title: Earth's field NMR flow meter: preliminary quantitative measurements.
abstract: In this paper we demonstrate the use of Earth's field NMR (EF NMR) combined with a pre-polarising permanent magnet for measuring fast fluid velocities. This time of flight measurement protocol has a considerable history in the literature; here we demonstrate that it is quantitative when employing the Earth's magnetic field for signal detection. NMR signal intensities are measured as a function of flow rate (0-1m/s) and separation distance between the permanent magnet and the EF NMR signal detection. These data are quantitatively described by a flow model, ultimately featuring no free parameters, that accounts for NMR signal modulation due to residence time inside the pre-polarising magnet, between the pre-polarising magnet and the detection RF coil and inside the detection coil respectively. The methodology is subsequently demonstrated with a metallic pipe in the pre-polarising region.
authors.affiliation: School of Mechanical and Chemical Engineering, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia. Electronic address: einar.fridjonsson@uwa.edu.au.
authors.forename: Einar O
authors.initials: EO
authors.lastname: Fridjonsson
authors.affiliation: School of Mechanical and Chemical Engineering, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia.
authors.forename: Paul L
authors.initials: PL
authors.lastname: Stanwix
authors.affiliation: School of Mechanical and Chemical Engineering, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Johns
keywords: EF NMR; Flow; Flow meter; Pre-polarisation