Design And Development Of Broadband Electron Paramagnetic Resonance Spectrometer

Electron paramagnetic resonance(EPR)spectroscopy is a method for studying materials with unpaired electrons.The improvement of microwave devices has revolutionized the way of modern telecommunication.And it also has pushed the limits of EPR measurement hardware.Higher frequency and constantly improving noise reduction schemes have led to a variety of EPR spectrometers with outstanding performance.However,the basic principle was kept unchanged throughout the years.It means that the spectrometers still operate in a narrow frequency band determined by the cavity resonance frequency.In some cases,it can't satisfy the requirements of scientific research.In this thesis,we have analyzed the limitations of conventional techniques and the advantages of broadband electron paramagnetic resonance.And we have designed a broadband EPR spectrometer with high sensitivity.This homebuilt EPR spectrometer consists of microwave bridge,a EPR resonator,a field modulation system and a magnet system.The probe of spectrometer is designed on the basis of coplanar waveguide structure.And broadband microwave components were used in microwave bridge.In this thesis,we have demonstrated broadband EPR measurements that cover broad frequency range from 2 up to 12 GHz with high sensitivity.We have made detailed analysis of the EPR spectrometer.Some potential problems of the homebuilt EPR spectrometer have been showed,and feasible improvement plans have been given.We have tested the homebuilt broadband EPR spectrometer.The results show that the EPR spectrometer can work on broad frequency range from 2 to 12 GHz.The sensitivities of the spectrometer at multi-frequency points have been given.At the frequency of 2 GHz,the sensitivity is 4.6 × 1013 spins · Hz-1/2·Gauss-1.At the frequency of 10 GHz,the sensitivity is 4.5 x 1012 spins · Hz-1/2·Gauss-1.At the frequency of 12 GHz,the sensitivity is 3.5 x 1012 spins · Hz--1/2·Gauss-1.