First Light in my First Metal Demo Fusor!

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Maxwell_Epstein
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First Light in my First Metal Demo Fusor!

Post by Maxwell_Epstein »

I've been meaning to post a fusor update for a month or so, but have always put it off for one reason or another. I have finally achieved first light in my metal demo Fusor 1.1 chamber, so I think that this is a good opportunity to write about what I've been doing for the past few months.

Fusor 1.1 Design:
At the time of my last post about my system, I was working with a borosilicate tube chamber that I made following the Makezine fusor article* that I called Fusor 0. I have since upgraded significantly to a 6" CF cross chamber. I attached 6" to 2.75" conflat reducers on all sides. I have attached a borosilicate viewport, high voltage feedthrough, conflat to 1/4" NPT adapter, and conflat to KF-25 adapter to those reducers. A Varian 531 thermocouple gauge embedded into a KF-25 flange is attached to the KF adapter and a 1/4" NPT to barbed hose adapter is screwed into the 1/4" NPT port on the conflat flange.

The vacuum system is, as of now, very crude: simply a piece of PVC hose connecting the chamber barbed adapter to a cheap 5cfm HVAC pump. Due to the pump's design and the parts I have on hand, I have not been able to conduct a true bulkhead test with this pump, but in a test where the hose is connected to the Varian 531 thermocouple tube via the two conflat adapters attached directly together with a Viton gasket and vacuum grease, it pulled an end vacuum of approximately 550 microns on the Varian 804-a thermocouple controller. I am in the process of upgrading the entire pump system to reach deep vacuums.

The HV supply is a pretty basic 12kV NST supply. I am using a tantalum grid and feedthrough that I bought from Steven Haid on the items for sale section of this forum. I am measuring grid voltage with a Fluke 80K-40 HV probe and current over a 10Ω resistor between the NST case and ground.

I'm monitoring the chamber with a Sony A7iii recording 1080p video.
The chamber as I was putting it together
The chamber as I was putting it together
Me with the demo fusor before the first test (if you look closely, you can see the fear in my eyes that the entire thing would fail)
Me with the demo fusor before the first test (if you look closely, you can see the fear in my eyes that the entire thing would fail)

First Light Test Results:
I achieved first light of Fusor 1.1 on November 14 at 11:14 AM (a little bit of serendipity there). The chamber was pumped down to approximately 650 microns before the variac was turned on. Plasma began appearing on the grid at approximately 9 Volts AC NST input. Over the duration of the test, I gradually turned the variac up (to a maximum of 50V to the NST) to send more power to the grid. Measured pressure increased as well, but I think that that was as a result of the thermocouple gauge being influenced by the expansion of gasses at high temperatures more than a significant leak or outgassing.

Voltage and current data:
fusor 1.1.1 table fixed.png
fusor 1.1.1 graph.png
Chamber Pictures:
396Vdc at 5.6mA (2.22W) at approx. 775 microns. 20.8Vac NST input.
396Vdc at 5.6mA (2.22W) at approx. 775 microns. 20.8Vac NST input.
500Vdc at 14.5mA (7.25W) at approx. 1000 microns. 40.0Vac NST input
500Vdc at 14.5mA (7.25W) at approx. 1000 microns. 40.0Vac NST input
The plasma clearly got more diffuse as I raised the power going into the grid. I need to do more tests to determine if this is as a result of the increased grid energy or the pressure increasing in the system. If the diffuseness is related to pressure, I will need to revise my thermocouple hypothesis.

I think that the sparkling on the grid is a result of detritus on the grid being vaporized and ejected, but I am not sure and haven't seen anything about this phenomenon discussed.


I plan to do many more tests in the near future (I'm on fall break the entire week) as well as to upgrade the vacuum pump to a Precision D-25 that will arrive very soon.

I have a blog where I have made a much more in depth post about the first light test (with more data and pictures) here: https://highschool-fusioneer.medium.com ... a3eba393d0
It's intended for people who are interested but do not know anything about fusors in general, so it might be tedious to read for someone who understands the lingo.


*https://makezine.com/projects/nuclear-fusor/
See my needlessly verbose fusor blog here: https://highschool-fusioneer.medium.com/!
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Richard Hull
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Re: First Light in my First Metal Demo Fusor!

Post by Richard Hull »

Great first light and a great report with images of you with your setup. You have all the right tools in spite of a rather high vacuum pressure limiting your results.

You are now in the plasma club.

It is normal, assuming no leaks, for the chamber to out-gas for quite a while as the walls are bombarded. The pressure is rising due to the moisture and other trash burning into vapor as the chamber is heated by bombardment. This is called glow cleaning. Give it some time.

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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Maxwell_Epstein
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Re: First Light in my First Metal Demo Fusor!

Post by Maxwell_Epstein »

Thank you for accepting me into plasma club! That as well as your compliments about my report both mean a lot.

