Chamber Interior
Look Familiar? Yeah, it really was a microwave oven at one time. The cooling is supplied with a cylinder of liquid CO2. That's frost on the heater grill from a cold run that just finished up.
The CO2 is squirted through a very small copper tube. The first time it cycled on, it almost blew itself off the table! I had to squash the tube down to a pin hole size to keep it from taking off.
The heater is controlled by the temperature controller via a solid state, zero-crossing relay.