Resonator and coupling structure for spin-echo ESR

Abstract

Any resonator can be characterised intrinsically by two parameters, the filling factor eta and the quality factor Q. The authors have derived the relations that relate them to the parameters of both CW and pulsed magnetic resonance, i.e. the signal-to-noise ratio and the RF magnetic field amplitude B₁.At X-band frequencies, they have compared a 'loop-gap' resonator to a cylindrical TE₁₀₁ cavity both theoretically and experimentally. It was found that the former had distinct advantages over the latter in pulsed ESR, and retained some of them even in CW ESR. A new coupling configuration is proposed, based on the 'Gordon coupler', to connect the loop-gap to a waveguide. This resonator and coupling structure are well suited for spin-lattice relaxation experiments in solids at low temperatures.