[Sneap] Electrical isolation and coolant

[Stephen Marino]

Paul,

In our single-ended 4-MV Van de Graaff we originally used Freon 113 
(R-113:  trichlorotrifluoroethane, CCl2FCClF2), which is fully 
halogenated, as a coolant for our ion source. . Since this was expensive 
and contributed to the greenhouse effect, we switched to DuPont Vertrel 
XF, which is marketed as a replacement for R-113 for high-voltage 
applications (http://www2.dupont.com/Vertrel/en_US/products/xf.html). It 
is  a hydro-fluorocarbon (decafluoropentane, CF3CHFCHFCF2CF3) and DuPont 
claims it "has zero ozone-depletion potential and low global warming 
potential". When we switched 4 or 5 years ago, it was about as expensive 
as R-113 but is not subject to termination of manufacture since it is 
not a completely halogenated compound. I don't know the relative prices now.

Steve Marino

-- 
Stephen A. Marino
Manager
RARAF
Columbia University
P. O. Box 21/ 136 S. Broadway
Irvington, NY  10533
Tel.:  914-591-9244         Fax: 914-591-9405
http://www.raraf.org/