I am summarizing here recent progress on BSC-ISI units

Blend Filters for the BSC-ISI

We have standardized the blend configurations. All the BSC-ISIs are equipped with 3 different blends filters: 'Start', 'T750mHz', 'Tcrappy'

BSC-ISI Controllers

All the BSC-ISIs are equipped with a working lvl3 controller for all the DOFs, Stage 1 and Stage 2

BSC-ISI config

The most robust configuration providing good performance on all BSCs is the following:

- control lvl3 on ST1 & ST2

- Tcrappy blend filters on ST1 & ST2

To properly turn this config on, see here.

Sensor correction Stage 1 to Stage 2 has been installed on all the BSCs but ITMY.

Tilt decoupling ST1 has been installed on all the units

Tilt decoupling ST2 has been installed on BS and ITMY. I started to do X tilt decoupling on ITMX but didn't have the time to do Y.

Matrices

After the reboot of the system on February 25th, old input and output matrices have been restored on BS and ETMX. This is not a big deal, we just have to find a quiet time to restore the new ones. This process might disturn the currnt alignment though.

Performance

Find attached BS performance plot. The behavior of the beamsplitter is very representative of the behavior on the other chambers. I took BS as an example because it was available at the time, but I expect to have the same kind of results on all the chambers.

Thre configuration are tested here:

- the robust Tcrappy on ST1 and ST2

- Tcrappy on ST1, Start on ST2 with sensor correction #1 (filter 'BandPass2')

- Tcrappy on ST1, Start on ST2 with sensor correction #2 (filter 'BandPass4') > more aggressive sens corr

It is interesting to notice the different compromise between Tcrappy and sensor correction. Also, we want to be careful with sensor correction and not reinjecting very low frequency noise.

This shows that there is still some room to tweek our blends/feedforward.

I haven't had the time to try your blend Rich (next time!), and the windy configuration.