From The DNP-NMR Blog:
Improving B1 field homogeneity in dielectric tube resonators for EPR spectroscopy via controlled shaping of the dielectric insert
Syryamina, Victoria N., Anna G. Matveeva, Yan V. Vasiliev, Anton Savitsky, and Yuri A. Grishin. “Improving B1 Field Homogeneity in Dielectric Tube Resonators for EPR Spectroscopy via Controlled Shaping of the Dielectric Insert.” Journal of Magnetic Resonance 311 (February 2020): 106685.
https://doi.org/10.1016/j.jmr.2020.106685.
We propose an approach for improving the homogeneity of microwave magnetic field amplitude in a dielectric tube resonator for electron paramagnetic resonance spectroscopy at X-band. The improvement is achieved by “shaping” (controllable variation of the outer diameter of a dielectric insert along its axial direction). Various shaping scenarios based on the principle of discrete solenoids and electromagnetic calculations have been considered. The dielectric insert having the most promising shape was manufactured from a bismuth germanate single crystal. The shaped insert increases the area at B1 > 0.9 B1max from 5.06 to 7.36 mm. Higher sensitivity and lower likelihood of quantitative errors have been achieved in pulse EPR experiments for “long” samples (whose length was comparable to that of the dielectric insert) in a shaped dielectric insert.
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