Ready for assembly!

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fpg
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Ready for assembly!

Post by fpg » Sun Aug 29, 2010 1:28 pm

All the parts have arrived and it is now ready for assembly. When it is finished it will look like pic 2.

In the right upper corner in pic 1 you can see the mating flange for my diffusion pump. Some guys in a steel workshop made it for me for a quite reasonable price of 25 dollars. Sadly they said that they didn´t have the tools to assemble the reactor so i have to find another workshop that can assemble it.

To cut cost i bought 2 full nipple flanges instead of 4 half nipple once.

Any advices before I start putting it all together is appreciated

Thanks in advance
Fredrik Parnefjord Gustafsson
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Linda Haile
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Re: Ready for assembly!

Post by Linda Haile » Sun Aug 29, 2010 5:21 pm

It may well pay to polish all internal surfaces at this point, however it is essential that all residue of polishing compounds etc are removed prior to welding.

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Carl Willis
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Re: Ready for assembly!

Post by Carl Willis » Sun Aug 29, 2010 6:34 pm

Hi Fredrik,

Looks like a good start. You should consider a throttle valve between the diffusion pump and the chamber, since a high pumping speed during operation will only waste gas. I hope that requirement doesn't obviate the quite-reasonable $25 coupling the shop made for you.

Good luck with the rest of the fabrication.

-Carl
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dbrown
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Re: Ready for assembly!

Post by dbrown » Sun Aug 29, 2010 7:55 pm

Trival but don't forget to add a forced air fan for the DF air heat exchange coils - will save a lot of back flow.

Speaking of which, welding in two flat partial plates to act as "non-line of sight" inline baffles for the DF pump/chamber would also improve ultimate pressure (but not pumping rate) and reduce oil vapor from getting into the chamber from the DF.

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Richard Hull
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Re: Ready for assembly!

Post by Richard Hull » Mon Aug 30, 2010 3:26 pm

Fredrik,

While polishing might be pretty, it is absolutely not required and outside of just being pretty, it has no beneficial effect on influence on fusion. The time spent on a pretty polish might be better directed toward actual construction.

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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fpg
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Re: Ready for assembly!

Post by fpg » Mon Aug 30, 2010 5:13 pm

Carl Willis

I don’t think that the high pumping speed should be much of a problem since I use a very weak roughing pump (2CFM). But it is probably a good idea because I will probably buy a better pump in the future.

Dennis Brown

I have several computer fans lying around so I will probably use them for cooling the DF pump. The "non line of sight" inline baffles you mentioned is an easy fix that I have thought of before and I will weld the two plates inside the half nipple flange as soon as possible.


Richard hull

I’m perfectly aware that the polishing won’t effect my fusion results but I thought that I might as well make it pretty since I had 20 min to spare.

- Fredrik PG

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Carl Willis
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Re: Ready for assembly!

Post by Carl Willis » Mon Aug 30, 2010 7:33 pm

Hi Fredrik,

Your diffusion pump has an effective speed somewhere in the 50-100 l / sec ballpark. To sustain a typical operating pressure in the fusor of 10 mtorr with this pump wide open on the system would require a very high gas throughput:

50 l/s * 10 mtorr = 0.5 torr l / s (~40 sccm)

I ran at about 1 sccm on all my projects, and my knowledge of others' systems suggests this is where they tend to be as well. I use a simple QF-25 manual shutoff valve as a throttle on a 50-lps diffusion pump, reducing the effective speed to an estimated ~1 l/s. 1 sccm is an easy value to achieve with capillaries, laser orifices, mass flow controllers, and metering needle valves, and will get you about 1000 hours of operating time from a deuterium lecture bottle. Too much lower throughput, and flow becomes difficult to control. Too much higher, and you'll blow through expensive gas at an uncomfortable rate.

The 2-CFM forepump (roughing pump) seems just fine to me for backing this diffusion pump.

-Carl
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lutzhoffman
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Re: Ready for assembly!

Post by lutzhoffman » Tue Aug 31, 2010 9:23 am

So far so good, all the advice has been spot on. Have you decided on what fluids to run in both of your pumps yet? There are two schools of thought on this, some prefer to run cheap but effective diffoil 20 in both pumps for simplicity, and others would say to use expensive Santovac 5, since it eliminates the need for a trap, and because your DP uses so little oil anyway.

Since you have the actual chamber design done now, you may want to put some serious thought into optimizing the vacuum system at this point. I would suggest at minimum also adding a copper wool filled trap between the RP and the DP. You can buy cheap copper scrubbing pads, and degrease them with soapy water, followed by rinsing with water, drying, and then a final solvent rinse followed by a high temp 300 deg F oven dry. This will absorb the back streaming RP oil, and prevent it from getting into your DP, and chamber. When these get dirty, then you just repeat the above cleaning. I adapted a fine mesh water filter unit from the hardware store, by unscrewing the cup and filling it with the copper wool. The transparent cup is great because you can see the oil when it gets dirty.

What ever you decide to do, searching the threads on vacuum stuff etc. in this forum will pay off big time in the long run. There is so much good information here, enjoy it. For D gas I have tried several ways to use D2O as a source, the best way for me was to pass D2O vapor through hot magnesium turnings in a quartz tube, with fiberglass plugs in the ends to hold the Mg in place. Hot Mg will also absorb nitrogen as well, if a small amount of air remains in the system. It is however best to flush the line with argon first. You can even use the chamber vacuum to suck the D2O vapor through the hot Mg, and aid in the evaporation of the D2O from the sealed flask, as it passes through the hot Mg, only D gas will remain.

Some folks add a dryer stage to D gas generated by various chemical and electrolytic methods, but some studies have show slightly increased fusion rates, with traces of remaining D2O, to the point where they even add a controlled amount. With the Mg method it tends to be pretty dry, when compared to electrolysis for example. You can experiment with H2O and Mg very cheaply to get familiar with the process, and then decide if you want to drop so much cash for the lecture bottle, and regulator etc. Take care and good luck, very impressive so far : )

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fpg
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Re: Ready for assembly!

Post by fpg » Thu Sep 02, 2010 7:28 pm

Carl Willis,

Good to hear that my pump will do I was actually a bit worried about it being too weak.

Lutzhoffman,

I have not thought so much about what oil to use but I will probably go for diffoil 20 as you mentioned (I´ve heard it´s good for starters). The santovac 5 is a little expensive for my taste . Is it absolutely nessesary to use an oil trap when using diffoil 20 or is it enought (for starters) with the "non line of sight" inline baffles as Dennis Brown mentioned? (correct me if I´m wrong I have never used a diffusion pump before but I will sertainly read the vacuum threads to learn more).

I will do as you said and experiment with the Mg H20 method and familurize myself with the method before I test the real deal, but first I need to weld it all together .


Thanks for your advices,
Fredrik Parnefjord Gustafsson

nemesistech
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Re: Ready for assembly!

Post by nemesistech » Thu Sep 02, 2010 9:13 pm

Here is a link showing how I built my chamber, maybe it may help you.
http://motionpicturetransportation.com/chamber1.html

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