Setupof the sublimation experiments. Panel A: cylindrical vacuum sublimation chamber with two observation windows. One is located on the top and one on the lateral side of the chamber. In the configuration shown, the light enters the chamber from above. Panel B: view through the lateral observation window into the inside of the vacuum sublimation chamber. The sample holder is firmly attached to the cuboid cooling shield. The object visible inside the cooling shield is the sample insolated from above. The green cables in the chamber belong to the different temperature sensors that monitor the temperature of the sample and the experimental setup. A camera is directed at the sample from outside.