Investigation of the influence of suspended optic’s motion on LIGO detector sensitivity Sanichiro Yoshida Southeastern Louisiana University

The beginning.. LIGO E2E (H. Yamamoto) (1) Interested in comparing mechanical simulation of e2e and measurement (stack motion, mirror motion). (2) Need good seismic motion data, including correlation. SLU (Students) (1) Interested in studying dynamics of LIGO suspended optics. (2) Measurement and modeling at site - Good for undergraduates. SLU (S. Yoshida) (1) Background- Input optics implementation. (2) Interested in effect of input optics to LIGO performance.

Suspended optics on HAM table Suspension point Shadow sensor Suspension wire Shadow sensor Wire standoff Shadow sensor Safety stop Stiffener plate Suspension tower HAM (Horizontally Accessible Module) table

(1) field and optics (2) mechanical motions (3) electronics (4) input data (seismic motion, frequency noise, etc) Table top motion (displacement 3, rotation 3) = ground motion (6) x stack transfer function (6x6)  =(x 1 - x 2 )/L? E2e simulation: HAM table  x1x1 x2x2 Vibration isolation stacks

Model of transfer of the floor motion to optic Optic motion (Output) Floor motion (Input) T G->Ht HAM table motion T Ht->Sp  1 Suspension point motion T Sp->Op Measurement 1 Measurement 2 Measurement 3 E2e simulation

LIGO research group at SLU Undergraduate students Raghuveer Dodda (Physics/Computer Science major) Tiffany Findley (Physics major) Physics Faculty David P. Norwood (Optics) Sanichiro Yoshida (LLO, UF LIGO)

Contents MMT3 motion - dark port signal coherence HAM1 table YAW motion measurement Floor motion measurement E2e boxes for MMT3 Model suspension analysis at SLU * MMT3 (Mode Matching Telescope on HAM1)

MMT3 motion - dark port signal coherence

MMT3 on HAM1 Input optics. Different color represents different subsystems. Optical lever is outside vacuum on a pier. Mode Cleaner Mode Matching Telescope To IFO MC2 MC1 MC3 MMT2 MMT1 MMT3 From PSL HAM1HAM2 Optical lever

MMT3 motion and correlation to dark port signal Power Spectrum of MMT3 – peaks seen ~ 1.5Hz, where MMT 3 has no resonance Coherence between MMT3 motion and ASC_Q beam – peaks seen ~ 1.5Hz

MMT3/BS coherence to dark port ~1.5 Hz Both data taken at the same time when arms are fully locked. BS MMT3 1.5 Hz

MMT3/BS to AS_I/AS_Q coherence base line data Arms not locked due to train

Resonant frequencies MMT3 resonance pendular: Hz pitch:0.627 yaw:0.506 side:0.732 vertical:12.32 HAM resonance U - U: 1.5, 2.3 Hz V - V: 1.6, 2.8 Vert - Yaw: 7.2, 8.0 U: beam line V: transverse

HAM1 table YAW motion measurement

HAM table motion measurement by shadow sensors

Measured HAM1 YAW

Floor motion measurement

Corner station seismometer spectra (LLO) X (U) Y (V)

HAM1 accelerometer spectra X (U) Y (V)

Floor motion correlation measurement P1 P2P3 P4 P5 X arm Y arm Portable seismometer location Beam splitter LLO

Phase delay in y component along x arm x Standing wave due to reflection at HAM resonance? ~1.5 Hz HAM

Phase delay in seismometer signal y x x y

E2e boxes for MMT3

Free hanging mirror model (SUS3D.box) iput = motion of HAM1 at the location of MMT3 as calculated by the OSEM-method oput = x,y,z,xtheta,ytheta,ztheta of MMT3 (as a function of time) The PS of the output reveals peaks at: MMT3 Yaw: 0.5 Hz (MMT3 yaw peaks), (HAM1 peaks) [ m(mmt3,sun) = m(mmt3,ham1) + m(ham1,grd) + m(grd,sun). Since, there is no m(grd,sun) in the iput, we should not see any m(grd,sun) peaks in oput. ]

Results of SUS3D.box – the free hanging mirror MMT3 YAW (output) HAM 1 YAW (input)

Floor to optic model (MMT3.box ) This box takes floor motion as input and outputs table motion (=suspension point motion) and optics motion x Op (t) x G (t) T Ht->Op T G->Htp x Ht (t)

Model suspension at SLU

SLU model suspension (1) Mechanical Oscillator L m

SLU model suspension (1) mass Mechanical Oscillator

Ring-down measurement (1) Damping coefficient estimated for three conditions.

Frequency response (1) Damping coefficient from ring-down measurement used for theory.

SLU model suspension (2) Mechanical Oscillator Suspension Block Mirror Block Front ViewSide View

SLU model suspension (2) Mechanical Oscillator Suspension block Optical lever beam CCD camera

Setup for yaw/pitch motion measurement Optical lever Mechanical oscillator Suspended mass wire

Yaw/pitch motion measurement x y Optical lever beam spot

Sample optical lever signal

Ring-down measurement (2)

Frequency dependence (2)

Summary E2e simulation of suspended optics –Influence on IFO Floor to table top modeling –Supporting data taking Table top to optic modeling –Model suspension Measurement of seismic motions with correlation is very important.