Quick and Dirty diff pumped system

Every fusor and fusion system seems to need a vacuum. This area is for detailed discussion of vacuum systems, materials, gauging, etc. related to fusor or fusion research.
Post Reply
teslapark
Posts: 49
Joined: Sat Jun 30, 2001 5:20 am
Real name:
Contact:

Quick and Dirty diff pumped system

Post by teslapark »

I've been reviewing alot of vacuum books lately, getting ready to build up a diff pump vacuum system the stainless steel fusor. Of course most setups show an isolation valve between the diff pump throat and the chamber, a foreline valve, a roughing valve, and two (or three) vent valves. That's a lot of valves!

I'm thinking (at least for starters) of just using one valve ("foreline valve") between the diff and mech pumps, so I can at least close the system off when under vacuum. I can't see any reason why this wouldn't work as long as I made sure the diff pump was absolutely cool before venting it. I wanted to toss this past the vacuum experts, since it's about time to assemble the chamber.

Adam Parker
quinnrisch
Posts: 24
Joined: Thu Sep 13, 2001 3:26 pm
Real name:

Re: Quick and Dirty diff pumped system

Post by quinnrisch »

Yes, you can do that, but be prepared to wait a long time between pump downs.

I would suggest, having valve between each component on your vacuum system. This way, if any one part goes wrong you are not putting the system in danger, or more importantly yourself into danger. Venting a hot diff pump to air can be deadly, and the leaks can occur from both the chamber and roughing pump.
DaveC
Posts: 2346
Joined: Sat Jun 30, 2001 1:13 am
Real name:

Re: Quick and Dirty diff pumped system

Post by DaveC »

I would agree... you CAN do without the HiVac valve between diff pump and the fusor, but cycling time will be long...probably greater than 1hr per cycle. Of course if your diff pump is water cooled, your COULD use chilled water from a bucket of ice water.. to bring it down more quickly, but one absent minded vent to air when the diff pump heater is hot and your expensive oil is char.

You CAN do it, but be careful. I would go for the extra valves. You need only four total. Roughing, Foreline, Hi Vac (the expensive one) and a vent valve...any Whitey or other "back to air" type works. More is nice but unnecessary and ... more valves mean more leak and maintenance opportunities!

Dave Cooper
Jon Rosenstiel
Posts: 1494
Joined: Thu Jun 28, 2001 1:30 am
Real name: Jon Rosenstiel
Location: Southern California

Re: Quick and Dirty diff pumped system

Post by Jon Rosenstiel »

Adam,
I just got my demo Fusor running tonight, and wanted to pass this along to you.

For the past year or so I have been dinking around making x-ray tubes. One thing I have learned, it is really, really, really hard to control the vacuum using bleed valves. (I even had the double micrometer kind)!

My newly rebuilt system now incorporates a gate valve just above the diffusion pump. I figured it would be nice to have so I would be able to open the chamber without having to cool down the diff pump. Tonight I discovered another use for it.... It makes controlling the vacuum a dream! Before I could never stabilize the vacuum, now it's a snap! I just open the bleed valve a tad and leave it, and then fine tune the vacuum with the gate valve.

So, based on my recent hard won experience I would strongly recommend that you incorporate a gate valve, (or some kind of throttling valve), in your system between the diffusion pump and the Fusor.

Jon Rosenstiel
teslapark
Posts: 49
Joined: Sat Jun 30, 2001 5:20 am
Real name:
Contact:

Re: Quick and Dirty diff pumped system

Post by teslapark »

Great to hear your fusor is up and running Jon! It seems that the first passes are getting better and better as good info accumulates and more and more interested "doers" are joining the list. While on the topic of "hands on", great job on discovering something to make your vacuum control easier! This is the kind of thing that people need to know who actually decide to build something and it is the kind of data that is best (read only) obtained by actual experimentation.

Now I feel obligated to put a gate valve in my system, and will do so just as soon as one is available to me. In the mean time, I will be hard headed and go ahead and run my system virtually valve free, hopefully producing neutrons though suffering the plight of an unweildly and difficult system.

Congrats again on your first light, can't wait to see some photos.

Adam Parker
Post Reply

Return to “Vacuum Technology (& FAQs)”