Last night, undamped transfer functions of H1 TMSY were ran (Phase 3a) with the ISI damped. 3 different drive amplitudes were tried to see if cables are not adding non linear effects.
- The first attachement shows the comparison between the three drives
In orange excitation amplitude is 10000, in black drive is 150000, in pink drive is 20000. TF is consistent throughout the drives.
- The second attachement shows how one of this measurement compares to TF taken last year on TMSY, when it was in chamber, under vacuum.
Differences in frequency of resonnances can be seen in the L V R P degrees of freedom:
First roll mode at 0.68Hz splits in three modes 0.68Hz 0.72Hz and 0.79Hz
First Pitch mode at 0.74Hz splits in two modes at 0.72Hz and 0.79Hz
First Vertical mode at 0.69Hz splits in three modes at 0.67Hz 0.72Hz and 0.79Hz
Second Long mode at 0.74Hz (pitch coupling = first pitch mode) splits in two modes at 0.72Hz and 0.79Hz
All differences can certainly be explained by the change of cable routing when moving cartridge from BSC6 to BSC10. (For details on how the current routing looks like see pictures on alog 11021). Since the actuation is working properly, and the suspension still provides passive isolation above the resonnances, it seemed acceptable to move on with installation.
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The third attachement shows how the "first article" measurement (TMSY) is different than "production". This is to check if the damping loops can stay "generic". Since the loops are simple velocity dampers with low Q boost around main resonnances, it's ok.
- The last attachement shows how the damping is doing, with a spectra comparing undamped/damped
