Stainless steel pipe chamber

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Richard Hull
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Re: Stainless steel pipe chamber

Post by Richard Hull » Tue Apr 10, 2018 6:53 pm

10kw in a home is a snap for the dedicated experimenter. I originally had a 60 amp 240 line pulled to my home upstairs, finished attic lab. This did require my older home's 100 amp service to be upgraded to 250 amp service. The power company dropped a new line, no charge. Once it hit my home, I was responsible from that point. I bought a used 40 position breaker box from our scrap yard for $20 and a suitable length of very used #4 copper cable for another $30. I pulled the #4 line from upstairs to the box. No charge. At this point for, code reasons, I hired the next door neighbor who is a licensed, registered electrician by trade, to come over after hours and pull the old box and put up the new one. He also loaded the box with all the old breakers and the new dual breaker for the 60 amp line and wired every thing to code. I paid him $100.00 in 1989. This was for Tesla coil work upstairs.

I had already planned for a new lab being built onto my home in 1990. My tesla coil lab was built with a 100 amp service with breakers for its 100 amp service added to my 40 position home box. The lab has its own 20 position box, (my old house box). In additon to the lighting and wall outlet breakers I had a 70 amp, breaker, #2 line run in the lab to the Tesla coil power controller from the lab box. This gave me the capability in my lab of up to 16.8 KVA continuous power.

In subsequent Tesla coil work I did use as much as 60 amps on my largest system tests and long runs.

As noted all of this electrical effort was very easily accomplished, relatively cheap and not a big deal at all as I was quite simply committed to the effort.

Needless to say, No private residence in a city environment can have three phase power. Farms can have such drops brought in, as can businesses.
Thus, the reasonable maximum might be 24KVA or there about for the amateur scientist in a home or an attached private lab. This is often not possible for younger members here.

The fusor, even in its most advanced form, has no need for more than 3 or 4 KVA for is operation and all the associated pumps, instrumentation, and lighting. No major changes to a home need be made.

For those contemplating projects, such as a cyclotron, some electrical issues will face them. This assumes you want to pursue active experimentation with the finished project.

This cyclotron project, due solely to it magnetic requirements demands a lot of power be spent in just obtaining a significant field to allow the cyclotron to function. This is a true commitment to power usage within a home environment. Great work!

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

Michael Bretti
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Re: Stainless steel pipe chamber

Post by Michael Bretti » Tue Apr 10, 2018 7:39 pm

This cyclotron project has really inspired and revived my interest in these types of devices. Though I will probably not have the chance to pursue one due to a huge backlog of other ion beam systems I am working on, it has given me a lot to think about. Browsing through the literature, it does appear that there are numerous papers detailing the design and construction of permanent magnet based cyclotrons, generally for small and low powered portable systems, such as mass spectrometers. These appear to generally be in the lower energy range of tens of keV to less than 100 keV for protons, although I did come across a paper detailing a system aimed to operate up to 10 MeV. Such a system would be in theory smaller, lighter, and much easier to manage power-wise for the dedicated home experimenter than its electromagnet counterpart for low energies. However, this is not as simple as just sticking two large circular disk permanent magnets on the top and bottom of a cyclotron chamber. All of these permanent magnet designs still require very sophisticated knowledge and careful planning of the placement and design of various magnets along the pole pieces and yoke structure, and absolutely necessitates the use of magnetic modeling software and calculation.

Like a regular cyclotron, it requires a huge amount of research, planning, calculation, and simulation to get to work. Nevertheless, it is still an option that is available to the aspiring experimenter who may want to dabble with low-power cyclotrons but does not have the means to supply the power for it. Note that the yoke will still be very substantial and heavy to prevent saturation, especially if designing a system passing the 1 Tesla uniform field strength regime over a large pole piece face. The greatest challenge however is that you cannot turn on and off the magnetic field or change the field strength easily, and presents real safety risks in placing and supporting the magnets correctly along the pole pieces and yoke and preventing them from slamming together and crushing hands in the process. Also separating such high strength magnets from steel or iron structures, if placed in the wrong spot by mistake, with holding forces in excess of hundreds of pounds, presents other major technical construction challenges. I may look into designing and simulating a small low power permanent magnet cyclotron in the future as a fun side design project after my other major design work is done for my current systems.

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Re: Stainless steel pipe chamber

Post by Chris Mullins » Wed Apr 11, 2018 1:50 am

Yeah, 10 kW seems like a lot, but really isn't from an AC delivery standpoint. I've got a 200A service, and my house is fed from a 50 kVA transformer (which also feeds 3 neighbors), so there's plenty of capacity there. My cyclotron is within 20 feet of the service entrance and panel; it'd be pretty simple to put in a 50 or 60A breaker and run power to it with a high current cable and receptacle. Actually not quite that simple, since my panel is already full - would be really nice to have a lab subpanel, like Richard set up.

