MSC recent activities COMM Cascina 5 Feb 2007

EM-MSC Commissioning-oriented running activity Operation and interface updates Hardware checkup and specific tests MSC performance VS disturbance

EM-MSC Main topic of this report: MSC disturbance rejection strategies Global Inverted Pendulum Control Vertical Damping implementation Sensor blending and Hybrid filters suspended done

EM-MSC Winter issues: STD scheme and blending used until Dec 2006 ACC LVDT + HP LP cross IP f crossover = 50 mHz Compromise between: 30 mHz (wind disturbance through ACC) and 70 mHz (  seism disturbance through LVDT) Note: since 2005 we have much larger margin on number of digital filter coefficients in the DSP and speed.

EM-MSC Winter issues: hybrid filters (W2S tuning with no download) ACC LVDT + HP  LP  IP + HPw LPw mix cross mix =0.5 : “medium” attenuation of  seism noise oldnew mix =0 (wind): not worse than old filters against  seism + tilt noise attenuation below 50 mHz oldnew mix =1 (  seism) : “strong” attenuation of  seism noise with slightly worsened tilt noise attenuation. oldnew How much is it enough ?

EM-MSC Winter issues: test of hybrid filters in use versus ITFstep12 Calm period mix= Hz, (IP notch) Pitch excitation (payload mode) yaw bump (due to large zM correction) Large zM due to tilt disturbance through accelerometers 3 mechanisms (at least): F0_z zCorr, F0_z  x, F0_z  y

EM-MSC Winter issues: WSR7, heuristic threshold for mix adjustment wind (mix 0)sea (mix 1)hic sunt leones

EM-MSC Winter issues: trend data: wind, no-sea Affordable situation using mix tuning ( 0) or GIPC mm mm mm mm mm mm

EM-MSC Winter issues: trend data: sea, no-wind Affordable situation using mix tuning ( 1) mm mm mm mm mm mm

EM-MSC Winter issues: trend data: 200 mHz bump uneasy situation using mix tuning only ( 0.5), GIPC to be studied mm mm mm mm mm mm

EM-MSC Winter issues: trend data: All, problems ! Need to assess more quantitative specs for HP/LP features VS weather conditions exploiting the mixing range (0-1). mm mm mm mm mm mm

EM-MSC F0_z zCorr : towards a more detailed model based upon measurements - Mechanism of zCorr contamination through LVDT noise re-injection. result: reconstructed zCorr matches observed zCorr We can consistently trust zCorr noise re-injection model (closed loop TF with different blending shapes and mix) V/sqrt(Hz) Hz

EM-MSC Winter issues: IP legs TF have to be properly considered to obtain consistent model Hz,Q=0.5). ACC LVDT HPLP mix cross IP seism In order to work-out a specs for LVDT cutoff we have to separate direct effect of microseism at the IP top level with respect to LVDT sensing. CL TF reconstruction versus measurement helps to attain a trustable model.

EM-MSC F0_z  x : towards a more detailed model based upon measurements Calibrated  x disturbance due to z mirror (and then to F0_z).

EM-MSC LP/HP optimization, given the standard actual corrector (cross) CL TF ACC LVDT HPLP mix cross IP seism mix=0.70 mix=0.90 mix=0.95 mix=1 LP/HP ratio versus CL TF Hz Two regions can be distinguished: A) LP/HP ratio plays a role attenuating LVDT sensor disturbance (  seism) B) No effect of LP/HP attenuation LVDT noise projection into zCorr 1) Hz V/sqrt(Hz) HPLP performance and mix optimized, limited-band gain enhancer tested.

EM-MSC WSR7 => WSR8 optimization under test Hz  ms -2 LP: anti-  seism previousWSR7 WSR8 accel. comparison

EM-MSC WSR7 => WSR8 optimization under test Hz  ms -2 HP: anti-wind (  previousWSR7 WSR8 LP: accel. comparison note: cleaner blending allows to re-tune HP to improve tilt re-injection

EM-MSC WSR7 => WSR8 overall tuning (mix 0-1) LP/HP mix 0 => 1 wind => sea mix 1 => 0 sea => wind A) assessing how much it is enough to enhance LP/HP to beat tilt re- injection is not easy. B) more data needed in windy-only conditions… C) no significant role played around the crossing frequency.

EM-MSC F0_z  y : Non-linear (quadratic) effect Three solutions : - zCorr reduction (mix 0); - digital compensation (not done yet),; - re-allocation of zCorr to input mirrors marionette (tested).

EM-MSC Hierarchical: zCorr reallocation to input mirror A reallocation mix option is available for WSR8 in case of wind (reduction large zM by a factor 2 lightens gain request to AA).

EM-MSC Hierarchical: zCorr reallocation to input mirrors (0.5, step1)

EM-MSC Conclusions: Provided that vertical damping is enabled and high gain AA filters are running and significantly improving the overall sensitivity. A more quantitative criterium to improve sensor blending and hybrid filters has been developed. We are close to “alpize” the mix parameter. More data and experience in windy conditions will help to design tilt noise reduction. It is not easy to work out a universal strategy valid if wind and  seism appear together are very strong. In order to limit anti-wind noise re-injection and request to AA marionette re-allocation has been enabled. Times are reasonably mature to restart GIPC studies. In parallel Siesta simulation of tilts is starting (G.L.).

EM-MSC V-damp ON/OFF one-by-one and OFF/ON All ALL OFF ALL ON O-B-O OFF O-B-O OFF No crucial Improvement during OBO Test. Clear Improvement All OFF/ON Relationship with Angular fluctuations