How It Works[edit | edit source]

A resistance-wire heating element is wrapped around the upper cup-shaped part of an aluminum thermal conduit.

In the VTC, the cup encloses a quartz coldfinger. A copper wool packing is added inside, to provide excellent thermal contact between the cup and the coldfinger. In operation, the bottom part of the conduit (the cooling rod) is submerged in liquid nitrogen (LN). Because aluminum is an excellent thermal conductor, the entire conduit tends toward the boiling point of LN, about -196 °C. The quartz coldfinger easily reaches temperatures well below -185 °C.

When powered, the heating element warms the cup to a controlled temperature. The rate of heat flow between the rod and the cup is limited by a restricted-diameter connection between them. This enables the coldfinger temperature to be maintained accurately and minimizes heat loss (wasted energy), turbulence in the LN reservoir, and LN consumption.