1. New iKAGRA Configuration Yuta Michimura Department of Physics, University of Tokyo 11th KAGRA F2F (University of Tokyo) Feb 6, 2015

2. Original iKAGRA Configuration 2 2938.35 m FI from IMC REFL AS TRY TRX IMMT1 IMMT2 PR2 PR3 BS iETMY iITMY iETMXiITMX iBRT 2938.35 m iBRT 3 km FPMI at room temperature Type-Bp for ETMs and ITMs

3. 3 km Michelson at room temperature Fixed Type-Bp for ETMs No iBRT for TRX/TRY (we still need cameras for alignment) New iKAGRA Configuration 3 2991.73 m FI from IMC REFL AS IMMT1 IMMT2 PR2 PR3 BS iETMY iETMX 2988.40 m iBRT 3.33 m asymmetry

4. move PR3 and ETMs (since ITM wedge is gone) IMMT1 RoC = 19.5 ± 1 m flat IMMT2 Optical Layout Tweaks 4 FI from IMC REFL AS IMMT1 IMMT2 PR2 PR3 BS iETMY iETMX iBRT 5.3 mm 8 mm

5. Type-Bp to fixed Type-Bp Suspension Change 5 Type-Bp Fixed Type-Bp standard filter bottom filter intermediate mass test mass

6. Original iKAGRA Sensitivity 6 quantum seismic frequency 3 km arm silica 290 K 1W at BS Finesse 209 Type-Bp Perfect FSS with CARM (CMRR=1/100) 10 -4 Pa gas susp thermal

7. New iKAGRA Sensitivity 7 quantum no arm cavity seismic worse suspension frequency no CARM susp thermal 3 km arm silica 290 K 1W at BS Michelson Fixed Type-Bp Perfect FSS with IMC (3.33 m MICH asymmetry) 10 -4 Pa gas

8. Summary of Differences 8 Original iKAGRANew iKAGRA Configuration3 km FPMI3 km Michelson Temperatureroom temperature Test mass suspension Type-Bp (triple pendulum) Fixed Type-Bp (double pendulum) Sensitivity at 100Hz2e-22 /√Hz2e-20 /√Hz 3 km layout testwith arm cavitiesno arm cavities Frequency stabilization as far as CARMas far as IMC iBRT for ETM transnecessaryunnecessary

9. Appendix 9

10. Suspension Performance 10 Type-Bp (Original iETM) Fixed Type-Bp (New iETM) Type-C (IMC)

11. Frequency Noise 11

12. Frequency Noise with IMC Servo 12

13. Frequency Noise with CARM 13