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）我们设计了一个大规模的垂直开放结构圆柱磁屏蔽，并采用磁性摇动来构建它。开发的屏蔽由四个浓缩磁壳组成，该磁壳位于左右厚度约270厘米，厚度约1厘米，外径分别为67、72、82和97厘米的外表面。第一个（最内向的）壳是一个2.1毫米厚度和180厘米长的被动或其。第二，第三和第四壳由约5厘米宽，〜22μm厚的元格斯2705m无定形丝带制成。第二个壳是48层无定形丝带的220厘米长的螺旋结构。第三个壳，长度为243厘米和四个壳，长270厘米，分别由26和30层组成。 Sheild的毛重约为400千克，其中包括约68公斤的Permalloy和〜110千克的Metglas丝带。在极低的频率区域中，对于10μt外部磁场，实现了约10磅的D1横向屏蔽因子和相对大〜380轴向屏蔽因子，E…更大的开口效果。通过盾牌中心处的通量测量的摇动泄漏小于1 nt，同一位置上由鱿鱼磁力计测量的磁噪声场水平小于1 pt。（2）为最大轴向屏蔽因子和最大磁场内部磁场内部的最大平面分布提供了开放式圆柱磁屏蔽的最佳几何形状。在几何参数中，包括直径，D，长度，L和厚度，T和材料参数，渗透率μ，当L/d = 1 + log（μT/d）以及在L/d = 1 + log（d = 1 + log（μt/d）时，可获得L/d = 1 + log（μT/d）时轴向磁场的最大屏蔽因子，并获得平面分布。摇动增强的各向异性清晰。要屏蔽的磁场应平行于磁化的易于轴，而摇动磁场在方向上没有这种偏好。但是，当摇动磁场垂直于易于轴时，所需的摇动磁场的放大器比平行施加的轴垂直时要大十倍。较少的

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)。