Last stage SA F7 monitor/control Passaquieti Roberto University of Pisa & INFN-Pisa KAGRA-VIRGO Joint Meeting 18th Apr. 2016

SA Filter-7 monitor/control: origin/specs The Filter-7 (F7) monitor/control was first introduced in Virgo in 2003 after the Superattenuators (SA) installation/integration (initially not foreseen) Initial Virgo commissioning experienced serious problems with the SA setup monitor and control Tight constraints with frequent mechanical contacts Hard damping of the LF SA modes ( 16-30 mHz) excited by the Locking action forces The Virgo monitor/control architecture Specs: Operation in HV Precision (~ 0.1 mm, ~ 0.1 mrad), long term efficiency and reliability Longitudinal X, Z and yaw (ThY) d.o.f. monitor/control 3 horiz. LVDTs (Sens. ~ 130 mV / mm, noise spectr. 10 -8 m / Hz) sharing the secondary winding with a collocoted constant gradient Maxwell magnet-coil actuators Vertical Z d.of. On board LVDT measuring the vertical displ.of the floating filter “crossbar” (sum of all 6 SA filter LVDT s) (Sens. ~ 570 mV / mm, noise spectr.10 -7 m /  Hz) Angulat pitch (ThX) and roll (ThZ) High precision and HV campatible bi-axial ball tiltmeter (Res.= 0.1 microrad)

Virgo F7: mecanical constraints z x y Virgo F7 working point constraints: longitudinal X, Z d.o.f.: < ± 4 mm vertical Y : < ± 7 mm angular x< 3mrad, z < 8 mrad,y <10 mrad

Virgo F7: damping scheme  dashpot (F7ground) M  = -  d /d t 1 2 5 6 27 35 Virgo Marionette-Mirror TF Marionette-Mirror TF without damp. Marionette-Mirror Transfer Function with damping (F7-ground) =0.5 16 mHz 32 mHz

Virgo F7: actuator/sensor device Primary coil Magnet Secondary coils voltage/displacement: 0.20 mV/mm force/current:  = 73 mN/A Wide ±20 mm linear range dynamics to limit seism. noise

Virgo F7: monitor/control installation

AdV F7 monitor/control upgrade In AdV w.r.t. Virgo most of the F7 mechanical constraints have disappeared: the old IVC was removed from the test-masses towers Still the increased complexity of the F7-payload system required the upgrade of the F7 monitor/control. the actuation on the F7 body was extended to all 6 d.o.f. (Virgo x,z,thy) Following our experience we merged the requiered 6 sensors (3 hor.+3 vert.) and 6 actuators into 6 Virgo-like collocated Maxwell pairs of magnet-coils systems maximum force: 50mN; max noise ~ 1 nN/sqrt(Hz) @ 10Hz; low force gradient: < 1%/mm (to not reintroduce seismic noise);

AdV: New F7 monitor/control prototyping Space constraints induced a little re-scaling of the coil dimensions but still keeping a consistent dinamical range: axial clearance: 12 mm; radial clearance: a few cm; operating volume: 10x10x10 mm3; maximum force: 50mN; max noise ~ 1 nN/sqrt(Hz) @ 10Hz; low force gradient: < 1%/mm (to not reintroduce seismic noise). During the prototyping phase we tested new LVDT devices with a moving ferrite core in place of the moving primary coil: experienced a better sensing but with a much reduced linearity range. For the final set-up we came back to the Virgo F7 LVDT scheme: secondary Maxwell coils pairs fixed to groungd, with a the primary coil fixed on the F7 body, free to move inside the operating volume of the secondary windings. F7 monitor/control prototypes with ferrites

From prototype to final AdV design

Rendering of the AdV F7-payload system New IVC vessel F7 mon./contr. system