Rebuilding my fusor.

[William_Estlick]

And I am hoping this he3 detector with a paroffin moderator will detect any neutrons.

[JoeBallantyne]

William - if you make one more paraffin block the same size as the first two, then cut it in half lengthwise, remove the electrical tape holding the tube against the one paraffin block, then put each half on either side of the tube that is resting on the bottom paraffin block, and then put the last full size block of paraffin on top, you will have a very good moderator that is reasonably close to optimal thickness.

Doing that will work much better than your current configuration, and basically just requires that you cast one additional block of paraffin. You can use a hot knife to cut the paraffin.

Joe.

[Dennis P Brown]

Before wasting your heavy water to make deuterium gas, do test your power supply and vacuum system. Your vacuum must get down to near a micron (to check bottom vacuum achievable).

As for the power supply, being a low pulse rate design (only 60 Hz), measurements of current via a meter are essentially meaningless for power determination (one would need an oscilloscope for a trace) but voltage will be available. There you will need about 20 kV (during plasma ignition) and higher still would be better. However, that last small cap in series will provide very little net power. Detectable fusion usually needs near to 200 watts.

You should calculate the net max possible power from your final capacitor using your cap value (# uF?) and for a average total time, assume a value of 1/10 sec (this is a too high a value but assume its has that value). Take a max voltage from the NST of, say, 12,000 volts (again, an over value.) Your system will be actually much lower then this calculated value but this will give you a max theoretical value that you can compare to the previous min. value needed for detection.

Be aware, the fusor will (when still at an elevated pressure) act as a near direct short so the first firing of the cap will be similar to a short to ground with it at it's max. charge. The reason we all use a ballast resistor (50 - 100 k-ohm) in our power supply systems to limit draw when it first "turn's on", so to speak.

[Rich Gorski]

William,
Since you are trying to use 12kV NSTs to power your fusor, and the fact that they most likely have a grounded center tap you can get ½ the voltage out with respect to ground. That means 6kV RMS or about 8.4kV peak with the NST unloaded. So to get to > 15kV will need at least a 2X multiplier but 3X would be better. You will get some level of filtering the 60 cycle AC with your capacitor banks (0.33uF/16 = 0.02uF if I read the label on your capacitors correctly) but not a whole lot. You can use the power rating on the NST to give you a crude estimate of the current you can get from it at a certain voltage. Remember these old NSTs are magnetically shunted to limit current to around the value indicated. In your case (from photos) with two in parallel the power is 389*2 = 778 Watts and at 6kV the current limit will max out around 778/6000 = 130mA.

The trick with a fusor powered by NSTs will be getting the pressure low enough so you don’t just have something like a neon sign in the chamber which will significantly lower the voltage down to only a few hundred volts. You will need to get pressure down around a few millitorr (few microns) pressure to not just present a short circuit to the NSTs. Another way to look at it is by the load presented to the power supply at a reasonable fusor current level. Lets say you have 20mA fusor current at 15kV. That implies the impedance of the ionized gas is 15000/0.02 = 750k ohms. So your gas pressure inside the chamber must be low enough that the plasma impedance is > 750k ohms and not acting like a neon sign. A ballast resistor in series with the fusor will help but you will also drop some voltage across it.

So, the trick to getting detectable fusion on a fusor powered by NSTs and without a turbo or diff pump will be achieving low enough pressure .
Rich G.

[William_Estlick]

Making plasma with old cathodes, rectafier and a single transformer.

What you can't see these images are inverted "V"s that radiate from both cathodes.

I am going to replace the cathodes and add a capacitor bank to the circut to help filter the current.

[Dennis P Brown]

There is no useful reason to add a cap "bank". Certainly at 60 Hz it will do very little. What extra power it will provide will have no real improvement on neutrons production. Setting aside the NST and building a high frequency power supply would be better (through then having a properly shield fusor would be essential.) Not to say your efforts for the NST supplies are not good for a demo fusor.

But I assume you want a real fusor at some point from your desire to add deuterium and that you own a neutron detector system; as for your neutron detector, achieving proper fusor conditions - 20 kV or more, around 200 watts power, a few microns pressure with pure deuterium, are essential if you want to be able to detect neutrons. I do not believe your two NST's will be capable of doing that.

Your active plasma region is tiny - just between those rods. Building a larger more standard cathode would be better, if you intend to build a fusor system, IMO. Of course your current metal vacuum housing needs to be ground (and should be in any case.) Also, you should ground those metal cases that hold your NST's. I assume you already have a three wire (available ground wire) system to the NST.

