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

• 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

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.

本研究的主要目标是应用于一种重量轻、性能高的开口圆柱形结构的磁屏蔽（高2.76 m，外径0.98 m，内径0.67 m），采用钴基非晶磁带，采用磁振荡技术，并研究在进行脑磁图测量时，屏蔽系统的哪些部分需要改进。我们已经成功地测量了一名23岁男性志愿者的脑磁图α节律，然而，我们发现屏蔽内的磁噪声需要进一步改进以测量诱发的脑磁图。其他重要的结果和未来的问题总结如下：-导电布RF屏蔽包围磁屏蔽被发现是成功的恢复dc-SQUID的磁通-电压（φ-v）特性的水平，没有RF干扰。在磁振荡过程中观察到低频磁波动噪声，发现它与巴克豪森磁噪声有很强的关系。Metallic 2714 A非晶磁带的波动噪声比Metallic 2705 M磁带小得多。对螺旋壳和轴向壳的圆柱形磁壳开孔进行了主动补偿。在2 Hz的均匀外加磁场下获得55倍的改善，在10 Hz下获得20倍，在50 Hz下获得5倍。将偏置反转技术引入正交结构中，研制出稳定的磁通门磁力仪。提出了一种简单的线圈系统，用于产生均匀磁场的有源磁屏蔽。在屏蔽设计中，考虑第二和第三个结果，可以进一步消除磁噪声。

项目成果

E.Paperno, I.Sasada, K.Tashiro: "Experimental correction of the axial.shielding equation"IEEE Trans. Magn.. Vol.38,No.5. 3324-3326 (2002)

E.Paperno、I.Sasada、K.Tashiro：“轴向屏蔽方程的实验校正”IEEE Trans。

田代晋久, 笹田一郎, 吉富邦明, 風見邦夫: "小型アンテナによる磁気シールド内のRFノイズ測定-dc-SQUIDセンサに与える影響-"日本応用磁気学会誌. 26巻4号. 535-538 (2002)

Nobuhisa Tashiro、Ichiro Sasada、Kuniaki Yoshitomi、Kunio Kazami：“使用小型天线测量磁屏蔽中的 RF 噪声 - 对 DC-SQUID 传感器的影响 -”日本应用磁学学会杂志，第 26 卷，第 4. 535 期。 -538 (2002))

K.Tashiro, H.Koide, Y.Umeda, I.Sasada: "New Method of Canceling Line Spectrum Noise in a Magnetic Shield by Using the Beat Phenomenon"Trans.Magn.Soc.Japan. Vol.25, No.4-2. 1119-1122 (2001)

K.Tashiro、H.Koide、Y.Umeda、I.Sasada：“利用节拍现象消除磁屏蔽中线谱噪声的新方法”Trans.Magn.Soc.Japan。

T.Sasada, E.Paperno: "Magnetic sensors and Magnetometer, P.Ripka (Ed.), "Magnetic shielding"(分担)"Artech House, Boston and London. 410-424 (2001)

T.Sasada、E.Paperno：“磁传感器和磁力计，P.Ripka（编辑），“磁屏蔽””Artech House，波士顿和伦敦 410-424 (2001)。

K.Tashiro, K.Nagashima, A.Sumita T.Fukunaga, and I.Sasada: "Spontaneous magnetoencephaligraphy alpha rhythm measurement in a cylindrical magnetic shield employing magnetic shaking"J. Applied Physics. Vol.93, No.10. 6733-6735 (2003)

K.Tashiro、K.Nagashima、A.Sumita T.Fukunaga 和 I.Sasada：“利用磁力振动在圆柱形磁屏蔽中进行自发脑磁图 α 节律测量”J。