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Development of a light-weight, high-performance magnetic shielding system for MEG measurements

开发用于 MEG 测量的轻质高性能磁屏蔽系统

基本信息

批准号：
12355018
负责人：
SASADA Ichiro
金额：
$ 17.28万
依托单位：
Kyushu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12355018/
关键词：
Magnetic Shield Magnetic Shaking Amorphous magnetic tapes Active magnetic shield dc-SQUID magnetometer MEG Biomagnetics 生体磁気アクテイブ磁界補償

项目摘要

The main objectives of this three-year research are to apply a light-weight, high-performance magnetic shield of open-ended cylindrical structure (height=2.76 m, outer diameter=0.98 m and inner diameter=0.67 m), which was built by our own design using Co-based amorphous magnetic tapes and applying magnetic shaking technique, for the MEG measurements with first-order dc-SQUID gradiometers, and to study which parts of shielding system should be improved for the MEG measurement to be done. We have succeeded in measuring MEG alpha rhythm from a human brain of 23-year old male volunteer, however, we found magnetic noise inside the shield should be further improved for the measurement of evoked MEG. Other important results and future problems are summarized below :- Conductive cloth RF shield enclosing the magnetic shield was found to be successful to recover flux-voltage (φ-v) characteristics of dc-SQUID to the level of no RF interference.- Low frequency magnetic fluctuation noise is observed during magnetic shaking, which was found to be in strong relation to the Barkhousen magnetic noise. Metglas 2714A amorphous magnetic tape exhibits much smaller fluctuation noise than Metglas 2705M one.- Active compensation for openings of the cylindrical magnetic shell has been established for the helical shell and for the axial shell. 55 times improvement was obtained at 2 Hz of uniformly impressed magnetic field and 20 times at 10 Hz and 5 times at 50 Hz.- Stable fluxgate magnetometer was developed by incorporating bias reversal technique to the orthogonal structure.- A simple coil system for producing uniform magnetic field was proposed for active magnetic shields-Further magnetic noise cleaning should be needed, which can be realized by taking account of the second and the third-results in the design of the shield.

这项为期三年的研究的主要目标是将我们自行设计的采用钴基非晶磁带并应用磁振荡技术构建的开放式圆柱形结构（高度=2.76 m，外径=0.98 m，内径=0.67 m）的轻质高性能磁屏蔽用于一阶dc-SQUID梯度计的MEG测量，并研究其中的哪些部分应改进屏蔽系统以进行 MEG 测量。我们已经成功测量了 23 岁男性志愿者大脑的 MEG α 节律，但是，我们发现屏蔽内的磁噪声还需要进一步改进以测量诱发的 MEG。其他重要结果和未来的问题总结如下：-发现包围磁屏蔽的导电布射频屏蔽成功地将dc-SQUID的磁通电压（φ-v）特性恢复到无射频干扰的水平。-在磁振动过程中观察到低频磁波动噪声，发现这与巴克豪森磁噪声密切相关。 Metglas 2714A 非晶磁带的波动噪声比 Metglas 2705M 磁带小得多。 - 为螺旋壳和轴向壳建立了圆柱形磁壳开口的主动补偿。在 2 Hz 均匀外加磁场下获得了 55 倍的改进，在 10 Hz 下获得了 20 倍，在 50 Hz 下获得了 5 倍。 - 通过将偏置反转技术融入正交结构，开发了稳定的磁通门磁力计。 - 提出了一种用于有源磁屏蔽产生均匀磁场的简单线圈系统 - 需要进一步的磁噪声清除，这可以通过考虑第二个和第三个结果来实现。盾牌的设计。