Naval Facilities Engineering Command- NSRL:

NSRL Outside Photo

The Naval Facilities Engineering Command recently completed construction of a 22,000 sq/ft Nano Science Research Laboratory (NSRL) on the campus of the Naval Research Laboratory in Washington, DC. The building design included fourteen Imaging Rooms intended to house a variety of advanced, state-of-the-art SEM/TEM and other microscopes.

EMI Threat Specification

The building’s EMI threat specification required that ambient stray AC magnetic fields could not exceed 0.3 mG in each of the fourteen Imaging Rooms once the building was completed and occupied.

EMI Threshhold Requirement

FMS provided the project’s design and construction team with expert guidance to ensure that the required < 0.3 mG stray magnetic field EMI threshold requirement was met in all fourteen Imaging Rooms. FMS was able to achieve the requisite 0.3 mG threshold entirely by careful implementation of design decisions and construction techniques known to minimize stray field conditions. As a consequence, supplemental shielding and other mitigation measures were not required.

Threshhold Testing Plan

To verify that the AC Magnetic Field Levels With temporary loading conditions established on the building’s electrical distribution system, precision test and measurement equipment capable of making highly accurate measurements (within 1% at 60Hz for magnetic field strengths between 0.01 mG and 10 mG) was employed to verify AC magnetic field levels in all fourteen Imaging Rooms.

AC Magnetic Field Levels

With temporary loading conditions established on the building’s electrical distribution system, precision test and measurement equipment capable of making highly accurate measurements (within 1% at 60Hz for magnetic field strengths between 0.01 mG and 10 mG) was employed to verify AC magnetic field levels in all fourteen Imaging Rooms.

Line Plot of Precision Measurements

Typical line plot of precision measurements taken in each of the fourteen Imaging Rooms confirm that AC magnetic field environments had been successfully reduced to levels significantly well below the target EMI threshold of 0.3 mG. The NRSL facility has subsequently been occupied and sensitive microscopes are operating without EMI interference concerns.