Measurement results and improvements on an open EPR system

Electron spin resonance (ESR) is a spectroscopic method that allows to measure stable radicals induced by ionizing radiation. The EPR measurements can help to estimate the dose absorbed by people exposed during a nuclear disaster, detecting the number of radicals induced in their mobile phones due to the exposition [1]. Using conventional closed microwave cavities, the phone display must be fragmented in order to be introduced inside the resonator, becoming no more usable. The aim of this work is to develop a system, compatible with the spectrometer Bruker Elexys E500, able to preserve the sample integrity. The system uses an X-band resonant metallic cavity with a slit, realized on one side, for the leak of the excitation magnetic field and a Helmotz coil pair. The resonator allows measuring a sample lodged outside the cavity, while the coils produce a 100 kHz modulated field that encodes the output signal at a particular frequency and increases the SNR.