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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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In Reply to: resistor cryo screening update posted by jneutron on July 10, 2003 at 07:00:26:
I posted the info because previously I had asked if anybody has experience with the reliability of these types of resistors through cryo temperatures. Figured somebody might find the info useful.The resistors are used in superconducting magnets in the voltage tap wires. Because the magnets store somewhere between 50 kilojoules and a megajoule, are perfect inductors, and run from 200 amps to 20 kiloamps; when they quench and we have to take the energy out quickly, we need to have large voltages across the inductor (the rate we can take energy out the leads depends on the voltage we can allow across the leads).
If a V-tap wire arcs to ground during this high voltage time, the wire will vaporize; and because there are cryogenic temps and pressures where helium gas is a conductor, the arc would proceed all the way to the magnet. The resistors prevent that.
Magnets cost between 100 Kilobucks to a tad over a megabuck, so we have to be very careful when we test them.The v-taps are the best way to measure what's happening in the magnet, so the resistors have to be reliable..
Hence, the "dunk", which I don't recommend anybody use, cause it's really hard on the parts. Only the best survive..
Cheers, John
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Follow Ups
- Re: resistor cryo screening update - jneutron 07/11/0306:22:30 07/11/03 (0)
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