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{"_buckets": {"deposit": "469ee7e2-01dc-4bd9-a3a8-e76bf0011832"}, "_deposit": {"created_by": 1, "id": "523", "owners": [1], "pid": {"revision_id": 0, "type": "depid", "value": "523"}, "status": "published"}, "_oai": {"id": "oai:ir.soken.ac.jp:00000523", "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": "2006-03-24", "bibliographicIssueDateType": "Issued"}, "bibliographic_titles": [{}]}]}, "item_1_creator_2": {"attribute_name": "著者名", "attribute_type": "creator", "attribute_value_mlt": [{"creatorNames": [{"creatorName": "中野, 治久"}], "nameIdentifiers": [{"nameIdentifier": "0", "nameIdentifierScheme": "WEKO"}]}]}, "item_1_creator_3": {"attribute_name": "フリガナ", "attribute_type": "creator", "attribute_value_mlt": [{"creatorNames": [{"creatorName": "ナカノ, ハルヒサ"}], "nameIdentifiers": [{"nameIdentifier": "0", "nameIdentifierScheme": "WEKO"}]}]}, "item_1_date_granted_11": {"attribute_name": "学位授与年月日", "attribute_value_mlt": [{"subitem_dategranted": "2006-03-24"}]}, "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": "2006014", "subitem_description_type": "Other"}]}, "item_1_description_12": {"attribute_name": "要旨", "attribute_value_mlt": [{"subitem_description": "\u003cb\u003e1. Research Purpose\u003c/b\u003e\u003cbr /\u003e An anomalous transport in torus magnetic confinement plasma is expressed as\u003cbr /\u003e a product of electron density and potential fluctuations. In order to elucidate the\u003cbr /\u003eanomalous transport experimentally, it is necessary to measure simultaneosly lo-\u003cbr /\u003ecal electron density and potential fluctuation. A heavy ion beam probe (HIBP)\u003cbr /\u003eis only a diagnostics device to be able to measure electron density and potential\u003cbr /\u003esimultaneously with high temporal (~ μs) and spatial resolution (~ mm) in high\u003cbr /\u003etemperature plasma (1 keV ~). In the HIBP diagnostics, electron density and\u003cbr /\u003epotential fluctuations are measured as the fluctuations of detected beam current\u003cbr /\u003eand change of beam energy, respectively. However, such simultaneous measure\u003cbr /\u003ements in high temperature plasma have never been performed except ISX-B [l],\u003cbr /\u003eTEXT(-U) [2] tokamaks.\u003cbr /\u003e In Compact Helical System (CHS), the HIBP has been used to measure mainly\u003cbr /\u003ethe potential profile and its dynamics, which is much larger displacement than\u003cbr /\u003efluctuation, and density fluctuations. The first purpose of this thesis is to extend\u003cbr /\u003ethe potential ability of the HIBP and to achieve the simultaneous measurements\u003cbr /\u003e of electron density and potential fluctuations in all radial positions in CHS plasma\u003cbr /\u003eby improving its ion source of a part of the ion gun of HIBP. The second pur-\u003cbr /\u003epose of this thesis is to evaluate path integral effect, which is a well-known and\u003cbr /\u003e long-standing problem for the HIBP diagnostics, and to reconstruct local density\u003cbr /\u003efluctuation. The detected beam current fluctuation of HIBP contains information\u003cbr /\u003eof local electron density fluctuation at ionization point and fluctuations along pri-\u003cbr /\u003emary and secondary beam trajectories. The latter effect of beam trajectory is\u003cbr /\u003ecalled a path integral effect. Several previous articles l3-6] exist on simulating\u003cbr /\u003einfluences of its effect, assuming electron density and temperature and electron the\u003cbr /\u003edensity fluctuation profiles. In this thesis, a method is proposed to eliminate the\u003cbr /\u003epath integral effect in real \u003ci\u003e\" experimental data \"\u003c/i\u003e and to evaluate \" actual\" local elec-\u003cbr /\u003etron density fluctuation profile.\u003cbr /\u003e\u003cbr /\u003e\u003cb\u003e2. Simultaneous measurements of electron density and po-tential fluctuation\u003cbr /\u003e2.1. Improvement oHon Source \u003c/b\u003e\u003cbr /\u003e In CHS an ion source of alkali zeolite emitter type is used for the HIBP; the\u003cbr /\u003ecesium ions are released from the high temperature zeolite heated up to ~1000 ℃.