Open-source compact time-domain hydrogen (1H) NMR System for Field Deployment

This paper presents a compact, low-cost time-domain nuclear magnetic resonance (TD-NMR) system based on a 0.5 T permanent magnet designed for in-situ ${}^1$ H measurements. Unlike conventional high-field nuclear magnetic resonance (NMR) spectrometers, this system emphasizes relaxation times rather than chemical shifts, enabling material property analysis without large magnets or complex spectral processing. The hardware employs an off-the-shelf data acquisition and control system along with a custom PCB for signal conditioning, ensuring straightforward deployment and reduced costs. The system's core sequence is a Carr-Purcell-Meiboom-Gill pulse train, chosen for efficient $T_2$ relaxation measurements under varying magnetic susceptibilities. By focusing on relaxation measurements, this approach bypasses complexities of high-resolution spectroscopy, enhances signal-to-noise in low-field conditions, and enables robust characterization across challenging environmental settings. We validate the system using aqueous Copper(II) sulfate solutions, correlating T ${}_2$ values with copper concentrations to simulate environmental heavy metal contamination monitoring. Prior work has demonstrated versatility in fuel property analysis and environmental sensing, confirming broad applicability for this portable platform. While packaging and integration with ancillary equipment (e.g., flow-through systems) are not covered, the platform serves as a versatile foundation for specialized deployments. Its open-source design and affordability aim to democratize NMR technology and extending its utility beyond conventional laboratory environments. This accessible configuration fosters widespread educational and professional use.