This morning, according to the planned schedule, we attempted to switch on the NI and WI main CO₂ lasers.
After Nicola and Cecilia successfully restored the chillers and the Guardian system, the NI and WI main lasers were switched on at 08:17 UTC and 08:18 UTC, respectively.
Unfortunately, after about 1 minute and 40 seconds of operation, the WI main laser unexpectedly switched off (fig.1). Several attempts were then made to restart it, but without success.
At that point, Roberto and Flavio joined the investigation, and a series of checks was performed to determine whether the problem was related to the laser itself or to the driving electronics.
- The electronics in TCS room were swapped between the NI and WI systems. The NI laser switched on correctly using the WI electronics, while the WI laser still failed to switch on. This excluded the RF driver and the 5 V TTL signal generated in the TCS room as the source of the problem.
- We then proceeded with additional checks underneath the WI bench, where the laser electronic is installed. With all lasers switched off, Roberto verified that the RF signal was correctly reaching the RF driver.
A visual inspection of the bench, including the BNC connections and the laser itself, did not reveal any obvious anomaly. The laser status LED was correctly lit in red, and all RF driver dongles were green, as expected.
After closing the bench, we performed one final startup attempt. This time the WI laser switched on, but only at approximately half of its nominal power. After another power cycle, the laser briefly reached its nominal output power before dropping again to approximately half power (fig.2).
During the brief period in which the laser reached nominal power, I acquired a thermal camera image of the DAS beam (fig.3). No anomalies were observed.
These observations suggest that the problem is more likely related to the electronics than to the laser itself. To be understood.For safety reasons, we decided to switch off both lasers on the WI bench.
At the time of writing, the laser status is as follows:
- NI bench: both the auxiliary and the main CO₂ lasers are switched on, with all beams blocked on the bench.
- WI bench: both the auxiliary and the main CO₂ lasers are switched off.
The WI main chiller is off. The backup chiller is connected only to the NI.
For the auxiliary chiller, the valve to the WI branch has been closed to avoid circulating cold water through the switched-off WI laser.
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As a side note (but an important one), I am experiencing significant difficulties with online monitoring using Data Display, even when using the previous version (Dy/v11r2/Linux-x86_64-AL9). While monitoring the channels, the displayed data frequently disappear for several seconds before reappearing. After some time, the application freezes completely and has to be restarted (see Fig. 4 for an example).
