Design And Application Of Automatic Frequency Control In Continued Wave Electron Paramagnetic Spectrometer

Electron Paramagnetic Resonance,EPR,is a spectroscopic technique,which de-tects species that have unpaired electrons.During continued wave EPR experiments,it's of importance to keep source frequency equals resonance frequency of cavity for preventing distortion spectral line and raising its signal noise ratio.Therefore,auo-tomatic frequency control device is introduced into continued wave EPR spectrometer.There are disadvantages in existing designs like unstable locking function,large noise and unconvinient control system.Developing a new generation of automatic frequency control device has important practical significance.This subject is based on the frequency modulation of gunn oscillator and reflection characteristics of the resonant cavity.A set of automatic frequency control device is de-signed for continuous wave electron paramagnetic resonance spectrometer.The system function simulation in the Mathematica environment validates feasibility and stability of the automatic frequency control function.On this basis,the power supply scheme,noise reduction scheme,demodulation circuit,and digital controlled switch circuit are redesigned considering insufficiency of the old version in the physical design.Finally,the joint test of automatic frequency control device and EPR spectrometer shows that the new-designed AFC device is able to achieve automatic locking of source frequency and resonant frequency of cavity,as well as reduce the distortion of EPR spectral line at high cavity power.