Critique this turbomolecular pump backed by Welch 1400 setup

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.
John Futter
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Re: Critique this turbomolecular pump backed by Welch 1400 setup

Post by John Futter » Thu Mar 29, 2018 6:01 pm

pictures are needed

Jerry Biehler
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Re: Critique this turbomolecular pump backed by Welch 1400 setup

Post by Jerry Biehler » Fri Mar 30, 2018 7:47 am

$850 for an old belt drive pump? I can find you a much newer Adexien direct drive pump tested for about $500.

Big port connects to the fusor. Small port connects to the roughing pump. So you will need and ISO-100 fitting to adapt to whatever you put on the chamber.

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Re: Critique this turbomolecular pump backed by Welch 1400 setup

Post by ian_krase » Fri Mar 30, 2018 8:23 am

That is indeed a somewhat expensive rotary vane pump. Usable ones are available for less.

That turbo pump is a total gamble. The seller hasn't tested it, and does not take returns. I would not risk it. It also does not look like it includes the controller (unless that's actually a built in controller. Read the manual.) Controller can cost as much as the pump, though if you are very good at electronics you can build your own. A totally broken pump is almost totally worthless, a worn out but not destroyed one can be repaired by a dealer (for over a thousand USD) or by you (using expert knowledge of turbo internals, careful analysis of the manual, and the blessing of Divine Providence).


UHV valves can be... problematic. They optimize UHV ability over practicality at normal vacuum levels. A fusor does not get anywhere near UHV, even beam on target accelerator will probably consider UHV to be overkill. Common themes include needing way too much force to close, only being operable with a wrench, and needing rebuild or gasket replacement after only a few dozen openings/closings. Consult the manual.


In any case you need, as others have said, to adapt the LF on that pump (if you use that turbopump) to the CF on the valve (if you use that valve).

Personally I would probably just go with a 60 L/s turbo (common and comparatively cheap from the mass spec biz, the smallest size of turbo) and a KF50 angle valve. This doesn't open to full line of sight but that barely matters.


You also need some flexible tube (either the expensive metal bellows kind or the much less expensive plastic or rubber) to connect your rotary pump to your turbo pump. And ideally a valve there as well. Conveniently, most turbos will tolerate a downright terrible vacuum (1 torr or more!) in the foreline.

Michael Bretti
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Re: Critique this turbomolecular pump backed by Welch 1400 setup

Post by Michael Bretti » Fri Mar 30, 2018 12:12 pm

I agree with the above statements. Everything you are looking at is grossly overpriced and you can find things way, way cheaper if you are patient and look hard enough. Check ebay more, a lot more - I spent nearly half a year planning out just the vacuum system alone for my setup, including multiple CAD iterations, many, many pages of vacuum calculations, and significant budget planning, cost analysis, system optimization, and simulations, though most people building fusors don't really need this (but I would strongly recommend it.) I just finished the vacuum subsystem designing and planning a while ago, and I'm now working on the thermal management system, and the control system for automated pump-down control and monitoring. No need to rush and blow thousands of dollars when you can get everything for way less. Already the cost savings on my primary small system is on the order of many thousands of dollars, and I spent much less for my entire system than the total cost of the parts you linked to above, and has a lot of modularity and functionality, optimized for throughput and for use for a very large number of high vacuum experiments beyond just a fusor.

First, the roughing pump is way too expensive for a first fusor effort - while it is one of the more ideal ones, it is really not necessary. I am currently using a YellowJacket 93560 as my roughing pump. Brand new, it cost $350 on eBay, and I tested it down to 12.5 microns, and has more than enough overhead for even my very large 600 L/s diffusion pump. The 2.75" CF gate valve you can get much cheaper - I got a 6" throat one WITH a 6" butterfly valve for my larger system for only $100, free shipping, and in great condition. Smaller valves can easily be found for under $100. I also have a 2.75" CF manual gate valve like the one you linked to - it has an o-ring seal, so is much better suited for fusor work - chances are the one you linked to is similar, the metal-seal ones are rarer even though sellers list them as UHV. You can find valves for much less. The turbo can be hit or miss - I have never bought one myself, so I can't comment on them from eBay. Cheaper diffusion pumps will be more than enough for a fusor. For the 2.75" CF to KF25, I wouldn't necessarily go buying a bulk pack until you actually know exactly how your chamber will be built.

