= ISC Meeting on 2018/7/2 14:00 - 15:00 =
Participants: Kiwamu Izumi, Yutaro Enomoto, Yuta Michimura, Koji Arai, Kentaro Somiya, Yoichi Aso, Kazuhiro Yamamoto, Osamu Miyakawa

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

=== Next meeting ===
TBD. Maybe July 30 (July 16 is Japanese Holiday)?

2018/7/30 (Mon) 14:00-15:00 (JST)<<BR>>
2018/7/30 (Mon) 07:00-08:00 (CEST) (Michimura at Virgo from June 4 to August 17)<<BR>>
2018/7/30 (Sun) 22:00-23:00 (PDT)<<BR>>
https://www.timeanddate.com/worldclock/meetingtime.html?day=30&month=7&year=2018&p1=248&p2=4399&p3=137&iv=0

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

== Minutes ==
 * Low noise VCO [Enomoto] [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=8433|JGW-G1808433]]
  * G&H VCO for ALS AOM turned out to be too noisy
  * Make low noise VCO similar to aLIGO one
  * RF power seems to be enough to drive ALS AOM
  * Replacing Refcav AOM (currently at 110MHz) will be after ALS AOM

 * ALS status, follow up from the last meeting [Enomoto] [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=8393|JGW-G1808393]]
  * Check CARM to DARM coupling due to unbalance
   * not yet done
  * Check the effect of cavity pole in reflection
  * Check Refcav AOM saturation
   * OK
  * Check RF PD saturation
   * We decided not to use commercial ones. Modify our IR RF PD to green.

 * How to proceed with DC PDs for DC readout [Aso]
  * Calculations on DC power and circuit noise -> Somiya & Arai
   * Koji's calculation: [[KAGRA/Subgroups/IOO/OMC/DCPDCalculation|DCPDCalculation]]
  * Box for in-vac amplifier
   * VIC?
   * How to extract heat? Alumina coating? Fix on the optical table (be careful of electrical short)?

 * Harmonics Generator [Michimura]
  * Ordered Harmonics Generator for x3, x5, x6, x7, x8, x10, x16 for f2/8 = 5.62698725 MHz (FSR for IMC)
  * But it should be x2, x3, x6, x7, x8, x10, x16
   * Asking to Wenzel for modification

== Agenda ==
 * Main topics for Phase-2 [Michimura] {*}
  * Fix initial alignment scheme for full IFO
   * Enomoto?
  * Finalize ALS scheme and RF AM generation scheme and finalize lock acquisition scheme
   * Enomoto?
  * ISC modeling, especially ASC modeling, for intermediate IFO configurations
   * Tanioka for ASC?
  * Cabling diagram
   * Michimura's trial [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=8336|JGW-D1808336]]
   * Izumi will start from ALS cabling diagram and then FSS cabling
   * Making a whole cabling diagram would be tough, but cabling for RF PD/QPDs is kind of obvious and we can simplify them.
  * In-vacuum RF PD and RF QPD
   * Izumi will ask LIGO people first. And ask Doi for handling fabrication?
  * Readout DC PDs and OMC
   * DC PDs purchased. We have to make holders and in-vac amp. Somiya?
  * Design output optics on optical tables
   * Anyone?

 * Three-f or f3 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
  * f3
   * 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
    * EOAM cannot be done with wedged EOM
    * maybe we can do AM generation by other methods? Modulation by laser current? 5.6 MHz option?
  * For MZI experiment, Kokeyama/Yamakoh/Nakano/Michimura agreed on (June 1, 2018)
   * Continue MZI experiment at final positions (bypass of PMC necessary to work with PMC in parallel)
   * Decide the feasibility of three-f or other RF AM generation scheme by June 18
   * If MZI is not feasible, remove BS or replace it with a mirror and switch to three-f option
   * Delay line MZI can also be omitted if we are happy with 20W

 * Low noise VCO {*}
  * LIGO one (79-81 MHz) [[https://dcc.ligo.org/LIGO-D0900605|LIGO-D0900605]], spec [[https://dcc.ligo.org/LIGO-E1101019|LIGO-E1101019]]
   * needs 71 MHz reference source
  * at least 5?
   * FSS AOM (80 MHz), ALSX AOM (80 MHz), ALSY AOM (80 MHz), PLLX (40 MHz), PLLY (40 MHz)
    * 80 MHz for PLL possible? PFD spec?
   * draft of circuit production request [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=8339|JGW-T1808339]]
   * VCO modification [[https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=30869|LHO alog #30869]], [[https://dcc.ligo.org/LIGO-E1600292|LIGO-E1600292]]
  * Right now, Refcav AOM is driven at 110 MHz. If we make 80 MHz Low Noise VCO also for PSL AOM, we also have to change the AOM

 * 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
  * fiber layout determined? fiber length: 50m {*}
  * RF PD for green? {*}
   * Maybe we can do green PDH with commercial ones (Hamamatsu S3399?), but f3-f1, f2-f1, and 3f also need BB PDs. Maybe we should make BB PDs.
  * ALS status [Y. Enomoto] [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=8393|JGW-G1808393]]
   * A/I from ISC meeting on June 8
    * Check CARM to DARM coupling
    * Check the effect of cavity pole in reflection.
    * Check Refcav AOM saturation
    * Check RF PD saturation.
  * ALS circuit diagram [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=8394|JGW-D1808394]]
  * Summing node is necessary for ALS

 * 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

 * 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)
   * It should be x2, x3, x6, x7, x8, x10, x16 (Michimura realized this on June 30) {*} {*}
  * 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

 * KAGRA configuration for joining O3 [Michimura] [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=8172|JGW-T1808172]]
  * 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.
  * Possibility of PRFPMI operation?
   * Change f1 sideband frequency?
   * Use pick-off of BS for MICH signal?

----
 * 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.