Joe Ballantyne Fusor v1.

For posts specifically relating to fusor design, construction, and operation.
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Re: Joe Ballantyne Fusor v1.

Post by Richard Hull »

Great post on the moderator build. Others will benefit from this post, I am sure. While certainly the above post was part of Joe's fusor construction post, it related directly to neutron detection. I think Joe should also post a copy of this in the radiation forum so that it might be accessed in relation to that aspect of radiation detection. I just like to see a great post like the one immediately above posted where it won't be lost in the deep clutter of construction posts. Don't move it, just reproduce or copy it to the radiation forum. It is too good to get lost here in construction.

I am so glad I bought my moderator pre-cut back in 2020 from the local Piedmont Plastics facility here and picked it up in person. Joe's is a virtual same cut as we have the same 3He tubes. I put out a post on my work back then with a PDF. The total cost for it all 100% pre-cut HDPE with tax was $97.00

viewtopic.php?t=13553

If you are in possession of such a wonderful long tube, regardless of price for the HDPE, the finished project results in one of the most sensitive neutron detectors around, once all the electronics are hummed in to perfection. It creates a roar of counts from a whisper of neutrons.

I felt the pain of the recent price increases when I went back to buy pre-cut strips, 6 feet long to create a Lego/Lincoln Log-like set of small blocks of HDPE to assemble any number or forms of small HDPE moderators for activation work around the intimate contact rhodium/Russian STS-5 GM tube.

I got group of long strips of 1-inch thick X 1-inch and 1-inch X 1.5-inch HDPE all 6 feet long. This required my 10-inch chop saw to get a similar blade to what Joe purchased. I was fortunate to have to be able to cut only 1-inch and 2-inch cuts in a series of rapid, near instantaneous chops.

I find that for activation, a "fusor hugging" activation moderator, a "small block" assemblage is just the ticket, especially for fast decay isotopes where a GM tube can be placed for instantaneous counting at shutdown of the fusor. I still have a couple of those long, HDPE strips left, yet to be cut up and a box full of those "toy-like" HDPE blocks. This group of precut strips cost me about $125.00 one year later in 2021. (this was a plank of HDPE 1-inch thick, 6-inches wide and 6-feet long with several flawless, length-wise cuts by Piedmont.)

For the block moderator post, I turned into a FAQ found at......

viewtopic.php?t=14107

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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Re: Joe Ballantyne Fusor v1.

Post by JoeBallantyne »

Neutron Detection

Of course the vast majority of folks who embark on building a fusor, do so because they ultimately want to do fusion and prove that they have done so. That proof is that they can detect the neutrons which are produced by half of the D-D fusion reactions.

I was no different, and so last spring, soon after I got my deuterium supply system properly connected to the fusor in a vacuum tight way, I tried to make neutrons.

I failed.

Or at least I failed to successfully detect any neutrons that I might possibly have made.

In my experience, getting properly setup to detect neutrons, and getting to a state where you KNOW that your setup will detect neutrons is the hardest part of building a fusor and proving that it does fusion. Why? Because unless you just go fork over $4000 - $6000 to Ludlum to buy a brand new Model 15, or Model 12-4, or Model 2363, you can’t be confident that your neutron detectors will actually work properly. Without doing a lot of work.

I purchased a few used complete neutron detectors off Ebay. Given the overall cost of those used Ebay detectors, I would have been better off just buying a single new one from Ludlum. Especially since none of the used neutron detectors I bought were able to successfully detect the low levels of neutrons I was initially producing with my fusor. In the end it was a 1x24 inch Texlium He3 tube that I bought a few years back from Richard Hull at HEAS in the HDPE moderator I described in an earlier post, that I coupled to a Ludlum 2200 scaler for neutron detection. That 24 inch long He3 tube was by far the most sensitive neutron detection device of all the different tubes and meters that I had.

