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.


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.


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:

Langmuir Probe

12 07 2010

All photos.

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?

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