Condition: Thinest Atmosphere Possible

7 08 2011

All photos.

My goal today was to find the thinest atmosphere that still creates a plasma.

The oscilloscope attached to the langmuir probe reveals this behavior transition around 8 millitorr:

Above 8 millitorr the plasma is relatively stable. As the pressure drops below 8 millitorr, the behavior transitions to extreme spikes in floating potential. The electron gun is at 25KV, current limited to 1mA.

This transition is not apparent from watching the plasma or power supply. New information!

As the pressure continues to drop, the spikes become less frequent and more extreme.

Until eventually I heard a rather loud pop…. which blew out the trigger circuit on my coil power supply!

I’ll have to repaire the coil power supply now. I must point out the bleed resistors did their job and slowly discharged the coil capacitors. Crucial safety feature.

So we learned something and I broke something. Good day.

UPDATE: A continuity test of the coil failed. The coil is damaged. The coil power supply is fine

%d bloggers like this: