Design and Computational Simulation of a Modular Low-Field NMR Spectrometer Prototype Based on a Halbach Array of Permanent Magnets for Use at the Costa Rica Institute of Technology
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Abstract
This study addresses the design and simulation of a low-field Nuclear Magnetic Resonance spectrometer prototype based on a modular Halbach array of permanent magnets. The objective was to develop a low-cost system with high magnetic-field homogeneity for teaching and research purposes at the Costa Rica Institute of Technology. In the initial phase, six geometric–magnetic configurations were evaluated through stationary simulations in COMSOL Multiphysics, varying the number of rings and magnet grades (N52 and N55), achieving a field inhomogeneity of 1,14%. The configuration consisting of six N55 magnet rings produced a central field of 0,305 T, this is the array used. The spectrometer was modeled by incorporating a series RLC probe with the following properties: 1 µH, 8,16 Ω, and 150,15 pF, as well as an SR560 preamplifier and a BT00250-AlphaA RF amplifier. The simulation of the 90° excitation pulse and the generation of free induction decay (FID) signals validated a pulse peak of 59 µT and an experimental FID amplitude of 30,000 a.u. Spectral analysis clearly revealed the characteristic doublet of the XA₁ spin system centered at the Larmor frequency of 12,986 MHz, confirming the expected spectral resolution. The strong agreement between theoretical and experimental results demonstrates the robustness of the design and its suitability for low-field NMR applications, providing a reliable and cost-effective platform for future research and teaching activities.
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References
[1] M. H. Levitt, Spin Dynamics: Basics of Nuclear Magnetic Resonance. Chichester, U.K.: Wiley, 2001.
[2] J. U. Izunobi and C. L. Higginbotham, “Polymer molecular weight analysis by ¹H NMR spectroscopy,” Journal of Chemical Education, vol. 88, no. 8, pp. 1098–1104, 2011, doi: 10.1021/ed100461v.
[3] D. G. Lonnon and J. M. Hook, “O quantitative nuclear magnetic resonance spectroscopy of gasoline and oxygenated additives,” Analytical Chemistry, vol. 75, no. 17, pp. 4659–4666, 2003, doi: 10.1021/ac034339q.
[4] N. R. Babij et al., “NMR chemical shifts of trace impurities: Industrially preferred solvents used in process and green chemistry,” Organic Process Research & Development, vol. 20, no. 3, pp. 661–667, 2016, doi: 10.1021/acs.oprd.5b00417.
[5] M. Meribout and S. Sonowan, “Optimal Halbach magnet array design for portable NMR targeting multiphase flow metering applications,” IEEE Transactions on Magnetics, vol. 55, no. 1, pp. 1–7, Jan. 2019, Art. no. 4001207, doi: 10.1109/TMAG.2018.2877603.
[6] E. Danieli et al., “On-line monitoring of chemical reactions by using bench-top nuclear magnetic resonance spectroscopy,” ChemPhysChem, vol. 15, no. 14, pp. 3060–3066, 2014, doi: 10.1002/cphc.201402049.
[7] J. A. Borloz-Chinchilla and I. F. Céspedes-Camacho, “Resonancia Magnética Nuclear en Costa Rica: una perspectiva histórica,” Revista Tecnología en Marcha, vol. 37, no. 3, 2024, doi: 10.18845/tm.v37i3.6870.
[8] R. Battesti et al., “High magnetic fields for fundamental physics,” Physics Reports, vols. 765–766, pp. 1–39, 2018, doi: 10.1016/j.physrep.2018.07.005.
[9] Y. Iwasa et al., “Solid-cryogen cooling technique for superconducting magnets of NMR and MRI,” Physics Procedia, vol. 36, pp. 1348–1353, 2012, doi: 10.1016/j.phpro.2012.06.303.
[10] S. In, Y.-J. Hong, H.-K. Yeom, J. Ko, H. Kim, and S.-J. Park, “Thermal and structural analysis of a cryogenic conduction cooling system for a HTS NMR magnet,” Progress in Superconductivity and Cryogenics, vol. 18, no. 1, pp. 59–63, 2016, doi: 10.9714/psac.2016.18.1.059.
[11] S. Ito et al., “Long term operation of superfluid-cooled cryostat for 920 MHz NMR spectrometer,” IEEE Transactions on Applied Superconductivity, vol. 14, no. 2, pp. 1715–1718, Jun. 2004, doi: 10.1109/TASC.2004.831051.
[12] R. de Oliveira-Silva et al., “A benchtop single-sided magnet with NMR well-logging tool specifications: Examples of application,” Journal of Magnetic Resonance, vol. 322, Art. no. 106871, 2021, doi: 10.1016/j.jmr.2020.106871.
[13] T. Karasawa et al., “Homogeneous B0 coil design method for open-access ultra-low field magnetic resonance imaging: A simulation study,” Magnetic Resonance Imaging, vol. 112, pp. 128–135, 2024, doi: 10.1016/j.mri.2024.07.006.
