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

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Sydney Experiment: We Have Electron Confinement!!!

2 08 2011

All photos.

1 year,  7 months  and 8 days ago I learned of the copper coil Polywell that Joe Khachan and his team built.

I decided to repeat Joe’s experiment. Although challenging it seemed possible to achieve. I dubbed this endeavor the Sydney Experiment.

It took far longer than I expected to fabricate all the necessary parts for the experiment.

Today with great pleasure I ran the Sydney Experiment. Here we see what appears to be electron confinement:

This acquisition shows the floating potential of the langmuir probe.

This run was done with air plasma at 10 millitorr :

The electron gun was running  10KvDC @ 6.5mA:

The coil power supply was charged to ~ 400VDC:

This is just a first run. Now begins the actual experimentation and data gathering.

I do believe this is the WORLD’S FIRST AMATEUR POLYWELL!!!

 

The plasma during the run:





Langmuir Probe Test

29 07 2011

All photos.

Today I did a successful test of the Langmuir probe:

 

Here is a voltage reading of the floating potential:





If At First You Fail: Cheat

21 07 2011

All photos.

The delicate assembly I made yesterday fell apart when I tried to assemble it today.

So I’m taking the easy way out… I will use one strand from this stranded silver-plated teflon-insulated wire:

Much sturdier!

Now I have a fully assembled Langmuir probe:





Building the Langmuir Probe

20 07 2011

All photos.

Today I began fabricating the Langmuir probe.

I am using a tungsten light bulb filament as the probe tip:

The rest is just ceramic tubing to hold it in place.  The filament is so thin and so fragile.

I use insulating varnish to hold it all together. I have to let this cure over night:

This will attach to the feedthrough:

The Langmuir probe will show the floating potential of the plasma… The dependent variable in the Sydney Experiment.





Bellows Holder

19 12 2010

All photos.

Back in the lab today after some travel out west.

Previously I designed a bellows holder to keep the high voltage feedthrough from moving.

I received the part and installed it successfully today:

A real win using 3D metal printing.





Updates

16 07 2010

All Photos.

TV Asahi did a report from the lab:

We received the final ceramic for the Langmuir probe. It fits a little loose, but I think it will do.

Finally got a new drill… I’ve been borrowing my shop mate’s!

I started to explore the gas type calibration on the ion gauge. Until now it’s been set to air. But now we are running a deuterium atmosphere, so I tried setting the gauge to D2:

.

We saw the following difference in reading:

So 10 millitorr on the air setting is equilivent to 29 millitor on the deuterium setting. Big difference.

The lower pressure threshold to strike a plasma is ~20 millitoor in deuterium mode.

Discuss.

So it was noted on the fusor forums that I’m getting about 10% of the fusion I should be for the power going in. This is likely due to a leak or other contaminant in the chamber. Carl Willis suggested I drop rubbing alcohol into each gasket individually and check for a change in plasma color (hydrocarbons glow a steel gray compared to the purple of the deuterium plasma).I took a first stab at this but didn’t see any color changes. Here is a dropper of alcohol:

I also got a mirror for safer viewing of the plasma (the mirror does not reflect xrays):

Speaking of safety, I have a meeting with Dept of Health’s Dr.Karam. He’s a scientist and he sounds genuinely interested in the project. A radiation specialist, he is bringing a wide array of detectors to get a full profile of our radiation output. Should be really educational. Looking forward to it.

And finally I had lunch at Google NYC the other day:








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