Signal Enhancement for Fast Field-cycling Relaxometry by Dynamic Nuclear Polarization: Basic Principles, Hardware and Methods
In this chapter, the basic principles of NMR signal enhancement by dynamic nuclear polarization (DNP) and its application in DNP-enhanced fast field-cycling relaxometry (DNP-FFC) are introduced. After a brief introduction to DNP effects in liquid and solid samples, practical aspects of DNP-FFC are considered, including common radicals and exemplary applications, together with the necessary microwave equipment and the requirements for DNP-FFC probeheads. Guidelines for the choice of the polarization field strengths are given and also considerations regarding dielectric sample heating effects. Finally, a basic DNP-FFC pulse sequence-based continuous-wave microwave irradiation method is introduced and an outlook on the future development of DNP-FFC is provided.