Featured Fusor

19 08 2009

A college professor once told me that an hour in the library can save ten in the lab. Well now the library is the internet, but the adage still applies. Towards that end, I’ve been reading up on Fusors that have come before. One Fusor in particular stands out:

RTF Technologies’ Mark 3. This thing is incredible. I think it’s the first Fusor ever with a liquid cooled grid.  The engineering is amazing. It even incorporates it’s own heavy water electrolysis and centrifuge. It also sports some novel ion injection technology which pre ionizes the deuterium prior to injection to achieve maximum reaction.  It has a thompson scattering system to measure plasma density at the focal point.

Just amazing. Hats off to Andrew Seltzman!

I’m particularly interested because he has tackled the difficult task of combining high voltage with liquid cooling in his liquid cooled grid. Our superconducting Polywell will face similar challenges.


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Categories : Fusor

Superconducting Magnet

13 08 2009

I spent some time yesterday with my friend jewelry design Max Steiner. He helped me design and fabricate a small acrylic bobbin for testing the YBCO as a superconducting magnet. This will fit in the dewars flask:

IMG_3926

The silvery metal is the Hastelloy substrate the YBCO is deposited on.

I’ll test this out when we receive the DC magnetometer.


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Categories : superconductors

Progress Update

12 08 2009

Todd T. From Swagelok stopped by the shop and we quickly built a parts list for the deuterium system and the RGA. Turns out we are using a VCR style Swageloks, and they require a single use steel gasket much like the copper gasket in a conflat.

Also made a first pass at building the persistent switch. Here you see 50cm of insulated nicrome wire wrapped around 5cm of YBCO:

IMG_3915

Cover in Kapton tape:

IMG_3916

Connect a multi meter across the YBCO, and wire up the nicrome wire to a variable power supply:IMG_3920

And into the cold:

IMG_3921

Unfortunately I was not able to get any reliable readings from the ohm meter. Before I turned the heater on, the meter registered between -0.5 ohms to  0.4 ohms. Any change in resistance from turning on the heater was lost in the meters margin of error. However the heater does turn on and work. You can hear the LN2 boiling off when you set the heater current to about 1.5 amps. So not exactly sure how to meter and test the persistent switch… for all we know this one works. And really this makes perfect sense: the resistance of the multimeter probes should be greater than the strip of superconductor even in it’s resistive state.

Coming out of the LN2:

IMG_3922


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Categories : cryogenics, heater barrel, Residual Gas Analyzer, superconductors, Vacuum

Truncated Cubic Magrid

11 08 2009

I’ve been working on shrinking down the design of the superconducting magrid to fit inside the smaller chamber. I’ve been running into difficulty finding enough room to pass the 4.2 mm thick superconducting cable from coil to coil.

Finding myself stuck, I’m toying with the idea of moving to a truncated cube design to simplify things. The dodecahedral design is exciting, but not at the expense of building a working superconducting magrid. I made a new branch in the repo to try it out. Got the basic shape created:

chassis_cubic

Further Progress:

chassis_cube_cutout


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Categories : polywell

Persistent Switch

10 08 2009

I’ve decided to run the superconducting magnet tests inside the dewar of liquid nitrogen. This will give us maximum cooling with minimal loss of LN2. The dewar is non-magnetic. The experimental apparatus must pass through the 50mm opening of the dewar.

I have 180cm of insulated nicrome wire which will serve as a heater for the persistent switch. This length of wire clocks in at 40 ohms, so 0.222 ohm/cm. I’ve ordered Kapton Tape W/silicone Adhesive:

We’ll use this Kapton Tape to secure the nicrome wire to the YBCO cable, and to provide some insulation for the nicrome heater.

Liquid nitrogen boils at 77 K (−196 °C). The critical temperature for YBCO is ~ 92K (-181 °C ). So we need to raise the temperature of the YBCO by 15 °C.

Unfortunately we really don’t know how much of the heat from the nicrome wire is going to warm up the YBCO, and how much is just boiling off LN2. Should be pretty easy to find how much current we will need  with a little trial and error.


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Categories : cryogenics, superconductors

Swagelok

10 08 2009

So we’ve been really struggling with the Swagelok interconnects. Amazingly we were able to get a representative from Swagelok to come out to our lab! He’ll be here on Wednesday the 12th at 10am. Hopefully we can fully spec and purchase all the remaining parts for the deuterium handling system, the RGA unit, and possibly cryogenic interconnects. Shout out to Deez for making this meeting happen.


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Categories : cryogenics, Vacuum

DC Magnetometer

9 08 2009

Just bought this DC Magnetometer from AlphaLab to measure the strength of the superconducting magnets we are about to build:


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Categories : superconductors

Glass Insulator

6 08 2009

Ordering this glass tubing to protect the atmosphere side of the high voltage feedthrough. Hopefully they can cut it to size for me. They will get back to me about that.


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Categories : High Voltage

Lab Notes

5 08 2009

Someone left this on our lab whiteboard:

IMG_3800


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Categories : Uncategorized

Assembling the Fusor

5 08 2009

Time to try assembling the reactor. Deez polished the core to remove flux and oxidation:

IMG_3891Here we are assembling the whole thing. This took several attempts adjusting the core depth:

IMG_3900

The view through the window:IMG_3896

Looks like it holds a vacuum!


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Categories : Fusor

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