The figure shows a revised version of the pumpdown curves. The variation of the pressure with time for BSC 6 is still
slower than 1/t. A least squares fit to the curve gives a dependence of 1/t^0.865 which as indicated before implies some diffusion
of water from inside of materials, the phenomena is not just desorption from the surface. The plastic in the cables or the viton could be 
the source. The pumpdown curve for BSC8 is the first formal continuous pumping of this chamber which occured about 20 days after the initial
roughing. John Worden made a time line graph of the various conditions of BSC8 in a prior entry. If you are interested in understanding
the reasoning for the curve plotted here look at John's time line. In the initial pumping of this chamber a broken feedthru was discovered 
and replaced. The chamber was being pumped or living in dry backfill gas for those twenty days. For water outgassing from the surface it 
should not make a great deal of difference whether the water is removed by a purge gas or by evaporating into a vacuum. Clearly a vacuum is
better as there is less repopulation of the surface, but the purge works too with some higher probability of repopulating depending
on the remaining humidity in the gas. The conclusion I draw from this is that the BSC6 is not so anomolous and that we will need
to take steps to reduce the water in the ISI for the next installations using techniques such as continuous dry purges in bags around the
ISI with the ability to gain entry for adjustments etc. If we want now to speed up the time to a pressure of 10^-7 torr it would take a
low temperature bake, say to 50C. The danger to the instrument associated with such a bake and schemes for carrying it out are being studied
at the moment.