From: utzoo!decvax!yale-com!leichter
Newsgroups: net.physics
Title: Re: long superconductors
Article-I.D.: yale-com.591
Posted: Sun Dec 26 11:25:52 1982
Received: Mon Dec 27 05:46:48 1982
References: sri-unix.4923

The only problem with the argument is that I can make it the other way just
as well:  I only need to HEAT one end to get the whole think up to the maximum
temperature!  So heat flux through the thing is very much an issue:  All heat
taken up anywhere along the conductor must flow down it and be "taken out" at
the cold end.  The amount of heat energy involved is going to be huge; it's
not easy to insulate against the difference in temperatures involved.  (A good
Dewar will hold liquid helium for quite a while, but consider its surface to
area ratio, and the total surface presented, compared to that of a long wire.)
Pumping liquid coolant along the thing essentially distributes the heat removal
problem to the point where you can handle it locally.
							-- Jerry
						decvax!yale-comix!leichter
							leichter@yale