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Plasma!

Posted: Tue Apr 23, 2019 5:21 pm
by David Lloyd-George
After some troubleshooting, we were able to get a plasma in our vacuum chamber. We achieved this after an interesting change to our set up. Our current measurement system uses a 10Ω 25W resistor bolted to our frame with one end coming from the HV power supply ground, and the other going to our star ground point. We couldn't achieve a plasma with this and out of frustration, we bypassed the resistor and had the HV supply ground go straight to our star ground point. This change made all the difference for us and we got our first plasma that way. We then set up our HV divider system however we got some interesting results that didn't fit with what we had expected. Our voltage reading stayed approximately the same even though we had cranked up the Variac to levels that should've given much higher voltages. We then decided to connect the HV divider to our power supply directly and got these values for our voltage:
(the voltage divider is approximately 1000X)

AC input voltage, DC output voltage of HV divider (measured with multimeter)
26 V, -7.5V
38.7 V, -10V
47.1 V, -12.5V
58.0 V, -15.1V

We will try and work out some of these issues regarding measurement. The plasma pressure was the one thing that we could measure and we found that 100mTorr gave us the best looking plasma. After that, the plasma started to disappear and completely disappeared once our vacuum hit 12mTorr.
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Any questions or comments are always appreciated.

Thanks,
David Lloyd-George & Beauregard Pearl

(If this qualifies us for the plasma club, we would like both of us to be admitted because we have been working on this together)

Re: Plasma!

Posted: Wed Apr 24, 2019 8:44 pm
by Richard Hull
Sounds like you have an open 10 ohm resistor or a poor connection to same. No functional 10 ohm current measuring resistor placed properly in the ground leg will ever thwart fusor operation! It is impossible.

Measure the resistor with an ohm meter.

Richard Hull