Alexey's fusor progress

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Dennis P Brown
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Re: Alexey's fusor progress

Post by Dennis P Brown »

There are not too expensive diodes from Chinese companies that can handle very high voltages and current; I got some 40 kV, 2amp units for about $30 each. Lower current and higher voltage (50 kV) diodes are cheaper and chaining those would work. The x-ray threat would be extreme operating at the higher end.
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Re: Alexey's fusor progress

Post by Alexey Khrushchev »

I think if you build a 50 liter fusor and run this transformer at full power, the energy of the thermonuclear reaction is enough to charge a cell phone)
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Re: Alexey's fusor progress

Post by Alexey Khrushchev »

Once again studied Liam David's guide to creating a HV feedthrough. I got the idea to put a metal ball between the glass tube and the cathode. This should increase the electric field strength at the cathode, reduce the emission of electrons from the center rod, and isolate the inside of the tube from the plasma.
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Re: Alexey's fusor progress

Post by Alexey Khrushchev »

Drove to my lab today and did a little fusor work. I made a new HV feedthrough and played with its parameters a bit. First I just inserted a tungsten loop into a 5mm diameter steel tube and ignited the plasma. There were a lot of flashes and sparks on the edges of the tube so I put a cap nut on the tube and drilled a hole for the loop. The sharp edges were filed off with a file. In this way the HV feedthrough worked much more stable, discharges and flashes completely disappeared. The voltage is now stable, but for some reason the current is still jumping in the range of 1-5 mA at 35 kV. I suspect it is the electromagnetic radiation that is driving my multimeter crazy. I have to think about an analog microammeter. But that's minor stuff, I'm glad I can control the voltage in the fusor much easier now. By the way, I placed the Radiocode 101 dosimeter 15 cm from the viewing window and it showed about 1.6 mR/h. Using the inverse square law, I calculated the dose rate just outside the glass and got 10 mR/h. The current was only 0.1 mA and the voltage was 30 kV. The plasma was glowing very weakly, it was possible to raise the pressure, but I had to go home. That's pretty low, should be about 1 R/h, but that's due to the low current in the plasma and I have yet to deal with that. BTW, I noticed that a single loop requires more pressure to ignite the plasma compared to two crossed loops, by about 10%. I think I'll go back to the double loop when I ignite hydrogen plasma. I also measured the X-ray spectrum. The funny thing is that I got a peak with a maximum at about 35 keV, which is close to the accelerating voltage on the cathode.
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Richard Hull
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Re: Alexey's fusor progress

Post by Richard Hull »

Remember the typical .060-inch SS walls act as an x-ray filter. Long ago, computations and measurements agreed that x-rays of 30kv and over would shine right through the chamber/reactor SS walls into the lab space. While a 35kv potential applied to the fusor will trap within it the bulk of the x-ray energy up to about 30kev, (maxwellian distribution), the 35kv tail of that distribution will shine through. Thus, you are seeing only "shine-through" x-ray energies.

If you have a simple glass viewport and place you x-ray spectrometer there, you will have shine through over a larger range of energies.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: Alexey's fusor progress

Post by Alexey Khrushchev »

Richard, I measured the spectrum in front of the glass viewport. The radiation did not pass beyond the metal walls of the fuser. I measured with two types of proven dosimeters, mica and scintillation. You have to be lenient with the spectrum, my radiocode 101 gamma spectrometer is very inaccurate below 50 keV, special calibration is needed. Since I did not detect any X-rays passing through the fusor walls it means that the energy of the quanta was not higher than 30 keV.
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Re: Alexey's fusor progress

Post by Richard Hull »

Thanks for the clarification. You chamber may have thicker walls in some fashion.
At 35kv applied in my my fusor,(.060-inch wall), I read 0.1mrem/hr with my victoreen ion chamber placed hard against the shell.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Alexey Khrushchev
Posts: 105
Joined: Thu Jul 06, 2023 3:36 am
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Re: Alexey's fusor progress

Post by Alexey Khrushchev »

