In Reply to: Cryo skin effect? posted by Rob Thomas on November 9, 2004 at 13:56:01:
Rob: ""Does this relate to cryo treatment, crystal lattices and such?""
Kinda It's because the resistance of copper goes down with temperature. Has to do with electron scattering, the electron interactions with the lattice. The mean free path of the electrons tends to increase as the temp goes down, from a room value of 3 times 10 -6 cm to about 4 to 10 cm.We have a magnet suspended in a dewar, cooled down to 4.5 Kelvin in liquid helium..We are gonna run it at about 50 to 100 Hz, at up to about 300 amps. The feedthroughs are solid copper, bout 1/2 diameter, and it will skin as a result of the increased conductivity..we estimate it will mean the outer 40 mils (.040 inches) of the copper will actually be handling the current.
Rob: ""Has cryo treament been demonstrated to have aresidual influence on skin effect?""
We've been running cryogenic magnet tests for about 20 years here, and nobody here has ever seen that happen, under any condition, with any metal ever put into the dewar..silver, alum, copper, nada...never.And the RF guys, with the niobium lined superconducting rf cavities for beam acceleration also find nuttin..
Course, somebody with more experience may be able to report sumptin...
Cheers, John
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Follow Ups
- Re: Cryo skin effect? - jneutron 11/9/0414:19:01 11/9/04 (6)
- Re: Cryo skin effect? - Rob Thomas 14:35:31 11/9/04 (5)
- Re: Cryo skin effect? - Steve Eddy 16:27:03 11/9/04 (4)
- need a job Steve?.. - jneutron 05:51:22 11/10/04 (2)
- Sure! - Steve Eddy 11:58:08 11/10/04 (1)
- Don't bother applying.. - jneutron 06:52:10 11/12/04 (0)
- Good stuff. Thanks. (nt) - Rob Thomas 21:49:04 11/9/04 (0)