New Fusor: progress

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Richard Hull
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Re: New Fusor: progress

Post by Richard Hull »

Good, step by step system assembly reports, with photos, are of interest to even the old boys here, but as noted really are a teaching moment for the newbies. Keep 'em comin'....

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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Dennis P Brown
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Re: New Fusor: progress

Post by Dennis P Brown »

Thank you Richard; from someone with your level of experience I really appreciate that feedback!

Well, there was a micro-leak at the center core of the electrode (between the steel core and ceramic body) - I used some liquid vacuum seal and baked it an hour at 300 C. Did the trick. My system (fore pump only) went from 70 microns to 4.5 microns! So, I'm very pleased with that pressure and that's w/o the turbo, of course.

I added an extra external ground box and used that to provide an independent star grounding for the chamber, power supply and key devices - with these voltages (and currents) one can't be too careful. Note I keep the HV cable well away from all metal parts, other wires, and vacuum system components. Cable insulation can fail and its also best not to test their capabilities.

With the system properly sealed, I ran the power to the electrode to use the trace air to create a plasma - the oxygen will further clean up the main chamber. The chamber (sealed off using the gate valve) climbs about 15 microns per minute from all sources(considering the large surface area, I am pleased with that rate.)

With that plasma run I now have "first" light; through, not yet with deuterium. But still a nice milestone in that I achieved routine fusor pressure levels with a plasma running.

Adding deuterium gas for a real run (the system is installed, though) will wait till I build a proper shielding system (not depending on the steel walls, that's for sure) and get my He-3 detector working (obviously, will require neutrons to really test). Those projects are now first up in the 'Q' and I hope to complete them in the near future. Then I will also try my new scintillation neutron detector and see if I can fire up my old Russian BF-3 tube (however, its operating voltage might be too high for my systems.) So when I get the He-3 detector up and running with a computer I will be ready to try some real fusion.

Still some minor odds and ends to finish on the vacuum system: run turbo for ultimate vacuum level check (at least 10^-5 torr), test my main gate valve for fine vacuum adjustment capabilities, add a mirror to indirectly see inside the chamber (need to avoid those x-rays), and adjust some equipment locations.

Bottom-line: As any experienced fusor knows, getting one's vacuum system up to speed is an absolute first required step before any fusion can be attempted - all else has to wait till that is functioning properly.

Aside: Newbies do note that if you want to get into the plasma club its important to demonstrate progress by giving some details of construction. This should also be done besides reporting plasma parameters - see my plasma photo with appropriate parameters cited as a possible example to follow. This furthers both your proof of your claim but also gets you noticed as a contributor. Furthermore, it makes getting to the ultimate goal - Neutron Club* - more likely (showing your path there.) Besides, this is what makes being a member of the forum fun!

Some plasma details for Newbie's: notice in the plasma picture the diffuse glow filling the entire field of view (chamber) - this shows that the plasma is really operating under 30 microns. The color is indicative of nitrogen gas (dominate ion emission.)

* Or attempt what I'm now trying to do - get on the list for successful nuclear activation via neutrons. In practice, getting neutrons first is the normal methodology but certainly one could do both simultaneously - demonstrate neutron detection via activation. But most of us first got in the neutron club using the normal method - demonstrated detection of neutrons using one of the proven detector methodologies.
Attachments
Lowest system pressure just with my fore pump running
Lowest system pressure just with my fore pump running
Chamber hooked up to my 32 kV, 38 ma power supply
Chamber hooked up to my 32 kV, 38 ma power supply
Air based electric plasma in chamber (can see faint hints of star mode; 8 kV, 28 ma, 12 microns pressure)
Air based electric plasma in chamber (can see faint hints of star mode; 8 kV, 28 ma, 12 microns pressure)
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Dennis P Brown
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Re: New Fusor: progress

Post by Dennis P Brown »

Decided to get an early start on finishing various tasks on the fusor before I can attempt ...well... fusion.

Installed all shielding. To get sufficient shielding coverage, I'm going with two systems: an inner shield based on tiles for a close to the fusor chamber in order to create a maximum shadow effect; and a vertically mounted outer shield (fully painted & framed, lead sheet) to provide better operator coverage (offset vertically and horizontally relative to the cathode for better operator protection). A side mirror (angled) to view the cathode/plasma - to the right of the fusor. I include a pic of the cathode as viewed by the operator.

Aside: I have a calibrated 'dosimeter' to wear and an X-ray/gamma scintillation detector to provide radiation measurements for shielding performance.

I tested the 'ultimate' vacuum level (after just ten minutes of high vac pumping) and it got into the low 10^-5 torr; more then sufficient to assume the fusor is 'clean' before addition of deuterium gas.

My two neutron detector systems: a fast neutron sensitive PMT assembly (home made) and a counter/power supply for it; and my CHM-32 3He detector with its power/pre-amp & computer interface box. I put the CHM-32 in its moderator container - yes, could be bigger but I also have a large paraffin block to add.

