This article is not directly related to DNP, however, for everyone interested in building NMR probes, this paper gives a nice overview of the different concepts of circuit elements in an NMR probe. While this article focuses on micro-coils, most of the concepts can be applied to RF circuit design for NMR probes in general.
Davoodi, Hossein, Mazin Jouda, Jan G. Korvink, Neil MacKinnon, and Vlad Badilita. “Broadband and Multi-Resonant Sensors for NMR.” Progress in Nuclear Magnetic Resonance Spectroscopy 112–113 (June 2019): 34–54.
It has always been of considerable interest to study the nuclear magnetic resonance response of multiple nuclei simultaneously, whether these signals arise from internuclear couplings within the same molecule, or from uncoupled nuclei within sample mixtures. The literature contains numerous uncorrelated reports on techniques employed to achieve multi-nuclear NMR detection. This paper consolidates the subset of techniques in which single coil detectors are utilized, and highlights the strengths and weaknesses of each approach, at the same time pointing the way towards future developments in the ﬁeld of multi-nuclear NMR. We compare the different multi-nuclear NMR techniques in terms of performance, and present a guide to NMR probe designers towards application-based optimum design. We also review the applicability of micro-coils in the context of multi-nuclear methods. Micro-coils beneﬁt from compact geometries and exhibit lower impedance, which provide new opportunities and challenges for the NMR probe designer.