EPR Signal Optimization

Scientists in various disciplines, from physics to food science, use electron paramagnetic resonance (EPR) spectroscopy to identify parameters of paramagnetic materials. To perform EPR spectroscopy, linearly polarized microwaves irradiate a paramagnetic sample in a modulated magnetic field. The sample partially absorbs the microwaves, which changes their polarization. A series of quasi-optics direct the microwaves back toward their source. In induction mode, the detected EPR signal is perpendicular to the initial microwave polarization. Imperfections throughout the quasi-optics necessitate a way to correct unwanted changes in polarization to optimize the signal-to-noise ratio (SNR). The solution is to include a tunable rooftop end mirror within the sample holder. However, manual rotation of the rooftop mirror results in imprecise optimization and inefficient data acquisition. Implementing an automated rooftop end mirror system, including a step-servo controlled by LabView with serial communication and a 3D printed connector with timing pulleys, improves the SNR in EPR spectroscopy by increasing angular precision.