Last spring (March 2022), I tried using a couple of Ludlum 2363 counters with the “Thors hammer” probe. I never got any counts that were statistically different from background. I tried using a couple different Ludlum Model 15s that I bought used off Ebay as well. Ditto on the failure to detect neutrons at statistically significant levels. (I think there may be issues with the tubes in both of those Model 15s. One of them has a tiny He3 tube, and the other has a larger BF3 tube.) Of course when I bought them, I had no way of really testing them, so I couldn’t know for sure if they worked before the window for returning them closed.

Bottom line is that you don’t know if the neutron detection equipment you are buying off Ebay actually works. The only way you can know for sure, is if you have a neutron source. If you don’t KNOW that your fusor makes neutrons, and you don’t have access to a neutron source, then you really are flying blind. If you don’t get any statistically significant counts, you don’t know if it is because your fusor is actually NOT making neutrons (certainly a very distinct possibility), or if your neutron detection equipment just doesn’t work, or isn’t calibrated properly, or the bias voltage level on the tube is too low, or the threshold on the meter is too high. Now I suppose I could have forked over some dough to Ludlum to calibrate one or more of the meters I bought, but I decided to go a different route. The do everything yourself route. It costs more, takes the longest, and is harder, but that is how you maximize what you learn.

I wanted to be ABSOLUTELY SURE that I could detect neutrons. The only way to do that, was to either purchase, build, or borrow a neutron source. I didn’t know anyone in my area with access to a source, so borrowing was not an option. Purchasing a source, I assumed would be hard. Now, I could be wrong about this, but I suspect that most entities with neutron sources, especially if they are reasonably strong sources, are probably required to have an RSO (Radiation Safety Officer), or a Health Physicist, or both. Certainly you can’t really find neutron sources on Ebay. At least I could not. I must confess I did try. Neutron sources are part of some kinds of moisture meters, and some kinds of density meters, but the kinds with neutron sources do not show up on Ebay. I’m pretty sure they are not supposed to ever show up on Ebay. In my experience, they don’t.

That leaves building a source. So, I thought I would just follow Carl Willis example, go the easy route, and buy an Antistatic Nuclespot 5mCi Polonium source for $289, and use it with a $50 Beryllium disk bought from Ebay to make a simple source. The Nuclespot would only last a year or so, but that would be sufficient time for me to test and calibrate my neutron tubes and meters. So, I tried. I ordered one back towards the end of August 2022. They told me it would be a 12 week wait. Well, it turned out that was wrong, because I finally called them towards the end of January 2023 and cancelled my order and asked for a refund. Nuclespots are in my experience, at least right now, impossible to get. Evidently the manufacturer made some changes to the manufacturing process, and due to that is now dealing with getting NRC approval for the modifications. At least that is the story they told me.

Siemens Pyrotronics F3/5A to the rescue… these are a LOT more expensive now on Ebay than they were just a couple of years ago. I bought a couple from a fellow member of this forum post HEAS, had another one I had purchased off Ebay a couple of years ago, and so was able to make a temporary, very weak ~200uCi Americium 241 Beryllium (AmBe) neutron source. This is only 1/25th as strong as the Nuclespot source would have been, but the advantage is that the half life of Americium is 1143 times longer than the half life of the Polonium in the Nuclespot. The Americium won’t be mostly decayed in a year. (In fact it still retains more than 90% of its original activity levels, even though it is on the order of 60 years old! Yes, it has been a LONG TIME since they put 80uCi of Am241 in a smoke detector… Modern ones have only 0.8uCi or thereabouts.) If I need a neutron source in a year, I can just put the Beryllium foil back in close proximity to the sealed Americium foil, and BINGO!, neutrons. Not very many neutrons mind you, but neutrons. Americium 241 is an alpha source, and Beryllium has the property that if you hit it with an energetic alpha particle, between 30 and 60 times out of a million hits, it will spit out a neutron. If we go with the low end of that estimate, 200uCi is 7,400,000 Becquerel (decays per second), which means we should be getting 7.4*30 = 222 n/sec. In reality the most counts I got with the source next to a neutron tube inside a moderator, was 100-200 cpm depending on the tube I was testing. But the point is, I could get counts! So I could be sure which neutron detection setups were working, and which were not.