I finally got my fusor to work consistently. But first things first. I had problems with voltage and current instability due to insulator breakdown. This time I decided to add two more pyrex tubes for better insulation. The total thickness of pyrex separating the hot electrode and the fuser chamber was 4 mm and 2 mm of vacuum. Alas it was not enough, the insulator was constantly punctured at voltages above 10 kV. Then out of desperation I decided to try another design. I drilled a hole in a glass plate 10x10cm and 15mm thick. In this hole I inserted a m5 bolt without a cap. For sealing I used 5 mm vacuum rubber which I pressed with nuts on both sides of the glass. Since the bolt was galvanized I had to remove the zinc with hydrochloric acid. Zinc has a high vapor pressure and really messes up the vacuum. I put steel tubing on the inside to keep the threads from creating a corona discharge. On the flange of the KF-50 I put a viton gasket lubricated with vacuum grease and put a plate on top. To my surprise this construction turned out to be very tight and what is most pleasant now the fuzor works without sparks and breakdowns. I just set the desired voltage on my precipitator, and the current depends only on the pressure in the chamber and does not jump at all. I spent so much time and money making homemade insulators, in the end they all don't work, and the one that does work I made from junk in 1 hour. At first I worked with air, then I switched to hydrogen. I noticed that the pressure required to ignite the plasma almost doubled. This is consistent with the specification of my thermocouple. Next time I will calibrate my controller to know the true hydrogen pressure. I got a very stable plasma beam at 10 microns pressure (actually I think about 5 microns), 30-35 kV voltage and 1-3 mA current. My dosimeter showed 4 mR/h at 10 cm from the glass and I recorded x-rays passing through the chamber wall at 35 kV. At the operator's place there was no excess of background, my shield works perfectly, except that I put a huge transformer weighing 50kg in front of me. Yes I bought it and dream of running it next week. Another addition I added today is a camera to view the cathode. And here I was in for a surprise. It kept shutting down due to electromagnetic interference. I wrapped it in foil and connected it to ground. After that there were no failures.
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Re: Alexey's fusor progress

Post by Dennis P Brown »

Good work; for a number of years I used a feed-thru using a telescope blank (20 cm diameter) that I drilled and installed a ceramic/steel rod through it that work very well for some time. I used a high temp epoxy to seal it and had an active fan keeping it cool. So, that arrangement for 35 kV should hold up well. Not sure it will work for 50 kV.
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Re: Alexey's fusor progress

Post by Alexey Khrushchev »

Are you into telescope building? Two years ago I made a 215mm F:2.8 light-aperture parabolic mirror. It was more complicated than I thought, I had to spend almost 9 months on grinding and shaping. Along the way I had to make a Bass interferometer to control the vergence. Then I assembled the telescope as a truss structure.
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Re: Alexey's fusor progress

Post by Dennis P Brown »

Impressive build for a telescope; for me, it was almost fifty years ago that I ground and polished a 20 cm one. But the telescope plate used a number of years ago was for my first fusor. It was the top cover, view port and high voltage feed-through section.
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Re: Alexey's fusor progress

Post by Alexey Khrushchev »

Today was my traditional thermonuclear weekend. I decided to test my new high voltage transformer by all means. The 150 kv diode hasn't been delivered yet, so I made a chain of 5 diodes for the microwave. I also made a new 1 Gohm voltage divider. I tested in a hydrogen environment at 5-7 micron pressure, 20-25 kV voltage, 2-5 mA current. After the precipitator it is a completely different level - crackling static electricity, ozone smell. It's a dangerous monster! Now I understand why it is necessary to cover all sharp edges. The cathode was red-hot. I felt like I could easily melt it, the power is very much there. The operator's place is 2 meters from the fusor, in front of it there is a neutron shield and a transformer, however I twice noted the increase of background up to 60 µR/h (natural background 10). This is certainly not dangerous, especially since I immediately turned off the voltage, but now I still intend to move the operator's seat 5 meters away from the fusor. I do not understand where this radiation came from, because I did not exceed 30 kV, very strange. I took the emission spectrum and it looks quite different from the precipitator, even though the transformer voltage was lower. Firstly, the maximum is at about 45 keV (precipitator - 35 keV), and secondly the peak is broader - the half-height is at 100 keV. Now I have something to think about until the next visit to the lab. The photo quality is poor, my webcam has a fixed focus, but I have already found a lens for macro photography - the focus reducer from the telescope fits perfectly. I just need to print the necessary adapters to fix it.
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Re: Alexey's fusor progress

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Nice work! Probably x-rays. I had intense x-rays issuing from conflat seals where I once used a viton gasket back in 1999. My homemade glass few port also scattered x-rays all around its circumference out into the lab. Traced it using a small mica windowed GM pencil tube back then. Photo of the little 6.5mm diameter tube attached. Great for sniffing leaks.

