Chandra R., Gerardo M., Kyle R., Tyler G.

Last week we had removed the retired/outgoing (22 years in service!) iLIGO Edwards Main Turbo Pump (a.k.a. the "Vertex MTP") and installed the new, incoming, Pfeiffer Turbo Station in its place.  I installed the 208VAC service cord this morning and ran the new turbo pump (backed by its local scroll pump) for most of the day (1 x 10-8 torr after a few hours). 

Chandra R., Kyle R.

We vented the Vertex this morning to facilitate the replacement of the HAM6 septum viewport.  The measured dewpoint of the air entering the Vertex was -37C.  Later, as the septum viewport crew finished ahead of schedule, we were able to switch backing pumps such that the new turbo was backed by the iLIGO Edwards QDP80 and then began rough pumping the Vertex (only for 1 hour at the end of the day - we will resume in the morning).  I noted that the measured dewpoint of the ~ 1 1/2 psi "blow down" air exiting the Vertex prior to pumping was also -37C.  The observation that the blow down air dew point was unchanged from that of the initial air at the start of the venting is of interest.  Typically, the dew point of the blow down air is much "wetter" than that of the initial vent air due to chamber door removal(s) and in-chamber incursions by people.  In the absence of chamber door removal(s) and in-chamber incursions, the air stayed dry as you would expect - brilliant!