Beam Propagation for bKAGRA Phase 1 with flat ETMs KAGRA Chief Meeting Feb 20, 2017 Beam Propagation for bKAGRA Phase 1 with flat ETMs Yuta Michimura Department of Physics, University of Tokyo

Summary Real ETM mirrors might not be available on time coating was to start in February, but will start in April at best case We might have to use flat ETMs If flat ETMs are used, beam radius at BS/PR3/SR3 will be ~171 mm, which is ~31% loss at BS (φ370mm, 45 deg) ~44% loss at PR3/SR3 (φ220mm, 0.686 deg) also, note that GVs in arms have φ100mm or φ150 mm for comparison, in iKAGRA, returning beam at BS (φ74 mm CA) had 76 mm radius, which is ~ 62% loss Beam radius at AS port will be ~ 8 mm we will need 3 inch in-vac mirror for steering AS beam to in-air optical table

bKAGRA Phase1 Layout 3 km cryogenic Michelson GW signal ETMY RoC 1.9 km Φ 220 mm PR2 RoC -3.0764 m Φ 250 mm IMMT2 RoC 14.005 ± 0.238 m Φ 99.75 mm 3023.335 m PRM RoC 458.1285 m Φ 250 mm BS RoC flat Φ 370 mm ETMX RoC 1.9 km Φ 220 mm IMC 5.017 m 14.7615 m 3.105 m PSL 11.0661 m 0.5 m 3026.665 m 6.290 m PR3 RoC 24.9165 m Φ 250 mm 15.7638 m SR2 RoC -2.9872 m Φ 250 mm IMMT1 RoC -8.910 ± 0.0029 m Φ 99.77 mm 15.7386 m 11.1115 m SR3 RoC 24.9165 m Φ 250 mm GW signal

Beam Radii with RoC1.9 km ETMs radii to arm / from arm ETMY RoC 1.9 km Φ 220 mm 68.04 mm PR2 RoC -3.0764 m Φ 250 mm 4.61 / 5.91 mm IMMT2 RoC 14.005 ± 0.238 m Φ 99.75 mm 4.53 / 4.74 mm PRM RoC 458.1285 m Φ 250 mm 4.49 / 4.99 mm BS RoC flat Φ 370 mm 37.44 / 48.56 mm ETMX RoC 1.9 km Φ 220 mm 68.15 mm IMC PSL REFL ~ 13.20 mm PR3 RoC 24.9165 m Φ 250 mm 37.96 / 49.15 mm SR2 RoC -2.9872 m Φ 250 mm 5.91 mm IMMT1 RoC -8.910 ± 0.0029 m Φ 99.77 mm 2.56 / 4.47 mm SR3 RoC 24.9165 m Φ 250 mm 49.15 mm GW signal ~ 5.21 mm

Beam Radii with Flat ETMs radii to arm / from arm ETMY RoC flat Φ 220 mm 68.04 mm PR2 RoC -3.0764 m Φ 250 mm 4.61 / 19.55 mm IMMT2 RoC 14.005 ± 0.238 m Φ 99.75 mm 4.53 / 0.83 mm PRM RoC 458.1285 m Φ 250 mm 4.49 / 4.39 mm BS RoC flat Φ 370 mm 37.44 / 171.02 mm ETMX RoC flat Φ 220 mm 68.15 mm IMC PSL REFL ~ 31.41 mm PR3 RoC 24.9165 m Φ 250 mm 37.96 / 171.56 mm SR2 RoC -2.9872 m Φ 250 mm 19.55 mm IMMT1 RoC -8.910 ± 0.0029 m Φ 99.77 mm 2.56 / 7.21 mm SR3 RoC 24.9165 m Φ 250 mm 171.56 mm GW signal ~ 8.18 mm

Input Stage

Arm (RoC1.9km ETM)

Arm (Flat ETM)

Output Stage (RoC1.9km ETM)

Output Stage (Flat ETM)