{"created":"2023-06-20T13:22:10.812710+00:00","id":2681,"links":{},"metadata":{"_buckets":{"deposit":"1a783a40-8b62-457b-aeb3-7e89d8678063"},"_deposit":{"created_by":21,"id":"2681","owners":[21],"pid":{"revision_id":0,"type":"depid","value":"2681"},"status":"published"},"_oai":{"id":"oai:ir.soken.ac.jp:00002681","sets":["2:427:12"]},"author_link":["0","0"],"item_1_creator_2":{"attribute_name":"著者名","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"MISHRA, Jyoti Shankar"}],"nameIdentifiers":[{}]}]},"item_1_date_granted_11":{"attribute_name":"学位授与年月日","attribute_value_mlt":[{"subitem_dategranted":"2011-09-30"}]},"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（学術）"}]},"item_1_description_12":{"attribute_name":"要旨","attribute_value_mlt":[{"subitem_description":"&nbsp;&nbsp;This study is focused on to address the pellet fueling issues such as ablation and mass redistribution in the large helical device (LHD). It has been found that the ablation dynamics strongly regulated by the local fast ion density profile generated due to the neutral beam injection (NBI) heating.  Owing to the asymmetric ablation in presence of the fast ions, three-dimensionality in the pellet trajectory, and subsequently change in the fueling characteristics has been observed. To explore the improved fueling properties by considering the 〓B structure of the injection location on the pellet ablatant, pellet injection studies are performed for the high field side, and the low field side injection locations. A comparative study of fueling efficiency is presented at different plasma conditions for these locations.\r\n&nbsp;&nbsp;To deliver an intact pellet within the curved guiding path for an injection location other than outboard side, a low speed pellet injector is developed.  This injector works on the combined operation of a mechanical punch and He propellant gas.  This injector can inject a 3 mm〓 ×3 mm〓 intact pellet with speed ≤ 275 ms−1 at a pellet formation temperature of 8.0 K, flexibly. The loss in pellet speed and mass inside the guide tube are less than 6% and 10%, respectively.\r\n&nbsp;&nbsp;Since, pellets are injected into the plasmas of 3D magnetic configuration; a three-dimensional pellet-plasma interaction can be predicted. Therefore, applying the stereoscopic technique, a 3D diagnostics system has been calibrated to image the pellet ablation process inside the plasma. This imaging system uses a fast camera (time resolution of µs scale) and bifurcated coherent imaging fiber. The calibration error of this system is < 〓 20 mm in the pellet penetration direction and within 〓5 mm in the transverse direction, and is able to measure the ablation dynamics with good accuracy.\r\nIn presence of asymmetric tangential NBI heated plasmas in LHD, an ablating pellet deflects in toroidal and vertical direction rather than continuing its 1D motion along its injection direction. Whereas, a both sided NBI has less significant effect on the pellet deflection. The toroidal deflection is ≤ 20 cm with acceleration of the order of 106 ms−2. The toroidal deflection is successfully explained due to the unilateral ablation by the fast ions on the pellet surface and the formation of the rocket force in passing fast ions direction. At higher ne, reduction in deflection speed indicates the reduction of fast ion effect. In addition, the role of rotational transform on the pellet ablation dynamics during its lifetime is explained.  The three dimensionality of the ablation behavior by associating with the change in pellet speed affects the pellet penetration inside the plasma, and breaks the general assumption of the penetration depth, considering the constant pellet speed.\r\n&nbsp;&nbsp;In case of the LFS injected pellet, similar to that of the tokomak results, an outward redistribution of the pellet mass has been observed in LHD. In tokomaks, owing to the 〓B induced redistribution of the pellet ablatant, a better fueling efficiency has been reported for HFS pellet injection. As the ideal HFS resides under the helical coil in LHD, it is difficult to access this location.  Therefore, in an alternative approach, injection of a pellet from the vessel inboard side with an oblique angle to a location closed to the helical coil has been considered. The injection position is optimized by performing a simple calculation for E × B drift effect on the plasmoid for that location. In alternative injection case, due to the fast ion effect, the pellet deflects three dimensionally to a location having similar characteristic as that of the LFS injection. Therefore, final mass deposition profile seems to be similar as that of the LFS injection case. The difference in pellet penetration and the deposition peak is around 15 - 20 cm. This indicates the outward redistribution of pellet mass. This behavior is also confirmed by analyzing the pellet ablation images, where outward mass drift at a speed of 8-10 kms-1 or more has been recorded. Considering the E × B drift effect for the alternative injection, it has been found that there are certain possibilities for enhanced deposition, if the pellet can be able to approach the calculated HFS location.\r\n&nbsp;&nbsp;This work leads to the conclusion that the fast ions play a significant role in the pellet ablation process.  While discussing the fueling process in the fusion reactor, the effect of the energetic ions on the pellet penetration process should be taken into account. Considering the similarity in redistribution phenomenon of the pellet ablatant in LHD and tokomak for LFS injection, it can be said that, the HFS fueling is necessary for reactor grade plasmas.","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1451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":"2011"}]},"item_creator":{"attribute_name":"著者","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"MISHRA, Jyoti Shankar","creatorNameLang":"en"}],"nameIdentifiers":[{}]}]},"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","filename":"甲1451_要旨.pdf","filesize":[{"value":"373.9 kB"}],"format":"application/pdf","licensetype":"license_11","mimetype":"application/pdf","url":{"label":"要旨・審査要旨","url":"https://ir.soken.ac.jp/record/2681/files/甲1451_要旨.pdf"},"version_id":"a2590194-d4a9-4b31-888d-ef3cd55daeb1"},{"accessrole":"open_date","date":[{"dateType":"Available","dateValue":"2016-02-17"}],"displaytype":"simple","filename":"甲1451_本文.pdf","filesize":[{"value":"11.8 MB"}],"format":"application/pdf","licensetype":"license_11","mimetype":"application/pdf","url":{"label":"本文","url":"https://ir.soken.ac.jp/record/2681/files/甲1451_本文.pdf"},"version_id":"1022f23b-dd03-4f3c-bd7e-61c9198d149f"}]},"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":"A study of pellet-plasma interactions using fast three-dimensional imaging in Large Helical Device","item_titles":{"attribute_name":"タイトル","attribute_value_mlt":[{"subitem_title":"A study of pellet-plasma interactions using fast three-dimensional imaging in Large Helical Device"},{"subitem_title":"A study of pellet-plasma interactions using fast three-dimensional imaging in Large Helical Device","subitem_title_language":"en"}]},"item_type_id":"1","owner":"21","path":["12"],"pubdate":{"attribute_name":"公開日","attribute_value":"2012-03-26"},"publish_date":"2012-03-26","publish_status":"0","recid":"2681","relation_version_is_last":true,"title":["A study of pellet-plasma interactions using fast three-dimensional imaging in Large Helical Device"],"weko_creator_id":"21","weko_shared_id":-1},"updated":"2023-06-20T15:47:12.559216+00:00"}