1D Cathode with Neutron Run

For posts specifically relating to fusor design, construction, and operation.
Post Reply
User avatar
Trent Carter
Posts: 23
Joined: Tue Dec 20, 2016 8:38 pm
Real name: Trent Carter
Location: Melbourne, Florida

1D Cathode with Neutron Run

Post by Trent Carter » Sat Aug 31, 2019 10:13 pm

I do not post nearly as much as my research warrants. This is because sometimes I dont have a particular breakthrough and the specific tests are not really adding much to the forum.

Let me define research: Its includes things I do in my lab that interest me, usually a manifestation of "I wonder what would happen..." or "...what about this configuration...". Sometimes I am very scientific and methodological, sometimes I have embarrassingly little documentation, control, and data backed results.

I have made so many cathodes, easily in the 100+ range that I can pretty much make a fusion reactor cathode out of just about anything (assuming its vacuum safe, non sputtering, and has a high melting temp). If the cathode makes at least a little sense I can usually release a measurable amount of Neutrons.

Neutron detection is paramount to Fusion research. I have two neutron detectors (a third in Sept 19) that are uncalibrated but reliable, unaffected by gammas and very good noise rejection. They all have the ability to relatively easily do Moderated Vs Unmoderated testing. I plan to have 4x in house in 2020 and at that point I will rent a calibrated Ludlum 12-4 H3 to calibrate them. Currently I have H3, Boron10, and adding a second B10, and in 2020 a LiI(Eu)
1. GS-Neutron MKII - B10 - 15% Efficiency - 90mm HDPE - CHM-12
2. Ludlum 2000+H3 - H3 - 50mm HDPE
3. Ludlum 2200 - SNM11 - B10 - 15% Efficiency - 100mm HDPE (ETC Sept 2019)
4. LiI(Eu)-PMT of some type (ETA Q1 2020) They are expensive, fairly rare.

I have been focusing on two areas for the last year;
1. p-B11 Fusion - More on that research later. I have a few good ideas, but no Alphas as of yet. Not even sure this is the best forum, but my research is IEC. p-B11 like an amateur dead end.
2. 3D, 2D, and 1D Cathodes and the advantages in pressure, Neutrons, voltage and current based on geometry.

Today I will share a Neutron generating fusion run using a 1D Cathode.

3D Cathodes: Typical Farnsworth fusion cathode. Star mode generally in 3 Dimensions. i.e. the plasma jets would need three coordinate systems to describe their basic positions.

2D Cathodes: This is the path taken by David Coulter (First fusion person I stumbled across, not likely the “first”). They are usually cylinders made by two flat washers on each cap connected by tungsten rods or some conductive metal with a high melting temp. Their plasma jets can be described using two coordinate systems.

1D Cathodes: This is less explored. There are a few on this forum that have used them. Steven S. has a version of a 1D, some guy with a differentially pumped system, forgot his name, and recently by Joe Gayo. This system usually has only two plasma jets and is essentially a line. Think of a thick washer or bushing as a cathode.

Beam On Target: This is here for completeness as it is not IEC and its well understood. But it is also 1D. This you have an ION source of deuterons and you accelerate them toward a target of titanium or the like which has absorbed deuterium. This D-D beam on target is the typical commercial Neutron source.

1D Cathode Requirements:
1. Made from a material that does not sputter
2. Made from a material with a reasonably high melting point (so you can run for longer times at higher powers)
3. Made from a material that is workable
Pulse arc weldable
4. Made from a material that is vacuum safe

Cathode material options:
Stainless Steel [prefer 316]
Tungsten Carbide
Aluminum (advantage of lower bremsstrahlung)

To machine cathodes I recommend a small hobby drill press like the Microlux Micro-Mark. Then buy an X-Y bed and a machine vice. I recommend buying very good carbide bits and some diamond bits for tungsten and glass.

To weld, I recommend buying or making a Pulse Arc Welder. I did both. Enzo has a nice video on how to Pulse Arc Weld, and I am fairly sure he was making a 2D Cathode. Post welding put a brass brush on a dremel and brush the welds shiny. Wear safety goggles or you will lose an eye. Brass dremel brushes release brass shrapnel.

Vacuum Chamber: If you are not jealous of my Fusion Mark III chamber, then there is no hope for you. Its is the cream de la cream. Flexible, built in bake out, expandable, lots of attachments/options. Its make by Ideal Vacuum, called the Ideal Vacuum Cube. I have the 12x24.

Vacuum Pumps: Get yourself a good industrial 2 stage. Spend the 400-500 USD.
Turbo Pumps: Wait, then wait some more. Then buy a “used” but guaranteed working turbo pump with power supply. Make sure you have the fittings to mate it with your chamber as odd adapters are usually expensive. Never turn on a Turbo under 2 Torr or whatever the turbo manual specification states. It will destroy itself.

