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!