Alexey's fusor progress

[Alexey Khrushchev]

Hello everyone
I want to open a new topic, because I have already accumulated some parts of my future fusor and I would like to discuss them with specialists. Today I have almost assembled my high-voltage power supply, which is based on a Chinese 60 kV, 600 W precipitator. The scheme is presented below. The voltage divider was fixed on a piece of acrylic glass. I drilled several holes in the bottom for better oil circulation, I think this will allow the ballast resistor to be cooled more efficiently. I want to immerse the board and resistors in a box with transformer oil. Voltage regulation will be carried out using a glass rod, which I connected to a variable resistor on the board using a coupling. Please see if I did everything right, and after pouring the oil, it will be very difficult to redo anything.

[Richard Hull]

Your assembly looks interesting. The power supply for a fusor is one of the more critical components and among the most difficult to bring to bear successfully.

I have no personal experience with switcher systems, especially the Chinese one that you are attempting to use. Switchers are custom designed for one thing, as a rule. Repurposing them for another application can be tricky, especially when high voltage output is involved and currents within their watt rating is concerned.

Several people here at fusor.net have already dealt with these same Chinese supplies. I will defer to them on advising you beyond my admonitions above. I do hope you will receive advice from those here who are more competent in this matter, and wish you well in testing and using this supply setup you have given images of and your reasoning as to how you have prepared it for use.

I assume you have seen some of the efforts here by others. Please be aware that a number of people are here for the "win" of doing fusion. Once done, a significant fraction of those may disappear from these forums, moving on with their lives. As such, those who mastered the issue of the Chinese supply adaptation may no longer check into the forums here.

I hope someone sees this who can talk with you about their efforts from a point of actual hands-on experience.

Richard Hull

[Alexey Khrushchev]

It is a pity that some talented fusor builders are abandoning their projects. It seems to me that there are many interesting experiments that can be tested on an amateur fusor. For example, when I build my fusor, I want to test the effect of deuterium pre-ionization with Am-241. I will simply place the source from HIS-07 directly into the chamber (at the deuterium inlet, far from the electrode) and check how this will affect the lower pressure at which plasma is still beginning to form. Perhaps this will allow you to raise the voltage without the danger of arcing and thereby increase the efficiency of the reaction.

[Alexey Khrushchev]

I have seen many people install a ball or torus on the end of a high voltage electrode. I think this is a good solution to prevent localized charge buildup on the bolt tip. It is not very clear to me what to do with the sharp parts of the high voltage cable terminal. Ideally the terminal should be inside a hollow ball, then the charge will be evenly distributed on its surface. But this is difficult to realize. What happens if the terminal is placed under the ball as shown in the figure? And what diameter of the ball should be used?

[Matt_Gibson]

A few of us use small toroids on the top electrode of the hv feed through. I use one of those “30kV” feedthroughs with one and push 65-70kV.

As for abandoning projects, I just got busy with others. Still have the fusor ready to go if a neat idea comes along or I think up an idea to help push my voltage even higher.

-Matt

[Alexey Khrushchev]

A little bit about how I made a high-voltage feedthrough electrode. As a base for the electrode, I took a 15 mm diameter, 400 mm long mullite-silica tube with a 5 mm channel in the center. I drilled a hole in the KF50 plug and inserted the tube into it. To seal it, I welded the tube to the plug using pure indium. To do this I had to treat it with silver nitrate and calcine it at about 400C. The indium wetted the tube well, but the contact with the steel of the plug was not good and after some time it simply fell off. I should have coated the steel with copper, then this problem would not have happened. So I had to seal the outside of the tube (air side) with JB weld. The tube turned out to be porous and would leak air when pumped out, so I greased it with vacuum grease, then put on the 3D printed tube and filled it with epoxy. I used 1mm diameter tungsten wire as the center mesh material. I made two "horseshoes with legs" with a diameter of 10mm. To prevent the wire from breaking I heated it in the flame of a torch, but in this case I succeeded only on the 10th attempt... Inside the electrode I inserted a stud with a thread m4, on its end I put a steel tube in which I inserted the "legs" of the tungsten grid. Running at voltage up to 4 kV and current up to 20 mA showed that the grid works well, and the electrode is sealed. When I assemble the high voltage source, I will test at operating voltages, but so far I'm happy with everything. The electrode turned out to be very long - about 40 cm, but I did not shorten it for two reasons: firstly, this length excludes external breakdown of the arc on the chamber. Secondly, the longer the electrode, the less heat will reach its upper part, where the metal is in contact with the epoxy.

[Richard Hull]

A fabulous, though tortured, piece of work on that insulator! This vacuum to air HV connection is always an issue in making a fusor.

I hope this holds as you increase the voltage. Homemade arrangements sometimes defy reason and logic when brought into service. All the best of luck. We are looking to your future reports on your efforts.

Richard Hull

[Alexey Khrushchev]

In case something goes wrong with this electrode, I have a plan "B". I have a pair of KF25 compression adapters for the 14mm tube. The lower adapter connects the glass tube to the chamber, and the upper adapter creates a sealed connection and has a high voltage cable connected to it for voltage. It is clear that inside the tube there is a metal rod connecting the cathode and the upper adapter. On the forum someone experienced people did something like this and it worked well, can't find where it is now.

[Alexey Khrushchev]

For my birthday, my wife gave me a bottle of heavy water as a gift. It is probably the most unusual gift I have ever been given). My son made a fusion reactor for me in Minecraft. I wonder how your friends and relatives feel about your unusual hobby?

[Richard Hull]

There are many hobbies that are bizarre by the standards of most people. Amateur science and related technologies are really rather common. However, this attempt to do fusion is relatively new by any standard. Thus, it seems a bit weird to the common person as they can't see a reason to invest money and time into doing fusion with no demonstrable energy or useful product once it is done by the amateur.

I find this reaction odd, as many hobbies produce nothing of great value beyond the satisfaction of enjoying the effort. The positive part is that you learn to do things you have never done before as part of a growing skill set and expanding knowledge.

Richard Hull

[Alexey Khrushchev]

I've been thinking about a problem for a while. My fusor is in an unheated workshop in a country house. The temperature in the room drops below -10 C in winter. When I turn on the heating, the workshop quickly warms up to room temperature, but condensation forms on cold surfaces. It is particularly unpleasant that condensation forms on the box containing 5 litres of oil in which the precipitator is located. If water gets into the oil, it will be a big problem. It might be worth warming the oil to prevent condensation. I have a 2.4kOhm/10W resistor, if I dip it in oil and connect it to 220V it will draw 20W, which is twice the rated value, but as it will be in the oil I think it will be fine. Of course I will use a 0.5A fuse and also monitor the oil temperature with a thermocouple.