= Simulation meeting 2021 Sep 30 15:00 =
Zoom2: https://zoom.us/j/6676627462

== Participants ==
Naoki Koyama, Hirotaka Yuzuhihara, June Gyu Park, Keiko kokeyama, Kentaro Somiya, Marc Eisenmann, Matteo Leonardi, Osamu Miyakawa, Satoru Takano, Tomotada Akutsu, Yoichi Aso, Yuhang Zhao, Yuta Michimura, Haoyu Wang

== Agenda ==
=== Updates from Projects ===
 * Birefringence
   * Slide for updates [[ https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=13335|link]]
   * As we use division when combining TWE maps, it will create infinity values when the denominator is zero. This may affect the accuracy of the generated birefringence map.
   * We have calculated the power conversion map from S to P. The conversions are different when the input beam has different polarization angles. The difference comes from the change in Phi, while the alpha-minus is independent on polarization angle.
   * We also try to simulate the single bounce beam shape when applying the reflectivity (birefringence) map, but we have errors from FINESSE. We are addressing this problem now. Manually modify the map, try to use more higher order modes, try to use fake map with smooth changing reflectivity, and try to use cavity command.
   * We should quickly calculate the average loss from S to P (use a Gaussian beam shape).
   * Beam shape and resonance measurements (one arm test) of S and P could be necessary at site.
   * TWE measurements at 15, 30, 60, 75 degrees are necessary. The rotation angle control should be accurate (may be under 0.5 degree is better).

 * GUI
   * The alignment simulation has been implemented. The transfer function for each port has not been done.
   * The sensitivity has not been finished yet. The sensitivity mainly means the quantum noise sensitivity. For the radiation pressure noise, we need the mirror mass.

 * OMC model
   * June Gyu ever used models with LIGO phase maps for ITMs to simulate the mode content at the AS port. We now need to prepare the birefringence maps and apply them to his model. June Gyu and Haoyu will work together on developing the model.

 * WFS signal simulation
   *Satoru gave a talk on simulation of WFS signals using FINESSE [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=13337|Takano Slide]].
   * WFS signal’s dependence on arm cavity finesse has been studied.
   * Cavity is not on resonance when mirrors are tilted, because they cavity length has changed.
   * Higher order mode effect should be taken into account.
   * The analytical reconstruction of WFS signals matches with FINESSE simulation.
   * The lock command should be used. But the lock (in the simulation) fails when the cavity finesse is high.
   * It is better to know how the lock command works and set up the gain and accuracy parameters carefully.

 * Pygwinc
   * Marc is currently developing pygwinc to calculate the sensitivity to aid for the filter cavity design (frequency dependent configuration, back-scattering). He is happy to give updates sometime.