PORTABLE DEDICATED ELECTRON SPIN RESONANCE SPECTROMETER

摘要

An electron spin resonance spectrometer which is dedicated to a specific narrow range of tasks is reduced in size such that, as contrasted with the usual laboratory ESR spectrometers, it is easily and readily portable and can be carried to various locations to conduct tests. It uses a much smaller magnet structure than usual, a self contained single board computer, and a microwave source which is adjustable by the computer. The microwave source operates in the 2 GHz range and is connected through a circulator with a matching circuit which inductively couples the microwave signal to a sample chamber/resonator positioned in the magnetic field of the magnet structure. An oscillator provides a audio frequency signal which is combined with a slow ramp signal from the computer to modulate the output of the magnet structure. Reflected energy from the sample chamber/resonator is detected and supplied to a special amplifier which separates detector current and the ESR voltage signal, sending the detector current signal to the computer for controlling the microwave frequency and the ESR voltage to a phase sensitive detector which compares it with the audio frequency reference signal from the oscillator. Most of the noise is removed in the phase sensitive detector since it passes only those parts of the ESR signal which are in phase with the oscillator signal. The computer uses this signal to provide an output and also to provide a correction signal to the matching circuit to maintain the optimum impedance match between the resonator and the matching circuit.