From: Geoffrey J. Gettelfinger
Sent: Wednesday, November 01, 2006 2:56 PM
To: Lawrence E. Dudek; Wayne T. Reiersen
Cc: 'fogartypj@ornl.gov'; James H. Chrzanowski; David E. Williamson;
Mike Cole
Subject: NCSX LN2 tube joints

Larry/Wayne:

This note attempts to capture our conversations today.

I suggest that any joint in the 1/4" modular coil tubing that is *practically impossible to service* be of a brazed butt/ferrule design having a fairly thick wall.  The heavy walled fitting would act as the heating point for the ox-acetylene torch (small tip) lessening the likelihood of an accidental tube burn-out.  The brazed joint would be pleasingly annealed to provide a stress relief point during subsequent handling.  We would have to do a modest bench testing program to see if purge gas is necessary to discourage unwanted chemical/surface effects in the bore of the joined tubes.

Mechanical joints may be used in the more accessible regions.  Brass Swagelok or Parker A-lok fittings will do well with the copper in these areas and will likely complete the service life of the stellarator without any need of attention.

National Pipe Taper threads with "Formula 8" or equivalent cryo pipe dope can be used as well especially with the affordable G-10/11 electric breaks we demonstrated in both 3/8" and 1" sizes in the coil test facility.

Geoff