= ISC Meeting on 2018/1/29 14:00 - 15:00 =
Participants: Kohei Yamamoto, Yutaro Enomoto, Koji Nagano, Koji Arai, Keiko Kokeyama, Kiwamu Izumi, Osamu Miyakawa, Eiichi Hirose, Yuta Michimura

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

=== Next meeting ===
2018/2/13 (Tue) 14:00 - 15:00 ??

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

== Minutes ==
 * Optickle simulation of RF AM generation using MZI [Kohei Yamamoto] [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=7724|JGW-G1807724]]
  * 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

 * bKAGRA RF cables [Michimura] [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=7586|JGW-T1707586]]
  * Agreed on the loation of the POX table and ISC racks.
  * Modification necessary:
   * REFL signals and POY signals should be demodulated by IOO rack since ISC racks are too far (~ 40m to 50m)
   * Use cable rack under SR2-SR3 pipe for cables to ISC racks
   * Use cable racks on +X side for AS signal

 * 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]]
  * E8663D with FM option or AOM driver for AOM VCO for green PDH
  * where to put a frequency offset: arm length or PLL offset
   * Both seems OK. More discussion on this on Jan 30 at U of Toyama.

== Agenda ==
 * KAGRA configuration for early phase of bKAGRA [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=7334|JGW-T1707334]] {*}
  * SRM reflectivity
   * Mirror ordered
   * Black coating for metal mass?
  * ITM asymmetry [Enomoto] [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=7565|JGW-T1707565]] {*}
   * ITM asymmetry is OK for early stages, but asymmetric ITMs cannot be used for achieving design sensitivity

 * bKAGRA Phase 1 [Michimura]
  * no AS optics for Phase 1, instead use reflection REFL beam from PRM
  * we have to prepare REFL optics
   * height of the beam from PR/BS breadboard will be 380 mm instead of 400 mm

 * bKAGRA Phase 2 schedule [Michimura] [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=7079|JGW-T1707079]]
  * meeting with SEO on Sept 6
  * Goal: 1 hour lock of cryogenic RSE with RF readout, probably with ASC, no sensitivity goal
  * input laser power not decided
  * when to swap ETM, SRM reflectivity, vacuum
  * schedule adjustment between AS WFS and OMC test necessary

 * bKAGRA RF cables [Michimura] [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=7586|JGW-T1707586]] {*}
  * we have to soon purchase RF cables, but cable lengths depend on the position of ISC racks
  * discussion and cable length measurements in the week of Jan 22

 * PSL EOM Layout re-consideration [Enomoto] ([[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=6748|JGW-T1706748]])
  * Delay-line length decided to be 2.66 m (instead of 8.88 m)
  * Modulation phase between f1 AM and PM is always aligned (we need this to be aligned)
  * Modulation index needed at each EOM is less than measured maximum index by Uehera ([[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=5611|JGW-T1605611]])
  * Optickle simulation by 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]] {*}
   * simulation on imperfections (MZ arm asymmetry, MZ lock, EOM phase difference control etc.)
   * start with hand calculation, simple setups, and then to full IFO simulation
   * Optickle model basically made, and checked with hand calculations
   * calculations for requirements on delay line lock displacement noise, parallel EOM MZ lock displacement noise, EOM modulation phase difference, EOM imbalance on-going
   * A/I: check phase noise calculations, requirements for f1 AM-PM mixed case [Kohei Yamamoto]
   * Requirements derived from full Optickle simulation and those derived from transfer function between displacement of MZI and sideband power do not match.
    * A/I: upload the code on SVN. RF AM camp in Ando group on Jan 18.
     * The discrepancy could be from residual AM requirement being pretty strict?
   * Relative f1 PM and f1 AM also needs to be adjusted. 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]]

 * 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]]
  * E8663D with FM option or AOM driver for AOM VCO for green PDH
  * where to put a frequency offset: arm length or PLL offset

 * 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))
    * seeking for vendors (Wenzel? API Technologies (Spectrum Microwave)?)

----

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

 * IR/green steering mirrors [Michimura]
  * mirrors arrived, mirror mounts and picomotor driver ordered, pedestals by Akutsu, vacuum cables by Aso

 * 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.