Venting the cryo chamber

A suggested sequence for venting the cryo chamber is as follows:

1. Close V9i, V10i and V11i.
2. Remove your sample, and warm up the anticontaminator (if installed). To remove the sample, see below.
3. Turn off the Penning gauge by pressing the ``Emis'' button on the controller that is located in the rack under the cryo table. The cryo interlock will take care of cutting the power to the Penning gauge and the piezos at the appropriate pressures.
4. Close the gate valve to the ion pump, by pushing the ``Ion Pump Valve close'' button on the cryo interlock front panel. The interlock will close this valve as the pressure in the chamber rises, but it is good practice to treat the ion pump as gently as possible.
5. Fill the styrofoam cup at the venting lines with LN$_2$.
6. Close the valve between turbo station and chamber, by pushing the ``Turbo Valve close'' button on the cryo interlock front panel.
7. Turn the turbo pump off. It will then vent itself with boil-off nitrogen.
8. Slowly open the up-to-air valve (VAT, black handle, Valve E) on the outboard side of the cryo chamber to vent with boil-off nitrogen. Watch the pressure on the convectron gauge (on the cart under the air table). Between 1 torr and 100 torr, the pressure should rise only very slowly, to avoid mechanical stress on the SiN entrance window. Above that, the conductance of the venting line limits the venting speed.