EPR Microresonators

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Magnetic resonance uses microwaves to exite transitions between different spin states and detects the oscillating magnetic field generated by the evolution of coherent superposition states of the spins. Excitation therefore requires the conversion of a microwave signal into an oscillating magnetic field and detection the reverse process. The efficiency of both processes can be enhanced by a suitable resonant structure, the microwave resonator. In most EPR spectrometers, these resonators consist of standing-wave cavities, whose dimensions are determined by the wavelength of the microwave field. For samples that are significantly smaller than this wavelength, cavities have a small filling factor, which reduces their sensitivity. The goal of this project is the design and implementation of highly efficient resonators for small samples. For this purpose, we use planar circuits with dimensions significantly smaller than the wavelength of the microwave. We design them such that the circuit impedance is 50 Ohm at the design frequency. The designs are simulated numerically and manufactured by standard lithographic techniques. Most of these resonators are delivered to other projects in the priority program, and we optimize the design for the requirements of these individual projects.