I decided to seal all of the NPT connections on the pump with epoxy and pulled as low as 60 microns in a subsequent test!!! I'll post some pictures and data soon. With this new vacuum capability as well as the D-25 pump that arrived today, I've got a lot of opportunity for more experimentation!

Thank you again for all of your advice, it has really been instrumental in achieving this milestone.

Max E.
See my needlessly verbose fusor blog here: https://highschool-fusioneer.medium.com/!
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Dennis P Brown
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Re: First Light in my First Metal Demo Fusor!

Post by Dennis P Brown »

Great work and nice initial setup; I started off in the plasma club before doing fusion. I notice your thermocouple (TC) unit is the type I use and I found mine to be very accurate - I checked mine against a known gauge and it tracked exactly from 2 - 20 microns and was very close from 30 - 100 microns; above that it doesn't really have any scale. So a very good TC gauge for controlling a real fusor since that is the key region for operating a fusor's gas pressure.

Keep up the excellent reporting here.
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Maxwell_Epstein
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Re: First Light in my First Metal Demo Fusor!

Post by Maxwell_Epstein »

Thank you, Mr. Brown for your comments. I saw the 531 TC tube used a lot for demo fusors (and there are plenty available for cheap) so I thought that it was a safe option. It is good to hear that someone very experienced agrees!

As i said a few days ago, I sealed my pump with epoxy and have reached vacuums as low as 60 microns. That is still quite high compared to what's needed for fusion, but I think that it's pretty good for a pump that could barely manage 500 microns a few weeks ago!

I have done a full test at the newly increased vacuum level:

Fusor 1.1 Test 3* Results:
The primary goal of this test was to obtain pictures and data at significantly lower pressure than was previously possible. I intended to keep the current going to the grid at about 5mA by varying the NST input voltage so that I could compare my data with a the plasma pictorial on the FAQ.

Plasma formed within the chamber at 11.7Vac NST input at a 100 micron vacuum. The system first reached 5mA NST output at 27Vac NST input at 180 microns. Pressure initially increased to 200 microns before gradually decreasing back to the 100 micron initial pressure.
At the end of the test, I decided to increase the variac output until the NST output amperage reached 10mA to observe voltage and pressure characteristics. Pressure again spiked, but decreased to 120 microns after about 5 minutes. I then slowly decreased NST input voltage until plasma extinguished and there was no measured current output. As I did so, pressure dropped to 60 microns, lower than the lowest measured pumpdown without plasma and the deepest vacuum I have achieved yet!
I am referring to the 5mA (±0.5mA) data that I have collected as the experimented range because the primary purpose of the test was to investigate behavior at that amperage and data outside that range is potentially less accurate.
I am referring to the 5mA (±0.5mA) data that I have collected as the experimented range because the primary purpose of the test was to investigate behavior at that amperage and data outside that range is potentially less accurate.
Not shown is pressure, the decrease of which allowed input voltage to be raised without increasing amperage.
Not shown is pressure, the decrease of which allowed input voltage to be raised without increasing amperage.
At a constant NST input, as pressure dropped so did current. This allowed me to increase the NST input to maintain 5mA current.
At a constant NST input, as pressure dropped so did current. This allowed me to increase the NST input to maintain 5mA current.
Increasing NST input (as pressure decreased) increased voltage output.
Increasing NST input (as pressure decreased) increased voltage output.
The increase in voltage as pressure dropped increased power as current remained relatively constant.
The increase in voltage as pressure dropped increased power as current remained relatively constant.
As pressure decreased, voltage (which is directly proportional to resistance as per Ohm's Law) increased, implying that chamber pressure is inversely related to the chamber resistance once plasma is formed. You all definitely know this already, but it was cool to determine using data that I collected myself (science, y'all!)

Pictures:
610Vdc 3.6mA (2.20W) at 200 microns. 20.8Vac NST Input
610Vdc 3.6mA (2.20W) at 200 microns. 20.8Vac NST Input
804Vdc 4.7mA (3.78W) at 180 microns. 27.0 NST Input
804Vdc 4.7mA (3.78W) at 180 microns. 27.0 NST Input
The bright spot at the center of the image jumped rapidly around within the grid. Although it is not clearly seen in the footage, there was an extension of that concentration that shot out to either the bottom or top chamber wall. This extension was clearly a jet of plasma and not similar to the damaging arcing experienced in Fusor 0.
The plasma was also still a pale purple-blue color, not the periwinkle that the camera captured. I am still in the process of fixing the white balance settings as I do not want to alter the images in post.
Fusor 1.1 Plasma. 1603Vdc at 5.0mA (8.02W) at approx. 110 microns. 42.2Vac NST Input
Fusor 1.1 Plasma. 1603Vdc at 5.0mA (8.02W) at approx. 110 microns. 42.2Vac NST Input
I decreased my camera's ISO for the last picture from 800 to 400 which is why it is so dim. The jet from the second image was brighter in the last one too. I will keep consistent camera settings for future runs.