None of the Ebay acquired all in one neutron detectors (the model 15’s and the model 2363’s) would register statistically significant count rates with my very weak source. This of course was quite disappointing.

Many of the folks on fusor.net who use stand alone neutron tubes, do so with specialized NIMBIN equipment. They use either homegrown, or specialized commercial preamps, coupled to shaping amplifiers, discriminators, and MCAs etc. I didn’t want to deal with any of that. I wanted to see if I could get some of these stand alone tubes to work directly with stock Ludlum meters – ala Mark Rowley with his Ludlum 3 and Russian CHM11 tube combination. (Although I guess in his case, he did put a bias/ballast resistor in series with the CHM11 tube.)

Well, it turns out that you CAN get standard He3, BF3 and B10 tubes to work directly with Ludlum 2200 and Ludlum 1000 scalers. No bias resistors, no preamps, no shaping amps, no discriminators required. BUT, not using a preamp, means you have to run at least the He3 tubes with a higher bias voltage, to get the tube gain up to a point where the stock meters will register the counts with their threshold adjusted very low.

In order to be sure that I knew exactly what the bias voltages and thresholds of my meters were, I bought a used Ludlum Model 500 pulser from a vendor in the calibration business, and used that to calibrate both the HV meter as well as the threshold potentiometer on the Ludlum 2200. (To double check the HV meters, I also bought a couple Sensitive Research electrostatic voltmeters off of Ebay. Which BTW are very cool pieces of hardware that require no batteries or external power source to function and to which you can directly connect the high impedance HV sources on radiation meters because the electrostatic voltmeter input impedance is on the order of 1e15 ohms.) The Ludlum documentation on the 2200 says that it will work with proportional tubes, but the threshold needs to be set to about 2mV for them. So, I increased the amplifier gain (screwdriver adjusting screw with a lock nut that is labeled DISC on the front of the 2200) on the 2200 by turning the set screw clockwise, so that 1.0 on the threshold pot was a 3.3mV threshold as measured on the Model 500, and 10.0 on the pot was a 33mV threshold. This allowed me to set thresholds anywhere from 2mV up to 30mV or so with better resolution on the pot than the initial lower gain amp setting allowed. After locking in the DISC amplifier setting with the lock nut, I adjusted the threshold pot down to 0.6 which corresponds to a ~2mV threshold.

The Texlium He3 tube has an HN RF connector on the end (many of the Reuter Stokes neutron tubes also have an HN connector on them), so I bought an HN to C adapter (UG-702/U) and screwed it onto the HN Texlium connector. Then used a stock Ludlum C to C cable to connect the Texlium tube directly to the Ludlum 2200. No bias resistor or preamp involved at all. (I intentionally did NOT use BNC connectors anywhere in the setup because I wanted to be able to push the bias voltage up to the 2500V limit of the 2200 if needed, without having to worry about significantly exceeding the HV capacity of the BNC connectors.) Put the tube in the moderator with the weak AmBe source and slowly started raising the bias voltage. Nothing at 1000V, nothing at 1500V, nothing at 1600V, nothing at 1650V. Finally when I hit a little above 1700V I got a single count. At 1800V I got a couple more counts. When I got up to about 1850V the count rate started to go up. Turns out, that if you run my Texlium He3 tube at 1900V with a 2mV threshold, it will work perfectly with a Ludlum 2200 no additional hardware required. Which makes it really easy to use.

Now granted, with a preamp, I could probably run the tube at a much “cooler” voltage of 1500V or so. So for the purpose of extending tube life as long as possible, using a preamp and a lower bias voltage is better. But this tube is not going to be running anything close to 24x7. More like a couple hours a week on average, absolute max. So for now, I am perfectly content to run it the simple way, directly connected to my Ludlum 2200.

