How to cool Ti body of Tyto SPM to 50mK? While probe and sample will be cooled via leads, cooling superconducting Ti body presents a problem. Thermal coupling via braid is insufficient at mK temperatures, both because of small effective cross section of the braid and small area of contact it would make when clamped to the body.
One idea is to make contact to solid Cu pieces over as much surface area of the body as possible (see pictures below). This Cu jacket would have inner layer, conforming to Tyto's surface (it will be sectioned into many pieces to distribute pressure uniformly) and outer layer, which will absorb the stress due to the whole assembly being pressed into the taper on mK cold finger. However stress on Tyto, particularly one caused by differential thermal contraction, will compromise the function of SPM. Alternative idea is to bolt Ag foil strips to Tyto on one side, and to mK cold finger on the other side.
This is the STM that we have used for several years at MIT. This system is currently running at room temperature, and will soon operate at 4K. Below are a few topography scans of a HOPG sample from this system.
Feb 5, 2014