New Inner Grid

27 10 2009

Yesterday I made a new fusor grid:

IMG_4406

With an 45mm OD, this grid is smaller (and prettier) than the previous at 65mm. The old and the new grid side by side:

IMG_4413

 

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Second Attempt

25 10 2009

Made a second fusion attempt today with a deuterium plasma. Using the new power supply and the mass flow controller together produced very stable plasmas. I tried a variety of voltages, currents, and pressures but no bubbles.

I have two hypotheses:

a) we are producing fusion, but the detector is not showing it.

b) we are not producing fusion because of grid misalignment.

While double checking the bubble detector, I noticed a relevant detail: the bubble detector must operate within 20˚ C to 40˚C. Today the room temperature was 16˚C. The detector has a built in liquid crystal thermometer. Black means the detector is out of range. To correct this, I put the detector in my pocket for 20 minutes. This warmed the detector to 34˚C :

IMG_4389

I want to get a geiger counter as a double check for the bubble detector. The geiger counter would respond to x-rays produced during fusion.

But really I think the problem is that our inner and outer grids are completely misaligned. From what I’ve read grid alignment is necessary for “star mode”. And it seems this is necessary for fusion.

It should be pretty easy to fabricate a new/better pair of grids.

Although we didn’t get fusion today, it was a success in other ways. The system is working smoothly. We have stable plasmas with voltages as high as -17kV. The mass flow controller minimized the deuterium use.

The mass flow controller also lets me adjust the gas flow at a safe distance, which is a welcome upgrade.

Here is a video of the deuterium plasma:





-30kV / 10mA

24 10 2009

If you’ve been following me on twitter, you know I received a -30kV / 10mA Glassman a few days ago. Now it’s online and it kicks ass. Current limiting, remote controllable… it’s the second unit from the top:

IMG_4371

Here is an air plasma it produced:

With current limiting and good air metering, we can get a stable plasma. I notice you get a sense for the plasma just by _listening_ to the glassman. When the plasma is unstable the glassman softly clicks along with the plasma burst.

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Mass Flow Controller Online

21 10 2009

Big day. Big win. Big upgrade.

Got the mass flow controller online!

IMG_4322

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Arcam EBM fabrication

19 10 2009

I’m exploring the Arcam EBM process for fabricating the magrid.

Our current scale is within their build envelope (250 x 250 x 400 mm and 350 x 350 x 250 mm).

Their process creates a fully solid / fully melted part using Ti6Al4V Titanium Alloy.

Titanium is non magnetic (paramagnetic). GOOD

Titanium has low outgassing (I _assume_). Not seeing good information on this, but I see articles about low outgassing. GOOD

The fully melted part should be vacuum tight. GOOD

Titanium can be welded, but it’s complicated. Gas shielding is required. WORKABLE

Titanium is difficult to machine. It requires specialized tools. It’s tough and springy. Too hot and it reacts chemically. The magrid part is likely too delicate to be secured for machining. We can still lap sand the faces for better mating. BAD/WORKABLE.

Titanium is strong. GOOD

Titanium is beautiful. GOOD

The part would be highly conformal. I do not expect the warping as with the prometal magrid. GOOD

Price. This same part would cost around $2500. Better get it right the first time. WORKABLE

Although it’s a path fraught with peril, it could lead to a fully functional superconducting magrid.





Cleanup

19 10 2009

With the large chamber gone, I’m able to setup properly:

IMG_4309_1

As the project gets complex, I must keep the lab organized.





Superconducting Magnet

15 10 2009

Gearing up for a second superconducting magnet test. This time computer controlled. Here is the new bobbin with 133 turns:

IMG_4262

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