On November 29, 2024, one of the two parallel, redundant UPS units at the WEB failed. All systems were left running on the IPS mains line without any UPS backup.

On December 4, 2024, a second failure caused a complete WEB blackout. After restoring power, the system resumed operation in “emergency mode,” with only a single UPS supplying the experimental UPS mains line.

On July 1, 2025, two new UPS units were installed and commissioned in parallel, redundant mode.

We focused on noise measurements taken before the UPS replacement (old UPSs) and after the installation of the new UPSs.

The selected measurement windows—chosen to avoid periodic noise from running equipment—are:

• Nov. 29, 2024 at 00:05:00, duration +300 s (old UPSs)

• July  20, 2025 at 00:10:00, duration +300 s (new UPSs)

Comparing the results:

• The overall noise level recorded by the UPS voltage monitors is lower with the new UPSs than with the old (purple = old; blue = new;    upper plots = voltage; lower plots = current).

• The low-frequency (~1 Hz) noise bump is substantially reduced.

• One exception: around the 50 Hz mains line, the new UPSs introduce two sidebands spaced by 6 Hz.

Coherence analysis with the experimental hall magnetometers at the WEB — dominated more by current consumption than by voltage noise — still shows a reduction at the 1 Hz peak and around even harmonics (e.g., 100 Hz), but an increase near the 50 Hz fundamental.