Imaging of dynamic magnetic fields with spin-polarized neutron beams

• Published in: New journal of physics Vol. 17; no. 4; pp. 43047 - 43064
• Main Authors: Tremsin, A S, Kardjilov, N, Strobl, M, Manke, I, Dawson, M, McPhate, J B, Vallerga, J V, Siegmund, O H W, Feller, W B
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 22.04.2015
• Subjects: Accelerator Physics and Instrumentation; Acceleratorfysik och instrumentering; Alternating current; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; Coils; Cold neutrons; Cold spinning; Diameters; Field strength; Fysik; Imaging; Magnetic domains; Magnetic fields; Magnetism; Mapping; Natural Sciences; Naturvetenskap; Neutron beams; neutron imaging; Neutrons; non-destructive testing; Physical Sciences; Physics; Position sensing; Precession; Solenoids; Spin dynamics
• ISSN: 1367-2630; 1367-2630
• DOI: 10.1088/1367-2630/17/4/043047

Precession of neutron spin in a magnetic field can be used for mapping of a magnetic field distribution, as demonstrated previously for static magnetic fields at neutron beamline facilities. The fringing in the observed neutron images depends on both the magnetic field strength and the neutron energy. In this paper we demonstrate the feasibility of imaging periodic dynamic magnetic fields using a spin-polarized cold neutron beam. Our position-sensitive neutron counting detector, providing with high precision both the arrival time and position for each detected neutron, enables simultaneous imaging of multiple phases of a periodic dynamic process with microsecond timing resolution. The magnetic fields produced by 5- and 15-loop solenoid coils of 1 cm diameter, are imaged in our experiments with ∼100 m resolution for both dc and 3 kHz ac currents. Our measurements agree well with theoretical predictions of fringe patterns formed by neutron spin precession. We also discuss the wavelength dependence and magnetic field quantification options using a pulsed neutron beamline. The ability to remotely map dynamic magnetic fields combined with the unique capability of neutrons to penetrate various materials (e.g., metals), enables studies of fast periodically changing magnetic processes, such as formation of magnetic domains within metals due to the presence of ac magnetic fields.