[Enomoto, Nakano]

The PMC remote control has been recovered. Now the PMC continued to lock for several hours with remote control mode. 

What we did

1. cabling of the transmission PD

Because the interface board has been changed to the new version, we lost the channel for PMC-TRANS. We connected BNC cable from the D-sub - BNC connector chassis at IOO lack to PMC TRANS DC PD. This channel is connected to ADC_1_13, so the k1psl has been modified.

2. Stabilization of the PMC control loop

After we changed an interface board and closed the loop, saw the fast control signal got oscillated at 8Hz. The cross over frequency might be too high and we put the 7dB extenuator on the SLOW output port of the PMC servo. Then the control loop seems to be stabilized.

I'm not sure why the control loop suddenly got unstable. The fast gain and common gain of TTFSS change the whole gain and should not affect to the cross over frequency. I feel auto locker of PMC has some problem. It is very complicated and switch the slow loop on and off. Actually we don't use it and we will ask to Guardian about auto locking system, so I broke the auto locker loop of the k1psl. 

3. Gain optimazation

The CG and FG were set to 10 dB both and the UGF is around 3 kHz.

Other things

1. PZT oscillation

We found that the thorlabs high voltage amplifier excite the PMC PZT at 60 Hz. We turned the control loop off and saw the transmission power of PMC. Then the power started oscillation if the high voltage amplifier is connected. We tried to beat this oscillation by turning other instruments off but failed.