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In big science projects such as the magnetically confined fusion-plasma science \u003cbr /\u003eand the high-energy accelerator science, highly efficient magnetic shields are required \u003cbr /\u003efor various devices sensitive to magnetic fields in order to reduce the strong fields \u003cbr /\u003egenerated by large magnets, including superconducting magnets, to fields less than the \u003cbr /\u003egeomagnetic field within a limited space to have no influence on their operation. \u003cbr /\u003e In physical science experiments including the above big science projects, the \u003cbr /\u003eferromagnetic shield employing enclosures made from pure iron, Permalloys or mild \u003cbr /\u003esteel is usually applied for the required shielding. However, there have stilI been \u003cbr /\u003edifficulties with designing the shielding system for devices operating under the \u003cbr /\u003elarge-scale equipment generating the strong field, probably because subjects on the \u003cbr /\u003eprediction of the shielding effectiveness and the material technology for the shielding \u003cbr /\u003eshell have not been definitely resolved. \u003cbr /\u003e For the subject on the prediction of the shielding effectiveness, it is proposed in \u003cbr /\u003ethis thesis that the effect of the hysteresis of the shell material on the shielding efficacy \u003cbr /\u003eshould be considered. The magnetic hysteresis is well known as a phenomenon \u003cbr /\u003echaracterizing ferromagnetic materials. The ferromagnetic shielding effectiveness must \u003cbr /\u003ebe affected by the hysteresis of the shell material because its magnetized condition is \u003cbr /\u003estrongly dependent on the previous state. \u003cbr /\u003e For the subject on the material technology, there has been less knowledge of \u003cbr /\u003epreparing shell materials simultaneously satisfying both high flux density and soft \u003cbr /\u003emagnetism. For example, the magnetic flux density is sufficiently high on pure iron \u003cbr /\u003ewith moderate permeability while it is insufficient on Permalloy in contrast with its \u003cbr /\u003ehigh permeability. It should be also considered that the magnetic properties of soft \u003cbr /\u003emagnetic materials are strongly affected by the strain, especially for the residual strain, \u003cbr /\u003edue to their structural sensitivities. \u003cbr /\u003e Although these subjects still remain to be solved, there have been few reports \u003cbr /\u003ediscussing effects of the hysteresis on the magnetic shielding effectiveness theoretically, \u003cbr /\u003eand some only treat them from a phenomenological point of view. Furthermore, there \u003cbr /\u003ehave also been few reports quantitatively investigating effects of the strain of the shell \u003cbr /\u003ematerials on the magnetic shielding effectiveness. \u003cbr /\u003e\u003cbr /\u003e This thesis aims at two subjects. One is to optimize the designing techniques of \u003cbr /\u003ethe ferromagnetic shielding from the strong magnetic fields for devices operating under \u003cbr /\u003elarge-scale equipments, based on the research on shell materials from a viewpoint of \u003cbr /\u003ethe material science. The other is to clarify the influences of the magnetic properties on \u003cbr /\u003ethe shielding effectiveness from a viewpoint of the electromagnetism, leading to further \u003cbr /\u003eunderstanding of the static ferromagnetic shield. \u003cbr /\u003e First, research on the shell materials is focused on the improvement of the soft \u003cbr /\u003emagnetism without reduction of the magnetic flux density. Additionally, the \u003cbr /\u003edeterioration of the soft magnetism due to a tiny amount of strain in the shell material \u003cbr /\u003eis quantitatively investigated because the shell material is subject to be strained by \u003cbr /\u003estress and deformation during the assembly and installation of the shielding system. \u003cbr /\u003e\u003cbr /\u003e Next, the effect of the hysteresis of the shell material on the shielding \u003cbr /\u003eeffectiveness is discussed against static magnetic fields. It has been qualitatively \u003cbr /\u003eunderstood that the shielding effectiveness can be seriously affected by strain of the \u003cbr /\u003eshell