Description of my Fusor (J.A.N.K.O)

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Anze A Ursic
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Description of my Fusor (J.A.N.K.O)

Post by Anze A Ursic »

Hello,
Before posting my appllication to the neutron club, I figured I'd show and explain my fusor system. For reference, this system was located in the basement of a building at Penn State and this system was, based on a few official records, the first successful fusor at Penn State. This project was not sponsored by anyone, nor did we really have that much funding, so a lot of stuff may seem a bit scuffed, but it worked!

VACUUM CHAMBER

The vacuum chamber used for this experiment was much larger-than-needed and had way too many connections, but it held vacuum spectacularly since it was built by an older Russian gentleman who was an expert in vacuum technology. I modified the chamber slightly from its original state by just adding a 30kV feedthrough, a gas inlet on the top and changing out two CF6.00 flanges.
chamber1.jpg
chamber.jpg

GRID

The grid was built directly on the 30kV feedthrough. A SS stalk was used to extend the grid to the center of the chamber and the grid itself was built from Tungsten. The grid was approximately 1.4" in diameter.
grid1.jpg
grid2.jpg

POWER SUPPLY

The power supply used was a Spellman DF3 which we found on Ebay for a suspiciously low price and it had no serial number. It often behaved erratically, including just shutting off once it ramped up to the required voltage. There is a trick I used to get this thing to work, since it would almost always shut down at some point because it said "mA regulator error" which, based on the manual, means the current was out of range from the set value. This was a problem since the current fluctuates during a fusor run and it's never constant at some pre-defined set value. So to fix this, I shorted the pin on the 50-pin connector on the back of the supply that would output a 0-10V DC signal based on the current level (0-10V corresponding to 0-80mA) to the pin that was reading what the current was supposed to be set at. That way, whatever the current was, was read as the correct value.
DF3.jpg

DEUTERIUM INLET

The 50L Deuterium tank can be seen in the chamber photo above. It was connected in series to a pressure regulator, a 10 SCCM MKS Mass Flow Controller (MFC) and a manual regulator. The MKS flow controllers units are usually controlled by a control box, such as the MKS 647B, which we had, but you have to manually input the flow rate on their small keyboard and press ENTER, which is a time-consuming and tedious process. To avoid this, I built a custom Y-split cable that connected to the 647B on one side and a 0-5V power supply on the other. Basically, I used the 647B to power on the MFC and used the 0-5V power supply on the pins of the MFC that control the flow rate, since it's just a linear correlation between voltage and flow (0-5V corresponds to 0-10 SCCM of flow). This way, I had an analog knob that allowed me to fine tune the flow rate of Deuterium and thus pressure. The power supply is shown in the remote control photo below.
mks.jpg

LabVIEW SCRIPT

The front-end and the "code" behind it is shown below. This GUI allowed me to remotely turn on / off the power supply, enable and disable the HV, read and set the voltage real-time and read / control the current. It also showed the pressure that was read from one of the Balzers pressure gauge units. Two MyDAQs were used in tandem with the script, those are described below.
labview.png
labview script.png

CONTROL HARDWARE

The control hardware consists of two NI MyDAQs that would read and write the power supply voltage and current, read the pressure from the Balzers pressure gauge, and display the voltage and current on time graphs, so I could see if there were instabilities. There was a 100kOhm ballast resistor in series between the power supply and fusor, so the "Voltage across plasma" was basically just the voltage readout - (current readout x 10^5). I also built a small little box that had two things required by law; a visual indicator showing the device is energized and thus is producing X-rays and an emergency stop button. One mydaq connected to this box, which then connected to the DF3 power supply via a 50-pin connector. Inside the box was a small circuit I built which was just 3 separate transistor ON/OFF circuits which were used to remotely turn on and off the power supply (seen in the LabVIEW script as the three buttons on the bottom).
BOX AND MYDAQ.jpg
BOX.jpg

