First Bubbles!

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Caspar12
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First Bubbles!

Post by Caspar12 » Sat May 14, 2011 11:33 pm

Today we finally received our long awaited bubble detector from BTI that Nick Depasquale was kind enough to forward to us. Since we started looking for one last December we of course immediately fired up the pumps to try it out!

The first 7 hours we spend to prepare everything for the first run (of course everything started to leak so we had to reassemble the chamber all over again) the detector didn't show any bubbles. So we measured no background radiation over a period of 7 hours.

Around 10 pm we were ready for the first HV testrun, only to find out one of the rectifier diode strings of the x-ray transformer failed. Because we had no more spare diodes we decided to go ahead and run the setup at half power. We can do this since it is a center tapped transformer thus by removing one of the rectifiers we only utilize one coil and get a half wave rectified output (you could call it a 50% duty cycle).

In the beginning we had a lot of trouble to control and stabilize the pressure while maintaining a deuterium flow of approximately 0.1 milliliter/s in a range that we could run the HV as high as possible. After 2 hours of tuning the D2 flow (with a needle valve) and diffusion pump flow (by squeezing a flexible tube between the chamber and diffusion pump) we finally had it fairly stable at 25kV.

We then started the first run averaging (due to variations in pressure) at 25kV peak at approximately 250W input power. This first run totaled to about 3 minutes at 25kV peak. And we were extremely pleased to discover the first bubble in the bubble detector.

The second run was at same voltage and power and lasted approximately 4 minutes at 25kV peak, this yielded no extra bubbles.

The third run at same voltages and power lasted approximately 5 minutes at 25kV peak and yielded another bubble!

Since we had no bubbles in the preceding 7 hours and received two bubbles exactly during the high voltage/power runs we are fairly certain we have finally achieved fusion! :-D

Our setup for the fusor is as follows:
- Chamber is a salvaged cylindrical steel chamber measuring 13.5cm in diameter
- The (steel) inner grid has a diameter of 3cm
- The pumps consist of an Edwards ES50 rotary vane pump for backing and an Edwards E02 diffusion pump (with DC704 oil)
- For the high voltage we use a 50kV (rms) 350W philips dental x-ray transformer housed in a custom oil container. (Since we don't use the center tap we run it at max 25kV rms)
- Deuterium supply consists of a electrolysis setup currently filled with 3ml of D20. Using platina electrodes at 15V, 0.1A and some baking soda we have a fairly efficient electrolysis setup. We dry the deuterium with silica gel and use a needle valve to regulate the deuterium flow.
- For pressure monitoring we use 2 Robinair thermistor gauges in a custom panel. Unfortunately these are not correctly calibrated but we estimate a pressure of 5mTorr during the runs. We want to add an ion gauge to get better information about the pressure.
- For hv voltage/signal analysis we use a fluke nixie multimeter and an analog hameg oscilloscope.
- To control the x-ray transformer voltage we use an 0-230V 5A variac.
- For radiation monitoring we currently use a DOM 410 geiger counter with a large glass gm tube.
- In the picture you can also see in the rack a pulse counter, heinzinger 10kV 10mA dc supply (currently not used), and our pc and I/O module in progress.

Hopefully we will be able to operate at full power (400W) next week when we have replacement diodes. We will try to get a higher neutron flux and try to operate it for longer periods since we had some difficulty to keep the voltage/power stable. Our future plans are to build a polywell in our new 28.5cm stainless steel vacuum chamber. (still under construction)

We will gladly answer any questions.

Bubbles from The Netherlands,

Martijn Rambonnet
Bent de Lange


Picture 1: The 2 bubbles in the BTI-pnd 30bbs/mrem on the left.
Picture 2: Clear starmode with D2, unfortunately the camera doesn't show the colours very well.
Picture 3: The entire setup.
Picture 4: More starmode
Picture 5: The chamber
Attachments
pic4.jpg
pic3.jpg
pic2.jpg
pic1.jpg
IMG_20110514_233152.jpg

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Steven Sesselmann
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Re: First Bubbles!

Post by Steven Sesselmann » Sun May 15, 2011 9:49 am

Bent,

Congratulations on first fusion, your neutron numbers will improve as you learn how to stabilize your system.

In the future could you report your experiment in full, so we can get a nice picture of how well it worked.


Deuterium supply..............:
Detector type....................:
Detector efficiency............:

Cathode Voltage Potential:
Current draw.....................:
Distance to detector..........:
Run time...........................:

From this we can estimate the neutron count

Well done, and hopefully Richard accepts you into the neutron club with two bubbles.


Steven
http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG

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Martijn Rambonnet
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Re: First Bubbles!

Post by Martijn Rambonnet » Sun May 15, 2011 9:46 pm

Hi James nice to hear you are still progressing with your experiments!

