Using the PT-410B vacuum gauge, we looked at the pressure in End-Y volume since its pumpdown began in early June 2012 (see attached plot). The first ~10 days is before the gate-valve that opens to the cryo pump was opened. Opening to the cryo pump reduced the pressure by a factor of 10. The start time for the plot (i.e., the offset that we subtracted from the time stamp) was adjusted (at the 0.1 day level) by hand so that the pre-GV opening segment was a striaight line in the log-log plot.

The two black lines are by-eye fits to the pumpdown curves. The slope of the first segment is 1/t^{0.68}; since the GV opening, the pumpdown is a little faster, at 1/t^{0.88}.

(Matt E, Peter F)