LVC meeting (parallel session)

• SH could join the LVC meeting only in the first two days (parallel sessions) mainly in AIC and joint instrument plenary

• DCC link to the agenda (Many of them are not KAGRA-readable)

Some topics picked up by SH

• kHz optimization for BNS post-merger (Haixing Miao)

  • Long SRC to dig into high frequency (kHz) region. Sensitivity will be limited by SRC loss.
  • Typically 6km arm with 150m SRC to make some detection of post-merger (~1 event/year)
  • 18 km arm may be needed to do some astronomy (~10 events/year)

• Finesse 3

  • python implementation
  • It enables custom detectors (e.g. homodyne detector)
  • It can take account of 3G detectors (e.g. polarizing beam for Sagnac)

• Low loss Faraday Isolator for squeezing injection

  • Try to reduce the optical loss which is limiting the squeezing level (currently ~3dB at LIGO)
  • Matteo's contribution mentioned

• High power laser for O4 and 3G

  • Original High Power Oscillator (HPO) was given up due to the maintenance issue and the beam jitter affecting the sensitivity
  • Two neoVAN-4S-HP (solid state) amplifiers (+70W each) in series following LIGO front-end laser (30W) or NPRO seed (2W) to get 140~170 W power for O4
  • Development of fiber amplifiers at LZH in progress. To be tested at AEI Hannover soon.
  • Coherent beam combining (CBC) with two neoVAN-4S-HP amplifiers and/or fiber amplifiers can be tested at AEI Hannover.
  • Benno's AEI Hannover group is always supportive to KAGRA

• Gingin facility at UWA (DCC link is not KAGRA-readable)

  • Study on Parametric Instability - possible collaboration for KAGRA+ ?
  • 5W 2micron laser for silicon mass cavity

• AdV suspension control status

  • Sensitivity improved from 25 Mpc to 40 Mpc by mitigating actuation electronics common mode noise coupled with electro-static charges
  • Electro static charge issue is important even for coil magnet actuator for Virgo (and KAGRA) and not only for ESD in LIGO
  • Still unknown noise around 100 Hz which avoids achieving stable sensitivity of 60 Mpc for Virgo (possibly still actuation noise ?)
• LLO commissioning (DCC link is not KAGRA-readable)
  • Noise projection to O3; ER14 120-140 Mpc
  • Stable operation with 40W laser power but more noise with 50W
  • 3dB IFO measured squeezing achieved
  • Reduced ESD noise and stray field monitoring
  • Non-uniform absorption at TM optics - serious problem avoided for now by moving the beam position

  • Musical VCOs => for more robustness

  • Should be no big surprise for O3
• Squeezing at MIT (DCC link is not KAGRA-readable)

  • Why not more than 3 dB ? => Angle noise, Losses, Pump power and Radiation pressure (in principle)

  • Loss inside IFO: 30% expected but in reality 4~50 %
  • Towards O4: more than 3dB, A+ goal: 6dB (measured squeezing level)

• Voyager update

  • Silicon Suspension design and noise estimation updated by K.Arai
  • Is it really good to use the ribbon suspension ? (SH's personal thoughts and also discussion with Helios)
  • Tuning of quantum noise to be considered ; one possibility like high frequency tuning (related to Haixing's talk)
• Coordination of prototypes (S.Hild)
  • Global coordination of prototype facilities is needed and also to be discussed among (LSC, Virgo, KAGRA, GWIC, ...) (David Shoemaker)
  • After the GW detection we are more restricted to keep observation for science (Ray Weiss)
  • If we have 4~5 detector in the world (including KAGRA and LIGO-india) we can rotate the down time for the upgrades ?
  • Still not clear conclusion in this meeting how to coordinate and define the roles of each prototype facilities

• Point absorvers at aLIGO

  • Looks like to be getting one of the major issues
  • 4 out of 8 TM optics at LHO and LLO show some indication of point absorption

• KAGRA+ (5~6 comments/questions were given)

  • (David) what is the time scale ? => Something like O5 and beyond

  • High power (HF) option is to give up the cryogenics ? => No we keep basically around 20 K by thicker and/or shorter fiber suspension

  • Suspension with different material with higher Young's modulus ? => We should consider about that

  • Long filter cavity possible ? => in principle yes but the space inside the tunnel is limited; 30m is Ok >30m needs some efforts

  • EPR entanglement should need shorter filter cavity => we should consider some QND for the far future options