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:
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.
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.
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:
Most of the parts for the Langmuir probe are here.
The probe will connect via the rear 8″ conflat:
Unfortunately, this 8″ conflat holds the chamber up! So I whipped up an 80/20 solution:
You can see the chamber is supported on either side by 80/20:
Stuart has the long socket wrench we’ll need:
We have ceramic tubes left over from the fusor grid. However, they don’t quit fit together. I’ll have to file the smaller one with a diamond file. Easy.
An open question:
Finally… I still need to purchase the super thin tungsten wire that will form the tip of the Langmuir probe. Anyone have a foot or so of thin tungsten wire?
Prometheus Fusion Perfection 