{"_buckets": {"deposit": "37fd2454-54ad-4b27-ae6c-199d0520700a"}, "_deposit": {"created_by": 1, "id": "538", "owners": [1], "pid": {"revision_id": 0, "type": "depid", "value": "538"}, "status": "published"}, "_oai": {"id": "oai:ir.soken.ac.jp:00000538", "sets": ["12"]}, "author_link": ["0", "0", "0"], "item_1_biblio_info_21": {"attribute_name": "書誌情報（ソート用）", "attribute_value_mlt": [{"bibliographicIssueDates": {"bibliographicIssueDate": "2008-03-19", "bibliographicIssueDateType": "Issued"}, "bibliographic_titles": [{}]}]}, "item_1_creator_2": {"attribute_name": "著者名", "attribute_type": "creator", "attribute_value_mlt": [{"creatorNames": [{"creatorName": "大森, 俊道"}], "nameIdentifiers": [{"nameIdentifier": "0", "nameIdentifierScheme": "WEKO"}]}]}, "item_1_creator_3": {"attribute_name": "フリガナ", "attribute_type": "creator", "attribute_value_mlt": [{"creatorNames": [{"creatorName": "オオモリ, トシミチ"}], "nameIdentifiers": [{"nameIdentifier": "0", "nameIdentifierScheme": "WEKO"}]}]}, "item_1_date_granted_11": {"attribute_name": "学位授与年月日", "attribute_value_mlt": [{"subitem_dategranted": "2008-03-19"}]}, "item_1_degree_grantor_5": {"attribute_name": "学位授与機関", "attribute_value_mlt": [{"subitem_degreegrantor": [{"subitem_degreegrantor_name": "総合研究大学院大学"}]}]}, "item_1_degree_name_6": {"attribute_name": "学位名", "attribute_value_mlt": [{"subitem_degreename": "博士（工学）"}]}, "item_1_description_1": {"attribute_name": "ID", "attribute_value_mlt": [{"subitem_description": "2008020", "subitem_description_type": "Other"}]}, "item_1_description_12": {"attribute_name": "要旨", "attribute_value_mlt": [{"subitem_description": "　　In order to avoid errors in the operation of devices subject to strong magnetic \u003cbr /\u003efields, shielding systems are applied to such devices that would be affected by magnetic \u003cbr /\u003efields. 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}