TMSY damping has been tested (before changing anything...), and works fine, see the attached spectra : 2013-04-30_Damped_vs_Undamped.pdf.
If the TMSY seemed to move a lot compared to the ETMY, it might have been due to an electronic issue. After Richard power recycled susb6 IO chassis and front end at the end station, the intriguing peak at around 1900Hz that was probably causing our suspicion suddenly disappeared. See the pink spectra on 2013-04-30_ETMY_vs_TMSY_NoiseCheck.pdf representing OSEM input signals of TMSY, before rebooting chassis vs blue spectra, after rebooting. This peak was also present for the ETMY but much lower in amplitude. See brown before reboot and red after (eg : last page of pdf). The spectra also shows that the low frequency noise floor is lower after the reboot...
more investigation to come...
The TMSY noise is very mysterious. It first appeared on 26th March when we were doing DC power supply work. It then apparently disappeared briefly on 1st April (one day before the site power outage, there was no accompanying reboot or restart at this time). After the site power outage is remained until today when the IO Chassis were power cycled. It only appears on the first adc of h1susb6. We will investigate this further when we get an opportunity to reboot/power cycle this system.