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AdV-TCS (CO2 laser projector)

berni, lumaca, nardecchia, spinicelli - 18:20 Wednesday 10 September 2025 (67678)

Variation of the WI CH TTL signal

At around 14:00 UTC, after the interferometer unlocked and we were close to the lower limit of the available WI CH power, we asked Piernicola and Francesco to go to the TCS room to switch the WI CH TTL signal OFF and then ON again. Unexpectedly, while acting on the wavefront generator in the TCS room and reducing the TTL signal pulse width (from 199 μs to about 95 μs), we observed a significant increase in power. Given this unexpected behavior, we decided to leave the laser at around 50% duty cycle. This suggests that the issue is more likely related to the electronics rather than to the gas running out.

We then adjusted the waveplate to restore the nominal injected power into the ITF.

This behavior is not completely clear to us. We will monitor it for a day to determine whether it represents a (strangely) stable situation or not.

Images attached to this report

67678_1757521201_Screenshot 2025-09-10 181933.png

Comments to this report:

nardecchia, nocera - 11:12 Tuesday 16 September 2025 (67717)

This morning we performed a measurement of the current from the DC power supply to the laser, as requested by the laser supplier.
No shutdown or restart of the laser was necessary.

WI CH laser results:

100% duty cycle (199 µs) → 5.1 A
50% duty cycle (95 µs) → 2.8 A

We also took the opportunity to perform the same measurements on the NI CH laser:

100% duty cycle (199 µs) → 4.7 A

These results will be communicated to the supplier to confirm whether they are within the expected range.