[Sneap] Electrical isolation and coolant

[Paul Voytas]

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