During a long-term, almost six month long, data acquisition in a proximity of scanning electron microscope I have found a significant source of magnetic field noise, which is altering the results. I have used the Spicer SC11 Magnetic Field Analysis system and focused on narrow-filtered RMS readings at 50 Hz. The readings are about 5 mG RMS, when the power was down the readings dropped to 0.3 mG RMS.
The problem is that the power line supplying the breaker panel is in the ceiling on the corridor next to the microscope and powers three precious devices drawing >5 kW each. Each consists of High voltage units, electromagnetic optics and supporting compressors and chillers.
The idea is to relocate the power line different way, which should reduce the EMF reading at the microscope. The microscope is supposed to be in a Farraday cage and the active EMF shielding is also installed in the lab.
Are there other options how to reduce 3 x 230 V @ 50Hz power line (IR) radiation to alter the results? Shieldings covering the cables, proper cable management, special cable arrangements, actual Farraday cage,etc.
So far I have found strategies how to protect wires and devices from the field outside. And some weirdos with aluminum hats. My target is to keep the field inside protecting the outside.