Abstract: An NMR probe head (1) for performing high-resolution, liquid-state DNP-NMR comprises a corrugated waveguide (3) for mw transmission, arranged along a longitudinal axis Z of the probe head; a system of at least two of mw reflecting mirrors (4-7) for mw beam transmission, focusing and reshaping the beam to match for a sample geometry; at least one RF coil (11,12) for NMR detection mounted in a way to allow mw passage to the sample area, characterized by a cooling system comprising a flow dewar tube (8) for feeding cryogenic fluid mounted at the side of the probe head and parallel to the corrugated waveguide and a thermally isolated sample chamber (26) surrounded by a chamber dewar (9); a sample spinning arrangement being configured to achieve uniform irradiation over a sample volume, to increase the sample volume under mw irradiation, and to reduce sample heating; a sample assembly (13) comprising concentric circular tubes or rods (15, 16) forming constraints for a sample layer (14).

Abstract: A microwave resonator device (1), being configured in particular for electron spin resonance measurements, comprises a resonator being resonant with first and second microwave field modes and including first and second resonance sections (7, 8) arranged along a longitudinal axis (2) of the resonator, and a coupling unit being arranged between the first and second resonance sections, wherein the coupling unit includes a conducting plate (16) being arranged on the longitudinal axis (2) and covering a central portion of a cross-sectional area of the resonator, the conducting plate (16) is adapted to adjust a first mode frequency of the first microwave field mode, and the conducting plate (16) is arranged at a field minimum of the second microwave field mode. Furthermore, a method of conducting an electron spin resonance measurement with a sample to be investigated is described.

Abstract: A microwave resonator device (1), being configured in particular for electron spin resonance measurements, comprises a resonator being resonant with first and second microwave field modes and including first and second resonance sections (7, 8) arranged along a longitudinal axis (2) of the resonator, and a coupling unit being arranged between the first and second resonance sections, wherein the coupling unit includes a conducting plate (16) being arranged on the longitudinal axis (2) and covering a central portion of a cross-sectional area of the resonator, the conducting plate (16) is adapted to adjust a first mode frequency of the first microwave field mode, and the conducting plate (16) is arranged at a field minimum of the second microwave field mode. Furthermore, a method of conducting an electron spin resonance measurement with a sample to be investigated is described.