利用高温超导直流量子干涉器件进行10^(-6)T量级磁场下核磁共振的研究

Detection of nuclear magnetic resonance in the microtesla range using a high T_c dc-superconducting quantum interference device

研究了水样品在10-6T量级磁场下的核磁共振谱.核磁共振信号由一个工作在液氮温度的高温超导直流量子干涉仪记录,测量在一个简易磁屏蔽室中进行.在7—70μT的磁场范围内都观察到了15ml水样品的核磁共振信号.相应的1H的核磁共振频率为300—3000Hz.在实验中获取的单次测量信噪比约为4,通过对信号的100次平均,信噪比可达到约40.进一步讨论了剩余磁场、预极化时间和采样时间对结果的影响.最后用数字滤波之后平均的方法初步得到了时域的自由感应衰减信号.

We have carried out nuclear magnetic resonance experiments in microtesla range. The free induction signal was recorded using a high Tc dc-superconducting quahtum interference device. The measurement was performed in a home-made magnetic shield room. Resonance spectra of 1H from a sample of 15 ml tap water was obtained in the field range from 7--70 μT, corresponding to resonance frequency of 300--3000 Hz, The signal to noise ratio in a single-shot measurement is around 4, which could be increased to about 40 after 100 times averaging.The effect of residual magnetic field in the shield room, prepolarization time and data acquisition time was investigated.