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Anyone know how to thermally insulated wires from 4.2K temperatures?

  1. Jun 11, 2012 #1
    The wires are allowed to reach 4.2K but preferably slowly. They will be run alongside a helium transfer line. Before the helium runs the wires will be at 78K.

    I thought there would be products for this, but looking around the best I've found is insulation good down to 172 K (http://wire.thermalwire.com/viewitems/ure-cable-single-conductor-1093-176-c-to-150-176-c/icone-rubber-motor-lead-wire-600v-single-conductor? [Broken])

    Thanks in advance!
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Jun 13, 2012 #2


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    Your question isn't very well defined.
    You need to give us more info. Are the wires in vacuum or in air? Do they need to be in direct contact with the transfer line?
    If it is in air, is moisture/ice an issue?

    ANY form of insulation will increase the time it takes the wires to cool from 78K to 4.2K So what kind of time-constant are you looking for.
    The main problem here is that many materials that are used for thermal insulation at RT become brittle and can crack if you cool them. However, PTFE (teflon) and many other materials work well so you always just use something like that.

    If you just want to insulate the wires, just put some PTFE spacers (or even tubing) between them and the LHE line. If you want a more "high end" solution (which also works in vacuum) you can wrap them in superinsulation (metallized plastic form used in cryogenic applications, I think you can buy it from e.g. Oxford Instruments)
  4. Jun 13, 2012 #3
    Kapton works well down to lq. He temperatures. Such wires are sold by the usual suspects (Oxford Cryospares, Lakeshore, ...)

    Kapton insulated wires also work reasonably well in vacuum, so you can also buy them from the usual suspects...

    To avoid unnecessary heat transport, keep the wire gauge as small as possible, and maybe use manganin instead of copper wire.

  5. Jun 13, 2012 #4
    Your link is for wires that carry 23 Amps and more. The only thing reasonable to do with that much current at lq He temperature is run a superconducting magnet....
  6. Jun 13, 2012 #5
    You guys are awesome, thank you. The link I supplied was just something I had found, but I felt like I wasn't in the right neck of the woods.

    I'm not sure what the preferred time constant is in this situation; it's good to know that something is out there though. Now I'll have to do some work and figure out how the wires behave in the current LHe setup and if they will incur an extreme temperature change in the new one.

    The setup I'm looking into is running an LHe transfer line alongside some wires that are being used for measurements. Both the transfer line and the wires could be insulated.

    My question had turned into: is ANY insulation available that can withstand such temperatures, and it appears to be yes.

    Thank you both very much and I will report back with questions/comments.
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