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The long awaited 1.33" Fusor construction write up.

Posted: Tue Feb 26, 2013 12:37 am
by TannerOates
The following are the images of the entire process of building the Fusor followed by plasma pictures. All mounting hardware is 316SS plated in 99.999% Silver to act as lubricant, the only exception is the MD5 leak valve which was lubricated with KJLC brand anti-sieze lubrication for threads.

Photo:

1.) This first image is of the main chamber. From wall to center of the cube it is .67", this 6-way cube was manufactured by KJLC out of their standard vacuum chamber stainless steel. The fittings on the chamber are 1.33"CF flanged with 8-32 x .5" tapped holes.

2.) This is an image of the MD5 series leak valve that also acts as the fore line valve between the chamber and roughing pump. This valve is capable of doubling as a leak free shut off valve as well, it can have a controlled leak down to 10^-7 Torr but will work as a shut off valve down to 10^-11 with a leak rate of 10^-12. I used this because I can basically use it as a flow control for the pump because of the small chamber size. The construction is all SS with a stellite knife edge and nickel diaphragm.

3.) This is a 1.33" close coupler provided by Kimball Physics, this part is used to join two tapped cf flanges of the same size. The coupler is needed to attach the MD5 leak valve to the chamber with minimal foot print. The holes are off set thus allowing access of a hex wrench. Standard SS construction.

4.) These are the two hemispheres of the grid before trimming of the excess materials. These are two evaporation filaments made out of Tungsten wire with a thickness of .092" by KJLC. There are many reasons for using two spiral hemispheres that are outlined in the grid assembly photo. After machining these filaments were cleaned in acetone followed by Isopropanol to ensure no particle contamination within the chamber.

5-6.) These two photos are of the completed inner Grid construction, as you can see they are attached to the feedthrough wires with inline barrel connectors constructed with BeCu and SS316 screws provided by KJLC. This two hemisphere design was chosen for a number of reasons, the first being any grid I could think of is too large to fit into the small hole of the chamber thus calling for a design that can be compressed then decompressed once inside the chamber, the second being with these two separately insulated grids it allows the ability to attach two AC leads as well as connecting a single DC lead, and the third would be the ease of precision construction in a small time frame. This grid can be replaced within a matter of minutes with a minimal amount of construction. The two ends of the conical filament fits perfectly into the ports of the 6-way cube. I am possibly switching to a more substantial feedthrough due to the fact that there is slight arcing at lower pressures. In spite of this, the design will remain the same except for the external dimensions of the feedthrough.

7.) This shows the grid installed along with the D2 gas feedthrough. This D2 gas feedthrough is all 1/4" swage-lok port connectors and elbows constructed out of SS. As shown, the grid tolerances are small but the fit is immaculate within the chamber allowing a relatively good amount of space to spare.

8.) This is the chamber with: the MD5 valve, power feedthrough, close coupling, D2 inlet, and a blank flange on the opposite side of the chamber behind the grid.

9.) This is the final product with the Lead glass viewport installed along with the second blank flange and 2.75"-1.33" conical reducer in the bottom of the image. This reducer (SS) is used to attach to the Turbo and roughing pump system.

10.) This is the first AC plasma out of the machine. This was created with an NST 15kv@30ma at around 80mbar.


Thank you for your patience.

Re: The long awaited 1.33" Fusor construction write up.

Posted: Tue Feb 26, 2013 12:44 am
by Tyler Christensen
Looks like nice hardware.

You put 50kv on that feedthrough? If you did, I'd love to know what potting compound you submerged it in so I can pot everything I ever make in it. Otherwise, I can effectively guarantee you're not close to 50kv. I'd seriously question even 10kv being on that feedthruogh in air. I doubt you could do 50kv even under the best dielectric oil money can buy.

Re: The long awaited 1.33" Fusor construction write up.

Posted: Tue Feb 26, 2013 2:11 am
by Carl Willis
Nice writeup, Tanner.