material. Therefore, an influence of a tiny amount of strain of the shell material \u003cbr /\u003eon the magnetic shielding effectiveness is analyzed. \u003cbr /\u003e Finally, a guiding principle for evaluating the maximum leakage field as a \u003cbr /\u003eshielding efficacy of the shell material, which is a reasonable and obtainable field in \u003cbr /\u003ethe worst-case scenario for the magnetized condition of the shielding shell, is discussed. \u003cbr /\u003eIt is determined by considering the hysteresis of the shell material, and it is revealed \u003cbr /\u003ethat the concept of the maximum leakage field is effective whether the shell material is \u003cbr /\u003estrained or not. \u003cbr /\u003e\u003cbr /\u003e The thesis consists of five chapters, which are summarized below. \u003cbr /\u003e Chapter 1 states the purpose and background of this study, providing an overview \u003cbr /\u003eof the prior researches, and describes the significance of this study. The first section of \u003cbr /\u003ethis chapter explains the necessity of the magnetic shielding from strong static fields \u003cbr /\u003efor devices operating under large-scale equipments, by introducing specific situations \u003cbr /\u003einherent in big science projects, such as the magnetically confined fusion-plasma \u003cbr /\u003escience and the high-energy accelerator science. In the second section, the novelties \u003cbr /\u003eand goals of this study are summarized. The structure of this thesis is outlined in the \u003cbr /\u003ethird section. \u003cbr /\u003e\u003cbr /\u003e Chapter 2, consisting of five sections, describes the research and development of \u003cbr /\u003ethe soft magnetic materials for the use of the magnetic shielding system. In the first \u003cbr /\u003esection, the purposes of the research in this chapter are addressed. \u003cbr /\u003e The second and third sections of this chapter focus on the strategies to improve the \u003cbr /\u003esoft magnetic properties of pure iron and to develop soft magnetic materials with both \u003cbr /\u003ehigher permeability and lower coercivity than those of pure iron without deteriorating \u003cbr /\u003eits high-magnetic flux density by the grain-coarsening technique. The developed \u003cbr /\u003eFe-1%Al alloy exhibits extremely large ferrite grains in its microstructure, and has \u003cbr /\u003ealmost the same high-permeability and low-coercivity as those of Permalloy B. \u003cbr /\u003eMoreover, it indicates high saturation magnetization, which is lower only by 2% than \u003cbr /\u003ethat of pure iron. \u003cbr /\u003e The fourth section of this chapter discusses an influence of a tiny amount of plastic \u003cbr /\u003estrain on the magnetic properties. It is revealed that the deterioration of coercivity due \u003cbr /\u003eto the plastic strain is alleviated in the coarsened grain microstructure. Therefore, it is \u003cbr /\u003eunderstood that the improvement of the soft magnetism by the grain-coarsening \u003cbr /\u003etechnique is effective for the prevention of the deterioration of coercivity by strain \u003cbr /\u003ecaused through damage. The results of the research in this chapter are summarized in \u003cbr /\u003ethe fifth section. \u003cbr /\u003e\u003cbr /\u003e Chapter 3, containing six sections, explains a prediction method for the magnetic \u003cbr /\u003eshielding effectiveness and a design concept for the double-layer shielding techniques. \u003cbr /\u003eThe first section of this chapter addresses the purpose of the research in this chapter. \u003cbr /\u003e In the second and third sections of this chapter, a new approach to the estimation \u003cbr /\u003eof the static ferromagnetic shielding effectiveness is proposed, in which the magnetic \u003cbr /\u003ehysteresis of the shielding materials is considered. The hysteresis effects of the shell \u003cbr /\u003ematerials are discussed on the ferromagnetic shielding, in which a relatively strong \u003cbr /\u003eexternal field is reduced below the geomagnetic field in a shielded space. The measured \u003cbr /\u003eleakage field in the shielding enclosure corresponds to the results of the finite element \u003cbr /\u003emethod (FEM) analysis when permeability considering the effect of coercivity is used \u003cbr /\u003efor the calculation