You really need a proper vacuum gauge that reads microns. That will tell you a great deal about your vacuum and indirect details on the plasma. Adding a HV voltmeter wouldn't be too difficult and would provide you with crucial information on the power supply's performance. I think you will find your voltage is far lower than what you think.

Then if you also add a milli-amp meter and record the various values (vacuum, voltage, current), you can join the Plasma Club. Besides, until you understand your real operating voltage, you have little chance to determine if you can even produce neutrons; again, if that is your end goal.

I assume I mentioned this previously but be careful of any possible UV; most plastics (and certainly glass) will stop that wavelength. But vey bright blue is also bad for the eyes - and can be damaging. Dark glassblower eyewear would be a good idea - if not, cover the clear upper plate with a nontransparent cover of some type.

[William_Estlick]

8 pair of capacitors in paralell to help smooth out the wave form from the fbr.
"If it wasn't leathel before, it is now."

The second cap bank I may turn into the 3x voltage multiplier.

[Rich Gorski]

William,

I refer you to the post below by Rich Feldman where he did an in depth look (with graphs) at the current-voltage-loading relationship of a typical NST. The data also shows how the NST voltage collapses with too much load as presented by gas filled tubes (fluorescent). So if you want to see fusion happen in a fusor powered by one or two NSTs the pressure in the chamber will be critical. You will need to get into the single digit mTorr range to have any hope of using the NSTs to do fusion. If you don't yet have a vacuum gauge on your system that might be the next thing to install to see where your at with pressure. After that you will need to set up a high voltage metering system so you will know what voltage your NSTs are achieving in your fusor.

There are many other posts here relating to NSTs as well. Please do a search and read. Much info out there. Also please post your results. If you're successful in detecting fusion with inexpensive NSTs that will be useful information for those just starting out.

Rich G.

viewtopic.php?p=80678#p80678

[William_Estlick]

I've replaced the cathodes , but one leaked.
I think there may be too much aluminum oxide mixed in with the porceline...try it again.

[William_Estlick]

New set of cathodes.
There have been improvements producing them. Now to see if they will hold up better.

[William_Estlick]

The new cathodes are holding up though there is still some ocasinal sputtering and I still need to find a better way to align the cathodes.

I am looking for a plasma that has a uniform stable structure.

I next want to see if there is any difference in the plasma with, and without the capacitor bank.

[Dennis P Brown]

Not clear on your goal(s). Maybe explain your need for those special made cathodes?

[William_Estlick]

Currently, the three main approaches being studied to create the conditions nuclear fusion are the Tokamak, Internal Confinement and Farnsworth fusors. All three hold the plasma and maintain ion density by squeezing it.

But plasma behaves like this squeeze ball, and before the ion density is high enough for a viable commercial fusion reactor, the plasma finds the weakest point and leaks out.

Now, if we pull the positively charged ions together towards a single point between two negatively charged cathodes, we get a stable coherent plasma able to take whatever shape it likes.

The funny thing is that even though the cathodes are electrically bonded and have zero electrical potential between them, the electric and magnetic fields emanating from the cathodes are 180 degrees of one another. This seams to make two distinct plasmas that have a boundary layer and merge together further out from the center.

Lawsons criterion states that there are three factors to create the environment for nuclear fusion, Ion density, heat and time.
I can hold a stable plasma indefinitely, now I just need to see if I can make the plasma hot enough and dense enough for fusion.

[Dennis P Brown]

Thanks for the clarification

[William_Estlick]

No problem.

[William_Estlick]

The percaline is melting and waring away through sputtering.

I am sintering the next set of cathodes because I think they will be stable after the heat treatment and I need them to last for at least 2 runs.
I want to see if there is any difference in the plasma first without and then with the capacitor bank.

[William_Estlick]

Image of plasma with new heat treated cathodes.

Then I inserted the cap bank
But no matter what I did, it just pulsed a bright whit arc and created lines in my camera.
I am sure if I added the proper resistor, I could stop it.

I am going to try this voltage multiplier I had made before, but concerned that I may have a similar problem.

[Dennis P Brown]

You have not explained what your problem is for this device.

[William_Estlick]

I think these voltage multiplyers need a higher frequency, electronics is not my thing.

[Richard Hull]

You are doing electrical arcs! Arcs typically have near zero impedances! This means near infinite current demands. 60hz DC ripple from a neon transformer will not supply the current or the voltage needed to do fusion in an arc condition.

Richard Hull

[William_Estlick]

I am just going to put both 12kn NST in paralell for now.

And I still need to get the PEM and neutron detector working as well.