Fusor Progress, Luke Harrill

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Joe Gayo
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Re: Fusor Progress, Luke Harrill

Post by Joe Gayo »

Was the backing pump a scroll? Did the backing pump automatically vent (I have a dual-stage oil vane that has this "feature")?
Luke Harrill
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Re: Fusor Progress, Luke Harrill

Post by Luke Harrill »

Hey Joe,
It was an Adixen 2-stage, rotary vane. That one should've had a anti-suckback system, but I'm not sure if it malfunctioned or a purge gas was the culprit. God only knows how many hours that pump's oil had on it before I changed it.

Part 2/3
High Voltage

The high voltage is supplied by a 125kVp 300mA oil-tanked X-ray transformer. This I removed the filament transformers from, and subsequently dropped in a 75kohm ballast resistor (brown ceramic coated). It is then ran to a Machlett HV-1 voltage divider for measurement. Next, it goes to the HV feedthrough I made.

At the moment, I am also running a shorted MOT "inductor" in series with my transformer primary to keep everything on a tight leash while testing. Once I finish sorting out a few problems, I will swap it out to a real inductor from a MIG welder. If that goes well, I'll take it off too.

For current measurements, I am using a 10ohm 7w 1% wire wound resistor from both center taps to the ground. The ground is ran from the cable to the star-ground on the back of the control unit. That is then connected via two 8ga copper cables to the shell where everything on the frame is star grounded. (Two cables were used for redundancy incase a ring connector or something failed.)
HV_System_Edit_2.jpg
I've done some work to the feed-though since it's use in Fusor-V1. I have beveled the edges internally and swapped to button headed bolts on the flange. I also opted to swap to a BNC connector for attaching the cable since it can be rotated but can't be pulled out. I then added some white silicone and a glass cylinder to it, just to be extra safe.
HV_Feed-through_Edit2.jpg
I'll talk more about shielding and thermals lower in this post, but something had to be done for both at the feed-through. To efficiently shield the x-rays, I wanted to get the lead sheet closer, but high voltage is the caveat here. So anyways, I had a styrene-acrylonitrile water filter housing, and decided to use it. (The breakdown voltage is 12-24kv/mm for SAN.) I cut some holes into the bottom of it and attached a PVC "T". On one side, I fed in the HV cable, and on the other, I attached a fan for cooling. The filter sits perfectly on the button headed bolts, creating an even gap around the entire flange.
HV_1_Edit2.jpg
Shielding

Shielding in this system is a necessity. X-Rays were rough at higher voltages. Most of the lead I used was from an X-ray film cabinet. They are entirely lined with 1mm sheet.

First thing was the viewport. I had always used a camera for Fusor-V1, but I finally I found some leaded glass: 1.6mm lead equivalency at 150kv. However, with horizontal mounting the scatter was pretty bad. Much of this is remedied by rolling a lead cylinder that fits closely with the glass.

Next up was the feed-through. I wrapped the SAN housing with 2mm, and made a 1mm skirt to cover the air vents at the bolt holes. After that, the body got wrapped with 2mm and the other parts of the same thickness received 1mm.

All good, right? No. The massive ISO160 currently uses an aluminum centering ring and a Viton O-ring. After a little thought, I found some pipe solder that would fit in the gap like an external ring. Two layers remained flush, and greatly reduced the rate. I had an excess of it, so I just wrapped it until I ran out. Later on I added a ring of the sheet stuff around the clamps to reduce it even more.
ISO_Shield1_Edit2.jpg
For the most part, all of that works great. The bottom of the ion gauge and back of the TC can put out at higher voltages, but it's not too concerning for the moment. I followed all of the lead up with some aluminum tape with a 300*F (149*C) max temperature.

Thermals

For now, I've been running under ~1kw, and haven't really soaked the grid with anything more than ~30 mA. Even then, it gets hot after a bit. I am currently limited by the big ISO flange and the Aluminum tape (180*C, 149*C). Initially I planned to water cool Fusor-V1, but we saw how that worked out... Anyways, I had already made a nice heat exchanger and reservoir. I don't plan to leave them there for looks. I will be adding something in the future hopefully. For now I just slapped on a truck temperature gauge to be conscious. Soon I'll add some thermocouples and more fans too.

