Keita, Sheila, Camilla, Georgia, Daniel

• some DCPDs are now working
• we can lock the OPO in green
• we aligned the CLF to the OPO and found a co-resonance
• the pump fiber chain transmission is 39%
• there is a bad connection with the filter cavity green sensing flipper on SQZT0

This morning Georgia moved G:M2 to unclip the pump reflected beam on the top periscope mirror.  We had marked the location of the beams on the SQZT7 panel before the fiber swap and pump alignment fix yesterday, so looked at the location of the pump beam relative to it's mark this morning before making the adjustment.  The beam was only a few mm from the marked location when we started low and to the -X direction.  Georgia moved the beam past the original position in the +X direction, so that the beams will be more separated on the periscope top (to make fitting the beams on different periscope mirrors easier, see photos 60137 for how close they were). I quickly realigned the path the the pump REFL diode.  Georgia and Keita are now working on realigning the SK path.

We were able to lock the OPO in green using the Thorlabs MDT694 PZT driver.  We locked with positive input polarity on the common mode board, 7dB of gain, 1 common boost (0/10Hz p/z), 1 slow boost (4/400Hz p/z), and the compensation filter in the slow path (4Hz pole).  We added the compensation filter because the MZPZT driver has a 1/10Hz pole/zero and a 400H pole formed from the PZT +output impendance. With these settings we measured a ugf of 3kHz and 20 degrees of phase margin, later I reduced the gain to 3dB input gain to reduce oscillations.  There is a large peak at 1kHz in the error signal, but the lock was stable enough that this may be good enough for now. 

We moved the CLF shutter trigger diode (a PDA 100A) on SQZT7 to monitor the beam diverter reflected beam, instead of alinging the dim beam all the way to the homodyne. Georgia used this signal to fix the alignment of the CLF/seed into the OPO.  With the cavity scanning, I adjusted the OPO temperature to line up the IR and green resonances, at 49.4 C. With the OPO locked, the corresonance is around 49.42C.

There was quite a lot of work on the DCPDs today, I will leave it to someone involved in that to alog.  The CLF and pump fiber rejected polarization PDs are working and aligned, so Daniel rotated the wave plates to minimize the rejected pump power.  This was actually a large improvement in the power to the refl diode, so we will need to adjust the PDH gain and the co-resonance temperature tomorow to account for that.

We checked the transmision of the pump fiber chain: 3.75mW input to fiber port on SQZT0, 1.45mW after the polarizer in HAM7, so 39% transmission.  There is a 50/50 BS for the SK path in the reflected beam, and 0.65mW arriving at the periscope and pump refl PD on SQZT7.

This morning we had to move the filpper out of the filter cavity green sensing fiber path on SQZT0, because it would not flip up.  He thinks there is a bad connection somewhere; the behavoir changed after switcing which feedthrough was used.  This is not fixed yet.