We will try to give some more detail on the deuterium supply soon but our electrolysis setup is extremely basic. We have modified a glass syringe for D2O (ebay) storage and we use the needle end of the syringe as a feedthrough for the platina electrode (platina wire from ebay). Experiments with other electrodes like graphite, stainless steel, steel, etc all failed. Over the electrode we have placed a smaller glass syringe upside down to which the deuterium line is connected and the outer electrode is connected from above. Our setup is quite similar to that of Andrew Seltzman (http://www.rtftechnologies.org/physics/ ... olysis.htm) but with a much lower budget (and nowhere near as nice as his setup). We borrowed his idea to use baking soda (NaHCO, ebay) as an electrolyte and we are very pleased with the results (opposed to for example kitchen salt).
To dry the deuterium we use silica gel (ebay, changes color from yellow to purple when is absorbs water damp) in a long piece of plastic tubing. Our whole electrolysis system is thus at approximately 1atm and we use a needle valve (CO2 aquarium needle valve, new ~15 euro) to regulate the flow into the chamber.

As I said we will try to give some more detail/drawings/photos in the future. We also have some other experiences from constructing the fusor on a very limited budget we will try to post soon.

Steven, for ease of reading a reformatted report of the experiment:
Deuterium supply..............: D2O electrolysis @ 1milliliter/second at 1atm
Detector type....................: BD-PND bubble detector
Detector efficiency............: 30 bub/mrem
Detector measurement.....: 2 bubbles

Cathode Voltage Potential: 25kV peak, 10kV average (half wave rectified)
Current draw.....................: 25mA at 10kV average (250W)
Distance to detector..........: 8cm
Run time...........................: 3 + 4 + 5 = 12 minutes

Using the your fusion calculator (http://www.beejewel.com.au/) this gives a fusion rate of 4e3 fusion/s and a Q in the order of 1e-11.

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Richard Hull
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Re: First Bubbles!

Post by Richard Hull » Mon May 16, 2011 2:16 pm

Great work guys!

This is the kind of stuff we like to see. Lots of adapting with less than ideal materials. Lots of fiddliing to make it go and, yet, success! Key here is that you are about the second or third electrolysis fusor. It is nice to see this workaround alternative to bottled gas turning out successful fusion.

Your detailed description of the effort and its results, along with a full rundown on your gear was enough to tell me you did fusion. Sounds about like my first blast with fusor III back in the late 90's. Lots of effort for a little fusion recorded on the Bicron Scintillation system. The BTI beats all other detection systems in the hands of "first timers" even at this lower level.

I have added you both to the neutron club. Keep us informed on future runs with higher voltages.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Carl Willis
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Re: First Bubbles!

Post by Carl Willis » Mon May 16, 2011 5:55 pm

Congrats, guys, on an operational and neutron-generating system. I know it can be more difficult for non-US fusioneers to round up their equipment, so kudos on overcoming those hurdles. I look forward to more reports on your efforts.
Carl Willis
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Caspar12
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Re: First Bubbles!

Post by Caspar12 » Tue May 17, 2011 2:59 pm

Thanks all for the kind responses! We are excited to have it working, and very surprised that we were able to produce some neutrons even on our first attempt. I can't say it all worked flawless, but apparently good enough for some fusion.

It has taken us about 8 months of experimenting with all kinds of chambers, HV-supply's, grids, seals, feedtroughs, windows, pumps and all the other equipment to get to this point. The electrolysis was probably one of the easiest parts of the project.
Part of the equipment we salvaged from the waste bin at one of the faculty's that were either defective or to old to be used. Other equipment was bought from a Dutch equivalent to Craigslist, of course ebay and things like the bubble detector with help from here. That were some interesting projects on their own.

We will make a more extensive report (with pics) on all the steps we have taken to get it to work. It might be interesting for other fusioneers who are on a low budget.

The diodes have arrived, so we'll be able to make some new runs at full power shortly. After that we'll try to get the photomultiplier/scintillation detector working. But mostly we'll be concentrating on our next project, a superconducting polywell.

Attached a picture of our first plasma from some months ago, with a tacky-tape HV-feedtrough.
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First plasma.jpg

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Martijn Rambonnet
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Re: First Bubbles!

Post by Martijn Rambonnet » Sun May 22, 2011 6:18 pm

Hello all,

We received the diodes this week and we did a run at full power. However the diode string quickly failed again (although we made it 40kV, 1A instead of 35kV, 1A). We tried again with a second diode string creating a 40kV, 2A diode, which was able to withstand the continuous full power of the transformer. However after a short time running the transformer setup began to produce some smoke from within the oil so we had to stop the experiment. We have a suspicion it is arcing at the high voltage output of one of the coils where two wires are very close together. We are going to try improve the isolation this week.