as a parameter representing the hysteresis of the shielding material. \u003cbr /\u003e The effects of both permeability and coercivity on the leakage fields are discussed \u003cbr /\u003ein the fourth section of this chapter, with regard to the magnetic properties of the \u003cbr /\u003eshielding materials by using the FEM analysis in combination with the results \u003cbr /\u003eobtained in chapter 2. The maximum leakage field, which is regarded as a figure of \u003cbr /\u003emerit of the shielding efficacy, is determined by the coercivity of the material used for \u003cbr /\u003ethe shield, and it is clarified that the coercivity should be considered for the estimation \u003cbr /\u003eof the leakage field in an actual design of the shielding system. It is also confirmed that \u003cbr /\u003ethe deterioration of the soft magnetic properties, not only permeability but also \u003cbr /\u003ecoercivity, due to the residual strain causes the reduction of the magnetic shielding \u003cbr /\u003eefficacy. Finally, it is concluded that the maximum leakage field is dominated by the \u003cbr /\u003ecoercivity of the shell material regardless of the shell material condition being strained \u003cbr /\u003eor not. \u003cbr /\u003e In the fifth section, the effect of the double-layer structure on the shielding design \u003cbr /\u003eis investigated by using the analysis with considering the hysteresis of the shell \u003cbr /\u003ematerial. The double-shell structure is definitely effective for abating the degradation \u003cbr /\u003eof the shielding efficacy in the strained shielding material in that the influence of the \u003cbr /\u003edeterioration of permeability of the inner shell material due to the strain is lowered \u003cbr /\u003ebecause the external field applied to the inner shell is reduced by the shielding effect of \u003cbr /\u003ethe outer shell. Accordingly, the enhancement of leakage field by the strain can be \u003cbr /\u003esuppressed below a field corresponding to the coercivity of the strained inner shell \u003cbr /\u003ematerial in the double-shell structure. It is concluded that the required property for the \u003cbr /\u003eshielding material is low coercivity that is subject to little change due to the residual \u003cbr /\u003estrain, adding to high saturation induction and high permeability which are \u003cbr /\u003econventionally required. The above results are summarized in the sixth section. \u003cbr /\u003e\u003cbr /\u003e Chapter 4, containing three sections, focuses on the application techniques, and \u003cbr /\u003edescribes the actual performance of the ferromagnetic shielding for devices operating \u003cbr /\u003eunder the large-scale equipment in big science projects. The first section of this chapter \u003cbr /\u003eprovides some practical uses of the soft magnetic alloy developed in chapter 2. The \u003cbr /\u003epractical applications of Fe-1%Al alloy to the magnetic shielding are presented for \u003cbr /\u003ephotomultiplier tubes (PMT), neutral beam injectors (NBI), and so on, which are used \u003cbr /\u003ein the magnetically confined fusion-plasma science and the high energy accelerator \u003cbr /\u003escience. In the second section, the shielding design for a neutralizing cell of the NBI, \u003cbr /\u003ewhich is used for the heating of the magnetically confined fusion-plasmas, are \u003cbr /\u003ediscussed as an example for the design optimization with the double-layer shielding \u003cbr /\u003esystem. The role of the outer shell under a severe condition, where a large volume is \u003cbr /\u003eshielded from strong external magnetic field, is addressed, and it is clarified that the \u003cbr /\u003einner shell design including the structure and the shell materials can be optimized by a \u003cbr /\u003eproper selection of the outer shell materials. It is also confirmed that the double-layer \u003cbr /\u003eshielding is effective not only for reducing the leakage field in the shielded space but \u003cbr /\u003ealso for abating the deterioration of the shielding efficacy in the strained shell material. \u003cbr /\u003eThe summary of this chapter is provided in the third section. \u003cbr /\u003e\u003cbr /\u003e Chapter 5 is the conclusion of this thesis. The results obtained in this study are \u003cbr /\u003esummarized, and