Satellite Meeting on Future Upgrade of KAGRA

Main F2F Page

Date/Time/Venue

August 21th (Wed.) 13:00 - 16:10 (We would like to finish the main discussions by 15:30, when the KAGRA site tour starts)

Venue: Multi purpose room (多目的ホール), Faculty of Science, University of Toyama, Gofuku Campus

(Note that different from the venue of F2F meeting, Kuroda hall)

Zoom(2) connection: https://zoom.us/j/6676627462

Anyone are welcome to join the discussions on site or via online and for even those who didn't make a registration.

Related information

• The last satellite meeting in April/2019

• FPC wiki

• FPC White Paper

Program

Minutes (by K.Yamamoto and SH)

• Sapphire mirror issue (M. Leonardi)
  • iLM(Geppo) is on last stage but his original proposal does not mention birefringence.

  • Now iLM is interested in studying birefringence issue => could be the best solution

  • For near future (O4), 200ppm/cm absorption can be accepted.
  • Internal stress causes birefringence ? Annealing parameter of vendor are not known.
  • ITM for O4 : By re-polishing and same time coating, finesse unbalance could be solved, but birefringence can not be solved (same order of magnitude).
  • Is it worth ? Budget and schedule should be considered. Evaluation by commissioing is necessary (which (finesse unbalance or birefringence) is large must be known).

  • Or fused silica for O4 ? -> coating thermal noise could be an issue. Suspension improvement is necessary. Thermal compensation system is necessary.

  • Silicon test mass ? -> still far future ?

  • IBF (Ion Beam Figuring) can solve only 1 DoF (S-pol) out of 2 (S,P-pol)
• Heat extraction capacity (T. Yamada)
  • Thermal resistance must be reduced and possible (factor 2) at least for the contact ones.
  • For the sapphire fiber, temperature dependence of thermal conductivity is not taken into account.
  • About 10 K/W out of 35 K/W are from sapphire fiber
  • Heat link is x2 longer than original design
  • 35 K/W may be achieved
• Upgrade plans and publication (S. Haino)
  • ET fixed with 1.5 um wavelength which CE2 is aiming at 2 um which have advantage in the scattering

  • Publication plan -> First purpose of FPC is PREPARATION of white paper.

  • For the publication, we have to discuss EO (about feasibility, budget, schedule)
  • WP should be prepared for the coming budget proposal, and contribution from FPC is expected ?
  • We should remove the recommendation part from the first release to make it as list of facts
  • Realistic option for O5(perfect 22 kg mirror and FDSQZ) proposed is minimum success.
  • Silicon mirror changes a lot of thing.
  • Ultimate goal of KAGRA (final BOSS)
  • Boundary condition must be defined at first.
• We would like to get agreements (understandings) by KAGRA collaborators on

  • By considering the current ITM issue, we should put a minimum success of O5 as BRSE+FDsqz (170 Mpc) with DRSE (150 Mpc) as a backup => this is a Broad-band option

  • Define the ultimate goal of KAGRA towards 2030's (until 3G observation starts) with heavy mass (100~200 kg) and high power (350~500 W) laser to achieve 300~500 Mpc sensitivity. => this is a broad-band option

  • The strategy and path between O5 and ultimate can be discussed according to the technological feasibility and science cases
  • White paper 2nd release to be prepared first as an internal document (Oct.~Dec./2019)
  • Then later, we would like to make it as a publication

Agenda

• Things happened since the last satellite meeting

  • O5 plans (A+,AdV+) and schedule are released to public

  • Schedule of 3G (ET, CE) released in GWADW 2019

  • A new proposal ozGrav-HF

  • iLM submitted a proposal to produce large sapphire bulk up to 200~250 kg and aiming low heat absorption (< 10ppm/cm)

  • ITM birefringence issue found (e.g. JGW-G1910369,[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=10495|JGW-G1910495])

  • Science study updated by A.Nishizawa JGW-G1909934 by considering LVK network

• We have a session dedicated to sapphire mirror and heat extraction
  • Understand the current status of sapphire mirror issues and future prospects
  • Maximum laser power is limited (at least) by the heat absorption and heat extraction capacity. We should understand the current estimation.
• We would like to get agreement/understanding on the followings:
  • Publication on the KAGRA future upgrades
  • Define the ultimate goal in long term towards 2030's
  • More realistic plans for O5
• Publication plan (Full KAGRA author)
  • Serve as the 2nd release of the white paper
  • Discussion about the ultimate goal and intermediate plants including O5
  • Share the same idea inside the collaboration as well as to inform it to LV and near-by communities
  • Submission/publication target just after KAGRA manage to join O3 (late 2019~early 2020 ?)

  • Target journal: PRL or PRD ? (depending on the number of pages/figures) c.f. iKAGRA => PTEP, bKAGRA-ph1 => CQG

• Ultimate goal of KAGRA
  • Time scale around 2030
  • It should fill the gap between O5 and 3G
  • 200 kg Sapphire as the primary candidate (iLM may help us a lot if their proposal is accepted)
  • Backup plan with Silicon ? Decision tree should be prepared

  • With 200 kg sapphire and 500 W laser, 500 Mpc may be possible JGW-G1910533

  • What is the name ? Naming is important: hKAGRA ? (hyper-KAGRA, or h as Heavy-mass and High-power), uKAGRA ? (ultimate-KAGRA) or dKAGRA ? (dream-KAGRA)
• More realistic plans for O5
  • Due to the ITM issues it may be difficult to achieve the design sensitivity during O4
  • One option is to achieve the design sensitivity (with detuning) of 150 Mpc in O5
  • Detuning doesn't go well with squeezing. Should we give up detuning but BRSE with FD squeezing (60m filter cavity ?)

  • High Freq. (HF) upgrade requires R&D and change of suspensions which may have a risk to worsen the sensitivity, while FD squeezing can be installed independently so that we can go back to detuning option if the installation of squeezing doesn't finish in time