I had a number of other tubes that I tested to determine what kind of bias and threshold settings were needed to run them directly connected to a Ludlum 2200. This is what I found along with typical counts per minute inside an HDPE moderator with my weak AmBe source, as well as typical background cpm:

Tube/Meter:.....................................Bias and Threshold:.........AmBe............Bkgnd:
Texlium stainless He3 tube 1x24.............1900V bias 2mV threshold..95cpm...........8cpm
Reuter Stokes Aluminum He3 tube 1x22....1900V bias 2mV threshold..101cpm.........12cpm
Russian SI19 1.125x8 He3 Corona............2050V bias 35mV threshold.70cpm..........18cpm
GE B10 1.5x17..................................715V bias 10mV threshold...40cpm..........1cpm
Nancy Woods BF3 1x6.........................1975V bias 2mV threshold...12cpm ..........5cpm
Ludlum Model 15 BF3.........................1750V bias ?? threshold.......2cpm............0cpm
Ludlum Model 2363 hammer.................?? bias ?? threshold............6cpm............6cpm

For the Ludlum model 2363 I just ran it as a unit as it was configured when I purchased it. I left the probe attached to the meter, and put the probe a few inches away from the unmoderated AmBe source.

Here is a picture of the tubes listed above: from bottom to top Texlium, RS, S19, GE B10, Nancy Woods, and the Model 15 BF3

IMG_20230211_123350380v2.jpg

Bottom Line:

1) Large He3 tubes are the most sensitive. But they are hard to come by and cost $$$.

2) You can directly connect many tubes to Ludlum 2200 Scalers and they will work perfectly – with an appropriately low threshold and a hotter bias than would be required with a preamp.

3) Ludlum 2200 scalers are great instruments that can be used to drive many different radiation measuring devices.

4) To be SURE you can measure neutrons with your instrumentation, you need a neutron source.

5) Ludlum 500 Pulsers are nice for making sure your instruments are properly calibrated and for accurately determining bias voltage and threshold voltage levels.

6) If you don’t buy a ready to go, calibrated, guaranteed functional, reasonably sensitive neutron measuring system, getting one setup and being sure it really works, is non trivial.

7) Ebay purchased neutron detection instruments like the Model 15, Model 12-4 and Model 2363 are most certainly not guaranteed to work in all cases. Sometimes (maybe more often than not) you will get a dud. Make sure you can figure that out before the return window closes. (ie: that neutron source I keep talking about, is kind of important…)

Joe.
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Re: Joe Ballantyne Fusor v1.

Post by Richard Hull »

A great report on neutron tubes and the use of a Ludlum 2200. The 2200 is a fabulous all in one instrument. I reported on mine here and Jim Kovalchick also gave his thumbs up to the 2200. It is the closest thing to a full NIM bin in a box.

As with a NIM Bin, you must learn about the internal electronics an understand how to use them at a level beyond the casual amateur dabbler. it just takes a bit of use, and successes to hone one's skills with the device, as Joe notes.

As to the tubes. I think Joe bought both his 3He tubes from me at HEAS and he paid dearly for them, but you see how sensitive they are in his tests. Nothing touches a large 3 of 4 ATM 3He neutron detector tube.

The Nancy woods tubes are deceptive they are vastly smaller than their external dimensions with very short sensitive regions. There is a smaller tube within the nice larger brass body with the HV BNC on it. BF3 tubes even with a good preamp don't work at all until you really pour in the juice (HV). If you have a good preamp and the voltage to make them sing, size for size they are every bit equal to a good 3He tube. Problem is the amateur is most likely not going to acquire a larger BF3 tube.