[14] K. K. G. Kurian, P. K. Madhu, and G. Rajalakshmi, “Solid-state NMR signals at zero-to-ultra-low field,” Journal of Magnetic Resonance Open, vols. 10–11, Art. no. 100049, 2022, doi: 10.1016/j.jmro.2022.100049.
[15] A. B. García García, “Aplicación de técnicas de resonancia magnética nuclear al estudio de miosistemas,” Ph.D. dissertation, Facultad de Veterinaria, Universidad Complutense de Madrid, Madrid, España, 2018. [Online]. Available: https://hdl.handle.net/20.500.14352/17022. [Accessed: Jul. 26, 2026].
[16] W. Wei et al., “Construction and testing of a high-homogeneity 55 T pulsed magnet for high-field nuclear magnetic resonance measurements,” Journal of Magnetic Resonance, vol. 374, Art. no. 107862, 2025, doi: 10.1016/j.jmr.2025.107862.
[17] J. Mitchell et al., “Low-field permanent magnets for industrial process and quality control,” Progress in Nuclear Magnetic Resonance Spectroscopy, vol. 76, pp. 1–60, 2014, doi: 10.1016/j.pnmrs.2013.09.001.
[18] N. Bryden et al., “An open-source, low-cost NMR spectrometer operating in the mT field regime,” Journal of Magnetic Resonance, vol. 332, Art. no. 107076, 2021, doi: 10.1016/j.jmr.2021.107076.
[19] G. Moresi and R. Magin, “Miniature permanent magnet for table-top NMR,” Concepts in Magnetic Resonance Part B: Magnetic Resonance Engineering, vol. 19B, no. 1, pp. 35–43, 2003, doi: 10.1002/cmr.b.10082.
[20] P. Yu et al., “A low-cost home-built NMR using Halbach magnet,” Journal of Magnetic Resonance, vol. 294, pp. 162–168, 2018, doi: 10.1016/j.jmr.2018.07.014.
[21] P. Blümler and H. Soltner, “Practical concepts for design, construction and application of Halbach magnets in magnetic resonance,” Applied Magnetic Resonance, vol. 54, pp. 1701–1739, 2023, doi: 10.1007/s00723-023-01602-2.
[22] Centro de Investigación en Productos Naturales, “Unidad de Resonancia Magnética Nuclear,” Universidad de Costa Rica. [Online]. Available: https://ciprona.ucr.ac.cr/unidad-de-resonancia-magnetica-nuclear. [Accessed: Mar. 10, 2025].
[23] K. Mora-Pérez, “TEC impulsa investigación y conocimiento de la Resonancia Magnética Nuclear,” Hoy en el TEC, Jan. 19, 2023. [Online]. Available: https://www.tec.ac.cr/hoyeneltec/2023/01/19/tec-impulsa-investigacion-conocimiento-resonancia-magnetica-nuclear. [Accessed: Jul. 26, 2026].
[24] K. Nishimura, “The strongest array beyond Halbach array,” Journal of Magnetism and Magnetic Materials, vol. 580, Art. no. 170933, 2023, doi: 10.1016/j.jmmm.2023.170933.
[25] L. Yang et al., “An easy-built Halbach magnet for LF-NMR with high homogeneity using optimized target-field passive shimming method,” Journal of Magnetic Resonance, vol. 357, Art. no. 107582, 2023, doi: 10.1016/j.jmr.2023.107582.
[26] Arnold Magnetic Technologies, “Sintered Neodymium-Iron-Boron Magnets: N52,” datasheet. [Online]. Available: https://www.arnoldmagnetics.com/wp-content/uploads/2017/11/N52-151021.pdf. [Accessed: Jul. 26, 2026].
[27] Arnold Magnetic Technologies, “Sintered Neodymium-Iron-Boron Magnets: N55,” datasheet, rev. 210802. [Online]. Available: https://www.arnoldmagnetics.com/wp-content/uploads/2017/11/N55-151021.pdf. [Accessed: Jul. 26, 2026].
[28] J. Wang, W. Mao, M. Qiu, M. B. Smith, and R. T. Constable, “Factors influencing flip angle mapping in MRI: RF pulse shape, slice-select gradients, off-resonance excitation, and B0 inhomogeneities,” Magnetic Resonance in Medicine, vol. 56, no. 2, pp. 463–468, 2006, doi: 10.1002/mrm.20947.
[29] D. Holmes, “NMR basic concepts handout,” Michigan State University, East Lansing, MI, USA, Feb. 2004.
[30] Q. Stern and K. Sheberstov, “Simulation of NMR spectra at zero and ultralow fields from A to Z—A tribute to Prof. Konstantin L’vovich Ivanov,” Magnetic Resonance, vol. 4, pp. 87–109, 2023, doi: 10.5194/mr-4-87-2023.
[31] S. Alcicek, P. Put, D. Barskiy, V. Kontul, and S. Pustelny, “Zero-field NMR of urea: Spin-topology engineering by chemical exchange,” The Journal of Physical Chemistry Letters, vol. 12, no. 43, pp. 10671–10676, 2021, doi: 10.1021/acs.jpclett.1c02768.