The muffle tube provides the mechanical interface between the furnace and the experiment sample and provides a level of sample containment should the fused silica ampoule rupture.
All instrumentation passes through the threaded interface located at the bottom of the tube.
At the top of the muffle tube is a narrow tip which provides sample support during launch and reentry. During the experiment, the tip is withdrawn from its holder, and is replaced after solidification. The fused silica ampoule contains the PbSnTe and is divided into three segments, one for each of the three boules of the material which are sealed under high vacuum. The thermocouples are sheathed, type K with MgO insulation and Inconel sheaths. They are laid into groves cut into the wall of the fused silica tube.