Today I’m taking some small steps toward building hot cathode electron gun v2.
Here is a physical diagram and schematic:
This is the hot cathode intended for an electron beam welder. It has 34 mΩ resistance:
The parts of the electron gun will be arranged like this:
This is more simple than most electron guns. I don’t need a carefully focused beam, I just want to shoot a crude beam of electrons into the Polywell.
The next step is to design and build a simple armature to hold the pieces together.
My goal today was to find the thinest atmosphere that still creates a plasma.
The oscilloscope attached to the langmuir probe reveals this behavior transition around 8 millitorr:
Above 8 millitorr the plasma is relatively stable. As the pressure drops below 8 millitorr, the behavior transitions to extreme spikes in floating potential. The electron gun is at 25KV, current limited to 1mA.
This transition is not apparent from watching the plasma or power supply. New information!
As the pressure continues to drop, the spikes become less frequent and more extreme.
Until eventually I heard a rather loud pop…. which blew out the trigger circuit on my coil power supply!
I’ll have to repaire the coil power supply now. I must point out the bleed resistors did their job and slowly discharged the coil capacitors. Crucial safety feature.
So we learned something and I broke something. Good day.
UPDATE: A continuity test of the coil failed. The coil is damaged. The coil power supply is fine
If you wish to replicate the Sydney experiment, you must first obtain a Langmuir Probe.
I have requested quotes for these commercial Langmuir Probes:
Automated Langmuir Probe (ALP) System
BTW, how do you pronounce Langmuir? I imagine it rhymes with “pang-doer” or maybe “ma-doer”. ANSWER: it rhymes with lang-meer.
Now that our Fusor seems to be working, I must operate it from a safe distance. Last night I did the first successful remote run. I connected an iSight to the Fusor mac (G4 running OS X Tiger). Then I used VNC to remote control the Fusor mac from my laptop:
I made headway with the command line program to control the fusor and record data in mysql via ruby. It’s currently setup to record vacuum chamber pressure, voltage and current according to the Glassman, and the effective flow rate of the mass flow controller. Currently I can enter commands to turn the high voltage on/off and set the flowrate of the mass flow controller. Next I want to control the voltage and current on the Glassman.
I also got a geiger counter:
It takes two D batteries. There is a BNC connector for headphones. I have a BNC connector on order with mcmaster. In the meantime I improvised a connection to some computer speakers to test it out. Seems to be working. It picks up the expected background radiation producing that erie clicking sound. You can definitely hear an uptick in the clicks when I run the Fusor.
I’m working towards producing a comprehensive mapping of this device’s performance envelope using computer control to search the parameter space and record the results.
This is all so fun and exciting.
We got the butterfly value installed and tested out the new grid. Beautiful stable plasmas. Air plasma:
Deuterium plasma in star mode:
No bubbles yet. This video shows the stable air plasma:
If you’ve been following me on twitter, you know I received a -30kV / 10mA Glassman a few days ago. Now it’s online and it kicks ass. Current limiting, remote controllable… it’s the second unit from the top:
Here is an air plasma it produced:
With current limiting and good air metering, we can get a stable plasma. I notice you get a sense for the plasma just by _listening_ to the glassman. When the plasma is unstable the glassman softly clicks along with the plasma burst.
YES! Check this business:
Here it is with the color levels adjusted so you can see more:
This is really really exciting.
First thing I learned is you need some gas in that chamber to start a plasma. I started at pressures around 1 e-6 torr and got nothing. What you really need is pressures above 1 e-3 torr. My gauge doesn’t work in this range, so I was flying blind.
I had to install a valve to leak air into the chamber to keep the pressure where I needed it:
Just playing with this device for 10 minutes gave me more of an intuition for plasma than most of the reading I’ve done on the topic.
I’m now one small step away from first fusion. FUCK YEA.
Before we worry about a vacuum, we can operate the magrid on air. If you look at the transcript for “Should Google go Nuclear” , on page 10 Bussard says of the WB2: “All these tests were run on air or argon”, accompanied by this picture:
I think this means forming an electron cloud in the center of the magrid, despite presence of air. This sounds like a Non-neutral_plasma . I suppose you would operate the magrid normally… bring the shell to a high potential, turn on the electron beams, bring the magrid up. The streaming electrons ionize the air. The air ions rush to the center. Some of that energy is released as light. Even if it’s possible to burn air, it may take low pressure air, requiring a vacuum vessel and pumps.
Prometheus Fusion Perfection 