We swap the PD_PMC_<2018 (1mm diam) used for the PMC lock until now with a PD_PMC_>2018, 3 mm diam. (The latter was originally a spare for the IMC).
The purpose is to be less sensitive to possible beam displacement on the PD (larger PD)
PD_PMC_>2018 does not have a 28 MHz notch as PD_PMC_<2018.
PD_PMC_<2018: R_DC = 1000 ohm, R_AC = 3100 ohm
PD_PMC_<2018 is powered (+/-24V) with a flat 5 pins connector
PD_PMC_>2018: R_DC = 250 ohm, R_AC = 1250 ohm
PD_PMC_>2018 is powered (+/-15 V) with an EGO style 6 pins connector
PD_PMC_>2018 gives a signal with 180° extra phase wrt PD_PMC_<2018 !!
# PD_PMC_>2018 issues
we face some issue with while using PD_PMC_>2018: sine noise spread on the PDH signal ~ 2,2 MHz
This effect is present also when using PD_PMC_<2018 but with a level reduced by a factor ~4
It turns out it is linked with the 6-pins-connector EGO style. We short circuited inside the PD the 3 pins not used.
No clue yet.
The sine noise freq depends on the side bands freq as follow:
- f_mod_synthe = 14.230 MHz -> PDH has 500 kHz sine noise
- f_mod_synthe = 14.07 MHz -> PDH has 2 MHz sine noise
- f_mod_synthe = 13.90 MHz -> PDH has 3.5 MHz sine noise
rem.: f_mod_synthe: freq delivered for the injection lock and PMC lock
Comments to this report:
cleva - 8:24 Thursday 22 March 2018 (40860)
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