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 * How did we score the significance (Shinkai, Ando) ?  * How did we score the significance ?
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 * It is suggested to use Feasibility only instead multiplying by significance (Ando)
   * We will consider for that
 * It is suggested to use Feasibility only instead multiplying by significance

Satellite Meeting on Future Upgrade of KAGRA

Main F2F Page


Apr. 18th (Thu) 13:30 - 18:30

Venue: Room 1320, Faculty of Science Bldg. 4, University of Tokyo Hongo Campus (note: different from the main F2F venue)

Access to the building can be found here: Faculty of Science Bldg. 4

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



Subject and Title




FPC white paper

Introduction from FPC and current status of the white paper

S. Haino and FPC



Science cases

Review of KAGRA+ science cases

A.Nishizawa et al.





Discussions on the technological issues

KAGRA+ upgrade options and roadmap towards O5

FPC et al.


Frequency-dependent squeezing simulation and filter cavity implementation strategy in KAGRA mine

E.Capocasa, M.Leonardi et al.


Issues and possible upgrades for cryogenic suspensions

K.Yamamoto, H.Vocca et al.

Kazuhiro Helios



General discussion on White Paper

  • How did we score the significance ?
    • The significance is only in case of KAGRA upgrades but not for the general GW detector
  • It is suggested to use Feasibility only instead multiplying by significance
  • How do we weight between science and technology ? For example what if we have one strong science case which needs difficult technology or oppositely we can also make a judgement based on technological feasibilities
    • We should take both into account, is we achieve some upgrades in the next 5 years we have to put some weights on the feasibility. For the moment our recommending two options (FDsq and HF) also show strong science cases but more qualitative evaluation should be done
  • What is the advantage of underground detector ?
    • This is mainly for the low frequency sensitivity (well below other noise such as thermal) and stable operation (not visible in sensitivity).

Science cases

  • We should consider not only the gain w.r.t. bKAGRA but also A+/AdV+ network. Currently, only localization and polarization consider the network.
  • The originality of KAGRA is one important aspect to consider the science case
  • Should we make a decision now or can we wait until e.g. O3 results ?
    • We may want for O4 after O3, but we have to decide in a short time.
  • How about narrow band design to look for particular source ?
    • Detuning of quantum noise is possible but mirror thermal noise which is rather broadband will eventually limit the sensitivity

Technologies (Filter cavity)

  • 60m cavity may be possible but we have to consider the conflicts with cryostat door and so on
  • Putting the filter cavity in the arm tunnel can be also possible but it will increase the complexity of optics
  • Putting the filter cavity to the entrance side or to the PSL room may have more difficulties
  • LIGO/Virgo have more gain with 300 m filter cavity while KAGRA has more limited by suspension thermal noise in low frequency, so the gain with 300m is not so significant as LIGO/Virgo
  • 15 ppm RTL with 60m is realistic ? - 10 ppm with 10 m cavity is demonstrated so it is not too much optimistic
  • 25~30 cm diameter of vacuum tube may be OK for 300 m cavity and 25 cm for 60 m one (~10 cm diameter mirror).
  • For the squeezer, we assume very similar system as LIGO/Virgo and 15 dB is already demonstrated by AEI.
  • So far there seems no difference between in-air (Virgo/GEO) and in-vacuum (LIGO) OPO
  • We will ask to SEO to consider a new subsystem for squeezer development

Technologies (Suspension)

  • It is known (in the 1990's literature) factor of a few (2~3 ?) improvement is expected by surface polish.
  • 30 cm is the minimum fiber length we can make without significant modification of cryopayload (bending length).
  • Thicker fiber further reduces the elongation below 20 um and makes the mechanical tolerance more strict.
  • Size effect may not work with thicker fiber but impurity or lattice defect may become more important.
  • We will need to increase the cooling power if we put higher power in the arm cavity

LCGT/Meeting/f2f/2019Apr/FuSat (last edited 2019-04-19 11:03:26 by SadakazuHaino)