Add a used Sorensen 10 kW DC supply from ebay and single-phase to 3-phase converter (all the big DC supplies are 3 phase in), and I'm set (and set back $3K or so). Rolling my own constant current, programmable, 100V/100A DC supply would be a fun project too, but I've already got a year's worth of cyclotron upgrades ....

Michael, there are a couple of previous discussions here on permanent magnet cyclotrons:

Microcylotron: viewtopic.php?f=15&t=7236

A compact DIY cyclotron package solution: viewtopic.php?f=15&t=7189

Despite some very cool ideas there, I shied away from a permanent magnet design for a few reasons:

1. I figured it would be easier to get a traditional design working first. Once I got the easiest, most documented type of cyclotron working, I could consider tackling something untraditional.

2. Working with those super strong, very large (4" diameter or more) magnets seemed dangerous, and likely beyond my relatively poor mechanical skills. That's even considering the good practical advice Richard gave on exactly how to mount them in a yoke in the link above.

3. Really large NIB magnets are expensive.

4. You can't vary the magnetic field easily - this is a big one for me. You could operate at a fixed field strength and matching RF frequency, but I wanted graph beam vs. field strength to map out H+ and H2+ resonances, their harmonics, etc. You could mechanically move the poles to do that, but see #2

5. Like you said, you can't turn them off - at best, that would be pretty annoying. I didn't want to be continually annoyed by a project I'd be spending a lot of time with.

It would cost about $5K for someone to make a duplicate of my cyclotron magnet, starting from nothing.

That said, building a small permanent magnet cyclotron would be a really cool project. I've had visions of something with these features:

1. 3 or 4" diameter NIB magnets, or maybe a ring of smaller cylinders like in the 2nd link above.

2. Single custom pcb with electrometer, RF generator and amp, filament and bias supplies, etc. to eliminate rack of equipment. Some good info by Richard here: viewtopic.php?f=12&t=12062
on building your own electrometer - not that difficult. The other pieces are straightforward too.

3. tiny diffusion pump, along the lines described here viewtopic.php?f=10&t=4096 and here http://diyvacuumtubes.com/mini-diy-diff ... p-t12.html

That would definitely be fun to create - could even be a group project down the road.

Chris Mullins
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Re: Stainless steel pipe chamber

Post by Chris Mullins » Wed Apr 11, 2018 2:09 am

Michael,

Yeah, the other cyclotrons I studied all had a rigid support from the RF feedthrough to the dee. The existing dee and filament system were pretty much thrown together at the last minute; we'll likely end up scrapping that and starting over. Our machining skills are not good, that will be a bit of a challenge for us.

One idea I had to improve the vacuum was to use another 1 or 2 KF16 ports in parallel back to the pump. That would increase the conductance. There are at least two spare KF16 ports on the chamber now.

That's great advice on using tubes for the RF amp. As a (mostly former) ham, I'd heard of the legendary ruggedness of tubes, but never built a tube amp. I'll do some research on designs with the GU-5B - thanks for the suggestion!

Michael Bretti
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Re: Stainless steel pipe chamber

Post by Michael Bretti » Wed Apr 11, 2018 2:17 am

Chris,

Thanks a ton for the links! I didn't realize miniature permanent magnet cyclotrons have been explored here before! I will post the papers I found for permanent magnet cyclotrons, they might give others some new ideas for different ways of going about constructing them. I think a very small and optimized system would definitely be in a very affordable low budget range, considering these magnets are pretty cheap nowadays, and could still allow for a lot of experiments. I will definitely keep all of this in mind, and think that maybe I will consider building one after all once I get my main vacuum system running. I would be very interested in seeing if I could optimize a tiny cyclotron to pump up to 100keV protons out of as small of a system as possible. Man, so many awesome projects to cover and not nearly enough funds for everything!

You are also definitely right about paralleling your single diff pump using the spare ports to increase your conductance, that would help your pumping speeds and gas load handling ability a lot. Since you have a blank-off on the top of your diff pump adapter, it would not be too difficult to make a simple replacement aluminum plate adapter with several KF adapters vacuum-epoxied into bored holes like you did with the sides of the cyclotron chamber. That way, you could have several other hose connections coming out of your existing setup and increase your throughput with minimal investment.

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Re: Stainless steel pipe chamber

Post by Chris Mullins » Wed Apr 11, 2018 2:19 am

Scott,

Thanks for the offer, I'm sure I'll need some help when I begin modeling!

Tim's cyclotron pages were the initial inspiration for this project. Later I spent many hours scrutinizing all sorts of details from his images, reading the student papers, cyclotron operating manual, etc. I noticed it moved from the Rutgers domain to his own - I guess the cyclotron itself also moved?

