Fig. 1

Overall schematic diagram of low-field solid-state MAS probe structure

Fig. 2

Schematic diagram of the miniaturized MAS unit structure design

Fig. 3

3D exploded view of the miniaturized MAS unit

Fig. 4

Simulation diagram of the miniaturized MAS unit drive gas path. (a) Air pressure distribution diagram;(b) Flow velocity distribution diagram

Fig. 5

Geometric structure diagram and key parameters of the solenoid coil

Table 1

Simulation optimization of solenoid coil turns

Fig. 6

Simulation results of the B1 field distribution of the solenoid coil, where magnetic flux density refers to the magnetic induction intensity of the radio frequency field, and the color from blue to red indicates the magnetic induction intensity from weak to strong

Fig. 7

Physical picture of the miniaturized MAS unit

Fig. 8

Physical picture of the solenoid coil

Fig. 9

Matching network of the radio frequency circuit and the physical picture. (a) LC parallel resonant network; (b) Photograph of the RF circuit

Fig. 10

Physical picture of the low-field solid-state MAS probe. (a) Probe for 7Li NMR signals; (b) Probe for 1H NMR signals

Fig. 11

Test results of the probe S11 parameters. (a) Test results of the S11 parameter for the 1H probe; (b) Test results of the S11 parameter for the 7Li probe

Fig. 12

Rotate speed test diagram of the MAS unit. (a) Low-field solid-state MAS probe; (b) Pneumatic control console

Table 2

Correspondence table of no-load rotor speed and air pressure

Fig. 13

Block diagram of the low-field nuclear magnetic resonance testing platform composition

Fig. 14

Probe and magnet combination diagram. (a) Combined physical diagram; (b) Physical image of a bare magnet; (c) Combination schematic diagram

Fig. 15

1H NMR spectra of the adamantane sample. * the rotating sideband

Fig. 16

Test results of 7Li NMR spectra. (a) 7Li NMR spectrum under high field reported in the literature[10]; 7Li NMR spectrum of LiFePO4 (b), Li3PO4 (c), LiCoO2 (d) and LiMn2O4 (e) under low field