I went in the PSL enclosure this morning for:

• measuring beam powers at various points in the downstream of PMC
• and fixing an issue with the PMC transmitted light monitor.

Power measurements

This is a part of the effort to get better estimation of how much laser power we will get in the upcoming commissioning test. All the measurement was done with a hand-held power meter, Ophir Vega, and a thermal-type power meter head, 10A-V2-SH. The results are shown below:

The issue with the PMC transmission monitor is fixed

After a short shut-down of PSL on 28th of October (alog 8297), we found that the PMC transmission monitor (H1:PSL-PWR_PMC_TRANS) kept showing a very low number e.g. ~ 1.5 W which was supposed to display ~ 12 W. It has been unclear why it happened and what caused it. We started suspecting that somewhere in the analog chain is acting funny. So I took a look at the PD this time. The alignment of the beam on the PD looked good when I looked with a sensor card. Then I started checking the LEMO connector which sends the signal from the PD to the digital system. Surprisingly, disconnecting and re-connecting the LEMO connector at the PD fixed the issue. Also, I was unable to reproduce the same low-readout situation any more. I believe it was due to some sort of loose connection at the connector. Anyway it now displays 11.6 W which is what it is supposed to be. Good.