Interestingly, my voltage is significantly higher than the voltage in the plasma pictorial and the plasma looks a lot less well defined. Do I have a faulty gauge or is something else going on here? If my gauge is sound, then the assumption is that the resistance between my NST and ground is significantly higher than in the pictorial. I need to do some more tests to figure this out.


Viewport Residue:
After the test, I noticed a significant amount of deposition on the viewport that almost looked like shattered glass. I initially thought that this was the result of sputtering, but the most common description of sputtering that I have read is that of a gradual browning of the viewport, not of large particles.
My viewport after test 3
My viewport after test 3
The grid seen through the cloudy viewport
The grid seen through the cloudy viewport
This is definitely a liquid of some sort on the inside of the viewport glass. I am almost certain that this is vacuum pump oil that was drawn into the system after pump deactivation and before I could vent the chamber to atmosphere. I assume that I'll have to open one of the 6" flanges to clean out the inside of the chamber which I'm not really looking forward to. I'll try to avoid this in the future by starting to vent the chamber before shutting off the HVAC pump.


New Pump:
The Precision D-25 pump that i ordered (thanks everyone who provided advice!) arrived and was completely filthy. Luckily, the pump gear turns freely and the motor spins when plugged in (I removed the belt for that test). I am in the process of figuring out a good first system to connect the pump to the chamber and have run into a slight issue in that I am not fully sure what the inlet connector is. the inner and outer diameters of the connector are 0.5 and 1.25 inches respectively. It is likely a standard vacuum connection that I am too inexperienced to recognize, but I want to make sure I know what it is before I order any adapters.
PXL_20211123_164450831.jpg
PXL_20211123_164433609.jpg
PXL_20211123_164436003.jpg
The pump came with a rubber hose, but the other end was a weldable connector and I do not know how to weld or know of anyone locally who would be able to do vacuum-tight welds for cheaper than a KF adapter and length of KF flexhose.


Once the new pump is hooked up, I want to experiment with different grid diameters and shapes as well as to start measuring the chamber temperature as I know both will be important for increasing neutron count later on. I'm looking forward to more plasma tests and to hopefully getting the D-25 pump hooked up




*Test 2 failed due to my own impatience
See my needlessly verbose fusor blog here: https://highschool-fusioneer.medium.com/!
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Dennis P Brown
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Re: First Light in my First Metal Demo Fusor!

Post by Dennis P Brown »

Nice experiments and playing with the plasma by varying parameters and recording related data is both science, a great learning experience, and fun. Good work.

As for the 'particles' on the view port, certainly open the system and check. Obviously if it is oil, then you will need to open the system and clean it out thoroughly - alcohol, gloves and lint free cloths. Consider a oil vapor trap between the pump and your system - even the new pump can have back flow issues (but usually it is just vapor, not liquid oi.) Certainly, liquid oil in your chamber is disastrous.
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Richard Hull
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Re: First Light in my First Metal Demo Fusor!

Post by Richard Hull »

On all Precision belt drives, the pump to hose connection is their standard superb hose barb with their rubber seal ring. Cherish it!! Use only it!! Replace the hose, of course, and on the other end of the hose put what ever connector you want on it. Never use someone elses hose! Now just a matter of cleaning the pump with new oil and a long blanked off run. Drain refill and test.

You absolutely must have a good shutoff valve between the pump and the demo fusor chamber. keep the entire foreline hose very, very short (see diagram)

operation

1. valve closed
2. start pump
3. after 1 minute open valve
4. pump chamber to whatever vaccum you want
5. When ready to shutdown the system..........Close valve!
6. shutoff pump
7. vent pump to valve line

This is called a foreline valve. You gotta' have one! Your current pump probably has no suck-back prevention valve as it is not a scientific pump. Never trust any pump's anti-suck-back valve! Use a foreline valve.

Richard Hull
Attachments
Demo System.jpg
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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Re: First Light in my First Metal Demo Fusor!

Post by Maxwell_Epstein »

Thank you very much for the advice and the diagram. I'm definitely planning to include a foreline valve in my D-25 vacuum system, is something like this a good option? Would I use the same type of valve for air admittance?

As for the oil problem, I opened up the 2.75" viewport flange to clean it and saw a congealed puddle of oil in the bottom of the chamber that was clearly the result of a significant leak from the pump. I know that this is very bad, but I was still able to pump down to ~90 microns consistently (I guess oil outgasses at a lower pressure/higher temperature). I plan to partially disassemble the chamber to clean it as soon as I have time and before doing any more plasma runs. I have also began removing the KF flange for the thermocouple before turning off the pump so that the chamber is at atmospheric pressure before I turn off the pump. I won't have to do this with the new pump and foreline valve, of course, but it seems to work for now.

