{"_buckets": {"deposit": "20ce1091-8d9e-4816-bc15-b51d44ee3224"}, "_deposit": {"created_by": 1, "id": "528", "owners": [1], "pid": {"revision_id": 0, "type": "depid", "value": "528"}, "status": "published"}, "_oai": {"id": "oai:ir.soken.ac.jp:00000528", "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": "2006-09-29", "bibliographicIssueDateType": "Issued"}, "bibliographic_titles": [{}]}]}, "item_1_creator_2": {"attribute_name": "著者名", "attribute_type": "creator", "attribute_value_mlt": [{"creatorNames": [{"creatorName": "KHAN, RIAZ"}], "nameIdentifiers": [{"nameIdentifier": "0", "nameIdentifierScheme": "WEKO"}]}]}, "item_1_creator_3": {"attribute_name": "フリガナ", "attribute_type": "creator", "attribute_value_mlt": [{"creatorNames": [{"creatorName": "ハーン, リアズ"}], "nameIdentifiers": [{"nameIdentifier": "0", "nameIdentifierScheme": "WEKO"}]}]}, "item_1_date_granted_11": {"attribute_name": "学位授与年月日", "attribute_value_mlt": [{"subitem_dategranted": "2006-09-29"}]}, "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（理学）"}]}, "item_1_description_1": {"attribute_name": "ID", "attribute_value_mlt": [{"subitem_description": "2006504", "subitem_description_type": "Other"}]}, "item_1_description_12": {"attribute_name": "要旨", "attribute_value_mlt": [{"subitem_description": "　　　　The ballooning mode is a magnetohydrodynamic (MHD) instability that is excited\u003cbr /\u003ein finite beta plasmas. The energy source of the ballooning mode originates\u003cbr /\u003efrom the pressure gradient in a locally unfavorable magnetic curvature region, typically,\u003cbr /\u003ein the outboard of the torus. The proximity of the measured edge pressure gradient\u003cbr /\u003ein H-mode to the critical gradient for ideal ballooning instability has led to the\u003cbr /\u003eproposal that these instabilities might have a role in triggering edge localized modes\u003cbr /\u003e(ELMs). New nonlinear theoretical models describe ELMs in terms of filaments that\u003cbr /\u003eerupt from the plasma. This is supported by strong experimental evidence from the\u003cbr /\u003eMAST tokamak[1, 2, 3] that the ELM does indeed exhibit a mode structure predicted\u003cbr /\u003eby the nonlinear ballooning mode theory. This thesis presents the nonlinear dynamics\u003cbr /\u003eof the ballooning mode and its relation with ELMs by means of numerical simulations\u003cbr /\u003ein spherical tokamak (ST) devices in the framework of MHD model and the drift\u003cbr /\u003emodel. Our simulation reproduces the characteristic features of ELM crash phase.\u003cbr /\u003e　　　　The nonlinear simulations using MHD model are executed in a three dimensional\u003cbr /\u003efull toroidal geometry. The initial MHD equilibrium for the simulation is given\u003cbr /\u003eas an axisymmetric numerical MHD equilibrium, which is obtained by solving the\u003cbr /\u003eGrad-Shafranov equation on the poloidal cross-section. The profiles are selected to be\u003cbr /\u003emoderately broad in the core region following the conventional experiments. During\u003cbr /\u003ethe linear analysis, the intermediate-n modes (i.e., n = 5\u0026#8722;9) have larger growth rates\u003cbr /\u003ethan others, where n is the toroidal mode number. It is shown that these intermediate-n\u003cbr /\u003emodes have a ballooning mode nature in that the mode structures are poloidaly localized　in the bad curvature region, and have a wide envelope consisting of several\u003cbr /\u003epoloidal components. In the nonlinear phase, the MHD ballooning modes evolve into\u003cbr /\u003ea nonlinear structure that results in the formation of a number of hot plasma filaments,\u003cbr /\u003eelongated along a magnetic field line, but localized about it. These filaments extend\u003cbr /\u003eout into the scrape-off layer on the outboard side but remain connected back into the\u003cbr /\u003epedestal region on the inboard side. This filamentary structure is correspondent to the\u003cbr /\u003econvection motion of the plasma flows, which forms a twin-vortex flow pattern in such\u003cbr /\u003ea way that the plasma moves in outward direction, pushing