Thanks,
Chris

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Re: Stainless steel pipe chamber

Post by Michael Bretti » Wed Apr 11, 2018 4:29 pm

Here are a bunch of papers I have found so far on low power permanent magnet cyclotron design and construction:


Also browsing around online, there are some suppliers that seem to sell permanent magnet fixtures which could potentially be used for a miniature cyclotron, such as this:

http://www.magnetomachinery.com/magnetic-source-8.htm

I don't know the details or pricing of such a magnetic assembly, but it could also be another additional option to explore if someone wanted to go this route as well.

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Bob Reite
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Re: Stainless steel pipe chamber

Post by Bob Reite » Wed Apr 11, 2018 9:25 pm

You can get three phase power in a residence if there is already three phase power going down the road. One of my amateur radio friends who is into restoring old AM Broadcast vacuum tube transmitters, had a Gates 21E that he moved frequency wise to the 160 meter amateur band. The Gates 21E requires 3 phase power. Yes, he could have modified it for single phase, but A. He wanted to keep it as original as possible and B. It might have not be possible to get the larger capacitors needed to smooth 120 Hz ripple (as compared to 360 Hz for a 3 phase full wave supply) into the cabinet.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.

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Richard Hull
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Re: Stainless steel pipe chamber

Post by Richard Hull » Wed Apr 11, 2018 11:14 pm

Wow! three phase at home. I guess, like you say, if it is on the road by your home it is possible, but you would probably not see that in the inner city or in a normal housing development, unless you lived in an old area where large businesses sprang up later. We have some of that here where an old home or two remain after the old homes around them were demolished and industry moved in.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

Chris Mullins
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Re: Stainless steel pipe chamber

Post by Chris Mullins » Sat Apr 14, 2018 7:36 pm

Rich,

I dared to take the chamber out of commission temporarily to measure the lid deflection.
Short version: "edges simply supported" wins vs. "edges clamped".

Using r=5 inches, psi = 14.7, Poissan ratio of 0.27, Young's modulus for 304SS as 1.9E11 N/m^2, plate thickness of 0.2 inches, and using the two formulas shown here: http://www.roymech.co.uk/Useful_Tables/ ... lates.html (after converting to SI units) gives:

"Circular Plate , uniform load , edges simply supported": max deflection = 0.030 inches
"Circular Plate , uniform load , edges clamped": max deflection = 0.007 inches

Actual measured max deflection: 0.033 inches at rough vacuum.

The lids are attached with 2-56 screws torqued to just 41 in-oz. The o-ring isn't 100% compressed - there is still a gap between the chamber and lid, so understandable that it's closer to "edges simply supported" rather than "edges clamped".

Long version:

First, I wanted to measure the gap at the pole diameter, since that's where I often shove a small gauss meter probe. The chamber is resting on the bottom pole, so the gap at the top includes the sum of the top and bottom lid deflections. Something's not quite flat, since the gap in the front and back are not the same.

Front gap (in mils): 26 at room pressure, 47 at rough vacuum
Rear gap: 12 at room pressure, 47 at rough vacuum

Measuring front gap:
IMG_8432.JPG
I'm not sure why the gap differs at room pressure, but evens up under vacuum - must be differences in o-ring, gland depth, or lid screw tightening. I use a torque screwdriver on the screws, so that shouldn't vary much.

Next, I took the chamber out of the poles and attached it directly to the pumps so I could measure the lid deflection directly. Using a carpenter's square (hopefully straight to within a few mils), I measured the gap at the center:

room pressure gap (mils): 11
rough vacuum gap: 44
IMG_8435.JPG
It doesn't look like it in the image, but the square was across the center of the lid.
That gives a deflection of 33 mils, very close to the calculated 30 with the "edges simply supported" formula. That's what I used originally a year ago (after Rich pointed out that site), in part as a worst case since it was larger than the other formula. Ultimately we ended up putting the gland in the lid anyway, which was another reason to have a thick lid.

I also measured the change in gap between the lid and chamber. The gap at a screw was 15 mils at room pressure, and 16 mils under rough vacuum - an increase of 1 mil (the edge of my measurement ability).
lid_gap.jpg
Gap in between screws wasn't as easy to measure (ports in the way), but appeared to also be around 1 mil increase. That 1 mil increase would be consistent with the lid bowing inward, pivoting on the o-ring and internal wall of the chamber? 33 mils down at the center, 1 mil up (roughly) at the edge.

I also tried visualizing the deflection with a clear plate and a liquid (alcohol). The edge deflection was too small to see, but the center deflection was visible:
bubble.png
For some exciting video:

lid deflection with straight edge: https://youtu.be/e9MX1KcrUVA
lid deflection from top with alcohol: https://youtu.be/OZSfsuwLX4o

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