Specimen warming

When warming a previously cold specimen, for example to freeze-dry it, one naturally creates a lot of water vapor in the vacuum chamber. The ion pump is not capable of handling this amount! In fact, even with the turbo running, the chamber pressure can go up into the mtorr range.

Specimen warming should be done in the following way:

1. Start up the turbo pump.
2. Valve off the ion pump.
3. When the turbo is at a good pressure (low $10^{-5}$ torr range), open the solenoid valve between the turbo and the chamber. Now that the chamber is being pumped by the turbo, the sample can be warmed up by turning up the current on the temperatur controller.