the future prospects of the ferromagnetic shielding techniques are \u003cbr /\u003epresented. Additional challenges for the further improvement are proposed from a \u003cbr /\u003eviewpoint of both the material science and the electromagnetism. The results obtained \u003cbr /\u003ehere on the designing techniques and the material techniques for the magnetic \u003cbr /\u003eshielding should contribute to future development in not only big science projects but \u003cbr /\u003ealso general physics researches as invaluable techniques. \u003cbr /\u003e\u003cbr /\u003e", "subitem_description_type": "Other"}]}, "item_1_description_18": {"attribute_name": "フォーマット", "attribute_value_mlt": [{"subitem_description": "application/pdf", "subitem_description_type": "Other"}]}, "item_1_description_7": {"attribute_name": "学位記番号", "attribute_value_mlt": [{"subitem_description": "総研大甲第1127号", "subitem_description_type": "Other"}]}, "item_1_select_14": {"attribute_name": "所蔵", "attribute_value_mlt": [{"subitem_select_item": "有"}]}, "item_1_select_8": {"attribute_name": "研究科", "attribute_value_mlt": [{"subitem_select_item": "物理科学研究科"}]}, "item_1_select_9": {"attribute_name": "専攻", "attribute_value_mlt": [{"subitem_select_item": "10 核融合科学専攻"}]}, "item_1_text_10": {"attribute_name": "学位授与年度", "attribute_value_mlt": [{"subitem_text_value": "2007"}]}, "item_creator": {"attribute_name": "著者", "attribute_type": "creator", "attribute_value_mlt": [{"creatorNames": [{"creatorName": "OMORI, Toshimichi", "creatorNameLang": "en"}], "nameIdentifiers": [{"nameIdentifier": "0", "nameIdentifierScheme": "WEKO"}]}]}, "item_files": {"attribute_name": "ファイル情報", "attribute_type": "file", "attribute_value_mlt": [{"accessrole": "open_date", "date": [{"dateType": "Available", "dateValue": "2016-02-17"}], "displaytype": "simple", "download_preview_message": "", "file_order": 0, "filename": "甲1127_要旨.pdf", "filesize": [{"value": "459.9 kB"}], "format": "application/pdf", "future_date_message": "", "is_thumbnail": false, "licensetype": "license_11", "mimetype": "application/pdf", "size": 459900.0, "url": {"label": "要旨・審査要旨", "url": "https://ir.soken.ac.jp/record/538/files/甲1127_要旨.pdf"}, "version_id": "5f891aad-ed69-4984-9e54-3c6bd7d116d2"}, {"accessrole": "open_date", "date": [{"dateType": "Available", "dateValue": "2016-02-17"}], "displaytype": "simple", "download_preview_message": "", "file_order": 1, "filename": "甲1127_本文.pdf", "filesize": [{"value": "11.4 MB"}], "format": "application/pdf", "future_date_message": "", "is_thumbnail": false, "licensetype": "license_11", "mimetype": "application/pdf", "size": 11400000.0, "url": {"label": "本文", "url": "https://ir.soken.ac.jp/record/538/files/甲1127_本文.pdf"}, "version_id": "5f56acf4-ca0e-463b-8c9a-0db5363053d4"}]}, "item_language": {"attribute_name": "言語", "attribute_value_mlt": [{"subitem_language": "jpn"}]}, "item_resource_type": {"attribute_name": "資源タイプ", "attribute_value_mlt": [{"resourcetype": "thesis", "resourceuri": "http://purl.org/coar/resource_type/c_46ec"}]}, "item_title": "強磁場大型装置環境下における磁気遮蔽に関する研究", "item_titles": {"attribute_name": "タイトル", "attribute_value_mlt": [{"subitem_title": "強磁場大型装置環境下における磁気遮蔽に関する研究"}, {"subitem_title": "Study on Ferromagnetic Shielding Techniques from Strong Static Fields for Devices Operating under Large-Scale Equipments", "subitem_title_language": "en"}]}, "item_type_id": "1", "owner": "1", "path": ["12"], "permalink_uri": "https://ir.soken.ac.jp/records/538", "pubdate": {"attribute_name": "公開日", "attribute_value": "2010-02-22"}, "publish_date": "2010-02-22", "publish_status": "0", "recid": "538", "relation": {}, "relation_version_is_last": true, "title": ["強磁場大型装置環境下における磁気遮蔽に関する研究"], "weko_shared_id": -1}
強磁場大型装置環境下における磁気遮蔽に関する研究
https://ir.soken.ac.jp/records/538
https://ir.soken.ac.jp/records/538bf80c435-b277-4e84-bbe1-3ec9274b135a
名前 / ファイル | ライセンス | アクション |
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Item type | 学位論文 / Thesis or Dissertation(1) | |||||
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公開日 | 2010-02-22 | |||||
タイトル | ||||||
タイトル | 強磁場大型装置環境下における磁気遮蔽に関する研究 | |||||
タイトル | ||||||
言語 | en | |||||
タイトル | Study on Ferromagnetic Shielding Techniques from Strong Static Fields for Devices Operating under Large-Scale Equipments | |||||
言語 | ||||||
言語 | jpn | |||||
