CAL Meeting on 2016/11/24 10:00- 12:00
Participants (ABC order): Haino, Inoue, Kanda, Kokeyama, Michiura, Tomaru, Ushiba, Yamamoto, Yokozawa,
Agenda
Pcal/Camera updates slides - Inoue
- Material properties (Young's modulus and Poisson ratio) have individual dependence. We assumed that LIGO's values are measured one. Eventually we need to measure them for each test mass on which Pcal will be injected
- There is a question that in an extremely small scale the macroscopic FEM approach is ok or not but according to the past experiences it should be OK at least in a few % order
- The camera performance is better than expected; the double lines around the center (separated by 100um?) can be identified
- It is also important to measure the spacial linearity by using a grid reference or putting the reference marker periodically
- We also need to plan how to put a reference point on the actual system; cryostat and mirror; at least in the initial (installation) phases mirror edge can be seen (not blocked by baffles)
Calibration plan and possible digitization issues - Yamamoto, Haino, ...
- For the offline analysis, where we can restrict the frequency band, the number of polynomial terms can be reasonable.
- For the real time system where we need cover wider frequency range, number of terms will increase significantly and we should make sure that they don't introduce additional systematic errors.
- Like LIGO, reconstruction of h(t) from both error and feedback signal is important to reduce such errors.
- We have to check the hardware part of the digital filters (AA,AI,ADC,DAC,etc.) on the individual dependencies and time variation in order to make sure they do not affect on the systematic errors significantly.
- It is important to compare the calibration uncertainties between without and with Pcal during the initial phases of bKAGRA.
- During iKAGRA calibration, some of important information was not recorded in the frame files, which made us difficult to completely reproduce; we need to consider it for bKAGRA from the beginning.
Injection test with Pcal - Yokozawa, Inoue pdf
- CW injection for ~year scale integration is not so easy (the signal is too small); with Pcal it might be possible
- By the time, KAGRA joins the GW observation network, it is good to have an advantage. We need to consider from theoretical/analysis side. Injection strategy can depend on that.
Virgo Pcal - Haino
- In Virgo, Pcal is injected horizontally on the center of the mirror. This is mostly due to the hardware restrictions and historical reasons (they are not putting periscopes since the initial phase)
- Instead they are planning to excite Drum mode to enhance an actuation in high frequency range.
- In case of KAGRA, we still have some freedom in the basic design so it is better to take account of possible advantages from both LIGO and Virgo
- Next meeting
- Most of CAL people don't have experience of iKAGRA calibration. Everyone knows the principle but the practical issues are not so clear.
- In the next meeting, it is good that one of those who did iKAGRA calibration (Michimura-san ?) can give us a review of iKAGRA calibration process and issues.