MagViz: A Bottled Liquids Scanner Using Ultra-Low Field NMR Relaxometry

摘要

Field Forensics, Inc. (FFI) has built a bottled liquids scanner utilizing ultra-low field NMR relaxometry. This device, called MagViz, is based upon a prototype developed at the Los Alamos National Laboratory (LANL) (Espy et al. Appl Supercond IEEE Trans 21(3):530, 2011; Espy et al. Supercond Sci Technol 23:034023. doi:10.1088/0953-2048/23/3/034023, 2010) [1, 2]. Despite using conventional Faraday detection coils in lieu of SQUIDs, MagViz, has demonstrated sufficient sensitivity to identify a number of threat liquids of interest to the Department of Homeland Security (Matlashov et al. Appl Supercond IEEE Trans 21(3):465-468, 2011) [3]. By accurate measurement of T_1 and T_2, liquids contained in opaque bottles and even non-ferromagnetic metal containers can be reliably identified. Protons are aligned using a 50 mT pre-polarizing field. T_1 is determined in the pre-polarizing field, and T_2 relaxation time is typically measured at 2,048 Hz in a 48 μT field. The coil assembly is contained within a table-top 0.79 m tall magnetically shielded enclosure. Although primarily intended for commercial and security applications, MagViz, works at Larmor frequencies that correspond to timescales that are characteristic of a host of interesting, slow, molecular dynamic processes like diffusion and intramolecular motion as well as biological processes such as protein folding, catalysis, and ligand binding and could conceivably serve as a COTS research instrument for fundamental studies in these areas.