Travis S, Darkhan T,

Overview

On August 4th PcalX maintenance measurements were taken at EX. During maintenance we adjusted AOM bias. The offset value for the OFS drive was also adjusted, but incorrectly (see details). Today we re-ajusted OFS offset value to +5.14V.

Details

During Pcal maintenance measurements of the Pcal laser power in the Transmitter module were taken to assess Pcal drive range. Analysis of the measurement will give us an efficiency of an AOM driver (max diffracted power), assessment of pick-off power levels for the transmitter PD, OFS PD, maximum available output power modulation range. At the moment the measurements have not been fully analyzed.

The AOM bias voltage was adjusted for it to give ~50% out of max available AOM drive when the OFS loop is open. The OFS offset was adjusted accordingly in the front-end. Originally this was not done correctly, cause the OFS offset was adjusted when the loop was not closed.

Later when Evan tried to close the loop, the error signal, i.e. sum of the OFS PD signal and the OFS offset (when excitations and injections are turned off), saturated the AOM driver.

This is now fixed by adjusting the OFS offset to +5.14V.

We turned back on the excitations (currently one line with 39322 ct amplitude at 3501.3 Hz) and hardware injections.