ION Gun: Yes, they strip the electron off of the deuterium atom, then trap the electron and expel the deuteron ion (p+n). The expulsion is in the direction of ground. So aim it about at your cathode. This one was made and sold by a fellow fusor forum guru Andrew Seltzman. Technically its an ALIS “Anode layer ion source” by techplasmas. It can be found on eBay or his site. Can you make one yourself? Sure, have at it. but about half way through you will wish you just bought it. One note; you get the ALIS, unmounted, and have some work to do just to get in your reactor. You also need a separate +HV supply for the gun.

ION Gun in AIR (80% Nitrogen):
ION Gun in Deuterium:
NOTE: Note the color difference between Air (Nitrogen+Oxygen) and Deuterium.

I will address a specific 1D cathode, however many will function about the same. The cathode is Titanium with a M2 nut pulse arc welded to it. The M2 Nut is Stainless 316. This particular cathode could have just been drilled an tapped because it has a thick core.
Length: 15mm
OD: 12mm
ID: 5mm

I am testing the largest one (on the right) in this session:
This cathode gets red hot. But has not deformed at 20-30kV @ 8.2mA ~ 250watts of input power from HV and another few watts from the ION Gun.

The requirements for a 1D Cathode include:
It shall have a conductive outer diameter
It shall have a hollow inner diameter
It shall be constructed of an electrically conductive material
It should be constructed of a thermally conductive material
It should have a cross section with enough surface area to attract ions toward the inner diameter
It shall not change from a solid to a liquid at nominal operating temperatures
It shall not be made from a material known to sputter in a plasma vacuum
It shall be positioned in a vacuum chamber capable of reaching low pressures
The vacuum chamber pressures should be able to reach 10-5 Torr
The cathode shall be connected electrically to a high voltage feedthrough
The high voltage feedthrough shall insulate against a minimum of 25kV DC
The high voltage feedthrough should insulate against a minimum of 50kV DC
The vacuum system shall include a conductive valve between the pumping system and the vacuum chamber

This reactor setup works best if you follow this basic usage model:
Vacuum down to a two stage pressure, like ~100micron and run your HV and ION Gun. Do this for 10-20minutes with a good plasma glow. Sort of “demo fusor ish” This will Plasma clean your newly made cathode. I know you touched it with your oily and wet fingers. If you don't do this you will have a long path to “condition” your new cathode.
Switch on the Turbo (or diffusion pump) and pump down to your max base pressure. Hopefully:
Minimum: 10x-4
Recommended: 10x-5
Best: <<10x-5
NOTE: We are plasma cleaning without using our precious Deuterium. Thats why its more Purple than Pink.
3. Once your pressure asymptotes off, at the reactor minimum switch on your ION Gun and -HV supply. On your -HV supply start at the bottom like 500 volts.
4. Now move your Butterfly-Valve (between Turbo and Chamber) from wide open, to 10% open. The pressure will rise to some equilibrium, probably around 5 microns.
5. Open your D2 valve. This gas should go into your ION Gun if you have one. Raise the pressure to 40-50 microns.
6. Now use your Butterfly-Valve to reduce the pressure to 50 if not already there.
7. Raise the -HV until your current is 80% of max. Likely around 5kV at this point. Depending on many factors including -HV supply current capability and if your pressure gauge is calibrated to Nitrogen (likely) or Deuterium (Unlikely). If you don't know what I am talking about; take a break and research it.
8. Now slowly pull the pressure down by opening your Butterfly-Valve. This increases the vacuum pumping conductance. Another term you need to be successful.
9. As the pressure slowly drops from the previous step, slowly increase the -HV. Keep an eye on the current. If you exceed your supply current it will likely trip-off or worse. Why is there so much current? Current = moving electrons. The pretty plasma you just made can be as conductive as copper! The pretty pink studs is like a wire to the grounded shell. If your shell is not grounded you probably did not live long enough to read this far.
10. Continue this process until you get to at least 17kV. Preferably 20-22kV. This is a sweet spot where most chambers are making little x-rays but you can make and detect Neutrons. Its a nice place to operate. x-ray shielding is easy and cheap, just do it. Always run a geiger counter that can efficiently detect x-rays where you are sitting. Don't forget about your head and feet. Sweep your silhouette. I recommend both 1/16 and 1/8 lead. 1/16 can wrap around almost anything, and 1/8 is rigid enough to sustain a wall shape.

The smallest lightsaber in the known universe it is.
11. You should now see Neutrons. This in itself is a complex topic. Most gas based detectors and their associated electrics are susceptible to all types of noise in the electromagnetic helm. Test this by:
A. Remove and ReApply the Moderator during a run when Neutrons are ticking up. Do this without disturbing the tube.
B. Run with Nitrogen (Air) and no Deuterium with the same conditions. You can have Neutrons, so if you see them there it is noise from something.
C. Watch the waveform on an oscilloscope. If it looks like noise, it is noise.
D. Use several detectors. Preferably different types. i.e. H3, B10, LiI(Eu) Scintillation, BTI Bubble detector. Although I int like the last one as it does not provide real time counts, only lasts for N months, and is hard to get in a unit 1x.
For the video referenced here I had a good run, with and without a moderator. I removed the moderator from one of two neutron detectors. The neutron detector with the moderator removed had a dramatic slowing of counts. When the moderator was re-installed the counts increased dramatically. This is great way to “prove” it is Neutrons and not Noise, Gamma, x-Ray, Pizza or anything else that might cause your detector to report erroneous events.
GS-Neutron : Tube center 150mm from Cathode - Background is 0.08N/min
Ludlum-2000 H3: Tube center 250mm from Cathode - Background is 0.2N/min

