40m TAC, 10/13/05 1 Lock acquisition procedure towards detuned RSE Start with no DOFs controlled, all optics aligned. Re-align each 1.5 hours. ITMy ITMx BS PRM SRM SP DDM 13m MC 33MHz 166MHz SP33 SP166 AP DDM AP166 PO DDM

40m TAC, 10/13/05 2 Lock acquisition procedure towards detuned RSE DRMI + 2arms with offset ITMy ITMx BS PRM SRM SP DDM 13m MC 33MHz 166MHz SP33 SP166 AP DDM AP166 PO DDM Average wait : 1 minute (at night, with tickler) T =7% I Q 1/sqrt(TrY) 1/sqrt(TrX)

40m TAC, 10/13/05 3 Lock acquisition procedure towards detuned RSE Scripto-matic: ITMy ITMx BS PRM SRM SP DDM 13m MC 33MHz 166MHz SP33 SP166 AP DDM AP166 To DARM PO DDM AP166 / (TrX+TrY) CARM DARM + + Short DOFs -> DDM DARM -> RF signal CARM -> DC signal 1/sqrt(TrX)+ 1/sqrt( TrY) Discretionary: CARM -> Digital CM_MCL servo

40m TAC, 10/13/05 4 Lock acquisition procedure towards detuned RSE Reduce CARM offset: Go to higher ARM power, switch on AC-coupled analog CM_AO servo, using REFL DC as error signal. Locks somewhat stable at 85% of maximum power. ITMy ITMx BS PRM SRM SP DDM 13m MC 33MHz 166MHz SP33 SP166 AP DDM AP166 To DARM REFL DARM PO DDM AP166 / (TrX+TrY) G PR =5 Up next: RF control of CARM: REFL166 (POX/POY 33 ?)

40m TAC, 10/13/05 5 Ready for Transition to RF CARM

40m TAC, 10/13/05 6 Progress in last 2 months  Use CARM DC signal to creep closer to full arm resonance (signal goes away at resonance) »combined PRC and arm gain as high as 60, 85% of the way to peak, corresponding to offset of 8 pm, assuming arm losses of 200ppm (inferred).  Progress due largely to improvements in loop filtering, to obtain more gain and reduce noise  Also significant improvements in automation of lock procedures.  all DOFs diagonalized (3x3 + 2x2)  Lock is lost because of large frequency noise (presumably)  Effort to reduce frequency noise using CM servo »digital CM servo to MC works well »analog servo using DC signal seems to work, RF under development  Much effort to reduce frequency noise  Noise may be coming from in-vac PZTs