I have spoken to the nice ancient GE boron lined tubes of the 50's and 60's in a number of posts before. They are great tubes and use to be cheap on e-bay. Not any more. They will not respond to the ham-fisted amateur as the bias voltage is hyper critical. Most idiots will chase them into their Geiger region and think they are counting neutrons. They are proportional tubes and require a preamp and a critically set voltage to detect neutrons. The 2200 is the ideal instrument to play "let's find the proper bias voltage" when seeking to bring a boron lined tube to heel and count neutrons.

The use of a pulser and digital o'scope aids not only in setup and calibration, but also as a big learning experience.

I can tell that coming out of his trials (expensive ones), Joe is now a self-trained near expert in the use, and more importantly, the understanding of just what it takes to make neutron tubes actually count neutrons! He understand the tubes and the electronics at a core level.

Again a great teaching post...! Too bad it is deeply buried in a post thread in the wrong forum. This needs to be in the Radiation detection forum as a first post


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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Re: Joe Ballantyne Fusor v1.

Post by Paul_Schatzkin »

Jeez, Joe, I sure hope you're using voice dictation for these posts. I cannot imagine typing all that!

I sure hope others appreciate and benefit from your painstaking attention to the details.

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Paul Schatzkin, aka "The Perfesser" – Founder and Host of Fusor.net
Author of The Boy Who Invented Television: 2023 Edition – https://amz.run/6ag1
"Fusion is not 20 years in the future; it is 60 years in the past and we missed it."
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Re: Joe Ballantyne Fusor v1.

Post by Richard Hull »

I have been typing my brains out for years in long posts, especially in the FAQs. Many folks arriving here need to be taken by the hand and "spoon fed" materials in long form. This often demands a completeness that folks in the know can assume and arrive at through logic, but not many noobies are so endowed. Even then, for all my efforts, they do not read for comprehension. One would like to think we attract a higher order of folks, but it ain't always the case.

Long typed FAQs are also all about being explicit enough to keep people safe as we do venture into so areas where safety and good procedure is a must.

As I noted, Joe did a great job. The Ludlum 2200 is a great all in one instrument. I realized his great post related to the 2500 would forever be lost and buried deep in this long construction thread. The effect of this and Joe's post kicked me in the butt to write a FAQ around it and its use in the radiation forum FAQs. It, too, is somewhat of an epistle.

viewtopic.php?t=14785

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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Re: Joe Ballantyne Fusor v1.

Post by JoeBallantyne »

Neutron Club Entry Request

So on 11 Jan 2023, I was finally able to get my fusor to do provable fusion, by making neutrons that I could detect at statistically significant levels with my neutron detection setup. In addition to working on neutron dectection in the months since March 2022, I also made several changes to the configuration of Fusor v1. I moved the fusor onto a utility cart, along with the D2 cylinder gas supply system and Spellman DXM 70N600 power supply. I moved the Welch 1402 vacuum pump to a different utility cart. Ultimately the plan is to move the gas supply from the fusor cart to the other cart, so that I have a gas supply and vacuum system that is independent and isolated from the fusor itself. That way I can just attach it to whatever fusor I am currently working with. I plan to keep Fusor v1 in permanent operational condition and NOT cannibalize it for parts for future fusors.

I moved the D2 gas inlet for the fusor from its original location on the top of the KF16 4 way cross, to the KF50 flange on the far end of the KF50 tee containing the cathode. This way the D2 gas enters the fusor on one end, and has to flow through the cathode and all the rest of the KF50 tubing of the fusor before it gets to the KF40 butterfly leading to the KF40 bellows that goes to the vacuum pump. In the original setup, the inlet gas could flow directly out to the vacuum pump without ever flowing through the cathode. In the new configuration this is not possible. In order for the gas to get out of the fusor, it MUST flow through the cathode location. (Realistically this probably doesn’t make much difference at all, but it is nice from a conceptual standpoint.) I also swapped out the original hard to use KF50 ball valve, for a KF50 to KF40 conical adapter and a proper MDC KF40 butterfly valve that is MUCH easier to use than the ball valve, and is what I use for throttling the vacuum and controlling the pressure in the fusor. MDC makes some really nice butterfly valves.