The short run, a few minutes at ~30kV peak, full wave rectified, resulted in one bubble. We also did a background reading over three days but this yielded no bubbles.

We also attempted and endurance run with the Heinzinger operating continuously at 10kV and 10mA which resulted in a burned fuse. The third thing to fail was the electrolysis power supply (max 30V, we run it at 15V for electrolysis) which decided to go berserk and suddenly output 45V for no apparent reason.

Also a few hours were invested into the initial construction of an HV control panel (19 inch 1U unit) which incorporates an emergency stop button, two key switches as HV interlock (one key for each operator), and some computer/externally controlled relais to switch HV sources (x-ray transformer, photomultiplier power supply and in the future ion guns, electron guns, etc).


Current fusor construction history and details
As requested a short overview of our experiences from constructing a fusor on a minimal budget.

Vacuum chamber
Our first vacuum chamber was our diffusion pump. When we got the pump the diffusion pump was a mess and we had taken it apart for cleaning. After some initial tests with the first chamber and some major leaks we did a quick run with a Plexiglas lid on top of the diffusion pump and an electrode through it. Crazy idea of course but hey it worked and we were very happy to see our first plasma!

For the real chamber we use 2 cylindrical steel pieces with flanges we salvaged from the scrap metal bin of a workshop. This had 3 major problems. Viewing port, seals between flanges and material (see photo 1).

Since it is made from steel we probably have a somewhat larger outgassing rate. Leak/outgassing is usually about 0.1-0.5mTorr per second (@50mTorr) when it has been open and it is currently 0.006mTorr per second (averaged over 0-700mTorr). Either way this is well within the range of the pump near the required pressure around 5-10mTorr for fusion. It just uses a little bit more deuterium but that is of no concern to us.
The other problems with steel is that it corrodes quite easily and for aesthetics we have coated the outside with a little bit of oil to reduce corrosion. On the inside we have not seen any corrosion but since we keep the chamber under vacuum and very dry this is logical.

The second problem was sealing two flanges. Depending on which flange there is only a few millimeters of space for the seal. Our first attempt was to use tacky tape to make a vacuum seal. Normally this is used for vacuum bagging of composite parts for vacuum injection and can probably be best compared to bubble gum and clay. It is reasonably sticky but can be easily removed, any small residue can be dissolved with white spirit. We use a very thin ring of tacky tape on the outer flanges to make a good connection (where there is only 3mm of space). At the inner flange we use a custom o-ring. It is made from o-ring cord (nitrile rubber I think) which is cut to size and glued together at the ends with a cyanoacrylate type glue The major problem with this is that the o-ring is not fixed in a groove so it can easily pop out between the flanges when it is not carefully placed. other o-rings we use are for the inlets and outlets which consist of normal plumbing o-rings. For the window we have also used cyanoacrylate glue to seal some screws.

Since our vacuum chamber is not compatible with standard vacuum connections and due to obvious cost reasons we have made our own viewports. The initial viewports consisted of plexiglas plates which were bolted against the outside flanges (see photo 1). We discovered that Plexiglas was very prone to outgassing when it was being hit by beams from the plasma and this very much interfered with the pressure and stability of the plasma at higher voltages (>5kV). The other problem was that Plexiglas shields almost no radiation (I am pretty sure we would measure near 1000cps at 25kV with our glass beta/gamma gm tube). The current windows consist of a metal end plate with a sheet of glass clamped against it with an o-ring in between. The front window is a small Plexiglas window with a glass plate in front of it (n the vacuum chamber). This has greatly reduced the radiation and solved any outgassing problems.

High voltage
The first step in our high voltage carreer was to use a (multiple) car ignition coil(s) which were switched by several cooled 2n3055's at high frequency (basic 555 driver). This was enough for some nice plasma's but had very limited power. The second step was using a neon sign transformer (8kV, 25mA center tapped). We were unable to succesfully remove the center tap and could go no further than 4kV but this was again a step in the right direction. After investigating possible other power supplies (spellman, glassman etc very nice but way to expensive) we found an x-ray 50kV, 7mA transformer on ebay for 60 euro's. We created a container where the transformer could be submerged in oil (we use aviation mineral oil). For recitifcation we have tried to work with microwave diodes but they did not survive long. Currently we are using two strips of 35 1N4007 diodes (1kV, 1A, 0.02 euro a piece). For voltage monitoring we have a made a voltage divider from a special 10MOhm 30kV resistor from an old HV probe.

As an high voltage cable we use 20kV cable from ebay (few euro's, it is probably also possible to use an HV cable from a crt monitor but we haven't tried it yet) shielded by 2 layers of silicone (vacuum) tubing.