2/3
-Luke Harrill
Luke Harrill
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Re: Fusor Progress, Luke Harrill

Post by Luke Harrill »

Part 3/3

Grid

The current grid is the same one that I had in Fusor-V1. Just maybe a little uglier. (It wanted to move around too much, so I had to tie a mess into it at the top.) It's 1.5" diameter and 4-ring. I intend to make a new one soon, as well as try a cylinder and simple ring.
Grid_Edit1.jpg
Neutron Meter

Right now, the moderator for my counting system is a 2 foot section of 6" and 1" pipe, nested and filled with paraffin wax. This surrounds a Texlium "Special" P4 He3 tube with an active area of ~1"x22." Attached directly is a gutted Ortec preamp enclosure that has been modified with an HN connector and rebuilt with a Cremat CR-110. The tube is biased by an Ortec 459 recently I have been running at 1.5 or 1.6kv with the other settings adjusted for such. After the preamp, the signal runs into an Ortec 571 shaping amp, and then to a Ludlum 2221 that acts as an SCA and scaler/ratemeter. (I want to run full NIM eventually, but I currently lack a ratemeter for such.) After all is said and done, I measured and marked where it is sitting on the frame: 37.16cm away, axis-to-axis, centered.
NeutronSetup_Edit2.jpg
Neutron Oven-V1

My oven consists of 8 slabs of HDPE stacked together with a tray for the center one. Generally it is rotated so that I have 3 layers in front of the sample and ~5 behind it. This puts my tray volume at 15.56cm away from the center point.
Oven1_Edit1.jpg
Silver samples

My first sample is a 1922 silver dollar that I keep as a necklace. It's 90% Ag 10% Cu: the first thing that I activated.

The second sample is roughly the same diameter as my silver dollar (37.86mm), but it is 99.999% Ag, 9.17g, and 0.815mm thick. I hammered down a 31.1g sample, trimmed it, used a hydraulic press to flatten it more, then it was rounded, polished, stamped, and etched. It isn't foil by any means, but it's a fair target.
Samples1_Edit1.jpg
Run Photos

First light of Fusor-V2 took place on 2021-11-13, the grid was adjusted after this, so you will notice that the ion beams aren't coming in the same sections of the grid, but they always occur along the axis of the chamber.

The second image is of my first activation-yielding run on 2021-11-20, I didn't even have my neutron system up and running yet, but was able to hold extended run times at low power (2mA, 50kv, 15min). I managed to get a massive total of 38counts/30sec in the first timed count on my necklace!!! Hahaha. Background average was 17counts/30sec. Since then, I've done some much better activation work. I'll be posting them with a formal report.

The third image is with a little more power on 2021-11-24 while testing the neutron setup and sorting a few things out. I think that photo was around 15mA at 45kv.
Plasma_Edit2.jpg
-Luke Harrill
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Dennis P Brown
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Re: Fusor Progress, Luke Harrill

Post by Dennis P Brown »

Congratulations on your first plasma in the new system; your builds are massive and impressive as are your updates ;) . I really enjoy reading such details and seeing the images. Glade you are being extremely careful with the x-ray issues - a concern of mine (in my case, a bit overly) but with your voltage and current I realize that must be a huge concern. I was distressed about your power failure and loss of the turbo - that is not something any one would want and a worry of mine of late (turbo loss but more due to age of the unit for me.)

Interesting that I was considering running my new fusor (w/deuterium) yesterday but decided to hold off. Not long after a tree took out all local power for much of the day. Both good and bad timing.
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Richard Hull
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Re: Fusor Progress, Luke Harrill

Post by Richard Hull »

Luke great work and reporting on your system. Very well done and well reported. I look forward to your future activation reports. I really like the custom labeling of the pure silver disk you made up. I am glad you obtained and worked out a piece of pure silver for activation. I have not seen many fathers who are there for their kids to the level you dad is. I always enjoy chatting with you guys at a meal when you are up for HEAS.

Fail-safe setups are on most all fab lines and large scientific lab systems. I have always said never, ever, trust an anti-suck-back valve in a mechanical pump. Assume it is not there on your pump, even if it is and even if it works perfectly. A belt and suspenders approach.

Jim Kovalchick is also one of those special fathers who backed Mike,, who is now graduated and in the nuclear biz. After Mike made the neutron club, Jim started his own separate effort some years back and has earned his place among the elite fusioneers doing activation.

Thanks naturally goes out to all those unmentioned father and parental heroes who supported their child during their swing at fusion.


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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