keita.kawabe@LIGO.ORG - posted 11:41, Friday 04 April 2014 - last comment - 13:49, Friday 04 April 2014(11176)
More EY PLL work (it fully works now). (Keita, Daniel)
Opened the PLL CM board chassis (S1002641) and Installed a notch filter daughter board S1300952 in the fast option slot. The notch frequency is about 290kHz now.
Put a timing comparator in the remote rack.
Recalibrated the DC diodes (fiber power, fiber wrong pol monitor, BBPD).
Auto locker worked with these things in place.
One odd thing was, when we started working the beat note was -40dBm or something, a big decrease from yesterday.
Then we started calibrating things, touched some steering mirrors to center the beam on DCPDs and such.
Then something happened, suddenly we're back to -10dBm beat note. We couldn't find out any obvious cause for this.
Power levels:
Fiber output is about 60uW.
About 3uW is sent to the fiber power monitor.
About 55uW goes to the PBS.
This morning 31uW was on the wrong polarization monitor PD (it was less yesterday).
About 24uW goes to 50:50 splitter and is combined with Prometheus IR.
From the Prometheus, about 39mW is coming to the PBS.
HWP was adjusted to send 1mW to the IR monitor diode path and 38mW to the 50:50 splitter that combines Prometheus and fiber.
In the Prometheus IR monitor path that receives 1mW, there is a pick off mirror that throws away most of the power and send 10% or something to the actual PD, but I didn't measure the splitting ratio there.
The BBPD receives 19mW.