For the high voltage feedthrough we started of with a simple piece of metal through a plate of plexiglass. Due to heating of the electrode at high power this quickly failed. We now use an used 18mm aircraft spark plug. After some small modifications this worked great up to 10-15kV but at high voltage is still sparked from the electrode to the outside of the spark plug. We tried to prevent this by using a plastic tube (high outgassing with plasma's), glass tube (broke/burned almost immediately with a plasma), teflon (sparked through, danger this can produce extremely toxic gasses!) and finally we found a porcelain tube that we were able to fit around the electrode.

Vacuum
The vacuum backing pump and diffusion pump were obtained from the faculty who were throwing them away as scrap metal. The backing pump was in reasonable condition but the diffusion pump was pretty much broken. The heater had burned through, the oil had become a solid layer at the bottom, it was covered in tacky tape and several small parts were missing. We were able to obtain a new heater by chance from ebay (for only something like 20 euro's) and with a lot of effort we were able to clean the inside of the diffusion pump. With some improvisation were able to replace any missing parts and seals. The next problems was to find a small quantity of diffusion oil for a reasonable price. After a lot of calls and searching we were able to buy 25ml of DC704eu for ~40 euro's (still expensive, but other sellers only wanted to sell large quantities).

For vacuum connections we mainly used transparant vacuum tubing. To mimize outgassing we keep these lengths as small as possible and we use hose clamps to make sure they are thightly connected. For the chamber-pump connection we use a short large diameter reinforced piece of tubing with a clamp in the middle which we use to reduce the pump flow at low pressures.

For pressure monitoring we use 2 Robinair analog thermistor vacuum gauges with a range of 1mTorr-760Torr. Although they are currently not really correctly calibrated they are still extremely useful for reference values in tuning the vacuum for fusion.

As you probably have guessed we had our fair shares of leaks. Usually we have a suspicion were the leak is and we either use tacky tape to close the leak (and confirm the location) or we drench the connection in acetone (which gives a large jump in the vacuum measurement, warning: this will require some gas ballasting to get the acetone out of the backing pump oil, also this is not compatible with tacky tape seals). We have played around with an old ultrasonic leak detector but without any results.

Electrolysis
See our previous post for some details on our electrolysis system. Bent is currently working on a rendering and schematic of the exact details which will be posted in the near future.

Radiation detection
For x-ray monitoring we use a DOM 410 geiger counter with a large (~15cm long) glass geiger muller tube. It is sensitive to gamma and (hard) beta radiation. By chance we were able to buy a cheap CDV-700 with a 5979 front-end mica window probe which is also sensitive to (hard, not the low energy) alpha radiation. This proved to be very sensitive to x-rays but the probe unfortunately started leaking (if someone in the US wants a 5979 Richard Hull has a lot for sale).

For neutron detection we found no better alternative than a BTI bubble detector. We want a computer readable and non-expiring neutron detector so we are now working on a photomultiplier setup with the neutron scintillation foil from geohot.

Future plans
We are currently working on a larger stainless steel vacuum chamber (same design as Jeroen Vriesman's). We had taken a chance and bought a micro-ion gauge from ebay with an rs-485 interface but it seems to be broken so we will be looking around for an other ion gauge which will be necessary for the polywell.

Other efforts are focused on the design of the oil cooled (not yet super conducting) polywell design. We will also begin experimenting with electron and ion guns.

Photo 1: Third iteration of the reactor with large Plexiglas viewports
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IMAG0029.jpg

Jeroen Vriesman
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Re: First Bubbles!

Post by Jeroen Vriesman » Mon May 23, 2011 7:31 am

fantastic!

you are planning to make a superconducting polywell wow.

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Martijn Rambonnet
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Re: First Bubbles!

Post by Martijn Rambonnet » Mon May 23, 2011 9:20 am

The idea of a superconducting polywell is based on the fact that Bussard encountered a lot of problems with running his coils continuously (he did not use superconducting magnets).

This does however pose 2 major problems. The first is getting a superconductor; unless we can find some funding buying superconducting wire is too expensive, but it is also possible to make your own super conductor (YBCO).

The second problem is cooling the superconductor. Superconductors like YBCO require LN2 which ofcourse is a hassle to obtain/store but not impossible (a small cryocooler would be ideal but even diy ones are expensive).

Thus we are going to start with cooled restive magnets and if the results are interesting enough we hope to continue with superconducting magnets

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Richard Hull
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Re: First Bubbles!

Post by Richard Hull » Mon May 23, 2011 1:46 pm

Very laudable effort on the future polywell work. It is good you are doing a simple fusor first. You are seeing just how tough it is to do simple stuff, or stuff that seemed simple. It is a big learning curve and you must master the simple fusor, vacuum, HV, gas (dueterium) handling, etc., before proceeding heavily into the polywell project.

Neutron detection is always a big issue too, but the BTI bubble detector doesn't lie.

Nice overall report on the physical setup and sorry you are experiencing numerous issues, system wide, but they will be solved one by one allowing much better operation.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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