We are leaving the PLL as it is locked in order to see the long term stability. And we will check the results in early morning of tomorrow.
DO NOT disturb our PLL !!
(what we did)
After Mott left, Matt and I started to put feedback signals to the temperature control of NPRO.
During doing some trials Matt found that NPRO temperature control input has an input resistance of 10kOhm.
Then we put a flat filter ( just a voltage divider made by a resistor of ~300kOhm and the input impedance ) with a gain of 0.03 for the temperature control to inject a relatively small signal, and we could get the lock with the pzt feedback and it.
In addition, to obtain more stable lock we then also tried to put an integration filter which can have more gain below 0.5Hz.
After some iterations we finally made a right filter which is shown in the attached picture and succeeded in obtaining stable lock.
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