Thanks again!
Max E.
See my needlessly verbose fusor blog here: https://highschool-fusioneer.medium.com/!
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Liam David
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Re: First Light in my First Metal Demo Fusor!

Post by Liam David »

The valve you linked to would work fine, but I suggest scouring Ebay and other surplus sites as nearly $400 for a valve is quite overboard. Something like https://www.ebay.com/itm/321820303728?h ... SwRQlbJfmB would be better as an air admit valve (also much cheaper). It allows you to slowly vent, as opposed to cracking a flange which isn't quite as gentle.

Oil was sucked into your chamber because the pump doesn't have an anti-suckback valve, and stopping the pump allows atmospheric pressure to push the oil back the other way.

Certainly replace the small plastic tube, as it's ruining the pumping speed. KF flanges are usually the way to go.

Great work, and keep up the experiments.
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Richard Hull
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Re: First Light in my First Metal Demo Fusor!

Post by Richard Hull »

Liam's valve recommendation is ideal in every way as an admit to air valve! Keep this simple as you will only use it at every shutdown and only at that time. It forever remains shut after being opened for only 2 seconds! The valve you show is an ideal chamber valve on a large serious fusion 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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Post by Maxwell_Epstein »

It's been a while since I last made an update on my progress and a lot has happened. First of all, thank you very much to those who made valve recommendations. I bought a right angle valve and a vent valve and both worked very well.

With the help of those in the new user chat area, I was able to get the D-25 reconditioned and working well and was able to pull an end vacuum of 15 microns. I attached the D-25 to my chamber with a kf-25 vacuum manifold that also includes attachments for the vent valve and thermocouple along with the main right angle valve. The manifold serves as the attachment point for both the pump and the thermocouple so there was an open 2.75" CF flange on the chamber. I planned to blank it off until I need the opening for a gas inlet, but when I ordered a blank on eBay I received a viewport instead so my chamber now has two viewports looking in perpendicular to each other (and I got a viewport for very cheap so there's that too).

The upgrade from the old pump has allowed me to create plasma all the way down at 25 microns as well as to achieve star mode in the system. The NST has also, as expected, been able to output significantly higher voltages than ever before (with the drop in amperage that entails), all the way to 5.7kV at 13mA. I recognize that isn't that impressive here, but progress is progress!

I plan to continue experimenting with star mode and would like to better understand experimentally the differences between halo and star mode as well as the transitory period between the two. Now that I have a much more adept vacuum system, it sounds like the next step is to start looking into building a supply from the 30kV x-ray transformer that I have acquired but that is still quite a ways away timing wise.

Thank you all again for your specific help as well as for the site in general, I am very relieved that it is back up.

Max E.

P.S. Now that this post is no longer about my first light in the system, would it be best for me to make a new post with a more generic title ("Max Epstein's Fusor 1," or something similar)? I don't want to clutter up the Images du Jour forum with my posts, but I would also like to make sure the post title fits...
Attachments
Star Mode.jpg
fusor 1.2 vacuum manifold.jpg
fusor 1.2 vacuum manifold attached to chamber.jpg
Fusor 1.2 test 1 data.jpg
Fusor 1.2 test 1 graph.jpg
See my needlessly verbose fusor blog here: https://highschool-fusioneer.medium.com/!
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Richard Hull
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Re: First Light in my First Metal Demo Fusor!

Post by Richard Hull »

Great work mike! You are working at this the right way, slow but sure. You will see that the neon sign transformer will keep giving mo0re voltage as your vacuum improves over times. It is part of the learning process.

You might start a new thread called, update on Mike Epstein's fusion efforts. This covers a broad range of postings. Remember, in the Image Du Jour forum the first post must have an image. Subsequent posts may or may not have images, but should have images to show what you are doing.

The construction forum may have images in some postings, of course, but it is not demanded. Most folks use the construction forum for long progress reports on their work with images so replies are allowed as the thread builds.

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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Maxwell_Epstein
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Re: First Light in my First Metal Demo Fusor!

Post by Maxwell_Epstein »

Thank you Mr. Hull!

It's been close to a year since I've been able to make much real progress, mostly due to the college application process taking up the vast majority of my free time (I am applying to many schools for engineering physics to hopefully continue my journey into particle physics and fusion!).

However yesterday I was able to rebuild my (demo) Fusor 1 system with a turbopump and begin pumpdown testing it. At Mr. Hull's advice, I am migrating further progress reports and specific questions to a post in the fusor construction section of the forum. I just made a post there now:
viewtopic.php?p=97658
My completed Fusor 1 vacuum system
My completed Fusor 1 vacuum system
Thank you all again for all of the guidance and encouragement!
Max E.
See my needlessly verbose fusor blog here: https://highschool-fusioneer.medium.com/!
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