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)设计了一种大型垂直开口结构圆柱形磁屏蔽体，并采用磁振法进行了施工。研制的屏蔽体由四个同心磁壳组成，磁壳分别位于长270 cm、厚101 cm、外径67、72、82和97 cm的纸管的外表面上。第一个（最里面的）壳体是2.1 mm厚和180 cm长的被动坡莫合金壳体。第二、第三和第四层壳由宽度为1.5cm、厚度为1.22 μm的Metalloy 2705 M非晶薄带制成。第二层壳是由48层非晶带组成的220 cm长的螺旋结构。第三壳长243 cm，第四壳长270 cm，分别为26层和30层的轴向结构。屏蔽体的总重为1400公斤，包括168公斤坡莫合金和110公斤金属带。尽管e = 100，但横向屏蔽系数为150，轴向屏蔽系数为380 ...更多信息 在10 μT外磁场下，在极低频区实现了开口效应。用磁通门在屏蔽中心测得的振动泄漏小于1 nT，用SQUID磁强计在同一位置测得的磁噪声场小于1 pT。(2)最佳的几何形状的开口的圆柱形磁屏蔽的最大轴向屏蔽因子和最大的平面分布的磁场内的屏蔽。当几何参数包括直径D、长度L和厚度t以及材料参数磁导率μ时，当L/D = 1 + log（μt/D）时获得轴向磁场的最大屏蔽因子，并且当L/D = 1 + log（μt/D）+ C时获得最大平坦分布，其中C = 0.75 <$1.0。(3)明确了磁各向异性对振动增强的影响。被屏蔽的磁场应平行于易磁化轴，而振动磁场在方向上没有这样的偏好。然而，当振动磁场垂直于易轴施加时所需的振动磁场的幅度是平行施加时所需的振动磁场的幅度的十倍。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)。