Design, construction, and performance of a magnetically shielded room for a neutron spin echo spectrometer

A double-layer magnetically shielded room (MSR) has been designed and constructed for the neutron spin echo (NSE) spectrometer at the Spallation Neutron Source (SNS) in Oak Ridge, Tennessee. The primary objective of the MSR is to ensure an undisturbed operation of the spectrometer in terms of external magnetic fields from high-field magnets at neighboring beamlines and from other external devices. Because of the required mobility of the spectrometer along its beamline the MSR features a total length of about 17 m, which makes it the largest MSR worldwide. Several physics and engineering aspects addressed in the design phase and during the construction of this unique MSR are described in this article.