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LIGO ETM 20ppm and 700ppm requirement is 500ppm

ISC Meeting on 2015/11/30

14:00 - 15:15 on SeeVogh

Participants: H. Yamamoto, Michimura, Aso, Akutsu, Okutomi, Hirose, Somiya

1. Requests for coating requirements from LMA (Aso)

  • We got requests to relax requirments for coating of various mirrors from LMA.
  • The following changes will be made
    1. Green transmission for TMs
      • Finesse of the arm for green should be higher than 6 to avoid unwanted resonances of higher order modes. For safety, we decided to make it 50. With the relaxed transmission error, the finesse will be in the range of 40 - 60, which is still fine.
      • Old: 6% +/- 0.5%
      • New: 6% +/- 1%
    2. ITM AR reflectivity
      • ITM AR reflection will be used as POX and POY. Therefore, we need non-zero reflectivity. The PRC cavity can tolerate a loss of 1000ppm.
      • Old: 200ppm +100/-0
      • New: 300ppm +/-100ppm
    3. ETM AR reflectivity
      • The ghost beam from the ETM AR will be separated inside the BRT when the beam size becomes small.
      • Old: <50ppm

      • New: < 100ppm

      • Reference: LIGO requirement is < 500ppm. Actually measured value vary a lot from 20ppm to 700ppm.

      • The difference between 50ppm and 100ppm is insignificant
    4. PRM/SRM AR reflectivity
      • Separation of the PRM ghost beam was not yet considered.
      • Old: < 50ppm

      • New: < 100ppm

    5. SRM HR transmission
      • Old: 15.36% +/-0.1%
      • New: 15%+/-1%
      • The linear range of the SRCL signal is fine with this relaxed error range.
      • The WFS shot noise change only about 5% with the above error.
      • Somiya-san will check the effect on the sensitivity.

1. Electronics Preparation Status (Michimura, Aso)

  • Cable (Michimura)
    • Delivered to the site. Now in the tunnel (低温機械室)
    • Need to check if RF flexible cables are included (Michimura)
  • RF distribution (Komori, Michimura)
    • The panel should have been delivered to Kamioka
    • Need to arrange people to assemble the box
  • RFPD/QPD (Aso, Doi)
    • The first delivery will be in the middle of Dec.
    • For MC lock, we need one extra RFPD. We have the stuffed PCB but no box. Fujisawa-san at Toyama University is now making a box. Asked Doi-san to supervise her and finish the box production by the end of the week of 11/30.
  • Diff-to-Single converter
    • For bKAGRA, we need to make official converters.
    • For iKAGRA, we can use a passive conversion boxes. Just connect the cold line to GND through a resistor (1kOhm or so).
    • The above box needs to be made

1. Magnet Noise (Michimura)

  • Decided to reduce the size of BS magnets by a factor of 30 from the current design. RM magnets will also be smaller.
  • VIS members (Mark and Fabian) will design new flags for the BS and SR

1. OMC (Somiya)

  • We need to decide where to level the beam in the output chain: Befoer OFI ?, after OFI ?
  • Do we need steering mirrors before OFI ? -> Needs to be discussed with quantitative assesment of scattering noise from various optical components.

  • How much light power will be picked off for the AS WFS ? -> 1%

1. FFT Simulation (Hirose, H. Yamamoto)

  • No update

KAGRA/subgroup/ifo/MIF/Minutes20151130 (last edited 2015-12-02 10:12:49 by YutaMichimura)