[Sneap] Electrical isolation and coolant

[Chris Westerfeldt]

Paul,
    You probably used R-113.  We still use it in our Helium source for
cooling - it is still available but expensive.  I do not know of a direct
replacement.  I would recommend revisiting the DI water cooling option.
We have several home built systems in use and they work well.  We have a DI
service company change the canisters every six months and don't have
conductivity problems.  This is less than $100 as I recall. The highest
voltage difference is just 200 kV however.
Regards,
- Chris
-- 

Chris R. Westerfeldt
Research Scientist / T.U.N.L. Radiation Safety Manager
Duke University Physics Department &
Triangle Universities Nuclear Laboratory
Science Drive, Box 90308
Durham, NC  27708-0308
Tel: (919) 660-2600
Fax: (919) 660-2634
Email: Cwest at Tunl.Duke.Edu


> From: Paul Voytas <pvoytas at wittenberg.edu>
> Reply-To: Symposium of Northeastern Accelerator Personnel
> <sneap at tunl.duke.edu>
> Date: Mon, 12 Nov 2007 14:11:55 -0500
> To: Symposium of Northeastern Accelerator Personnel <sneap at tunl.duke.edu>
> Subject: [Sneap] Electrical isolation and coolant
> 
> Fellow SNEAPers,
> 
> Short statement of problem:
> I'm searching for a high resistivity, non-flammable, non-corrosive,
> non-oil, ozone-safe, low greenhouse effect, fluid to use as coolant in
> an atmospheric pressure cooling system.
> 
> Long story:
> We have an old, small, single ended accelerator we are trying to get
> reliably in shape for use as a teaching tool. The accel has a rollaway
> tank and historically, it's been run without the tank on. To get the
> voltage up and the xray dose down, we run with the tank on now (With SF6
> at atmospheric pressure).
> The problem is cooling the up-to-1000W RF source . With the tank off, a
> squirrel cage fan keeps everything fine. With the tank on, there's a
> heat exchanger (=radiator) in front of the fan that we can run coolant
> through. The coolant system is designed to be at atmospheric pressure
> and historically it used a freon ( 134a maybe?). Due to freon expense
> and ozone protection issues, I'm now using a perflourinated hydrocarbon
> (Dow performance fluids 5060 or 5080 ). I'd tried DI water, but the
> resistivity wasn't high enough--or didn't stay high enough and I don't
> have an active DIing system. The perfluorinated fluids are not cheap
> either (and they're pretty bad (good?) greenhouse gases) and I'm worried
> that the fluorine containing decomposition products (from the high x-ray
> fluxes) will end up corroding the system. I'd rather not us an oil if I
> can avoid it because a leak would cause a terrible mess that I'm not
> sure I could clean off the machine. I'd also rather not use
> flammables... I think the list is getting pretty short?
> 
> Question:
> Does anybody have info on any fluids besides the perfluorinated
> hydrocarbons that satisfy these (or most of these) constraints?
> 
> Thanks for any ideas,
> -Paul Voytas
> 
> -- 
> 
> pvoytas at wittenberg.edu
> office: 937-327-7823
> fax:    937-327-6340
> 
> Physics Department
> Wittenberg University
> P.O. Box 720
> Springfield, OH 45501
> 
> alt email: pvoytas at uwalumni.com
> 
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