[Sneap] Electrical isolation and coolant

[Nicholas Pastore]

Paul,
 
 It sounds as though we're using the same thing in our SNICS and Alphatross
that Pertti uses in his.  Ironically, this morning (Nov. 13) I had a
discussion about this coolant with Andy Soderholm of NEC.  I have only known
it by the acronym "LOBS", which stands for "Low Odor Based Solvent".  It is
an aliphatic hydrocarbon.  Andy stated that their first consideration in
choosing this coolant was its electrical isolation properties.
Unfortunately in that regard I don't have any numbers to give you.  I know
from experience that it cleans up easily with water, or with an alcohol such
as isopropyl or ethanol.  It is also inexpensive.
 As an aside, we had a coolant leak at our Alphatross that at this time
seems to have been strictly external.  However it appears to have crept,
diffused, or permeated through an o-ring into the vacuum system.  I think
this is possible if the coolant is a straight chain compound.  Someone more
knowledgeable might be able to confirm or refute this idea.
 Needless to say, the intrusion of LOBS necessitated the complete
disassembly of the ion source.  I am replacing the quartz bottle, the BN
insulator, the canal, the canal holder, and all of the o-rings.  The rest of
the parts will be thoroughly cleaned and oven dried.

All the best finding the right coolant.
Nick Pastore

______________________
Nicholas Pastore
Operations Manager
Louisiana Accelerator Center
UL Lafayette
______________________




Date: Mon, 12 Nov 2007 14:11:55 -0500
From: Paul Voytas <pvoytas at wittenberg.edu>
Subject: [Sneap] Electrical isolation and coolant
To: Symposium of Northeastern Accelerator Personnel
	<sneap at tunl.duke.edu>
Message-ID: <4738A57B.40603 at wittenberg.edu>
Content-Type: text/plain; format=flowed; charset=ISO-8859-1

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