1 Fumiko 2006 Elba Meeting Current status of the 4m RSE

2 Introduction Control Scheme Experimental Parameters Experimental Setup Current Status Schedule In This Talk

3 To demonstrate LCGT’s control scheme to lock the RSE The Goal What Is 4mRSE A broadband (tuned) power-recycled RSE interferometer, prototype of LCGT interferometer, built inside NAOJ’s campus Introduction

4 L+ = (Lx + Ly) / 2 L- = (Lx – Ly) / 2 lp = (lx + ly) / 2 l- = (lx – ly) / 2 ls = (lsx + lsy)/2 Degrees of Freedom lsy PRM SEM LASER lsx ly lx Ly Lx BS ITMxETMx ITMy

5 Control Scheme PM(f1) AM(f1) l- LASER Diff.(f2-f1) ls lp SEM PRM BS L- L+

6 Michelson Asymmetry Recycling Cavity Lengths Sideband Frequencies Other Parameters Experimental Parameters

7 Michelson Asymmetry dl AM reflect from Michelson PM transmit through Michelson dl = (ly – lx)= 3.5m dl /λ f PM (17.25MHz) f AM (103.5MHz) 1/2 3 lx PM AM SEM PRM ly PM AM SEM PRM ly lx

8 Recycling Cavity Lengths Length P ower R ecycling C avity 4.34 m S ignal E xtraction C avity 4.34 m f2 Carrier Transmission curves of PRC and SEC Carrier PRC SEC f1 (17.25MHz)(103.5MHz) f1 (17.25MHz)

9 Sideband Frequencies f2= n × f1 n = 6 f1f2Ca. Beat between carrier and f1 Beat between f1 and f2 Mix if n= 2 f2 When n = 6 4 th order of the f1 sidebands…small enough Clear beat signal between f1&f2 f2 f1Ca.

10 Other Parameters Arm finesse122 Power recycling gain15 Arm length4.05m

11 Mach-Zehnder To avoid SBs of SBs f2 Ca. f2 Ca. f1 f2 f1 EOM f1f2 Ca. Sidebands of sidebands f1f2 Ca.

12 Current Status FPMI Locked(single demodulation) Redesign of a Suspension System MZ Lock (w/o AM EOM in) Ready for Double Demodulation

13 FPMI Locked PM(f1) L+ l- LASER L- Time(sec ) Power Inline FP Arm Perpendicular FP Arm Michelson

14 Redesign of a Suspension System Q of Picth 15 Q of Yaw 7 l d = l m Damping magnets glued ldld lmlm Actuator magnets close to damping magnets Glue free Far from damping magnets Coupling between Pitch and Yaw fixed Uses Eddy Current Damping Cu mdmd m m d = m m

15 Schedule Lock Michelson on double demodulationJuly August September October November December 2007 Lock Arms with L- from Dark Port Put in Power Recycling Mirror Lock PRFPMI Put in Signal Extraction Mirror Lock full RSE Noise characterization, Test Delocation Scheme

16 Have locked FPMI on single demodulation Redesigned the suspension system Mach-Zehnder locked Double Demodulation getting ready What Has Been Done Control Scheme Single modulation and demodulation for FP arms Double modulation and demodulation for the central part of the IFO Summary