Again, I highly, highly recommend CADing out your system - sit down, plan, and take your time. No need to rush. Research high vacuum systems thoroughly, familiarize yourself with all the basics and standards of the field. It will save you a lot of money in the long run (of course if you have tons of spare cash to blow on whatever then this isn't much of an issue, but for most in the fusor field we operate on a very tight budget.) It is very surprising how often new people getting into the hobby will just rush to build a system as fast as they can without any effort to plan (or even study) the vacuum system. After all, it is the most critical part of the fusor setup, and often is the area people encounter the most problems and troubleshooting. If you want an example of full system planning, take a look at the walkthrough I posted a while ago in how I went about planning the system - it is very long, but there is lots of info:

viewtopic.php?f=10&t=12114

Also the walkthrough is posted here:

http://appliedionsystems.com/high-vacuu ... roduction/

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Re: Critique this turbomolecular pump backed by Welch 1400 setup

Post by Richard Hull » Fri Mar 30, 2018 6:21 pm

The yellow jacket is a great pump. Mine has hit 10 microns on fusor II and fuosr III. All are correct above. A good, used and warranted 1400 might hit 20 microns and should never cost more than $150. The yellow jacket has 5 times the pumping speed!

Richard Hull
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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.

Rex Allers
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Re: Critique this turbomolecular pump backed by Welch 1400 setup

Post by Rex Allers » Fri Mar 30, 2018 8:17 pm

A bit on the Edwards Turbo pump. The EXT255 does have a built-in controller. The pump runs on 24 Vdc and has a serial interface where you can send commands to control the pump and read its status. I have an ETX75DX which is a smaller version of the same pump.

I really like the built-in controller but my pump runs with a very annoying screaming whine noise. As John Futter mentioned in this post:
"Rebalancing turbopump rotors / vibration analysis"
viewtopic.php?f=10&t=4087&p=26166&hilit=Edwards#p26166
this is apparently not uncommon with Edwards Turbos. Mine may be getting ready to die.

So buying a turbo pump from eBay is a very big gamble. I agree with all the thoughts other posters have provided.
Rex Allers

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Re: Critique this turbomolecular pump backed by Welch 1400 setup

Post by Jerry Biehler » Sat Mar 31, 2018 2:58 am

The turbo pump is not a terrible price and like Rex says it has the controller on it, it is not that old of a pump.

And the seller has the turbo listed as used which means it must be in good working condition or he has to take it back. Ebay will enforce this. If he wants to sell it with no chance of someone sending it back if it does not work he must list it under "Condition: For parts or not working"

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Re: Critique this turbomolecular pump backed by Welch 1400 setup

Post by ian_krase » Sat Mar 31, 2018 6:16 pm

Even though they say that they don't take returns?

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Re: Critique this turbomolecular pump backed by Welch 1400 setup

Post by Tom McCarthy » Sat Mar 31, 2018 6:33 pm

Yeah, all the sellers that say "no returns", "sold as is" etc and have their item listed in used condition have to refund you or provide returns if it's not fully functional. Ebay's definition:

Used

An item that has been previously used. The item may have some signs of cosmetic wear, but is fully operational and functions as intended. This item may be a floor model or an item that has been returned to the seller after a period of use. See the seller’s listing for full details and description of any imperfections.

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Re: Critique this turbomolecular pump backed by Welch 1400 setup

Post by Andrew Seltzman » Sun Apr 01, 2018 9:54 pm

I would recommend a pfeiffer duo 2.5, or pfeiffer duo 1.5 vacuum pump if you are going to back a turbo. They are nice scientific pumps with an NW10 flange and available on ebay at a low cost. The Yellowjacket pump is designed for air conditioning service and will require some adapting to provide a compatible flange.

I would recommend a pfeiffer turbo (with a 4.5 conflat, iso 63 or 2.75 conflat flanges, anything bigger is unnecessary). I would avoid the edwards turbos as they tend to have some problems.

The pfeiffer tmu 071 is a particularly nice pump with an integrated controller, and a molecular drag stage so you can back it with a quad stage diaphragm pump if you want. Here are some on ebay:
https://www.ebay.com/itm/Pfeiffer-TMU-0 ... SwA3dYfsMY
https://www.ebay.com/itm/Used-Pfeiffer- ... SwcaFZEA26
https://www.ebay.com/itm/Pfeiffer-D-356 ... SwFMdaXOGf

You can back them with any dry diaphragm pump capable of <~15torr
Andrew Seltzman
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