Interplay among recovery time, signal, and noise: Series- and parallel-tuned circuits are not always the same

The quality factor, Q, of the magnetic resonance probe and the manner in which the probe is coupled to the spectrometer play important roles in the quality of the obtained experimental data, affecting the signal-to-noise ratio (SNR), the probe recovery time, radiation-damping, and the coupling between multiple coils. For example, high SNR often requires a high-Q probe, while a short recovery time to observe of broad signals generally requires low Q. Here, we discuss effecting a compromise between SNR and recovery time by adjusting the coupling of the probe and preamplifier by mismatching their impedances. Unlike the more common impedance-matched case, the conditions for optimum performance for parallel- and series-tuned probes are found to differ significantly.