- PMC loop set to ½ of the gain margin (1)
- PDH = 2.0 Vpp
- 9 dB Att_RF
- PMC_REFL_DC ~ 0,4 V once locked (2)
- Gain margin ~ 18 dB
Remarks:
(2) PMC_REFL photodiode is PSL_MELEC-1801-01 (3 mm), associated OptDensity = 0,64 (Tr = 0,224)
(1) Unlocks for Att_RF >18 dB / locked for Att_RF = 0 dB Att_RF
# Nichols and Bode plots
the gain is adjusted to get the UGF mid-way between low (~450 Hz) and high freq (9 kHz) instability zones.
As a result the ~ 1,8 kHz oscillation (*) will be part of the PMC error spectrum.
This is not an issue unless somebody complains
(*) 1,8 kHz structure in the Bode plot, part of the curve inside the circle 6 dB in the Nichols plot
