A NMR (nuclear magnetic resonance) transmit/receive switch according to
some embodiments of a nuclear magnetic resonance apparatus includes
receive-path and/or transmit-path superconductors, which are selectively
quenched to switch the connection of an NMR radio-frequency coil between
transmit and receive circuits. In the transmit state, the transmit-path
superconductor is in a superconducting state while the receive-path
superconductor is quenched, to isolate a receive-path amplifier from the
relatively higher powers of the NMR pulses applied to the sample by the
transmit circuit. In the receive state, the receive-path superconductor
is in a superconducting state while the transmit-path superconductor is
quenched. A DC power source is used to supply supercritical current to
the superconductors to quench the superconductors.