L波段三维ESR成像系统的研制(Ⅱ)——L波段三维ESR成像系统

DEVELOPMENT OF L-BAND THREE DIMENSIONAL ESR IMAGING SYSTEM(Ⅱ)--L-Band Three Dimensional ESR Imaging System

叙述了一个L波段 (1 .0 5GHz)用于ESR和ESR成像的装置 ,用这套自制装置实现了 3DESR成像 .该装置由L波段ESR谱仪、三组梯度场线圈及控制单元和PC机数据采集系统组成 .样品腔是一个 3 环 2 缝再进入式谐振腔 ,可放入直径为 2 0mm、长 30mm的H2 O样品 ,空谐振腔的频率是 1 .0 5GHz.微波振荡频率用自动频率控制 (AFC)的方法自动锁在有载腔的频率上 .梯度场线圈沿X ,Y 和Z 轴产生线性梯度场 ,在中心 40mm球形范围内梯度场强度为 2mT/cm .依照Lauterbur’s方法进行 3DESR图像重建 .用该系统检测了样品中TEMPO氮氧自由基的 3D空间分布 .得到了TEMPO的 2D、3DESR图像、用像素灰度表示的自旋密度分布图及 3DESR CT图像 .

An apparatus for ESR and ESR imaging at L-band (1.05 GHz) was built in our laboratory, consisting of L-band ESR spectrometer, three sets of gradient coils and a personal computer-based data acquisition system. The sample cavity is a 3-loop 2-gap reentrant resonator, accepting samples with sizes up to 20 mm in diameter and 30 mm in length. The resonance frequency of unloaded resonator is 1.05 GHz. The microwave oscillator frequency is locked to the resonant frequency of loaded resonator by means of automatic frequency control (AFC). Linear magnetic field gradients (up to 2 mT/cm in amplitudes) in the X-, Y-, and Z- directions are produced by gradient coils, and have a linear range of 40 mm measuring from the center of the magnet. All projections in imaging were acquired as single scans with constant sweep time. To accurately compute the spatial distribution of the spins, the line shape function that causes line-broadening of the ESR signals needs to be removed from the observed projections. Three- dimensional ESR image is constructed based on the Lauterbur's method. Using this system, we studied the spatial distribution of TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) nitroxide radicals in sample tube. Stack images of ESR-CT and 2D, 3D ESR images were obtained.