資源タイプ | ||||||
資源タイプ識別子 | http://purl.org/coar/resource_type/c_46ec | |||||
資源タイプ | thesis | |||||
著者名 |
大森, 俊道
× 大森, 俊道 |
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フリガナ |
オオモリ, トシミチ
× オオモリ, トシミチ |
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著者 |
OMORI, Toshimichi
× OMORI, Toshimichi |
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学位授与機関 | ||||||
学位授与機関名 | 総合研究大学院大学 | |||||
学位名 | ||||||
学位名 | 博士(工学) | |||||
学位記番号 | ||||||
内容記述タイプ | Other | |||||
内容記述 | 総研大甲第1127号 | |||||
研究科 | ||||||
値 | 物理科学研究科 | |||||
専攻 | ||||||
値 | 10 核融合科学専攻 | |||||
学位授与年月日 | ||||||
学位授与年月日 | 2008-03-19 | |||||
学位授与年度 | ||||||
2007 | ||||||
要旨 | ||||||
内容記述タイプ | Other | |||||
内容記述 | In order to avoid errors in the operation of devices subject to strong magnetic <br />fields, shielding systems are applied to such devices that would be affected by magnetic <br />fields. In big science projects such as the magnetically confined fusion-plasma science <br />and the high-energy accelerator science, highly efficient magnetic shields are required <br />for various devices sensitive to magnetic fields in order to reduce the strong fields <br />generated by large magnets, including superconducting magnets, to fields less than the <br />geomagnetic field within a limited space to have no influence on their operation. <br /> In physical science experiments including the above big science projects, the <br />ferromagnetic shield employing enclosures made from pure iron, Permalloys or mild <br />steel is usually applied for the required shielding. However, there have stilI been <br />difficulties with designing the shielding system for devices operating under the <br />large-scale equipment generating the strong field, probably because subjects on the <br />prediction of the shielding effectiveness and the material technology for the shielding <br />shell have not been definitely resolved. <br /> For the subject on the prediction of the shielding effectiveness, it is proposed in <br />this thesis that the effect of the hysteresis of the shell material on the shielding efficacy <br />should be considered. The magnetic hysteresis is well known as a phenomenon <br />characterizing ferromagnetic materials. The ferromagnetic shielding effectiveness must <br />be affected by the hysteresis of the shell material because its magnetized condition is <br />strongly dependent on the previous state. <br /> For the subject on the material technology, there has been less knowledge of <br />preparing shell materials simultaneously satisfying both high flux density and soft <br />magnetism. For example, the magnetic flux density is sufficiently high on pure iron <br />with moderate permeability while it is insufficient on Permalloy in contrast with its <br />high permeability. It should be also considered that the magnetic properties of soft <br />magnetic materials are strongly affected by the strain, especially for the residual strain, <br />due to their structural sensitivities. <br /> Although these subjects still remain to be solved, there have been few reports <br />discussing effects of the hysteresis on the magnetic shielding effectiveness theoretically, <br />and some only treat them from a phenomenological point of view. Furthermore, there <br />have also been few reports quantitatively investigating effects of the strain of the shell <br />materials on the magnetic shielding effectiveness. <br /><br /> This thesis aims at two subjects. One is to optimize the designing techniques of <br />the ferromagnetic shielding from the strong magnetic fields for devices operating under <br />large-scale equipments, based on the research on shell materials from a viewpoint of <br />the material science. The other is to clarify the influences of the magnetic properties on <br />the shielding effectiveness from a viewpoint of the electromagnetism, leading to further <br />understanding of the static ferromagnetic shield. <br /> First, research on the shell materials is focused on the improvement of the soft <br />magnetism without reduction of the magnetic flux density. Additionally, the <br />deterioration of the soft magnetism due to a tiny amount of strain in the shell material <br />is quantitatively investigated because the shell material is subject to be strained by <br />stress and deformation during the assembly and installation of the shielding system. <br /><br /> Next, the effect of the hysteresis of the shell material on the shielding <br />effectiveness is discussed against static magnetic fields. It has been qualitatively <br />understood that the shielding effectiveness can be seriously affected by strain of the <br />shell material. Therefore, an influence of a tiny amount of strain of the shell material <br />on the magnetic shielding effectiveness is analyzed. <br /> Finally, a guiding principle for evaluating the maximum leakage field as a <br />shielding efficacy of the shell material, which is a reasonable and obtainable field in <br />the worst-case scenario for the magnetized condition of the shielding shell, is discussed. <br />It is determined by considering the hysteresis of the shell material, and it is revealed <br />that the concept of the maximum leakage field is effective whether the shell material is <br />strained or not. <br /><br /> The thesis consists of five chapters, which are summarized below. <br /> Chapter 1 states the purpose and background of this study, providing an overview <br />of the prior researches, and describes the significance of this study. The first section of <br />this chapter explains the necessity of the magnetic shielding from strong static fields <br />for devices operating under large-scale equipments, by introducing specific situations <br />inherent in big science projects, such as the magnetically confined fusion-plasma <br />science and the high-energy accelerator science. In the second section, the novelties <br />and goals of this study are summarized. The structure of this thesis is outlined in the <br />third section. <br /><br /> Chapter 2, consisting of five sections, describes the research and development of <br />the soft magnetic materials for the use of the magnetic shielding system. In the first <br />section, the purposes of the research in this chapter are addressed. <br /> The second and third sections of this chapter focus on the strategies to improve the <br />soft magnetic properties of pure iron and to develop soft magnetic materials with both <br />higher permeability and lower coercivity than those of pure iron without deteriorating <br />its high-magnetic flux density by the grain-coarsening technique. The developed <br />Fe-1%Al alloy exhibits extremely large ferrite grains in its microstructure, and has <br />almost the same high-permeability and low-coercivity as those of Permalloy B. <br />Moreover, it indicates high saturation magnetization, which is lower only by 2% than <br />that of pure iron. <br /> The fourth section of this chapter discusses an influence of a tiny amount of plastic <br />strain on the magnetic properties. It is revealed that the deterioration of coercivity due <br />to the plastic strain is alleviated in the coarsened grain microstructure. Therefore, it is <br />understood that the improvement of the soft magnetism by the grain-coarsening <br />technique is effective for the prevention of the deterioration of coercivity by strain <br />caused through damage. The results of the research in this chapter are summarized in <br />the fifth section. <br /><br /> Chapter 3, containing six sections, explains a prediction method for the magnetic <br />shielding effectiveness and a design concept for the double-layer shielding techniques. <br />The first section of this chapter addresses the purpose of the research in this chapter. <br /> In the second and third sections of this chapter, a new approach to the estimation <br />of the static ferromagnetic shielding effectiveness is proposed, in which the magnetic <br />hysteresis of the shielding materials is considered. The hysteresis effects of the shell <br />materials are discussed on the ferromagnetic shielding, in which a relatively strong <br />external field is reduced below the geomagnetic field in a shielded space. The measured <br />leakage field in the shielding enclosure corresponds to the results of the finite element <br />method (FEM) analysis when permeability considering the effect of coercivity is used <br />for the calculation as a parameter representing the hysteresis of the shielding material. <br /> The effects of both permeability and