High Schooler Fusor Amataur

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Maxwell_Epstein
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Real name: Maxwell Epstein

High Schooler Fusor Amataur

Post by Maxwell_Epstein » Tue Jul 20, 2021 5:17 am

Good morning/afternoon/evening/appropriate greeting for your timezone! I'm Maxwell Epstein, a High School Junior as of whenever school starts. I've been a lurker on this site for a few years now, but this summer I finally decided to take the leap and build a (demo) fusor myself. Just an hour ago (much longer than an hour now that I finish this post) tonight, I powered on my demo fusor (that I've taken to calling a proto-fusor, is that fair? what do you think of the semantics?) and encountered a few problems with arcing to the outside of the vacuum chamber that I will post questions about elsewhere.

After I repair/replace some of my demo fusor and get it where I want it, I have two separate fusion projects that I want to pursue. I, of course, aspire to building a full fusor and am already searching for components (and summer jobs to finance) for that project. I've also wondered what the cheapest way to build a demo fusor is. I know that there are many resources here and elsewhere, but I feel like the entry price for a standard demo fusor is too high. Expense was the primary reason why I could not start working on my fusor earlier and I'd like to do what I can to lower that barrier for other people, I obviously need way more practical experience before writing some sort of guide, but if anyone has any advice as to how I might develop a budget design or links to any designs out there, I would be very grateful.

As for my demo fusor, I mentioned a few problems above and I need to make some changes to the design, but I think that what I have is enough to qualify for Plasma Club as is. With that said, I'm not entirely happy with my design so I'm going to keep on improving before moving to greater things. Anyway, here's my fusor:
Image
Please ignore the mess, my parents won't let me do high voltage inside (for good reason, we have cats) so I'm working out of our unfinished basement.

The design is pretty standard as far as I know, I have a vacuum chamber with a spherical stainless steel grid inside that's being fed around 12kV from a neon sign transformer going through a diode rectifier. It's really basic but I wanted to get the essentials down before moving on to cooler things. I achieved plasma generation and while I want to tune it more and rebuild the grid (I believe that imperfections in the grid fabrication lead to the arcing mentioned above), I'm pretty happy with this as a first try.

Info:
Voltage: Measured with a multimeter and a cheap high voltage probe, attained with 12kV neon sign transformer and homemade diode rectifier: 12-13kV without load, fluctuates with load (that might be how I'm measuring it, though (touching the probe to a contact as opposed to attaching the contact directly with a terminal)
Current: Same method: max of 25mA, but fluctuated (likely due to the measurement method)
Pressure (or lack thereof): Measured with an analog (mechanical) pressure gauge on the top of the vacuum chamber and a digital gauge that attached to the vacuum pump which caused leaks so I removed it for the full test, attained with an eBay vacuum pump: 35 microns min (with pump running) Edited: I put in the wrong number
Time: I ran the fusor for three sessions, the first ran for approx. 3 minutes (with an extra minute of vacuum only), the second for approx. 2 minutes (with an extra minute of vacuum), and the third for approx. 1 minute (with an extra minute of vacuum) - this was the one where the arcing was worst and when i stopped as the glass was singed. I decreased the time as it took less and less time before serious arcing.

Results:
The fusor when plasma first began forming:
Image
and the fusor at full power:
It's a lot blown out here, but it looked great with a plasma center and everything (although no "star formation"). After all of my work on this, it was an amazing feeling to see it work almost perfectly
Image
I'm sorry for the grainy images, I didn't want to set up a tripod and camera for the first test out of fear of an implosion damaging my lens (I have lots of self-confidence /s) so I asked a parent to film and she forgot to zoom in
I achieved sustained plasma inside the grid for a while before it began arcing. After that, I may have ran it too long trying to figure out what was causing the arcing and it arced to the glass so I hit the cut off. I'm going to take it apart tomorrow to clean it and to replace the grid with a better one (I suspect that the grid was a bit lopsided and the solder joints were too big).

In short:
1. I built a "vacuum safe" vessel out of borosilicate glass and aluminum plates that I bolted together
2. I acquired a viable vacuum pump (a 2 stage Vevor pump)
3. I tested the chamber with an electronic vacuum gauge (and a mechanical one) although due to logistical reasons, the electronic one was not used during the fusion test, but was used directly before
4. I built a fully variable DC power supply of 13kV with a variac, neon sign transformer, and diode rectifier
5. I used a multimeter with a HV probe to measure the voltage and current going into the system
6. The entire body of the vacuum chamber of my fusor is a view point which I used to take (unfortunately grainy) photos of the plasma that I created. I will upload more when I get it running again
7. I built a centrally located, spherical grid out of stainless steel wire that was used to create and contain plasma

Is this enough for membership in the Plasma Club? If not, what else do I need?

