= ISC Meeting on 2018/5/7 14:00 - 15:00 =
Participants: Yutaro Enomoto, Kiwamu Izumi, Osamu Miyakawa, Kentaro Somiya, Eiichi Hirose, Yuta Michimura

eZuce meeting: "KAGRA ISC Meeting" in the KEK community.

=== Next meeting ===
2018/5/22 (Tue) 14:00 - 15:00 ?? (Michimura is traveling on Monday 5/21)

[[LCGT/subgroup/ifo/ISC/Meetings|back to Meetings page]]

== Minutes ==
 * Summary of Phase-1 measurements
  * Memo can be found in [[KAGRA/Commissioning/Phase1/Operation/MeasurementsSummary|MeasurementsSummary wiki]]

 * KAGRA configuration for joining O3 [Michimura] [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=8172|JGW-T1808172]]
  * There was a request from Ohashi/Kajita to consider FPMI option.
  * Conclusion: We will keep RSE scenario. But we might switch to FPMI at some points (every end of Sep/2018, Dec/2018 and Mar/2019) if preparation is judged as insufficient for RSE.

 * bKAGRA RF cables [Michimura]
  * ordered 30m SMA cables on Apr 18 (takes 3 weeks)
  * this should be the last order of SMA cables

 * RF generation scheme [Michimura]
  * ordered two units of Wenzel Harmonic Generator on Apr 21 (takes 14 weeks)

== Agenda ==
 * Summary of Phase-1 measurements [[KAGRA/Commissioning/Phase1/Operation/MeasurementsSummary|MeasurementsSummary wiki]] {*}

 * KAGRA configuration for joining O3 [Michimura] [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=8172|JGW-T1808172]] {*}
  * There was a request from Ohashi/Kajita to consider FPMI option.
  * Conclusion: We will keep RSE scenario. But we might switch to FPMI at some points (every end of Sep/2018, Dec/2018 and Mar/2019) if preparation is judged as insufficient for RSE.

 * bKAGRA RF cables [Michimura] {*}
  * ordered 30m SMA cables on Apr 18 (takes 3 weeks)
  * this should be the last order of SMA cables

 * RF generation scheme [Michimura]
  * f1 = 3/8*f2, f3 = 10/8*f2
  * we need 2*f1, 2*f2, f3-f1, f3-f2 as well
  * use harmonics generator (x3, x5, x6, x7, x8, x10, x16 for f2/8 = 5.62698725 MHz (FSR for IMC))
   * Wenzel specsheet [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=8028|JGW-D1808028]] {*}
    * ordered two units on Apr 21 (takes 14 weeks)
  * Usage of 6 Agilent N5181B [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=6762|JGW-T1706762]] {*}
   * Current use: fFSS, fIMC, ISS AOM, f1, fALSX at UToyama, spare at Ando-Lab
   * Possible use in near future: fPMC, fFSS, fIMC, fALSX, fALSY, ALS AOM, ISS AOM, f1, f2, f3
    * buy new RF signal generators for fPMC and fFSS?
   * Final use: fPMC, fFSS, fIMC, fALSX, fALSY, f1/f2/f3 with harmonics generator
    * Use AOM drivers for ALS AOM and ISS AOM

 * SRM doughnut metal mass status? {*}


 * RF generation using Mach-Zehnder interferometer [Kohei Yamamoto] [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=7309|JGW-G1707309]] [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=7655|JGW-G1807655]] [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=8029|JGW-G1808029]] {*}
  * simulation on imperfections (MZ arm asymmetry, MZ lock, EOM phase difference control etc.)
  * calculate requirements on MZI displacement, EOM modulation phase difference, EOM imbalance
  * Requirements derived from full Optickle simulation and those derived from transfer function between displacement of MZI and sideband power kind of matched after implementing RAM into calculation for the latter. However, we need more investigation on the following issues:
   * Modulation depth for RAM generating EOM changes the requirement.
   * Spectrum shapes of the requirements for mid-fringe do not match. Maybe coming from accuracy of the mid-fringe?
   * Unknown frequency response of the transfer function from the displacement of MZI and sideband power
   * Check if caluculated RF oscillator amplitude noise is relative one or not with simple Optickle model
  * calculations for requirements on delay line lock displacement noise, parallel EOM MZ lock displacement noise, EOM modulation phase difference, EOM imbalance on-going
  * Relative f1 PM and f1 AM also needs to be adjusted ([[http://iopscience.iop.org/article/10.1088/0264-9381/31/9/095003/meta|CQG 31, 095003 (2014)]]). Another EOM for f1 or relative amplitude adjuster between two EOMs?
  * Requirement on carrier power loss?
  * Comment from Stefan Ballmer
   * Similar calculation was done in LIGO in the past. Displacement noise requirement for MZ was tough (~1e-14 m/rtHz).
   * Any in-air interferometer suffer from jitter and frequency noise which cannot be suppressed.
  * Ref: [[https://dcc.ligo.org/LIGO-T040119/public|LIGO-T040119]]
  * MZI implementation starts in May, probably before high power laser installation
  * RF oscillator noise requirements for MZI should also be calculated

 * Three-f or 3f for early phase of bKAGRA ?
  * Three-f (THD)
   * Needs RF tripler for 16.88 MHz and 45 MHz, RF PD for 50.64 MHz (3*f1) and 135 MHz (3*f2). Broadband photo detector? ([[https://dcc.ligo.org/LIGO-D1002969/public|LIGO-D1002969]])
   * operational frequency range of IQ demodulator: upto 100 MHz
  * 3f
   * needs RF differential frequency generator (or harmonics generator) for 39.39 MHz (f3-f1) and 11.25 MHz (f3-f2), RF PD for those frequencies.
   * needs Mach-Zehnder modulation

 * ALS configuration [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=7416|JGW-E1707416]] [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=788|JGW-T1200788]] [[KAGRA/Subgroups/IOO/ALS|ALS Wiki]]
  * where to put a frequency offset: arm length or PLL offset [Enomoto] [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=7726|JGW-L1807726]]
  * fiber selection meeting on March 23  {*}
   * determined to use end-cap for both
   * there was a suggestion to lay IR fibers also

----
 * IMMT1 and IMMT2 transmission [Michimura, Takeda]
  * IMMT2 transmission optics are too much squeezed

 * DC QPD holder [Michimura]
  * beam height should be 4inch to use similar mount, with small modification of spacer (instead of 3inch in [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=2607|JGW-D1402607]])
   * RF PD, RF QPD boxes are designed for 4inch beam height
  * stages are not needed for ISC DC QPD
  * design new ones; they can be very simple [-> Michimura?]
  * calibration can be done in different ways
  * put strain relief and anchors for cables to protect QPD board

 * OMC and OFI [Somiya]
  * look for OFI with larger aperture [Somiya]
  * DC PD and DC QPD [Michimura]
   * DC PD not available. Look for product with similar specs
   * DC QPD available from RS

 * In-vacuum RF PD and RF QPD {*}
  * we need them within 1 year, considering OMC REFL and AS RF

 * In-vac beam-dumps {*}
  * required spec?

 * Actuator noise modeling [Michimura,Miyamoto]
  * Summarized in the paper [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=7051|JGW-P1707051]]
  * Needs to implement frequency noise, but FSS modeling with ALS is complicated [student!]
  * Discuss mirror vibration from heat link {*}
   * Meeting on July 14 [Yamada, Miyamoto, Ushiba, Michimura]

See [[KAGRA/subgroup/ifo/MIF/Minutes20170410|this page]] for other agendas.