Electron Gun Power Supply

5 06 2012

all photos (1/2)
 all photos (2/2)

The light bulb electron gun test had to be put on hold because we didn’t have suitable power supply, so we built one. Here’s the schematic:

The schematic of the power supply which will drive both the hot cathode and the accelerator anode.

Here’s the real thing:

It’s really two power supplies in one. Put simply, it will convert the 120v AC current coming out of the wall into a source of lower voltage, higher current, AC power for the hot cathode, as well as a source of positive potential for the accelerator anode.

This is how the hot cathode power supply will work:

1) AC 120 volts from the wall to a switch.


2) From the switch to a 0.5 amp fuse. This, as suggested by Rehan, will prevent a current overload should the cathode arc to the wall of the vacuum chamber.


3) The the current will go to a variac auto-transformer which will allow us to regulate the voltage and current of the hot cathode.


4) Out to the hot cathode.

This is how the accelerator anode supply will work how it will work:

1) Current from the wall will enter the box and go to the same switch as the cathode power supply.

(see above for photos)

2) The current enters a stand-alone DC power supply. It is essentially a transformer which steps the voltage down to 24v and then a rectifier which converts it to DC.


3) The current goes into a high voltage power supply which steps it up to 500 volts DC.


4) The negative HV output is capped, because we have no need for it. The positive high voltage output (which will ultimately create the large positive potential on the accelerator anode) goes into a potentiometer, which will allow for a variable potential on the anode, anywhere from zero to the maximum voltage output of the power supply.


5) A 2 MΩ resistor. This will act as a sort of safety-net resistor. If there is an arc from the hot cathode to the anode, this will prevent the cathode’s larger current from flowing into the HVDC power supply.


6) A voltmeter. Self explanatory.


7) Out to the accelerator anode.

And that’s all there is to it.

Domenick Bauer





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