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

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Discussion Overview

The discussion centers on the appropriate voltages to be used for the focus and deflection plates in an electron gun, specifically for an accelerating potential of 5-8 keV. Participants explore methods for determining these voltages and share insights based on existing technologies, such as CRT tubes.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about the specific voltages required for the focus and deflection plates in an electron gun setup, expressing uncertainty about how to calculate these values.
  • Another participant references literature on the subject, suggesting that there are resources available that may provide guidance.
  • A participant mentions that typical CRT electron guns operate with around 12 VAC for the filament and 20-28 kV for the anode, implying that similar principles may apply to the construction of a new electron gun.
  • The original poster clarifies their setup, stating they have 14 VAC for the filament and 20 kV for the anode, and seeks advice on the power supply for the focus electrode and deflection plate, questioning if there is a relationship between them.
  • There is a suggestion that a voltage range of 150-200 V might be applicable for the deflection plate, although this is not confirmed and remains speculative.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the specific voltages for the focus and deflection plates, and multiple viewpoints regarding the appropriate values and methods for calculation are presented.

Contextual Notes

The discussion lacks detailed calculations or established relationships between the voltages for the focus and deflection plates, and the assumptions underlying the proposed voltage ranges are not fully explored.

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

davenn said:
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
 

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