REMOTE CONTROL STATION

To appease the University's safety requirements and lawsuit avoidance, I built a remote-control station that was located in the hallway outside the room in which the experiment was conducted. This way, the safey personnel, who were present at the fusor runs, were more lenient with me producing ionizing radiation, as long as it did not leak outside the room. The remote control station stood proud and tall on a beer pong table from Walmart. From left to right, referencing the figure below, there was a live-view monitor directly connected to my Sony videocamera, which also recorded all the experiments, then my laptop, which showed a live-view of the power supply's front end to confirm voltage and current values. The front end also had errors that would pop up in case of power supply failure, so it was useful for viewing those too. Underneath my laptop there was a 0-5V DC power supply used to regulate the MKS MFC as described above and lastly, my PC which ran the LabVIEW script.
REMOTE.jpg

Anyway, this was the system, it was old, barely held together and to this day, I have no idea how I got to nearly 30kV on this monstrosity. But I'll be damned if this isn't the coolest thing I've ever built. There was a lot of trial and error and anyone who has seen any of my previous posts will know that. I also worked for years on a different vacuum chamber which leaked badly and none of those experiments were successful. But I learned a lot in the process and having to design each aspect of this fusor on my own really pushed me, but the experience gained is immeasurable.
I have some good footage to upload soon, but if I have missed anything or you would like to know more about any aspect, feel free to ask, I will try and respond as fast as possible.

It goes without saying but this would not have been built without the support of all of you on the Fusor forums. So thanks!

Anze
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Rich Gorski
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Re: Description of my Fusor (J.A.N.K.O)

Post by Rich Gorski »

Wow, what a setup! I'm jealous of all that great equipment... and all the personnel at Penn State at your disposal. It looks like you will be generating fusion neutrons very very soon. Did you mention what your neutron counter is?

Rich G.

Ps. Listen to your safety officer. Install those safety interlocks. That PF3 is capable of generating lots of nasty X-rays as well as giving you a good jolt. Be careful.
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Richard Hull
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Re: Description of my Fusor (J.A.N.K.O)

Post by Richard Hull »

Thanks for interesting images and explanations. This is, indeed, a monster of a system of huge volume. I would hate to pay the D2 bill. We look forward to your neutron club application report. Nice work with such a large system.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Anze A Ursic
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Re: Description of my Fusor (J.A.N.K.O)

Post by Anze A Ursic »

Rich, I already measured a neutron flux on several runs in October, I will be posting results here soon. I used the safety officers' provided Eberline NRD detector with a Ludlum 2241-2 survey meter and my own BD-PND bubble detector I bought. And yes I took safety very seriously, including borrowing 0.75 metric tons of lead bricks (a perk of going to a school with an amazing nuclear engineering program) to create shadow zones for any potential X-rays. Way overkill but better safe than sorry.

Richard, yes it was a big system, but I wasn't footing the bill for the D2, the lab did. God bless research funding! :-)
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Dennis P Brown
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Re: Description of my Fusor (J.A.N.K.O)

Post by Dennis P Brown »

Look forward to your data on neutron detection. Nice setup - well equipped labs are a gold mine for scrounging!

As for the X-ray 'hazard', I'd be surprised if you could even detect any x-rays. At 30 kV, that steel chamber will stop any threat. Your window is so far away that again, bet you get a near null reading there as well. I know this because I have an identical main chamber as you are using, have a 32 kV, and have never been able to detect any x-rays - even through my main window (though that is pointed away from me and I use a simple mirror for monitoring the plasma.)

Speaking of safety - those lead blocks are supposed to be either painted or sealed. Your safety department has dropped the ball by missing that requirement (OSA). Handle with gloves and do wash your hands afterwards since the Pb dust can spread everywhere.
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Anze A Ursic
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Re: Description of my Fusor (J.A.N.K.O)

Post by Anze A Ursic »

Dennis,

Agree, this lab was like a playground for me. We had closets full of vacuum parts, pumps, feedthroughs, etc, etc... and I was given free reign to build and / or modify my system however I liked. It was a really fun process!

Also, there were detectable X-rays right outside the viewport. They had a current meter there and I believe the levels were above 5mr/hr at 26kv+.

As for the safety comment, the lead blocks were encased in several layers of plastic. It's perhaps not visible from the pictures, but the plastic was there. Even then I always wore gloves and washed my hands.

Anze
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