Alexa, Keita, Evan

Alexa and I performed our usual loss measurement: P_on = 1257(5) ct, P_off = 1304(2) ct, giving a loss of 140(16) ppm in the Y arm.

Next, we wanted to assess the amount of scatter in the arms by looking at the amount of IR light on the baffle PDs. With the arm locked to IR and the IR WFS running, we misaligned the green light and looked at the ITM/ETM baffle PDs, both with their 40 dB and 60 dB gain settings. Then we removed the IR from the arm by unlocking the modecleaner and misaligning PR2. This allows us to get the dark counts on the baffle PDs.

Relevant times are as follows, all on 2015-01-09 UTC:

• 18:25:15 to 18:26:15 – Y arm locked on IR, PD gains are 40 dB
• 18:27:35 to 18:28:35 – Y arm locked on IR, PD gains are 60 dB
• 18:31:10 to 18:32:10 – no IR, PD gains are 60 dB
• 18:33:00 to 18:34:00 – no IR, PD gains are 40 dB

We're still working on analyzing the data.