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Surplus tube from AN-PDR-27 military GM counter.<br />It was used as a gamma only tube inside the case.<br />This made its mica window useless!!<br />It may have been an emergency use in the absence of the normal 5980 tiny glass gamma only tube.<br />Tiny mica window closed the left end of the tube seen here.
Surplus tube from AN-PDR-27 military GM counter.
It was used as a gamma only tube inside the case.
This made its mica window useless!!
It may have been an emergency use in the absence of the normal 5980 tiny glass gamma only tube.
Tiny mica window closed the left end of the tube seen here.
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Alexey Khrushchev
Posts: 105
Joined: Thu Jul 06, 2023 3:36 am
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Location: Moscow

Re: Alexey's fusor progress

Post by Alexey Khrushchev »

Have you used a GM pencil tube to look for x-ray leaks? Sounds cool. To be honest, I'm afraid to go near a live fusor. I was hoping that 2mm of lead would stop any radiation from the fuser, but it doesn't seem to be enough. I rule out the possibility of x-rays reflecting off the ceiling or walls since they are wood.
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Re: Alexey's fusor progress

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No expert but it appears you are pushing a lot of power through the fusor - more than 2-5 ma. Mine reached 30 ma @ 22 kV and made only part of the cathode glow. Also, if your measured voltage is 30 kV, then your peak RMS voltage is 42 kV - that will make many fusor's with typical steel wall thickness's rather transparent to x-rays; or so from what I've read here.

You mention your emission spectrum and not clear what 100 KeV has to do with that measurement?
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Re: Alexey's fusor progress

Post by Alexey Khrushchev »

Like many on this forum I used a 10 ohm resistor to measure the current through which the fuser was grounded. I don't know what could have gone wrong..... I don't know, I think 150W for a 12mm grid is enough to red-hot it. A 100W bulb shines very brightly, of course its coil is much thinner, but intuitively I feel that the cathode in the fusor should heat up very much at that power. Strange that at 660 watts your cathode doesn't get white hot.
You are correct that the RMS voltage could reach 40kV and the chamber becomes transparent to x-rays. This is consistent with the variac readings - I was applying about 60V to the primary of the transformer and expected to get more than 40kV at the output, but the values did not go above 25-30kV. I just missed it.
About the spectrum. I wanted to point out that the peak is wider compared to what it was in the case of the precipitator. Because of the large peak width there are more quanta with energy of 100 keV.
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Re: Alexey's fusor progress

Post by Dennis P Brown »

I too missed the RMS issue so rather aware of it now. A transformers voltage can drop when loaded - again, found out the hard way (lucky Richard pointed this out to me.) So, yes, your voltage reading can be lower than expected due to core saturation (compared to the input voltage on the transformer.)

I added a milli-amp gauge to the high voltage input of my fusor. This confirmed my amp reading in my power supply. Being isolated on top of the HV input terminal, makes it is a rather easy gauge to add and operate. Of course, my max. voltage was 22 - 23 kV. Great for a 'sanity' check to prove your other gauge is working correctly.
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Re: Alexey's fusor progress

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Placing an milliammeter in the hv line to the fusor will make that meter and all of its guts at HV potential! Getting near it is lethal!

The Farnsworth team did this, but put the meter inside of a hot terminal on top with a cutout and read the meter with a telescope.

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It was instant death if you touched the meters here.  You had to use a remote telescope through the cave walls to measure current to the fusor back in 1966
It was instant death if you touched the meters here. You had to use a remote telescope through the cave walls to measure current to the fusor back in 1966
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Alexey Khrushchev
Posts: 105
Joined: Thu Jul 06, 2023 3:36 am
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Location: Moscow

Re: Alexey's fusor progress

Post by Alexey Khrushchev »

A slight cold prevented me from coming to the lab this weekend. But I will still describe what I managed to do at home this week.

