= Simulation meeting 2022 Jan 13 15:00 =
Zoom2: https://zoom.us/j/6676627462

== Participants ==
Naoki Koyama, Marc Eisenmann, Haoyu Wang

== Agenda ==

=== Updates from Projects ===

 * Birefringence simulation
   * Theta map and alpha-minus map have high spatial frequency components (sharp features) which is a problem for simulation. [[ https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=13599|F2F_talk]]
   * Theta is wrapped due to the tangent function. We are trying to unwrap theta, which can make the map smooth. [[ https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=13599|unwrap_theta]]
   * The offset (zero-order Zernike polynomial) of TWEs at two rotation angles may be different. Then the subtraction of two TWEs will have errors. This will contribute errors in calculating theta.
   * How to ensure the offset of TWE stay the same after rotating the mirror in real TWE measurements?
   * We are currently simulating round-trip loss in one arm cavity when birefringence is considered with the MZ model with fixed parameters (without maps).

 * Birefringence characterization of Spare ETMY in NAOJ (Marc)
   * The maximum value of Delta-n map is close between calculation and measurement.
   * The calculation of theta map shows some sharp features while the measurement is quite smooth. There may be two reasons: 1) the denominator in calculating theta will be zero (if the subtraction of two TWE is zero), 2) theta is wrapped.

 * GUI
   * Koyama is writing his thesis and is going to graduate next month.