Design And Development Of Specialized Gradient Coil For High Field NMR Spectrometer

Gradient coil is one of the most important components of NMR spectrometer.It is mainly used to realize automatic shimming and spectroscopy pulsed gradient detection technique,so as to obtain better signal quality and more detection information.In recent years,non-linear gradient and microfluidic NMR detection have opened a new direction in the field of NMR.Z2 gradient coil can provide new detection information for new spectral methods such as iMQC and improve spectra resolution.Microfluidic nuclear magnetic resonance(MFNMR)can be used to detect in situ chemical reaction intermediates and analyze cell metabolism.The commercial gradient coil of superconducting pulsed NMR spectrometer has limited usable space and no non-linear gradient coil adapted,so it is not suitable for installation and detection of microfluidic chips and Z2 gradient field experiment.The structure of microchannels is complicated and varied,and sometimes needs multiple inlets.Therefore,the width and size of microfluidic chips is larger,and the corresponding NMR microRF coil is also microstrip structure,which puts forward a larger coil space demand for the microfluidic probe of NMR spectrometer.Therefore,it is of great significance to study the Z2 gradient coil and the gradient coil adapted to the microfluidic chip.Based on the principle of non-coil gradient coil and the technical characteristic of microfluidic NMR technology,a new method of Z2 gradient coil and for high-field superconducting pulse NMR spectrometer and biplanar three-dimensional on-chip micro-gradient coil(XYZ-Gradient-coil-on-Chip)for microfluidic technology are proposed through theoretical analysis and design simulation.First,the main methods of gradient coil design,including forward design method and target field design method,are discussed,and the performance index of gradient coil is studied.On this basis,the design scheme and development index of Z2 gradient coil and 3d on-chip gradient microcoil are proposed.Second,with theoretical analysis,the self-shielding Z2 gradient coil and the three-dimensional micro-gradient coil on chip are designed by COMSOL Multiphysics,and the efficiency,effective region and linearity error are analyzed.Finally,on the basis of the design and simulation,an on-chip micro-gradient coil is developed and its performance is tested.The results showed that the Z2 gradient coil and three-dimensional micro-gradient coil had better performance.Compared with the unshielded coil,the self-shielding effect of Z2 gradient coil is at 20 mm away from the XY plane,and the magnetic field intensity is reduced by 91.7%.The gradient efficiencies of on-chip gradient coil XYZ in three directions are 5.66 Gs/(cm A),4.15 Gs/(cm A),2.12 Gs/(cm A),and the linearity errors are 2.32%,5.3 1%and 1.09%,respectively.