The pressure is dropping as 1/t^0.87. There is still water diffusing out of
materials. It should be safe to open the gate valve to the trap and the beamtube
for periods of hours. If the pressure drops below 2 x 10^-8 torr when the chamber
is exposed to the trap and the beamtube, the gate valve can be left open permanently.
The plot shows the current trend.