Questions:
Is the arcing likely caused by a bad grid? If not, what else do I need to fix for sustained plasma generation? My vacuum seal is far from perfect, could that be an issue in this case?
The plasma visibly arced to the borosilicate glass tube in the vacuum chamber. I hit the cut off immediately, but there is a bit of black residue on the inside of the glass. It does not look structurally compromised in any way. Do I need to replace the glass or risk implosion? My intuition says that I should probably check before running it again with the same glass.

Thank you so much for this wonderful resource and I look forward to being a part of it in the future!

...now i need to sleep.


The preview isn't showing the images, so I'm going to put the links below (in order) just in case:
https://photos.app.goo.gl/YgRRMcmHc7htDHjQA
https://photos.app.goo.gl/Tbap73puDo9sNd5e8
https://photos.app.goo.gl/FXQq3KmeF4sXAdW68
Last edited by Maxwell_Epstein on Tue Jul 20, 2021 12:26 pm, edited 1 time in total.

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Richard Hull
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Re: High Schooler Fusor Amataur

Post by Richard Hull » Tue Jul 20, 2021 5:54 am

Semantics can be important. A demo fusor is typically a device that can never and will never be made to do fusion. Yours is of this type.
A proto-fusor is a demo fusor that, as presented, can be made to do fusion. That is, it will only need a gas port, a vacuum system capable of submicron pumping and a power supply and input insulator improvement that will allow real fusion to be done.

Proto-fusors are rather rare among younger people who cannot afford the fusor rated, stainless steel, welded, demo assemblies using standard vacuum rated fittings.

Photos are easily up loaded via the "attachments" symbol at the bottom left of your postings composition page.

Welcome, and read the FAQs for answers in the related forums when you have a question. It has already been answered, most likely.

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.

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Mark Rowley
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Re: High Schooler Fusor Amataur

Post by Mark Rowley » Tue Jul 20, 2021 6:27 am

Congrats on your current work Maxwell.
Keep the initiative strong and you’ll meet your goals.

Mark Rowley

Maxwell_Epstein
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Real name: Maxwell Epstein

Re: High Schooler Fusor Amataur

Post by Maxwell_Epstein » Tue Jul 20, 2021 12:25 pm

I'll definitely check the FAQs again for advice on my arcing problem, I took the vacuum chamber apart and I think that the grid was the problem so I'm going to fix that.

Assuming that I get that fixed and take better photos, would I have a good Plasma Club application? I think that I have everything on the requirements list, but I could have forgotten something.

I didn't know about the difference between demo and proto fusors. I'll definitely be more careful with wording in the future. I guess I know what I'm going to try building next

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Richard Hull
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Re: High Schooler Fusor Amataur

Post by Richard Hull » Tue Jul 20, 2021 7:30 pm

No on the application with your current setup. Read very carefully the qualifications on the plasma club membership. A glow in a jar will not cut it. A genuine and deep rooted interest to the point of viable instrumentation is demanded with accurate readings taken related to the plasma.

the rules are stated at....

viewtopic.php?f=54&t=13

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.

Maxwell_Epstein
Posts: 3
Joined: Tue Jul 20, 2021 3:08 am
Real name: Maxwell Epstein

Re: High Schooler Fusor Amataur

Post by Maxwell_Epstein » Wed Jul 21, 2021 3:39 am

Thanks for the clarification. I'll document my next tests much better - I was just really excited and not really thinking last night when I did the tests and made the post. Thanks for all of your help!

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Dennis P Brown
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Re: High Schooler Fusor Amataur

Post by Dennis P Brown » Wed Jul 28, 2021 12:44 am

I avoid links and prefer uploads here but I'll check them. Not sure where your issues are but I'll give my best guess - if the arcing is internal to your vacuum chamber, then it is purely an issue of pressure. Your not getting low enough and likely not in the micron range at all - at a few torr arcs often occur in the 10 kV range. If external, simply poor insulation work.

You need far better vacuum instrumentation to qualify (your micron gauge can't leak!) and of course, strike and hold a real plasma glow. That mechanical gauge is nearly useless and mostly a possible leak source. As for your micron measurement, you haven't posted info on that but I am concerned it isn't accurate if you are arcing at '35 microns'. If that pressure measurement is just on the pump head then certainly, your chamber is leaking and you are likely only in the torr range.

Good first work. Keep at it. Your build is ok but not safe - you need to put a shield of some type (wire screen) around the glass cylinder section (unless that is plastic in which case, no issue.)

As for cost of fusor equipment, keep an eye on ebay and how to search out useful equipment (gov surplus is sold by a number of companies.) There are often gold nuggets in the piles of junk. Requires knowledge, experience (by daily searches), learning what to look for, and proper bidding. When and if you find something, do post here and ask questions before buying. A lot of people here will aid you. No one here will attempt to under bid you so that shouldn't worry you.

It might take a lot of time but it can be done - people here have built extremely useful power supplies (yes, a good bit of work and learning but so worthwhile for a low cost, excellent supply.) See current threads! viewtopic.php?f=11&t=13907

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