slayer Exciter

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The build:
https://youtu.be/wCKQX6H1vj0

I'm currently enrolled in Physics 2426 and I am fascinated with the material. We recently covered some material on magnetic fields and transformers, so why not take the time to build a tesla coil?

But I've got a bit of an issue, I don't have the materials, or any money. I do have two MOTs I could wire in series and maybe get 33Kv - That would be sick - but I don't have much time, and the whole project would be pretty sketch. So I found an alternative:
The slayer exciter, I don't need a particularly high power supply to get a little bit of plasma and light up some fluorescent bulbs, and I have everything I need to throw one together real quick.

I did a couple of calculations before I started building; However, due to the time constraints I didn't get much down before I started. I knew the the longest piece of 1-1/4 PVC I had was about 27mm and based on the diameter of the wire (0.27 mm), I could get just about 800 windings (ended up stopping at 700). Additionally, I had TIP31A NPN power transistor which worked well with its base current of 1 amp.

I started by disassembling an electric motor from a blender and removing the magnet wire windings. I measure the length and width of the wire and the area of the entire coil (it was fairly square) in order to get an estimate of how much wire I actually had. 
I used this formula and found that I had more than enough wire to wrap the entire piece of PVC, as long as I soldered them both together. The wrapping process took an hour and a half, and I decided to stop at 700 turns. With 5 turns on the primary, this would give me a Transformer Turn Ratio of 140. Given an 18V input, I'd get about 2,520V on the secondary. I could probably calculate the spark length, but I there are a lot of variables and it would be easier to finish the project rather than find all those variables.

The circuit was fairly basic, I built it on a breadboard before transferring it to pegboard. I used a 20kohm resistor on the transistor gate which was sufficient to limit the current to the transistor gate, while still allowing it to open. A filter capacitor was added between the battery poles - I'm not sure if it was necessary, but it seemed to increase the spark length.

I had issues with the TIP31C getting hot, so I added a heatsink, but then replaced it with the 2n3055 which had significantly higher max current specs. Many people seem to be using the 2n2222 - I'm sure most of them blew out after a couple seconds.

How it works -
A current is supplied to the gate of the transistor and thus, the primary coil. The current in the primary creates a magnetic field which induces an opposing electric field in the secondary and a current. The current causes a potential difference between the top and bottom of the coil, which closes the transistor gate by pulling the battery current through the negative side of the secondary coil. The rapid on and off is essential as magnetic fields are only generated when current begins to flow. The fluorescent bulb is lighted by the current flowing through the air, and the bulb on its path to ground.


Concluding thoughts
I would love to explore some more efficient methods of winding the primary coil, tesla coils commonly uses a "saucer" shaped winding. I'm not very confident with the physics of transformer winding geometries. Additionally, I'd like to do some more current analysis to find out exactly what sort of circuit I could design to get the maximum plasma length. And finally, it would be cool to do some analysis with an oscilloscope to see how the current is changing through the transistor. I'm not even sure what the wave would look like. It would also be cool If I could play some music with the sound waves created by the plasma - I've seen it done before.

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