Calibration of the coil constants and nonorthogonal angles of triaxial NMR coils based on in-situ EPR magnetometers

Triaxial magnetic field coils are one of the most important components of magnetic resonance sensors. Traditional measurement methods for coil constants and non-orthogonal angles using fluxgate magnetometers are no longer suitable for small-volume nuclear magnetic resonance sensors. This study presents a method for measuring the coil constants and nonorthogonal angles of triaxial nuclear magnetic resonance coils using the dynamics of the electron paramagnetic resonance magnetometer without requiring any additional calibration equipment. After constructing the in-situ magnetometer, we measured the coil constants of the z- and the x-axes as 1189 nT/mA and 45.53 nT/mA, respectively. We obtained the nonorthogonal angle of approximately 0.18° between the z-axis and the x-y plane with a standard deviation of about 0.03° by solving the relevant trigonometric function. Additionally, the non-orthogonal angle between the x- and y-axes is approximately 1.70° with a standard deviation of about 0.17°. This study is significant for evaluating and reducing signal crosstalk errors and improving the accuracy of NMR sensors.