Vern, Peter, Nutsinee

Quick Conclusion: The power readout from the front end channel (CO2_LSRPWR_MTR_OUTPUT) agrees with the analog readout at the table. So this channel is an accurate representation of what goes to the periscope.

Details: We made four measurements at various spots (see attachment). First we measured the power going to the bottom periscope mirror (point 4) to confirm that the readout was indeed agreed with the front end channel and the maximum outgoing power was really ~2W (running with CW through 18 deg RS). After that we tried to identify where we lose the power. We lased the power using PWM at 12%. The power drop between point 1 and point 2 was ~8.5% which agrees with our measurement back in early Feburary (alog25410). However, the power drop between point 2 and point 3 was 65%, in Feburary we observed only 12% power drop at this point. This suggests that the beam must have clipped on either M4A or M4 mirror. Peter was saying the beam was hugh at this point (about the size of a nickel). The power drop between point 3 and point 1 was 87%, agrees with what we measured in February. This suggests further that the clipping at M4 mirrors is a new issue.