Data from Neutron Run:
The video is divided in segments. This data can be specifically verified in the video.
Segment 1: 20kV @ 5.5mA with 36micron(Nitrogen Cal) pressure
Moderated GS-Neutron : 10 CPM Neutrons warming up. 20 CPM Neutrons in operation
Moderated Ludlum-2000-H3 : 8 CPM N warming up. 20 CPM Neutrons in operation

Segment 2: 22keV @ 7.2mA 39micron (Nitrogen Cal) = ~112mT D2
Moderated GS-Neutron : 23 CPM Neutrons

Segment 3: 21keV @ 7.9mA with 45micron(Nitrogen Cal) =~132mT D2

Moderated GS-Neutron : 21.8 CPM Neutrons
UN-Moderated Ludlum-2000-H3 : 6 CPM Neutrons

Segment 4: 24keV @ 5mA with 38micron(Nitrogen Cal)
Moderated GS-Neutron : 25 CPM Neutrons
UN-Moderated Ludlum-2000-H3 : 10 CPM Neutrons

Segment 5: 25keV @ 3.35mA with 41micron(Nitrogen Cal) =~110mT D2
Moderated GS-Neutron : 61 CPM Neutrons
Moderated Ludlum-2000-H3 : 27 CPM Neutrons

It is clear that the Unmoderated neutron detector does not easily detect the high energy Neutrons. Had I removed the moderator and the counts remain the same we might conclude that the counts were more likely noise than Neutrons. Leaving the moderator on one of the two detectors makes this test quite clear as the moderated unit keeps counting at the same rate and the one that we remove the moderator from has a very large reduction in Neutron count rate.
If one can afford two detectors this could be a valuable test.
Note that the HDPE moderator for the GS-Neutron is fairly close to the Ludlum-2000-He tube. This HDPE is close enough to thermalize some Neutrons that will be detected at the UnModerated detector.

I ran these very modest numbers through Steven Sesselmann’s calculator:

Detector Exposure: 0.1 mRem
Neutron flux at detector: 6.83 e0 n/s/cm2
Neutrons isotropic 1.93 e4 n/s
Total D+D fusion reactions 3.86 e4 fusions/s

My detectors are not really calibrated (the GS-Neutron is characterized), but this is not a quantitative neutron generating exercise, more a practical example of a 1D IEC Fusor generating Neutrons at a respectable voltage / current and fairly high pressure.

Video 1:
1D Cathode Neutron Generating Fusion Run

Video 2:
General Lab walk-through

I live in Melbourne Florida and will gladly open up my home based lab to any fellow fusioneer who is interested, needs direction, can give me some direction, or wants to be a part of the amateur fusion efforts.

I would like to thank Richard for tirelessly maintaining this forum. Without it I would be wasting my disposable income on beer and ladies. My sons relentless interest in the nuclear field helps too.

Jim Enright
Posts: 21
Joined: Sun Aug 04, 2019 11:12 pm
Real name: Jim Enright

Re: 1D Cathode with Neutron Run

Post by Jim Enright » Wed Sep 11, 2019 1:47 am

Hi Trent, I am still in the early stages of high energy physics by doing as much research as I can. So much of what you have posted is still over my head, but I do wish that you lived closer, because I would welcome the opportunity to see someone's fusor first-hand! While in the midst of research, I am slowly trying to gather parts that I know I will need so I can find the best price for those parts - a teacher's salary isn't overly conducive to such interests, especially since I'm trying to do this for a high school club and without funding! I have found a heavy 40 year-old x-ray transformer and will be picking it up this weekend. It's a small start, but it would be great to see these items as a complete system to better understand how to assemble it. I look forward to reading about some of the results of your research and adjustments you make to your fusor!
“Whether you think you can, or you think you can't – you're right." Henry Ford

User avatar
Trent Carter
Posts: 23
Joined: Tue Dec 20, 2016 8:38 pm
Real name: Trent Carter
Location: Melbourne, Florida

Re: 1D Cathode with Neutron Run

Post by Trent Carter » Fri Sep 13, 2019 12:40 am

Jim, You should read this document. Its linked in the FAQ somewhere, but google works too.

[The design and optimization of an inertial electrostatic confinement fusion device]
by Hermans, E.C.G.

It outlines the entire fusion system quite well.

Jim Enright
Posts: 21
Joined: Sun Aug 04, 2019 11:12 pm
Real name: Jim Enright

Re: 1D Cathode with Neutron Run

Post by Jim Enright » Mon Sep 16, 2019 2:32 am

Thanks for the article Luke! I had not come across this article in my research, but it is now at the top of my pile of research articles!
“Whether you think you can, or you think you can't – you're right." Henry Ford

Post Reply