Travis and Darkhan's calibration measurements made two days ago indicated that the clipping observed at Xend is getting worse.

We think this reduction is almost completely one beam and that the reduction in Rx power is taking place on the Rx side of the ETM (more on this later).

We expect to go inside the vacuum envenlope and investigate at our next opportunity.  In the meantime, we are switching to using the Tx PD rather than the Rx PD for calibration.

We need to make this switch for calibrating the hardware injections too.

In the first attached plot, SLM-tool data, 60 sec.-long TTFs of the Pcal Rx and Tx PD signals is plotted, the receiver side (Rx) data divided by the transmitter side (Tx) data.

The second plot is a comparison of the GDS calibration to the Pcal calibration at 3 kHz using the Rx PD, and  the Tx PD in the last plot.

The mean magnitude ratio using the Rx PD is about 14%.  It is 8% using the Tx PD.