Sheila, Kiwamu,

The goal tonight was to add TOP and UIM of ETMY to the DARM actuator in order to increase the control bandwidth. This worked fine and the UGF was pushed a bit higher and it is now 4 Hz.

As Sheila reported on alog 11787, we prepared ETMY. So we started using ETMY in addition to ETMX. Since ETMY's ESD is not ready yet, we used only TOP and UIM of ETMY. This helped the DAC range of the UIM stage and therefore we could push the UGF a bit higher. At the end, we ended up a UGF of about 4 Hz. The infrared RMS is now about 90 Hz. We didn't redesign the low-frequency boost this time as our target was to have a higher UGF. The attached is the ALS diff spectrum (shown in red), with the spectra from yesterday for comparison. You can see that the noise is suppressed below 4 Hz. Currently the UGF is limited by UIM and TST which saturate at high frequencies.