8. EMI/RFI: Electromagnetic and Radio-Frequency Interference

A myriad of man-made and extra-terrestrial sources in the non-ionizing electromagnetic (EM) energy range (0 Hz to 750 THz) emanate electromagnetic and radio-frequency interference (EMI/RFI). All sources with emissions throughout this broad frequency range can potentially degrade the performance of high-resolution imaging instruments such as SEM, TEM, FIB, and STM. This chapter discusses: (a) the most effective methods to measure ambient EMI/RFI emission levels around proposed and existing building sites; (b) units of measurement and susceptibility; (c) recommended minimal EMI/RFI thresholds for scientific tools; and (d) AC Extremely Low Frequency (ELF) magnetic flux density simulations at power frequencies. Finally, corrective strategies and costs to attenuate and control elevated EMI/RFI environments will be presented including active cancellation systems, zero milligauss shielding systems, Rigid Galvanized Sheet (RGS)/Electrical Metallic Tubing (EMT) conduits for electrical power distribution, and other mitigation techniques.