cryostat

This term is highly specialized and belongs to the register of physics, chemistry, and materials science. It describes a specific piece of laboratory hardware designed for thermal stability at extreme lows, distinguishing it from a general freezer or refrigerator by its ability to maintain a precise, constant temperature over long periods.

In a technical context, the word is used to describe the environment surrounding a sample. Because it refers to a physical piece of equipment, it follows standard countability rules for laboratory apparatus.