We measured again the powers:
- at the input of the EOMs --> 43 W 09:27:45 (PMC TRA 0.53 V)
- after the 3 EOMs --> 41.6 W at 09:17:30 UTC (PMC TRA 0.53 V) --> 3% losses
- after M5 -- > 36.05 W at 09:51:25 UTC --> 16% losses
Optimization of the transmitted power
- tuning of the half waveplate at the input of the EOMs to maximize the power after M5--> we increased from 36.05 W to 37.45 W after M5
- tried to maximize again the power transmitted by IPC 1 --> no improvement
- small movements with BPL to see if we improve the transmission with the beam alignment in the EOMs --> with setpoints xset = -430 and the others to 0 we obtained 42.5 W after the EOMs at 12:21:45 (0.535 PMC TRA)
- zeroing of the corrections on PZT of LB M14 mirror (we moved the screw with loop closed to reduce the corrections of INJ BPL PZT LB M14H/V CORR) and recentering of the near field QPD to set the shift X from -300 to 0 (loop open and DC on we moved the h screw of the mirror just before BPL QN to bring INJ BPL X ERR from -300 to 0, and then changed the setpoint to 0 in the cfg file). Now all the setpoints are 0 and the corrections have been reduced to <1 V
We remeasured the input power and the power after the 3 EOMs getting 42.4/43.1 --> 2% losses in the 3 EOMs
power after M5 37.8 W --> 13% losses in the line EOMs + IPC + Faraday isolator
Since the biggest part of the losses occurr in the line IPC +Faraday we proceeded then measuring the power after M5 and better aligning the beam with the mirror just before the IPC. We also inspected the optics with a dentist's mirror and nothing strange was noticed
We got 39.3 W after M5. 39.3/43.1 (a second measurement of the power gave 38.3 W after M5, since it is slightly dependent on the beam impinging point on the calorimeter) --> 9-11% losses in the line EOMs + IPC + Faraday isolator
Characterization of the beam after M5 (to be compared with the last measurement done on the 4th of May 2026 #69064).
Beam profiler used: DataRay, power 4mW after M5 (reduced with IPC1) + filter OD 7, light in the LL switched off
| distance z from M5 [mm] | ellipticity | beam width [um] |
| 85 | 96% | 1340 |
| 140 | 97% | 1390 |
| 185 | 96% | 1420 |
| 235 | 96% | 1460 |
| 285 | 96% | 1510 |
| 335 | 94% | 1540 |
545 um (instead of 508 um on the 4th of May, to be checked the PMC TRA value) at z= -0.54 for M5
Realignment and calibration of EIB POUTto be checked
Set IPC1 back as before at 30W
nb: for the high power measurements we used the ophir calorimeter (avg 10s) with a diverging lens -30 mm in front of it (we do not have the serial number of the lens, maybe it is custom, but it seems to have an AR coating)