Participants : M. Eisenmann, D. Haba, S. Singh, K. Takeshita, K. Yamamoto, H. Wang

* birefringence measurements at NAOJ :

• 2D measurement :

Improved data filtering allows to see delta_n of new AZTEC at about 10**-7 currently limited by holder new holder design on-going

• 1D measurement :

Polarization Ray Tracing for coating going from local to global frame increases the circular retardation while decreasing the 45deg one : possible sign of misalignment

• Coating activities at U. Toyama :
  • Measurements :

Sato-san prepared slides for his defense Ti doping decreases the 20K peak for LMA coating but not for NAOJ one. now checking new NAOJ coating with Ti doping: still no 20K peak and same value as before maybe NAOJ coating not large enough and maybe annealing can help?

• Improvements :

plan to use smaller electrodes, further away to avoid cross-talk between actuator and transducer as measurement is relative, can only measure relative force

• ASC and birefringence at TiTech :

  • weigthed PD :

tuning the weigths to avoid PDH contamination studying the effects of birefringence fluctuations (beam jitter) to shot-noise In KAGRA it should be < few mm currently simulating with the full beam size on ITMs

• ML :

Using same parameters as for the weigthed simulation : the offset fluctuations seems to be reduced by 1000 times However the 16 split PD has worse offset that 4 split one? maybe due to small number of data used (10 000)? Now checking first pitch, then yaw