Scraps of text for incorporation in the VIS Meeting Minutes
Type B (Mark)
Report for the week 5/20
The highlight of the week is Terrence's measurement of the residual motion of the SR2 optic: it does fulfill the rms displacement and velocity requirements for lock acquisition and observation phases. See the report at klog entry 8949.
- After Akutsu-san's suggestion Terrence improved the air shield in two rounds, including a cylindrical cover around the viewport. This reduced the noise by about a factor of 10.
- He realized setting up the shield may have slightly changed something in the oplev and carried out another round of diagonalization.
- By exciting the pringle mode he balanced the optic coils, measured TFs and tuned the damping filters.
- The optic residual motion in L, P and Y showed a large peaks close to 0.2 Hz, which is where the micro-seismic may become apparent. This suggested the inertial damping system is not working in a suitable way. As a temporary measure he modified the filters and reduced the gain.
Lucia helped Terrence in starting the diagonalization of the SR2 geophones and provided belding filters that Terrence will optimize. (The blending frequency is 0.190 Hz for L,T and 0.260 Hz for Y). Klog 8905.
- Last week Akutsu-san suggested to improve the air shield around the oplevs.
- Terrence reported an unresponsive SR2 optic coil. We chekced and found the H3 coil cable disconnected.
We helped with the corresponding measurement of one of PR2 LVDT drivers. See klog 8952.
Report for Golden Week
- Mark monitored vent and pumpdown, and worked on vistools.py.
Report for the week of 5/6
- Lucia and Terrence got the blending working for the IP LVDTs and geophones.
- Terrence and Mark modified the models and MEDM screens to add a new IP block, IDAMP, for damping using the blended signal with inertial information, and a new DAMPMODE block for ramping smoothly between IDAMP and the old DAMP.
- Mark worked on vistools.py, improving the support for cdsMuxMatrix blocks (e.g., OSEM2EUL) and adding support for cdsRampMuxMatrix blocks (e.g., the newly introduced DAMPMODE). He also created two sets of unit tests, unittest.py and unittest.sh, for the two modes of use (as a Python module in other Python programs, and as a command-line utility in bash).
Report for week of 5/13
- Terrence measured Q's for nearly all modes on SR2 from TFs and then did some ring-down tests to get a better estimate of some high-Q modes.
- Terrence and Mark looked at the velocity and angular velocity noise of the SR2 as reported by the LEN and TILT OLs.
- The Y signal was fairly clean and the Y RMS angular velocity requirement was met. However the L signal was quite noisy, and was also contaminating the P signal due to the large cross terms in the diagonalization matrix. The RMS L from 5 Hz down with damping on was around 10 µm/s, which is 10 times the requirement. However little of this was due to pendulum resonances - most of the noise was featureless and broadband. In displacement units the noise was flat up to about 1 Hz and then smoothly rolled off to f^-2. The noise in the raw P and Y signals (not yet divided by the sum) was about 10 times the noise in the SUM.
- We tried improving the noise with different whitening settings. Increasing the overall gain, increasing it at the QPD but reducing it at the whitening filter, and switching off the 1-10Hz boost whitening filter (and compensating software filter) had no effect. Blocking the beam reduced the noise by about 2 orders and brought the raw P and Y in line with the SUM, suggesting that the problem was before the QPD. Akutsu-san says the noise spectrum looks like it may be limited by air currents, and we probably need better wind shielding.
Mark swapped in an improved version of vistools.py, debugged a few small issues, and simplified the TYPEB.py Guardian.
- Fabian embarked on a project to calculate the residual motion within KAGRA's observation band (beginning at 10 Hz) to make sure The Type B suspension fulfills the requirement, and calculate the speed of the optic to make sure we can acquire the lock.
- He modified Takanori's Simulink/Matlab simulation in order to include the length sensing oplev and its control feedback path.
- He imported Enzo's IM/GAS/IP-LVDT filters into the simulation.
- He imported into the simulation the measured LVDT floor noise (sensitivities).
- He calculated the IP-L, IP-T and IP-Y sensitivities.
Plan for week of 5/20
- Mark at Mitaka Mon, Tue; US from Wed till 6/11.
- Import Panwei's OSEM sensitivity measurements and calculate the sensitivity of the virtual IM sensors.
- Import geophones sensitivities and calculate the sensitivity of the corresponding virtual sensors.
- Import Licia's and Terrence's inertial sensing filters.
- Try to reduce the OL noise and get better estimates of the RMS velocity with damping on.
- Terrence's next visit from 4/18 to 7/27.
- Mark's US vacation from 5/22 to 6/11.
- Fabian at conference in Brazil from 5/31 to 6/17.
- Mark's final day 6/28.