For posts specifically relating to fusor design, construction, and operation.
This was a 5 minute run with the Fusor running with deuterium at the above conditions. The only difference was that the detector was outside of the moderator the entire time with the moderator far away. Now, my setup: My main chamber is a Cf2.75" 5-way cross. It has two view ports, I use a mirror in order to view and take pictures of the plasma. It also has a 30kv electrical feedthrough in the back, which you can't see except for in the top view. On the left hand side is a series of reducers that lead to my vacuum gauge and deuterium line. My deuterium line consists of a regulator and a micrometer leak valve that are connected by 1/4" SS tubing and swagelok fitting. My deuterium source is a 10L bottle from Sigma-Aldrich. It took quiet some time to convince them to sell me the deuterium. Most pictures have a 1/4" of lead shielding in them. My parents suggested I do this "just in case". My vacuum system consists of a Edwards E2M5 pump, a Veeco air-cooled diffusion pump, and a series of valves and hoses. The E2M5 pumps the whole system down to about 15 microns in two minutes. While it's pumping down, I turn on the diffusion pump fan. I then close the left-most ball valve and switch on the diffusion pump heater. After about 45-60 minutes I'm in the 10e-5 or 6 range.soon I’ll be getting a high vacuum gauge, but for now I know I’m down to a low enough pressure for fusion. I then turn up my 50kv spellman supply modified for 7ma output to roughly 10kv and start adding deuterium. As soon as the plasma ignites, I increase the voltage and begin to get the counts you see in the results. Inevitably, I have included far more information on one subject than I needed to have. I'm sure I didn't include enough information on another. Just ask, and I'd be more than happy to supply more pictures and data. I'm excited to further optimize my setup and possible someday add an ion gun.
20 mins even for an aircooled diff pump is nowhere near enough to get the working fluid degassed and doing what it does best as the working temperature balance has not been met. More over the pump fluid has not had time to clean itself properly.
(only gets worse when turbos are involved)
- Dennis P Brown
- Posts: 1654
- Joined: Sun May 20, 2012 2:46 pm
- Real name: Dennis P Brown
- Location: Glen Arm, MD
Overall, a very professional setup and I am sure you will overcome any vacuum issues soon, get down to 10^-5 torr or so, and be able to get a good fusion run with a stable plasma.
I should have made this more clear, but I get down lower than .1 microns. However, that is as far as I can measure the pressure. I’m trying to get a HV gauge soon, but for now I know I’m getting down to fusion levels.
As to vacuum...Remember, this is a microscopic volume to be evacuated compared to a large 6-8-inch spherical fusor. Pump down can be lightning fast compared to a larger system. Even with the small cross chamber, you are effectively only pumping down what in a larger more complex system are just vacuum "lines"!! I think this is all part of a new day dawning in a way that was just not seen or expected and it might just be due to a near perfect balance of size versus mean free path at pressure in a small fusion system. Dwell on this a while.......
What is the "take-away" from all this?There is such a thing as too small where arcing of the HV takes over and failure to reach voltages that allow for decent tunneling can limit results. There may be a point where smaller is better, even if it is not as pleasing and impressive to the eye as a lovely, impressive, big old spherical reactor chamber. This appears to be the case due to recent adventures by the less well heeled applicants, limited to "catch as catch can" small crosses and tees substituting for what has been a formal, separate fusion reaction chamber entity. Fusion may turn out to be cheaper and easier than even we thought. Sure, we are not doing power fusion and relying on quantum tunneling, but we are doing nuclear fusion. I have looked at quantum tunneling fusion, on our part, as flying at the coal face, (fusion wall), with hard hats on to get coal, (fusion), as "bull-heading" fusion. Yes, it is not elegant, but we do get a bit of broken shards of coal, (fusion), at the foot of the coal face for our efforts. There is little disgrace in quantum tunneling....It seems to have been the basis for the semiconductor, (transistor), revolution. Bizarre thoughts come to mind.....Like would fusion tunneling in solids be the lucky donkey that licks the fusion quest? Is hot fusion a must do thing or is it just another coal face we are banging our heads against? In a way this was a "lucky donkey" moment here at fusor.net! A bunch of newbies who were not trying to find a new, novel way to do fusion, but, instead, driven by the paucity of funds and resources have stumbled on a way to do fusion via tunneling in a much more economical way. I have refused to see this due to the fact that prior attempts in such tiny chambers were stumbling efforts with what could charitably be said to be poor neutron detection efforts. However, over the past two years, small chamber enthusiasts have put into their fusion efforts the money they saved in vacuum gear, plowing it into far better detection gear. They have been giving us good quantitative data that we have felt good enough to sit up and take notice. In the end, I am almost as excited by this new revelation as the day I first posted on "Songs" 20 years ago!
Retired now...Doing only what I want and not what I should...every day is a saturday.
- Scott Moroch
- Posts: 186
- Joined: Thu Apr 26, 2012 12:48 am
- Real name: Scott Moroch
- Location: New Jersey
"In the middle of difficulty lies opportunity"
Due to the amount of X-rays coming from the view port, the amount of lead shielding I had simply wouldn't have been enough to stop them. The shielding is in place to stop all of the shine through x-rays. I use a mirror to view the inside, so I'm far away from the direct line of the viewport.