the core plasma from inside\u003cbr /\u003eto outside of the torus. When the balloon structure is initially formed at the plasma\u003cbr /\u003esurface, the magnetic field lines on both sides of the separatrix are pushed against each\u003cbr /\u003eother by such perpendicular flows due to the spouting-out and the perfect conductor\u003cbr /\u003econserving the poloidal flux. Under this situation, the reconnection of the field lines\u003cbr /\u003ecan effectively occur by the driven reconnection mechanism. Once such reconnection\u003cbr /\u003eoccur, the plasma rapidly flows out through the reconnected field lines due to the\u003cbr /\u003eparallel pressure gradient, leading to the filamentary structure. After the internal free\u003cbr /\u003eenergy is partially lost by such convective processes, the system ceases to develop and\u003cbr /\u003ereaches a relaxed state. These results are compared qualitatively with the experimental\u003cbr /\u003eobservation of the ELMs in MAST and NSTX experiments. Good agreement is\u003cbr /\u003efound in the following characteristics formation of filaments separating from the core,\u003cbr /\u003enon-uniform growth of filaments due to toroidal mode coupling, time scale of ELM\u003cbr /\u003ecrash, triggering by the ideal ballooning mode, presence of intermediate-n precursors\u003cbr /\u003eand loss of plasma through convective process.\u003cbr /\u003e　　　　Moreover the finite Larmor radius (FLR) effect is also addressed using the simplified drift model, where the ion diamagnetic drift effect is included in the advection\u003cbr /\u003eterm of the equation of motion. This modification has been found to suppress the\u003cbr /\u003ehigher-n components linearly, since the mode growth is suppressed by the sheared rotation flows. However, it has been also found that the filament separation from the core\u003cbr /\u003ecan take place universally for FLR as well as the MHD case.", "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984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": "2006"}]}, "item_creator": {"attribute_name": "著者", "attribute_type": "creator", "attribute_value_mlt": [{"creatorNames": [{"creatorName": "KHAN, Riaz", "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984_要旨.pdf", "filesize": [{"value": "273.8 kB"}], "format": "application/pdf", "future_date_message": "", "is_thumbnail": false, "licensetype": "license_11", "mimetype": "application/pdf", "size": 273800.0, "url": {"label": "要旨・審査要旨", "url": "https://ir.soken.ac.jp/record/528/files/甲984_要旨.pdf"}, "version_id": "e8ba8b68-a9d4-411b-8005-1c7621bf9534"}, {"accessrole": "open_date", "date": [{"dateType": "Available", "dateValue": "2016-02-17"}], "displaytype": "simple", "download_preview_message": "", "file_order": 1, "filename": "甲984_本文.pdf", "filesize": [{"value": "6.2 MB"}], "format": "application/pdf", "future_date_message": "", "is_thumbnail": false, "licensetype": "license_11", "mimetype": "application/pdf", "size": 6200000.0, "url": {"label": "本文", "url": "https://ir.soken.ac.jp/record/528/files/甲984_本文.pdf"}, "version_id": "344f8044-c71e-41b4-8ad1-a823e5886e8e"}]}, "item_language": {"attribute_name": "言語", "attribute_value_mlt": [{"subitem_language": "eng"}]}, "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": "Simulation study on nonlinear dynamics of ballooning modes in a spherical tokamak", "item_titles": {"attribute_name": "タイトル", "attribute_value_mlt": [{"subitem_title": "Simulation study on nonlinear dynamics of ballooning modes in a spherical tokamak"}, {"subitem_title": "Simulation study on nonlinear dynamics of ballooning modes in a spherical tokamak", "subitem_title_language": "en"}]}, "item_type_id": "1", "owner": "1", "path": ["12"], "permalink_uri": "https://ir.soken.ac.jp/records/528", "pubdate": {"attribute_name": "公開日", "attribute_value": "2010-02-22"}, "publish_date": "2010-02-22", "publish_status": "0", "recid": "528", "relation": {}, "relation_version_is_last": true, "title": ["Simulation study on nonlinear dynamics of ballooning modes in a spherical tokamak"], "weko_shared_id": 1}