Oakland University Low Powered Fusor Update

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Brian_Neumeyer
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Oakland University Low Powered Fusor Update

Post by Brian_Neumeyer »

Hello All,

An update with a few questions!

First Run- Sort of Successful
Image
Last week we turned it on for the first time. While we did get a bit of that delightful purple glow, it did not achieve "star mode" with a ball in the center.

So we are at the trouble shooting part of this guy.

The Setup
Image
Going clockwise starting from the upper right E-Stop button
-Black thingy with white labels on it & gray wire: Vacuum gauge
-Silvery disc: Fusor chamber
-White cylinder with 3 wires: Rectifier
-Red cylinder: variac
-Gray box: neon sign transformer
-Outlet box: 2 constantly on, 2 attached to E-Stop
-Red & gray thingy: vacuum pump

The Stats-need to be updated. Ask for any other ones that you'd like
-Pressure: We seem to have a leak somewhere, or our pump is not as effective as advertised. We held around (1800 mTorr? @Aaron verify) for the duration of the run
-Voltage: We used a variac to go from 0 to 110 VAC, which with our neon sign transformer means we went from 0 to around (7-7.5 kV? @ Matt M. verify) for the run

We're pretty sure that the reason we didn't go star mode is due to the pressure issue. If there's any other potential reasons we'd love to hear it.

Some other questions though:
-There was some arcing at the base of our feed through stand off. It went on and off periodically, with seemingly no pattern. What could cause that, should we be worried, and how can we stop it? It didn't seem to connect with the inner grid at all, just fizzled around at the base.
Image

-We observed glowing at the pressure gauge nozzle input. We have two barbed brass fittings on the top for a vacuum and gauge. The gauge hole had a glow for the duration of the run, and it was more red/yellow than the purple of the inner grid. What could cause that? The other hole that led to the vacuum pump did not have the same behavior, at least not noticeably.
Image

This is an exciting progression for us, and we're still working to get a full star mode. If there's any experienced fusor-ers in the Oakland-Macomb County area around Oakland University (in Michigan) we'd love to sit down and bounce ideas over some coffee (or your drink of choice ;-))

*edit- apparently the bit code isn't fully implemented on these boards, hopefully this imgur trick will work
Last edited by Brian_Neumeyer on Mon Feb 15, 2016 9:37 pm, edited 1 time in total.
John Futter
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Re: Oakland University Low Powered Fusor Update

Post by John Futter »

Brian
no pics
This happens all to often with remote photo storage sites

It would be better to upload the pics to this site directly and place inline
Which will preserve this thread for all time
Jim Stead
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Re: Oakland University Low Powered Fusor Update

Post by Jim Stead »

Looks like he added bbcode to adjust the picture size in the img tags. The site doesn't seem to be accepting it.
Here are some URLs to the pictures-

http://i.imgur.com/rW9k9f2.jpg
http://i.imgur.com/QUf8dxw.jpg
http://i.imgur.com/mEENGIg.jpg
http://i.imgur.com/UTWiPpr.jpg
John Futter
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Re: Oakland University Low Powered Fusor Update

Post by John Futter »

Brian/ Jim

you need to adjust the picture size manually in something like Irfanview then under image/resize-resample to 1024 x 768 or lower resolution
re-save to a convenient upload subdirectory ready to upload to this board
Brian_Neumeyer
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Re: Oakland University Low Powered Fusor Update

Post by Brian_Neumeyer »

John Futter wrote:Brian/ Jim

you need to adjust the picture size manually in something like Irfanview then under image/resize-resample to 1024 x 768 or lower resolution
re-save to a convenient upload subdirectory ready to upload to this board
I guess bit code isn't fully implemented on this board. Found a work around with imgur though.

With Imgur, if you add an "m" to the url immediately before the ".suffix" it will decrease the size. Putting an "s" will make it even smaller.

So now that the formatting is good how's the content?
Jim Stead
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Re: Oakland University Low Powered Fusor Update

Post by Jim Stead »

Brian,

I noticed in your third picture that your pump oil is a yellow milky color. Appearance isn't everything, but that color reminds me of a water/oil mix. If that's what it is, and your pump oil is actually contaminated with that much water, it will affect your vacuum significantly.

Regarding the glow in the vacuum barb. I noticed the power cord for your vacuum gauge is not plugged into the same AC supply that the HV supply and transformer are, and that your chamber ground is coming off of your HV supply ground. I'm wondering if there is a ground potential difference that is causing that glow. Take a look at Richard's FAQ post regarding star grounding. If you put the gauge, pump, chamber, variac, the 1900 boxes, etc. all on the same central ground point I believe you will eliminate that glow... and increase your safety as well.
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Rich Feldman
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Re: Oakland University Low Powered Fusor Update

Post by Rich Feldman »

Brian et al,

1. I think the small inline images are sufficient in 95% of the cases, and make the board more friendly to mobile and non-broadband users. This time it was handy to have links to full size files for a closer look. Inconsiderate users sometimes embed huge images that nobody can view all at once without scaling, which is not the duty of a browser. Here's why the "upload file" forum tool is good. If the file is an image, you get an inline picture that loads fast and can be clicked to see the full uploaded file, preserved on the fusor.net server. I think it limits the file size to 1 MiB. Who needs more than that on a discussion forum that isn't about photography?

