Multicoil low-field nuclear magnetic resonance detection and imaging apparatus and method

A method for performing low-field NMR measurements with a Nuclear Magnetic Resonance (NMR) apparatus comprising an AC voltage generator, at least two detection coils wherein one or more of the detection coils serve as transmitting coils in a transmit mode and wherein one or more of the detection coils serve as detecting coils in a receive mode, at least two receive switching circuits, and at least two preamplifier circuits, the method comprising:

• in a transmit mode, generating, with the AC voltage generator, an alternating voltage waveform with an operating frequency, while allowing current from the AC voltage generator to flow through the one or more transmitting coils, and while maintaining the receive switching circuits in an opened state, isolating the preamplifier circuits from the alternating voltage waveform;
• the one or more transmitting coils creating an alternating magnetic field Bl which tips the NMR spin magnetization in a sample located within the low-field away from an axis of a static magnetic field BO, and sets the spin magnetization precessing about the BO field axis;
• in a receive mode, closing the receive switching circuits, inhibiting current flow through the detection coils, and detecting NMR induced voltages on the detection coils with electronics comprising the preamplifier circuits, wherein one or more of the preamplifier circuits has an input impedance greater than the impedance of a detection coil at the operating frequency.