coercivity on the leakage fields are discussed <br />in the fourth section of this chapter, with regard to the magnetic properties of the <br />shielding materials by using the FEM analysis in combination with the results <br />obtained in chapter 2. The maximum leakage field, which is regarded as a figure of <br />merit of the shielding efficacy, is determined by the coercivity of the material used for <br />the shield, and it is clarified that the coercivity should be considered for the estimation <br />of the leakage field in an actual design of the shielding system. It is also confirmed that <br />the deterioration of the soft magnetic properties, not only permeability but also <br />coercivity, due to the residual strain causes the reduction of the magnetic shielding <br />efficacy. Finally, it is concluded that the maximum leakage field is dominated by the <br />coercivity of the shell material regardless of the shell material condition being strained <br />or not. <br /> In the fifth section, the effect of the double-layer structure on the shielding design <br />is investigated by using the analysis with considering the hysteresis of the shell <br />material. The double-shell structure is definitely effective for abating the degradation <br />of the shielding efficacy in the strained shielding material in that the influence of the <br />deterioration of permeability of the inner shell material due to the strain is lowered <br />because the external field applied to the inner shell is reduced by the shielding effect of <br />the outer shell. Accordingly, the enhancement of leakage field by the strain can be <br />suppressed below a field corresponding to the coercivity of the strained inner shell <br />material in the double-shell structure. It is concluded that the required property for the <br />shielding material is low coercivity that is subject to little change due to the residual <br />strain, adding to high saturation induction and high permeability which are <br />conventionally required. The above results are summarized in the sixth section. <br /><br /> Chapter 4, containing three sections, focuses on the application techniques, and <br />describes the actual performance of the ferromagnetic shielding for devices operating <br />under the large-scale equipment in big science projects. The first section of this chapter <br />provides some practical uses of the soft magnetic alloy developed in chapter 2. The <br />practical applications of Fe-1%Al alloy to the magnetic shielding are presented for <br />photomultiplier tubes (PMT), neutral beam injectors (NBI), and so on, which are used <br />in the magnetically confined fusion-plasma science and the high energy accelerator <br />science. In the second section, the shielding design for a neutralizing cell of the NBI, <br />which is used for the heating of the magnetically confined fusion-plasmas, are <br />discussed as an example for the design optimization with the double-layer shielding <br />system. The role of the outer shell under a severe condition, where a large volume is <br />shielded from strong external magnetic field, is addressed, and it is clarified that the <br />inner shell design including the structure and the shell materials can be optimized by a <br />proper selection of the outer shell materials. It is also confirmed that the double-layer <br />shielding is effective not only for reducing the leakage field in the shielded space but <br />also for abating the deterioration of the shielding efficacy in the strained shell material. <br />The summary of this chapter is provided in the third section. <br /><br /> Chapter 5 is the conclusion of this thesis. The results obtained in this study are <br />summarized, and the future prospects of the ferromagnetic shielding techniques are <br />presented. Additional challenges for the further improvement are proposed from a <br />viewpoint of both the material science and the electromagnetism. The results obtained <br />here on the designing techniques and the material techniques for the magnetic <br />shielding should contribute to future development in not only big science projects but <br />also general physics researches as invaluable techniques. <br /><br /> | |||||
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