ?

Dave

 

[sardar]

Hello there,

It's great to hear that you are working on building an electron gun! As for your question about the specific voltages for the focus and deflection plates, there are a few factors to consider.

First, the voltage for the focus plate will depend on the desired beam diameter and convergence. Generally, a higher voltage will result in a smaller beam diameter. It's important to keep in mind that the voltage should not be too high, as it can cause the beam to become unstable. It's best to start with a lower voltage and gradually increase it until you achieve the desired beam diameter.

For the deflection plates, the voltage will depend on the required beam deflection angle. This can be calculated using the formula V = Ed, where V is the voltage, E is the electric field strength, and d is the distance between the plates. The electric field strength can be determined based on the desired deflection angle and the distance between the plates.

Additionally, it's important to ensure that the voltage for the deflection plates is synchronized with the voltage for the anode plate to ensure proper beam scanning.

I hope this helps guide you in determining the appropriate voltages for your electron gun. Best of luck with your project!