So, I need to mount these detectors, test them with all electronics running along with a plasma (no deuterium) to get a noise baseline. Then the really challenging task of using deuterium gas, control the gate valve/system pressure/feed rate and variac, while simultaneously trying to get the voltage to its upper range without over driving the x-former. Fun (not) stuff before I can hope to get any real neutron measurements.

Only then can I attempt Ag and maybe In activation (?). If I had realized I needed a moderator for the Ag foil the first time I tried this effort I could have done this experiment years ago with my first successful fusor. Well, now I have the chance for the 'fun' of firing this fusor up with all new parameters to master. Really a lot of parts and effort to get this experiment back up - I forgot just how involved getting a complete fusor up and running is - especially the issue of creating a stable plasma; and this time, my effort was 'simpler' because I have a turn key 3He detector system rather then the complete 'make your own' BF-3 detector system (where some parts need a lot of assembly! Not unlike Ikea ... ;) )

I'll mount the PMT detector mid level just in front of the tile shielding (to decrease x-ray issues for the PMT. See pic.) I'll mount the moderator tube, extra paraffin block & 3He detector almost against the rear of the chamber in line (horizontally) behind the fusor - again, see pic. Once I establish a baseline neutron measurement, I will convert that moderator tube into my "neutron oven". That is, I will place a Geiger tube wrapped in Ag foil in that moderator tube and measure 'gamma counts' in real time the moment I extinguish the plasma/power. Hopefully that will enable me to measure/record an activation decay curve.

My original and known BF-3 detector is not really viable this time around since its operating voltage is too high for my counter black box and I am not building another system again for that detector ... or hope I don't!
Attachments
Fast Neutron PMT and location
Fast Neutron PMT and location
3He Detector support and Moderators
3He Detector support and Moderators
Complete system w/shielding and operator position (In my mini-research building I posted about in an earlier thread)
Complete system w/shielding and operator position (In my mini-research building I posted about in an earlier thread)
Cathode Image in operator's mirror (Aux ground box in background image; those are just extra grounding wires)
Cathode Image in operator's mirror (Aux ground box in background image; those are just extra grounding wires)
Fast base pressure for the fusor system
Fast base pressure for the fusor system
The Fast Neutron PMT detector system & counter/power
The Fast Neutron PMT detector system & counter/power
The 3He detector system, black box and software thumb drive
The 3He detector system, black box and software thumb drive
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Richard Hull
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Re: New Fusor: progress

Post by Richard Hull »

Nice setup and the turnkey neutron detection system will be a winner for sure.

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
User avatar
Dennis P Brown
Posts: 3159
Joined: Sun May 20, 2012 10:46 am
Real name: Dennis Brown

Re: New Fusor: progress

Post by Dennis P Brown »

Hello every one; well I ran the fusor with deuterium and managed to get a stable plasma. Confused because it is operating below 1 micron to get over 20 kV. Never had that occur with my first fusor.

Tried running the PMT neutron detector - appeared to work or at least behave like it did - no counts with voltage below 15 kV; got a number of counts when over 20 kV; when I dialed back to 15 kV, the counts stopped and then started up as I ran to 20 kV. Got a lot faster when I was up near 27 kV; however, the counts where still lower than I liked so I decided to try various PMT voltages. In the higher range. That is when I started to have issues with the counter box/display and can't figure out what the problem is - appears to be having trouble again. Hope the voltage cut off diode did not fail again.

Decided this required another time to diagnose so I decided to run the 3He detector.

Of course the software for that device which worked perfectly yesterday (after I downloaded what I thought was a update fix as described on their site) now does not work at all today - refuses to load and offers no error. Some days one wonders about software and windows - both tend to be virus's that are meant to drive one to distraction. Of course windows changes their product and that ensures older software does not run. Companies supposedly supply fixes but it takes tricks to get their fixes to work - they forget to explain this since they don't have time to post these issues on their web site. See this far too often.

Well, at least the fusor ran in a stable manner but I am very confused with the fact that to get above 8 kV (@ 12 microns), my vacuum gauges (both!) indicate I'm below one micron - that makes little to no sense. However, I could easily control the current and voltage via the gate valve (normal) and use that to get any desired voltage (again, normal.) This was done while a controlled leak of deuterium being feed into the system.

Well, sent off an email and hope to get feed back on their software issue. Again, lack of information/instructions besides "load this" is not to me all that useful for a site to provide. I think they assume we are all administrators and experts in windows.

So much for a "Turn key" system; with windows, the concept of a turn key system is not what that term use to mean.
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Richard Hull
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Re: New Fusor: progress

Post by Richard Hull »

This is why I tend to go and build all electronics from scratch. You learn as you go, experiment as you go and if you need or desire software control, you grab an Arduino and program and debug it yourself. if you build and program something from scratch you can fix, modify, repair, reprogram and maintain it for as long as you find your build working to your desire.

As Dennis notes, you are at the mercy of the original manufacturer to cover all updates and changes by Microsoft with new software. I have had this issue in the past and have several PC's that are not on line that used to be online and down loaded good software that operated my OEM stuff in the past. They still do, with no issues. One is Win 98, two are XP and two are Windows 7. They will never go on line ever again. They are my main work computers and are isolated from Internet nasties and worthless updates.

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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