Ushiba, Akutsu

Replaced some light sources for oplevs with new ones; those were for ETMY-TM, ETMX-TM, and ETMX-MN. For reference, we checked the transmitting green flashing for each arm to confirm no strange behaviors happened during the replacing works. The serial numbers of the relevant light sources are

We centered the relevant QPDs as much as possible. And (not directly relating to these works) took back a stocked light source (S/N 203247) from the Xend so that send it back to the company according to our agreement with the company. Altough the older ones were degraded, they could still provide certain amount of light, so we stocked them at the center room in the tunnel in case.

Recovery of the SUM is shown in the following table. The numbers are in counts. So much recovery. Note that only for the EMTX-MN, as the light power on the QPD was close to saturation (~50000 counts), we switched the gain of the QPD circuit to the lower side.

We also roughly checked the oplevs spectra before and after the replacement; see the data at /users/AOS/20200109 , where we could find relevant improvement of the noise floor.