I agree with Tyler that one of the most interesting things about such a small fusor is how it handles voltage. You may not be instrumented to provide a convincing measurement of the grid voltage yet, and that's all understandable, but to me it is one of the more interesting data points that could come out of your experiment.

Thanks for the nice photos.

-Carl

Re: The long awaited 1.33" Fusor construction write up.

Posted: Tue Feb 26, 2013 3:03 am
by TannerOates
I am positive it handled 15kv@30ma of AC, but I am agreeing with you on the voltage for DC. I turned the local control on the glassman to max but the properties of the amperage drop, plasma, and pressure defiantly took a toll on it. Yes, like I said, I am getting a much mor substantial feedthrough.

Re: The long awaited 1.33" Fusor construction write up.

Posted: Tue Feb 26, 2013 3:05 am
by Tyler Christensen
Why do you think it held up to 15kv? An NST is ballasted, and when sustaining a typical fusor plasma, could drop to even less than 1kv.

Re: The long awaited 1.33" Fusor construction write up.

Posted: Tue Feb 26, 2013 3:08 am
by TannerOates
Hm, come to think of it, I only know for sure it went above 1k because it maxed out the voltmeter, but my biggest problem is the arcing on the atm side of the chamber which I believe will be fixed with the new feedthrough. Any surefire way to tell actual grid voltage being applied?

Re: The long awaited 1.33" Fusor construction write up.

Posted: Tue Feb 26, 2013 3:09 am
by Tyler Christensen
You should get a high voltage probe. They plug into a typical meter and generally divide by 100 and operate up to tens of kilovolts. You can get them on ebay for a pretty low cost usually.

Re: The long awaited 1.33" Fusor construction write up.

Posted: Tue Feb 26, 2013 3:11 am
by TannerOates
fantastic! Thanks!

Re: The long awaited 1.33" Fusor construction write up.

Posted: Tue Feb 26, 2013 2:47 pm
by Richard Hull
All here have re-echoed my original complaint. No way fusion level HV will ever enter this chamber as shown. You must meter the entire setup for pressure, voltage and current for DC readings when doing fusion reports.

Otherwise, your supplied images are perfect in every way. Very clear, clean and detailed. Every professional artifice is made use of in this effort. Must have cost a bundle.

For the first time, we are able to see and understand your chamber and effort. If it ever does fusion that is clearly demonstated beyond all doubt, I will be amazed. There just appears to not be much headroom for the voltages needed to do easily detected fusion via our normal fusor methodology and topography.

If you ever claim fusion with this please supply images of the grid when fusing, all voltages and currents and pressures as well as fully explain your neutron measurement system in some detail. As noted before, all of the reporting demanded is fully covered in the FAQ in the Admin forum with a full example in the FAQ located in the image du jour forum.

Again, thanks and good luck.

Richard Hull

Re: The long awaited 1.33" Fusor construction write up.

Posted: Tue Feb 26, 2013 7:34 pm
by Rich Feldman
TannerOates wrote:
> I am positive it handled 15kv@30ma of AC, but I am agreeing with you on the voltage for DC.
Tanner, with absolute respect and support:

The quoted statement indicates that you do not yet "get" some fundamental things about electricity and power supplies. Only in special cases (or never, in the case of a NST) will the voltage and current on the nameplate match those in the circuit.

Think about being prepared for live interviews by science fair judges (who, on average, are more technically competent at higher rungs of the tournament ladder). For practice: what are the approximate voltage and current if you put a 1 ohm resistor across a common 9 volt battery? How about a 500,000 ohm resistor across a 15-30 NST?

-Rich

[edit] Some high voltage probes like the ones mentioned by Tyler have a 40 kV rating and a 1000:1 divide ratio (when loaded by a voltmeter with 10 megohm input resistance). And are reasonably accurate for 60 Hz AC, for example from your NST.