Since the recent increase in the INJ-HVAC flow rate (from 30 May to 4 June 2025), a new noise feature has become visible on the microphones and accelerometers located on the Laser Bench and the External Injection Bench inside the Laser Lab.

The noise manifests as a characteristic doublet "bump", recurring approximately every 6 minutes. This suggests a mechanical or fluid-dynamic origin, potentially linked to the altered HVAC regime.

Before the intervention, the air flux was stable at 10 m³/h. After the change, it now oscillates between 20 and 60 m³/h. This fluctuation appears correlated with the observed noise.

• Has this change been requested by someone?

• Would it be possible (and advisable) to revert to the previous setting to mitigate the noise?