•Gas Discharge Tube

Introduction

Using a simple vacuum setup consisting of a single stage mechanical pump and some common lab hardware, small gas discharge tubes can be manufactured.

The goal of this project was to gain some experience with basic vacuum equipment so that I could advance to more complex projects like cathode ray tubes, fusors, and accelerators.

Design

Here is a sketch of the system:

One of the labels has an error – the line that points to the 0.25″ diameter plastic tube should be extended so that it leads to the tube that wraps around the 6mm glass pipe. In the diagram, it points to the layer of teflon tape that it wrapped between the two plastic hoses.

I used a Gast DOA-P704-AA pump I borrowed from a lab that used it for vacuum sealing. It only has an ultimate vacuum of 25.5″ Hg, which I was afraid wouldn’t be enough to witness any noticeable increase in spark length from atmospheric pressure. However, I was pleasantly surprised as I was able to create discharges a few inches in length using a 9kV 30mA power supply, the same one I used in my SGTC II. Under normal conditions, it would only strike at around half an inch.

Construction

April 21, 2011

Conclusion

And finally, some light!