Development of a large-scale vertical setting cylindrical magnetic shield - Realization of low-level, low-gradient magnetic field with current superposition

大型立式圆筒磁屏蔽研制——电流叠加实现低水平低梯度磁场

• 批准号: 09555129
• 负责人: SASADA Ichiro
• 金额: $ 7.87万
• 依托单位: KYUSHU UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1997
• 资助国家: 日本
• 起止时间: 1997 至 1998
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09555129/
• 关键词: clindrical magnetic shield; vertical structure; magnetic shaking; active compensation; low gradient; magnetoencephalogram; SQUID magnetometer; SOUID磁束計

(1) We designed a large-scale vertical open-structure cylindrical magnetic shield and constructed it employing magnetic shaking. The shield developed consists of four concentric magnetic shells positioned on the outer surfaces of paper pipes of 〜 270 cm length, 〜 1 cm thickness, and with outer diameters of 67, 72, 82, and 97 cm, respectively. The first (innermost) shell is a passive Permalloy shell of 2.1 mm thickness and 180 cm length. The second, third and fourth shells are made of 〜 5 cm wide and 〜 22 μm thick Metglas 2705M amorphous ribbons. The second shell is a 220 cm long helical structure of 48 layers of the amorphous ribbons. The third shell, 243 cm in length and fourth shell, 270 cm in length, are axial structure consisting of 26 and 30 layers, respectively. The gross weight of the sheild is 〜 400 kg including 〜 68 kg of Permalloy and 〜 110 kg of Metglas ribbons. An 〜 10ィイD15ィエD1 transverse shielding factor and a relatively large 〜 380 axial shielding factor, despite of the e … More ffect of openings, are achieved for a 10 μT external magnetic field in the extremely low frequency region. The shaking leakage measured by a fluxgate at the shield's center is less than 1 nT and the level of magnetic noise field measured by a SQUID magnetometer at the same position is less than 1 pT.(2) The optimum geometry of the open-ended cylindrical magnetic shield is presented for the maximum axial shielding factor and for the maximally flat distribution of the magnetic field inside the shield. With the geometrical parameter including the diameter, D, the length, L, and the thickness, t, and with the material parameter, the permeability μ, a maximum shielding factor for the axial magnetic field is obtained when L/D = 1 + log (μt/D), and a maximally flat distribution is obtained when L/D = 1 + log (μt/D) + C where C = 0.75 〜 1.0.(3) The effect of magnetic anisotropy on the shaking enhancement is made clear. The magnetic field to be shielded should be parallel to the easy axis of magnetization, whereas shaking magnetic field does not have such preference in direction. However, the amplitude of the shaking magnetic field required is ten times larger when the shaking magnetic field is applied perpendicularly to the easy axis than that required when applied in parallel. Less

(1)设计了大型立式开式圆柱形磁屏蔽体，并采用磁振法进行了构造。所研制的屏蔽由四个同心磁壳组成，分别位于长约270 cm、厚约1 cm、外径分别为67、72、82和97 cm的纸管的外表面。第一个（最里面的）外壳是一个被动的坡莫合金外壳，厚度2.1毫米，长度180厘米。第二、三、四壳由~ 5 cm宽、~ 22 μm厚的metglass 2705M非晶带构成。第二个外壳是一个220厘米长的螺旋结构，由48层非晶带组成。第三壳长243 cm，第四壳长270 cm，为轴向结构，分别由26层和30层组成。盾的总重量约为400公斤，其中包括68公斤的坡莫合金和110公斤的玻璃带。在极低频区，当外加磁场为10 μT时，其横向屏蔽系数可达~ 10 μT，轴向屏蔽系数可达~ 380 μT。磁通门在屏蔽体中心测得的振动泄漏小于1 nT， SQUID磁强计在同一位置测得的磁场噪声水平小于1 pT。(2)给出了具有最大轴向屏蔽系数和屏蔽体内部磁场分布最平坦的开放圆柱形磁屏蔽体的最佳几何形状。以直径D、长度L和厚度t为几何参数，以磁导率μ为材料参数，当L/D = 1 + log （μt/D）时，轴向磁场屏蔽系数最大；当L/D = 1 + log (μt/D) + C时，C = 0.75 ~ 1.0，屏蔽系数分布最平坦。(3)明确了磁各向异性对振动增强的影响。待屏蔽磁场应平行于易磁化轴，而振动磁场在方向上没有这种偏好。然而，当振动磁场垂直于易轴施加时，所需的振动磁场振幅比平行施加时所需的振动磁场振幅大十倍。少

项目成果

E. Paperno, H. Koide, I. Sasada: "A new estimation of the axial shielding factors for multishell cylindrical shields"Journal of Applied Physics. Vol.87, No.8 (in print 3 pages). (2000)

E. Paperno、H. Koide、I. Sasada：“多壳圆柱屏蔽轴向屏蔽系数的新估计”应用物理学杂志。

E.Paperno,H.Koide,I.Sasada: "A new estimation of the axial shielding factors for multishell cylindrical shields"Joumal of Applied Physics. Vol.87,No.8 (印刷中). 3 (2000)

E. Paperno、H. Koide、I. Sasada：“多壳圆柱屏蔽的轴向屏蔽系数的新估计”《应用物理学杂志》第 87 卷，第 3 期（2000 年）。

E.Paperno,I.Sasada: "Effect of magnetic anisotropy on magnetic shaking"Journal of Applied Physics. Vol.85,No.5. 4645-4647 (1999)

E.Paperno，I.Sasada：“磁各向异性对磁振动的影响”应用物理学杂志。

I.Sasada,E.Papemo,H.Koide: "Design of a large-scale vertical open-structure cylindrical shield employing magnetic shaking"Journal of Applied Physics.. Vol.87,No.8 (印刷中). 3 (2000)

I.Sasada、E.Papemo、H.Koide：“采用磁振动的大型垂直开放结构圆柱形屏蔽的设计”应用物理学杂志。第 87 卷，第 3 期（2000 年出版）。 ）

大下,笹田: "両端開口短軸円筒磁気シールドにおける軸方向磁界の低減と平坦化" 電気学会マグネティックス研究会資料. MAG-98-110. 7-11 (1998)

Oshita，Sasada：“减少并平坦化带有开口端的短轴圆柱形磁屏蔽”日本电气工程师学会磁学研究组的材料 MAG-98-110 (1998)。