Open-type EPR spectrometer to measure electron spins of a sample located outside a resonator

Abstract

An open-type electron paramagnetic resonance (EPR) spectrometer to measure a sample located outside a resonator was fabricated. As the resonator, the field modulation coils, and the main magnet were integrated on the resonator side in the sensor head, the space fora sample was opened. Thus, a large sample could be placed at the end of the resonator without much limitation on the size. For ah apptication of this apparatus, various coal masses were placed on the resonator of the sensor head and EPR measurements were performed nondestructively. It was found that the EPR signal intensity of coals showed a good correlation with the carbon-to-hydrogen ratio, one of the parameters for classifying coal.