Since high voltage is the most dangerous thing about typical fusors, I built a custom connection for my stock MPF KF40 30kV feedthrough with various PVC and CPVC pipe fittings and pipe, so that I can use the proper DXM x-ray high voltage cabling with the correct connectors on both ends (Claymount CA11), and plug it directly into the power supply, and into my custom HV feedthrough connector. I bought the proper CA11 socket to use on this connector and it also has a 225W 150kohm ballast resistor built in. This connector is designed so it can be filled with mineral oil, and hopefully will allow me to get to the full rated 70kV of the power supply without any arcing on the 30kV feedthrough. The connector is a modified and improved version of the dual o-ring design used by Joe Gayo and Jon Rosenstiel. My design does not require using a lathe to mill out the inside of the PVC pipe. It uses stock PVC and CPVC parts available at Home Depot, and a slightly larger o-ring than the one used by Joe and Jon. I plan on making a separate post describing the design and build in detail. This HV connection system ensures that there is no exposed HV anywhere on the fusor or the HV power supply system. The cable is a commercial HV cable and is designed to be used with the Spellman DXM supplies. This dramatically reduces the risk of and worries about getting zapped! (I still make a reasonable effort to stay away from the high voltage cabling and connector, but at least there is no exposed HV anywhere in the system.)

Vacuum System:
Welch 1402 mechanical pump with an ultimate vacuum of ~1 micron.
KF25 and KF40 plumbing to the fusor with 2 KF25 butterfly valves – one just above pump inlet, and one after a typically blanked off KF25/KF16 reducing T. (This normally blanked off KF16 inlet is very useful for doing vacuum testing of any vacuum items I purchase from Ebay or elsewhere. I simply remove the blankoff, and attach whatever I want to test to the KF16 port, and can then pump it down, and determine if it is functional and whether it leaks or not.)

Deuterium Supply System:
100L cylinder of 99.8% D2 gas from Cambridge Isotope Labs.
Matheson SS CGA350 dual stage regulator
¼ inch copper refrigeration tubing with SS Swagelok connectors
¼ VCR SS Needle valve

HV Power Supply System:
Spellman DXM 70N600X3547 70KV 8.5mA power supply
75KV HV cable with proper Claymount CA11 connectors on both ends (proper cable for DXM supply)
Custom made oil fillable HV feedthrough connector with CA11 socket and 150Kohm ballast resistor
Windows laptop to control the DXM using Spellman software and an Ethernet connection to the supply.

Fusor vacuum chamber:
¼ VCR to KF50 adapter (connected to D2 gas supply needle valve)
KF50 Tee
KF50 to KF40 conical adapter
KF40 30KV HV feedthrough (standard MPF 30kV feedthrough see http://mpfpi.com)
KF50 Tee
KF50 viewport
KF50 to KF16 reducing Tee
KF16 4 way cross
KF16 MKS901p
2 KF16 blanks
KF50 to KF40 conical adapter
KF40 MDC butterfly vacuum throttling valve
KF40 bellows – to the vacuum system

Neutron detection system:
Ludlum 2200 Scaler
1x24 inch Texlium SS He3 tube
Bias voltage: 1750V
Threshold: 2mV

I did 3 separate 10 minute neutron background measuring runs with the Texlium tube in the moderator, but the fusor turned off, and got the following counts for each 10 minute run: 72, 51 and 84. Which results in an average of 6.9cpm – which we will just call an even 7cpm.

I started the vacuum pump. Pumped the chamber down to 1.2 microns. Then I closed the gas needle valve, and opened up the valve on the low pressure side of the regulator just a bit. The pressure rose quickly in the fusor up to about 5 microns. (The needle valve does not fully close off the flow of the D2, and I didn’t want to damage it by trying to close it further.) At this point all 3 of the butterfly valves in the fusor and vacuum plumbing were fully open to the pump.