2. Since the pump oil was called into question, try reading FAQs about rotary pump maintenance. For a closer look you can drain some oil into a clear cup, then put it back into the pump. It should be non-cloudy & light in color, like vegetable oil.

3. There are lots of leak-detection hints in this forum, including the vacuum FAQs. It's good that your chamber has a dedicated port for the vacuum gauge. The same gauge would show a lower pressure if connected close to the pump inlet, because your skinny chamber-to-pump hose resists the flow of gas. Keyword: vacuum conductance.
All models are wrong; some models are useful. -- George Box
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Richard Hull
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Re: Oakland University Low Powered Fusor Update

Post by Richard Hull »

Brian, I have added your name to the plasma club.

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
Brian_Neumeyer
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Re: Oakland University Low Powered Fusor Update

Post by Brian_Neumeyer »

Richard Hull wrote:Brian, I have added your name to the plasma club.

Richard Hull
Richard,

While I do enjoy my name being in it, I am a part of a team. Would it be possible to have Aaron Garofalo, Matt Michalewicz, Matt Bloom, and Steve Stewart on the wall as well? If not, the Oakland University HC/SD Team would work instead of just my name.
AllenWallace
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Re: Oakland University Low Powered Fusor Update

Post by AllenWallace »

This looks very nice!

I suggest you hook up your vacuum gauge directly to the pump and determine the pump pressure. This will allow you to discover if your high pressure is due to a pump limitation or a chamber leak.

Please be careful about implosion. I don't see any shield about your vacuum chamber. You chamber is made out of glass?

The visible discharge in the gauge hole is a total mystery to me. I assume that the top plate is well grounded via the mounting bolts? I've seen discharges travel down tubes, much like a neon sign tubing. If you plug and/or disconnect your gauge does it change the discharge?

Look for leaks by squirting suspect areas with isopropyl alcohol, and looking for a change in your vacuum pressure. Have you used teflon tape? Please describe your high voltage feedthrough.

Good luck!

Allen
Aaron Garofalo
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Re: Oakland University Low Powered Fusor Update

Post by Aaron Garofalo »

Hi everyone,

We tested the vacuum pumps by directly connecting them individually to the vacuum gauge. Much better results this time. Our newer high-vacuum, high-speed pump (rated for 50 mTorr) measured in around 100 mTorr (close to 1/10 the original pressure). The older low-vacuum, low-speed pump (rated for 1 mTorr) measured around 200 mTorr. We have since flushed it out and changed oil an are still seeing the same results. Our next step for this pump is to look at the seals and whatnot inside, since it is an older pump and hopefully get closer to the 1 mTorr this pump is supposedly capable of.

We changed out the rubber hoses and hard-plumbed everything (vacuum gauge and vacuum pump). After doing this we ended up finally achieving star mode! (I will upload pictures later unless someone else on my team beats me to it). We still need to do more research on throughput and vacuum conductance to find the right material for the plumbing. For this most recent test we just used what we had on hand (brass and copper nipples and elbows) (I know, I know. Mixing metals for fittings isn't exactly the best, but it's what we had at the moment and it got the job done for the day). In response to a previous question on this post, yes, we have been using teflon tape for all appropriate connections. Our pump has a flanged fitting which we adapted to NPT; therefore, the flanged fittings do not have teflon tape, whereas the NPT fittings do.

In response to another question, our chamber is glass. It is borosilicate glass, and we ran the calculations and simulations to ensure it would be able to withstand atmospheric pressure while holding a vacuum without imploding. All good on that front! I should also mention that this will not be our chamber for fusion. We are currently looking into ordering a stainless steel vacuum chamber from a few different companies in our area. We just got our first quote back at $900 and are currently waiting on the rest.

Our HV feed through is a female threaded aluminum rod which is sealed in the center. The aluminum pass through is insulated by a hollow ceramic tube and sealed with JB Weld. We don't see any leaks here.

Lastly, our lab shares a common ground for all the outlets, so the gauge plugged into the wall and everything else into the e-stop shouldn't cause any anomalies. Just to be sure, we did plug everything into our e-stop. We still saw the glow in both the vacuum pump and vacuum gauge ports in the upper grounded plate. Any other advice/comments/thoughts on this would be very much appreciated.

Again, thank you to everybody who has commented on this for your help, and we hope to continue our progress and make our way to the Neutron Club this year!

-Aaron Garofalo
Oakland University HC/SD Fusor Group
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Dennis P Brown
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Re: Oakland University Low Powered Fusor Update

Post by Dennis P Brown »

Very glad your vacuum is improving! thanks for the update.
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