First, I printed a webcam attachment that allows me to use a focus reducer. I can also use this to insert the camera directly into the frame of the viewing window. Now the camera will be close to the viewing window and in order to reduce the effects of X-rays on the camera sensor I covered its lens with a piece of lead with a hole in the center. This creates a little vignetting around the edges of the frame, but hopefully it will reduce noise. I may cover the entire camera body with a sheet of lead, but I think that would be unnecessary.

Second, I bought panel-mounted 4-digit voltmeters to measure current and voltage more accurately and installed them in the printed panel. A thermometer will be installed in port 3 to show the temperature of the chamber.

I already wrote that I had problems with my cheap Chinese PEM cell, hydrogen synthesis almost stopped due to very high resistance. I increased the voltage to 30V and the cell is getting very warm, the current is 50-60 mA, the hydrogen production rate is 1-2 ml/min.... I think it's all about poor quality proton exchange membrane. I tried replacing the water with 1% KOH solution, I have nothing to lose anymore:) This increased the current and hydrogen yield by several times. I think it would be more correct to use sulfuric acid solution or even better sodium sulfate since it does not contain protons.
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Re: Alexey's fusor progress

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You could just use a mirror set at 45 degree (Pi/2 radian) and place the camera a good bit away. Then the camera can view the cathode with no x-ray issue. I simply use a mirror and visually watch the cathode/plasma.
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Re: Alexey's fusor progress

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I used a diagonal mirror to visually observe the cathode. My webcam focuses well at a distance of more than 40 cm, at this distance the cathode seems too small. When using a focus reducer the camera focuses in the 10-15 cm range, so again the diagonal mirror is not suitable.
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Re: Alexey's fusor progress

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I use a tiny older video circuit board with a small glass lense. Mine will focus down to 4mm from the lense surface!! Naturally, you need an NTSC video monitor. It is not some wonderful auto-focusing webcam. Its focus from infinity to 4mm is achieved by manually rotating the very fine thread lens barrel in or out.
When I bought this it was $15.00 back in the 1990's. At 4mm distance lighting must be from the side. I used this type of tiny camera to study minute details on stamps in my collection. Works at any range to any thing.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Alexey Khrushchev
Posts: 105
Joined: Thu Jul 06, 2023 3:36 am
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Location: Moscow

Re: Alexey's fusor progress

Post by Alexey Khrushchev »

The lead protection for the camera helped a lot, now there is no noise. I also moved the operator's seat another 3 meters away from the fusor and put an additional 5mm lead plate. Now the background stays within the normal range no matter what I do))))) I even thought something was going wrong, but as soon as I moved the dosimeter outside the shield it immediately showed high radiation levels. Also today I installed new panel voltmeters, from a technical point of view everything is fine, but the blue numbers are very bad to see from 3 meters, I will change it to a model with a green display. For temperature control I attached a thermocouple to the fusor body, but the display is constantly blinking, apparently electrostatic interference is affecting it a lot. By the way, I have now learned of another problem, which is the heating of the chamber. At 20 kV, 3.5 mA current, and 5 micron pressure, the chamber heats up to 50 degrees C in 5 minutes. I put in a 140mm fan, but that doesn't help. I have to do water cooling, I will try to wrap a silicone tube around the chamber and run water through it.
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Re: Alexey's fusor progress

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Heating is a forever issue with a simple fusor. To properly water cool you will need to wind a copper tubing around the fusor and preferably silver solder it to the body. 1/4-ich diameter copper tubing has been used in the past. Almost no one water cools a fusor. due to the complication of the process. However it is a good idea to do it.

Most just run their fusors until the shell temperature reaches about 80 deg C. Continuous operation can only be had by active and continuous removal of heat.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Alexey Khrushchev
Posts: 105
Joined: Thu Jul 06, 2023 3:36 am
Real name: Alexey Khrushchev
Location: Moscow

Re: Alexey's fusor progress

Post by Alexey Khrushchev »

Richard, thanks for the important information!
I really don't want to solder the tube to the fuser, but I realize that the low thermal conductivity of silicone will reduce the cooling efficiency. I'm thinking about the idea of printing a cooling circuit for the chamber. Basically it would be a rigid housing with water circulating inside, this housing would fit tightly over the chamber. The water would also cool the camera through a layer of plastic, but in this case the cooling area would be larger than with tubes.
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