On my Windows laptop I fired up the Spellman DXM control software – which you can download from the Spellman website. Selected the port type as Ethernet, and then set the network port to 50000 and the IP address to the default address used by the DXM of 192.168.1.4. (I had previously turned off the WIFI adapter in my Windows laptop, and set the Ethernet address of the wired port on my Windows box, to have a fixed IP of 192.168.1.2, with a mask of 255.255.255.0 and a gateway address of 192.168.1.1. I plugged both my Windows box and the Spellman into a wired Ethernet 8 port gigabit switch. There was no actual gateway on this local Ethernet, just my laptop and the DXM and the switch itself. Two CAT5 Ethernet cables, one between my laptop and the switch, and one between the DXM and the switch.)

After clicking OK in the DXM software network config dialog box, I got the software control panel for the DXM. Switched the control from local to remote. Set the DXM current mA limit to 8mA. Set the voltage to 16kV. This Spellman model voltage output is negative, so all of the actual HV values on the cathode are negative even though I will not make that explicit in this report – when interacting with the GUI you do not use negative values and it does not report the measured values as negative either. Then clicked enable HV. The monitoring voltage jumped up to ~16kV, but the current stayed really low, and there was no plasma, as the pressure in the chamber at ~5.5 microns was too low for the plasma to light off.

I then very slowly closed the KF40 butterfly valve on the end of the fusor to throttle the vacuum, and the pressure on the MKS901p steadily rose. I was focused primarily on the Ludlum 2200 counts and the viewport – to see when the plasma lit up. All of a sudden the Ludlum 2200 started counting! It was going slowly, but definitely faster than the background count rate. I checked the viewport, and the plasma was lit – it wasn’t very bright, but there was definitely visible plasma. I started making a video of the run as I was so excited about getting neutrons. The pressure was 24.4 microns, the voltage was at 15.91kV and the current was ~0.36mA. That first minute run generated a neutron count of 95 cpm!

It turns out that with those particular settings, 16kV on the cathode, ~24.5 microns pressure, and ~0.4mA, my fusor is very stable. The pressure is steady (rising very slowly), as is the current(also rising very slowly). So I decided to just let it keep running and not mess with any of the settings. I did another 1 minute run. At the end of that second run, the voltage was 15.91kV, the current was 0.36mA, and the pressure was 24.5 microns. The neutron count for that second minute was 142. I then reset the counter for a third minute run with the same 15.91kV, 0.36mA and 24.5 microns and got a count of 108 neutrons. Since the fusor was stable, lit, and making neutrons, I decided to try for a 10 minute run, and switched the Ludlum 2200 to count for a 10 minute interval. The fusor ran beautifully for the full 10 minutes! At the beginning of the run the voltage was 15.91kV, the current was 0.38mA, and the pressure was 24.5 microns. At the end of ten minutes the voltage was 15.91kV, the current was 0.43mA, and the pressure was 24.7 microns. The neutron count for that first 10 minute run was 1479.

I decided to do a second 10 minute run immediately after the first. So the initial voltage current and pressure at the start of that run are the same as the settings at the end of the first run, or 15.91kV, 0.43mA, and 24.7 microns. The voltage, current and pressure at the end of the second 10 minute run were 15.91kV, 0.46mA, and 25.0 microns. That run generated a neutron count of 1716. Interestingly, even the slight rise in the pressure and current during the run made a decent increase in the neutron count over the 10 minute span.

I realize that the voltage and current are both pretty low as typical fusor runs go, but the 24 inch Texlium tube is sensitive, and the difference between the background count of 7cpm, and the average fusor running counts of 148cpm and 172cpm for the two 10 minute runs, is a factor of 21x and 24x the background rate which is statistically significant in my book.

