Holding time

The modified LN$_2$ filling procedure has solved the vacuum loss problems experienced when filling and spilling LN$_2$. Also, the procedures of baking and mounting the getter have been improved, such that the pumping can start with a very hot getter inside the cryostat. The latest closing showed very good vacuum results during the pumping, but an unfortunate event of total loss of power turned off the vacuum pump and caused a sudden loss of vacuum which rapidly recovered probably at the cost of saturating the getter. The conclusive test of the cryostat behavior when stored with PTR cooling only is therefore still pending the next opening of NOTCam.