JGWT 1605595 Interferometer Design for b KAGRA Phase

JGW-T 1605595 Interferometer Design for b. KAGRA Phase 1 and Beyond Yuta Michimura Department of Physics, University of Tokyo for the MIF subgroup

b. KAGRA Phase 1 (-2018. 3) • Goal: - Start observation run using 3 km cryogenic interferometer by the end of March 2018 - TM temperature should be (close to) 20 K - No requirement for sensitivity • Configuration: - 3 km cryogenic Michelson - minimum success: cryo Michelson with LSC - strict deadline (KAGRA will die if cannot make it) - concentrate on Michelson first (no power recycling before Michelson operation) • Purpose: 2 - Test cryopayload and cryogenic operation

b. KAGRA 2018. 4 -6 • Interferometer team will have time after Phase 1 until ITM cryopayload installation, which starts on July 2, 2018 • Configuration: - 3 km cryogenic power-recycled Michelson - no strict deadline, but we have to finish it before ITM installation starts (try PRMI if it doesn’t delay the final b. KAGRA) • Purpose: - Test cryopayload and cryogenic operation - Try 3 -km cavity locking, multi-DOF locking - Spatial mode check 3

Steps for Cryogenic MI and PRMI • • • • 2017. 6. 5 PRs installed -> ~1 month integration (-2017. 7. 6? ) 2017. 8. 31 PSL+IMC ready Initial alignment to both ends, beam collimation (no PR 2 -PR 3 length tuning if beam is collimated well enough) 2017. 10. 31 ETMY CRYp installed Return the beam from ETMY to BS (we don’t try PR-ETMY cavity) 2017. 11. 15 SR 2 and SR 3 installed -> ~1 month integration (-2017. 12. 19? ) 2017. 11. 22 - ETMY evacuation -> 2017. 12. 8 cool down starts 2018. 2. 2 ETMX CRYp installed Return the beam from ETMX to BS Lock room temperature Michelson 2018. 2. 13 - ETMX evacuation -> 2018. 3. 2 cool down starts by 2018. 3. 31 Start observation run with 3 -km cryogenic Michelson [AFTER WE MEET THE DEADLINE] Shorten PR 2 -PR 3 length by 2. 4 cm (at max) Re-alignment connect remaining bellows/ducts and evacuate central area Lock cryogenic PRMI if not possible, lock more cryogenic Michelson * PRMI could be unstable if PR 2/3 Ro. C errors are the worst case 4

Configuration • • • Every detection port listed here has both PD and QPDs (for ASC), and placed on output optics tables in air invac fixed BRT (could be on isolated table; Green lasers are also installed GPT is on output optics table in air) (but not necessary for Phase 1) No requirement for vacuum level TRY IMC: Type-C with WFS PRM misaligned IMMT: Type-C when Michelson PSL ETMs: Type-A + ~20 K CRYp (CRYp not final ones) POP TRX IFI IMMT 1 T 2 W final PMC PRs: Type-Bp REFL high power EOM f. IMC = 13. 78 MHz f 1 = 16. 88 MHz frequency stabilized with Ref. Cav/IMC/(PRCL) intensity stabilized with PMCT and IMMT 1 T AS BS, SRs: Type-B invac fixed BRT invac fixed STM 5

Layout • Adjust layout slightly to compensate ITM wedge • Move PR 2 and PR 3 to stabilize mode of PR cavity (after Michelson operation) • see JGW-G 1605199 for more detail move PR 2 by 1. 2 cm move PR 3 by 1. 2 cm BS angle slightly changed (by 0. 0187 deg) beam spot on PR 3 5 mm off the center in –Y direction 6

Length Sensing and Control • Only use f 1 sidebands • Sensing matrix for PRMI: [W/m] MICH REFL_I +9. 92 e-01 REFL_Q +6. 61 e+04 AS_I +8. 97 e+02 AS_Q -1. 67 e+06 PRCL -7. 48 e+07 -3. 52 e+07 -2. 23 e-01 +4. 16 e+02 7

Alignment Sensing and Control • Only use f 1 sidebands (and TRX/Y DC) • Sensing matrix for PRMI: [W/rad] REFLA_I REFLB_I ASA_Q POPA_DC TRXA_DC TRYA_DC COMM +4. 98 e+02 -7. 01 e-01 +9. 80 e-01 +4. 04 e+01 +2. 30 e+01 -2. 30 e+01 DIFF +2. 36 e-01 -2. 91 e+00 +1. 87 e+02 +1. 49 e+01 +1. 71 e-01 BS -4. 16 e+02 -1. 93 e+00 +1. 56 e+02 -2. 41 e+01 +1. 93 e+01 -1. 91 e+01 PRM -8. 13 e+01 -2. 10 e+01 -1. 39 e-01 +3. 91 e+02 -1. 23 e-01 -1. 17 e-01 PR 2’ -2. 08 e-01 -1. 70 e-03 +1. 31 e-03 +8. 07 e+02 -5. 66 e-03 -3. 25 e-03 PR 3’ -1. 21 e+03 +3. 47 e+00 -2. 27 e+00 -1. 57 e+01 -6. 51 e-01 -6. 36 e-01 • See JGW-G 1605541 and JGW-T 1605362 for more detail 8

Transverse Mode Spacing for PRMI • g-factor 0. 8750 in pitch 0. 8958 in yaw (with designed Ro. Cs & lengths, PR 2 -PR 3 length shortened by 2. 4 cm) • See JGW-G 1605541 JGW-T 1605362 for more detail • how to measure: LIGO-G 080467 9

Commissioning Schedule FY 2017 BS ready (4. 13) PRs ready (7. 6) PSL+IMC ready (8. 31) PR 2 -3 duct connected (9. 8) connect after start of ETMY CRYp installation EYT installed (8. 24) IMMT to PR 3 (9. 11 -9. 15) ETMY install (9. 1 -10. 31) EXT after EYT for safety EXT installed (11. 24) PR 3 to Xend (9. 18 -9. 22) BS to Yend (9. 25 -9. 29) collimation (10. 2 -10. 27) BS to SR 3 (12. 20 -12. 26) AS invac (12. 27 -1. 2) ETMX install (1. 8 -2. 2) ETMX to REFL (2. 5 -2. 9) Michelson LSC (2. 12 -2. 16) AS table (1. 3 -1. 10) central area cannot be evacuated before SRM completion (3. 2) 1 week for preparation EX evacuation ready EX evacuation 2. 23 -3. 2 EX cooling start 3. 2 TRX table (12. 4 -12. 8) TRY table (11. 8 -11. 14) SR 2 and SR 3 ready (12. 19) connect bellows/ducts in the central area if there any chances EXT BRT invac (11. 27 -12. 1) EYT BRT invac (11. 1 -11. 7) Cryogenic Michelson Operation (3. 2 -3. 31) ETMY to REFL (11. 1 -11. 7) POP invac (11. 8 -11. 14) REFL table (11. 8 -11. 14) POP table (11. 15 -11. 21) 1 week for preparation EY evacuation ready EY evacuation 11. 22 -12. 8 EY cooling start 12. 8 [AFTER THE DEADLINE (2018. 4 -6)] PR 2 -PR 3 length adjust PRMI alignment, locking connect remaining bellows/ducts evacuate central area 10