I did pull the neutron tube from the moderator with the fusor running to check what happened to the neutron counts, and with the tube pulled, the counts went down to background level (I got 1 or 2 counts during a 20 second interval or so), and immediately rose again when the tube was reinserted in the moderator.

A week or so later, I did additional runs at significantly higher voltages, and got much higher neutron counts, but this is the data from the first day I made neutrons, and I consciously decided to not push the fusor, as it was running in such a stable way. When running at higher voltages, it is much more difficult to keep the current under control even for a full minute run, and the DXM will shut down when the current hits its upper bound of 8.5mA.

A few pictures of the setup on 11 Jan 2023.

The Ludlum 2200, Texlium neutron tube and moderator.

IMG_20230111_222112759.jpg

The Spellman DXM control software running on a Windows laptop.

IMG_20230111_225556943.jpg

The MKS901p with Bruce Meagher’s digital display unit.

IMG_20230111_225601016.jpg

Fusor V1 with commercial HV power cord feeding custom feedthrough connector.

IMG_20230111_234420443.jpg

Closer view of the custom feedthrough connector with ballast resistor.

IMG_20230111_234355989.jpg

Joe.
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Richard Hull
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Re: Joe Ballantyne Fusor v1.

Post by Richard Hull »

Joe this is a very full report and you are now inducted into the neutron club.. We look forward to more HV runs.

Suggestion: limit your pressure to 6 microns and bring up the voltage. you should over time be able to add more pressure.

The auto shutdown of the supply is a great disadvantage, but over time you will get to learn how to jockey the 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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Re: Joe Ballantyne Fusor v1.

Post by Paul_Schatzkin »

Congratulations, Joe.

And thanks for all the very detailed reports.

--P
Paul Schatzkin, aka "The Perfesser" – Founder and Host of Fusor.net
Author of The Boy Who Invented Television: 2023 Edition – https://amz.run/6ag1
"Fusion is not 20 years in the future; it is 60 years in the past and we missed it."
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Re: Joe Ballantyne Fusor v1.

Post by JoeBallantyne »

Thanks Richard and Paul!

Its nice to finally be able to make neutrons.

Joe.
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Re: Joe Ballantyne Fusor v1.

Post by Paul_Schatzkin »

And I'm sure it will make for some intriguing cocktail party banter.

"And what do you do, Joe?"

"Well, I'm retired now, so I make neutrons.."

Some guys go fishing. Some guys make wood furniture or paint.

Joe makes neutrons.

I just hope your wife approves.

--P
Paul Schatzkin, aka "The Perfesser" – Founder and Host of Fusor.net
Author of The Boy Who Invented Television: 2023 Edition – https://amz.run/6ag1
"Fusion is not 20 years in the future; it is 60 years in the past and we missed it."
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Liam David
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Re: Joe Ballantyne Fusor v1.

Post by Liam David »

Good work Joe and congrats on the neutrons! Here's to many more.
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Richard Hull
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Re: Joe Ballantyne Fusor v1.

Post by Richard Hull »

If you say you make neutrons most would not know the difference between making neutrons and making a thrombosis!
Always say "Oh, I do nucelar fusion at home in my spare time now that I am retired." This is much more accurate as neutrons are just the nuclear ash and is just one of the 4 waste products of doing fusion. You can go on to explain that the detection of neutrons during fusion proves beyond any doubt that you are doing fusion.

You'll have the best campfire story that will fascinate the plebeians gathered round. The best and most horrified among them might query what are the other three nuclear ash or waste products? Be prepared. As any good boy scout around a campfire should be.

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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Emma Black
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Re: Joe Ballantyne Fusor v1.

Post by Emma Black »

Congratulations on making the neutrons Joe! I have been greatly enjoying this thread, its a good read.

I can relate to the fun and games you had a while back cutting the HPDE, I regretted doing this inside, what a mess!
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Re: Joe Ballantyne Fusor v1.

Post by JoeBallantyne »

Thanks Liam and Emma!

Joe.
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