\u003cbr /\u003ePreviously, in an old socket, the cesium zeolite is indirectly heated through the\u003cbr /\u003eceramic case heated by a filament (Fig. 3.1(a)). The indirect heating of the\u003cbr /\u003esocket of this type may prevent the zeolite, from attaining the sufficiently high\u003cbr /\u003etemperature. Then, the structure of the ion source is newly developed to increase\u003cbr /\u003ethe higher beam current by direct heatly heating the zeolite.\u003cbr /\u003eThe new socket structure is shown in Fig. 3.1(b). This socket allows heating\u003cbr /\u003edirectly the zeolite, by setting the filament inside the zeolite. Using this socket of\u003cbr /\u003edirect heating, ten times higher beam current compared with the old is extracted\u003cbr /\u003efrom the present ion source.\u003cbr /\u003e\u003cbr /\u003e\u003cb\u003e2.2. Simultaneous measurements\u003c/b\u003e\u003cbr /\u003e Using the direct heating socket, simultaneous measurements of electron density\u003cbr /\u003e(detected beam current of HIBP) and potential fluctuations are successfully per-\u003cbr /\u003eformed in low density (\u003ci\u003en\u003csmall\u003ee\u003c/small\u003e\u003c/i\u003e ~ 5 x 10\u003csup\u003e18\u003c/sup\u003e m\u003csup\u003e-3\u003c/sup\u003e) high temperature (\u003ci\u003eT\u003csmall\u003ee\u003c/small\u003e\u003c/i\u003e = 1.0 ~ 1.5 keV)\u003cbr /\u003eplasma in CHS. The major and minor radii of the CHS plasma \u003ci\u003eR\u003c/i\u003e=1 m and minor \u003cbr /\u003eradius \u003ci\u003eα\u003c/i\u003e = 0.2 m.\u003cbr /\u003e The fluctuation distribution measurements were done with 2 mm resolution over\u003cbr /\u003ethe whole radius form center to near the last closed field surface (LCFS) [7], as \u003cbr /\u003eis shown in Fig. 3.9. It is the first achievement as the simultaneous fluctuation\u003cbr /\u003emeasurements for all radial positions in high temperature torus plasma, because\u003cbr /\u003ethe previous works did not measure them simultaneously in center region because\u003cbr /\u003eof insufficient beam energy and/or detected beam current. The fluctuation spectra\u003cbr /\u003emeasured in CHS shows broad bands characteristics to indicate turbulence nature.\u003cbr /\u003eIt is found that fluctuation amplitudes become larger toward the plasma edge as\u003cbr /\u003eis similar to the observations of ISX-B and TEXT(-U).\u003cbr /\u003e\u003cbr /\u003e\u003cb\u003e3. Reconstruction local electron density fluctuation\u003cbr /\u003e3.1. Reconstruction local electron density fluctuation profiIe\u003cbr /\u003e\u003c/b\u003e The average of the detected beam fluctuation amplitude is written by,\u003cbr /\u003e\u003cbr /\u003e \u003ci\u003eη\u003csup\u003e2\u003c/sup\u003e\u003c/i\u003e(\u003ci\u003ep\u003c/i\u003e\u003csub\u003e*\u003c/sub\u003e)= \u003ci\u003e\u0026xi;\u003c/i\u003e \u003csup\u003e2\u003c/sup\u003e(\u003ci\u003ep\u003c/i\u003e\u003csub\u003e*\u003c/sub\u003e)\u003cbr /\u003e -2\u003cfont size=\"5\"\u003e\u0026Sigma; \u003c/font\u003e\u003cfont size=\"5\"\u003e\u003ci\u003e\u0026int;\u003c/i\u003e \u003c/font\u003e \u003csub\u003e\u003ci\u003eli\u003c/i\u003e\u003c/sub\u003e <\u003ci\u003e\u0026xi;\u003c/i\u003e (\u003ci\u003ep\u003csub\u003e*\u003c/i\u003e\u003c/sub\u003e)\u003ci\u003e\u0026xi;\u003c/i\u003e (\u003ci\u003ep\u003csub\u003ei\u003c/sub\u003e\u003c/i\u003e)\u003e>\u003csmall\u003eE\u003c/small\u003e\u003ci\u003eS\u003csmall\u003ei\u003c/small\u003e\u003c/i\u003e(\u003ci\u003ep\u003csub\u003ei\u003c/i\u003e\u003c/sub\u003e) w\u003csmall\u003ei\u003c/small\u003e(\u003ci\u003ep\u003csub\u003ei\u003c/i\u003e\u003c/sub\u003e)d\u003ci\u003ep\u003csub\u003ei\u003c/sub\u003e\u003c/i\u003e (1)\u003cbr /\u003e \u003csup\u003e\u003ci\u003ei\u003c/i\u003e=1,2\u003c/sup\u003e\u003cbr /\u003e + \u003cfont size=\"5\"\u003e\u0026Sigma;\u003c/font\u003e \u003cfont size=\"5\"\u003e\u0026Sigma;\u003c/font\u003e \u003cfont size=\"5\"\u003e \u003ci\u003e\u0026int;\u003c/i\u003e \u003c/font\u003e \u003csub\u003e\u003ci\u003eli\u003c/i\u003e\u003c/sub\u003e \u003cfont size=\"5\"\u003e\u003ci\u003e\u0026int;\u003c/i\u003e \u003c/font\u003e\u003csub\u003e\u003ci\u003elj\u003c/i\u003e\u003c/sub\u003e <\u003ci\u003e\u0026xi;\u003c/i\u003e (\u003ci\u003ep\u003csub\u003ei\u003c/i\u003e\u003c/sub\u003e)\u0026xi; (\u003ci\u003ep\u003csub\u003ej\u003c/i\u003e\u003c/sub\u003e)>\u003csmall\u003eE\u003c/small\u003eS\u003csmall\u003ei\u003c/small\u003e(\u003ci\u003ep\u003csub\u003ei\u003c/i\u003e\u003c/sub\u003e) S\u003csmall\u003ej\u003c/small\u003e(\u003ci\u003ep\u003csub\u003ej\u003c/i\u003e\u003c/sub\u003e) w\u003csmall\u003ei\u003c/small\u003e(\u003ci\u003ep\u003csub\u003ei\u003c/i\u003e\u003c/sub\u003e) w\u003csmall\u003ej\u003c/small\u003e(\u003ci\u003ep\u003csub\u003ei\u003c/i\u003e\u003c/sub\u003e)d\u003ci\u003ep\u003csmall\u003ei\u003c/i\u003e\u003c/small\u003ed\u003ci\u003ep\u003csmall\u003ej\u003c/small\u003e\u003c/i\u003e\u003cbr /\u003e \u003csmall\u003e\u003ci\u003ei\u003c/i\u003e=1,2 \u003ci\u003e j\u003c/i\u003e=1,2\u003c/small\u003e\u003cbr /\u003ewhere, \u003ci\u003eη\u003c/i\u003e=δ\u003ci\u003eI\u003csmall\u003ed\u003c/small\u003e/I\u003csmall\u003ed\u003c/small\u003e\u003c/i\u003e, \u003ci\u003e\u0026xi;\u003c/i\u003e = \u003ci\u003eδn\u003csmall\u003ee\u003c/small\u003e/n\u003csmall\u003ee\u003c/small\u003e, S \u003c/i\u003eand \u003ci\u003ew\u003csmall\u003ei\u003c/small\u003e\u003c/i\u003e are detected beam current fluctuation\u003cbr /\u003erate and local electron density fluctuation rate point, ionization rate and integral\u003cbr /\u003eweight, respectively.Where \u003ci\u003eI\u003csmall\u003ed\u003c/small\u003e, n\u003csmall\u003ee\u003c/small\u003e\u003c/i\u003e represents detected beam current, local elec-\u003cbr /\u003etron density, respectively, andδindicates fluctuation. The ionization rate can be\u003cbr /\u003eestimated as a function of electron density and temperature from Lotz\u0027s empirical\u003cbr /\u003eformula [8]. The electron density and temperature can be given with Thomson\u003cbr /\u003escattering measurement. The bracket with subscript E, < >\u003csmall\u003eE\u003c/small\u003e, represents the en-\u003cbr /\u003esemble average,and the terms including the bracket are the correlations between\u003cbr /\u003e density fluctuations at two spatial points. If the correlation terms of fluctuations\u003cbr /\u003eare evaluated, local electron density fluctuation is estimated by solving the above\u003cbr /\u003eintegral equation. \u003cbr /\u003e On the right-hand-side of Eq. (1), the second and third terms are effects around\u003cbr /\u003eionization point and along the beam trajectories, respectively. They are under-\u003cbr /\u003estood if assuming a limiting case that the fluctuation should have the infinitesimal\u003cbr /\u003eshort correlation length and the ensemble averaged terms should be expressed as\u003cbr /\u003etheδ-function. In addition to this, several simplification makes the Eq. (1) take\u003cbr /\u003ethe followlng form, as\u003cbr /\u003e\u003cbr /\u003e \u003ci\u003eη\u003c/i\u003e\u003csup\u003e2\u003c/sup\u003e = (1-〓\u003csmall\u003ec\u003c/small\u003e+〓\u003csmall\u003ec\u003c/small\u003e)\u003ci\u003e\u0026xi;\u003c/i\u003e\u003csup\u003e2\u003c/sup\u003e (2)\u003cbr /\u003e\u003cbr /\u003ewhere the first , second and third terms represent the local density fluctuation, the\u003cbr /\u003escreening effect and the accumulating effect. From this simplification, the path\u003cbr /\u003eintegral effect is found to be composed of the screening and accumulating effects.\u003cbr /\u003eThe degree of the path integral effect, whose coefficient ζ, is estimated from the\u003cbr /\u003esum of the second and third terms in Eq. (2).\u003cbr /\u003e Fig. 4.2(a) shows the dependence of the coefficient on electron density and\u003cbr /\u003etemperature, using cesium ion beam. The coefficient is calculated for our HIBP\u003cbr /\u003egeometry and CHS plasma assuming that the correlation length is 1 cm and the\u003cbr /\u003eused beam is cesium ion. Here, the primary and secondary beam trajectory lengths\u003cbr /\u003eare 0.2 m, corresponding to the CHS plasma radius. In this calculation, the\u003cbr /\u003ecoefficient is 0.1 when \u003ci\u003eT\u003csmall\u003ee\u003c/small\u003e\u003c/i\u003e ~ 1 keV is 0.1 in \u003ci\u003en\u003csmall\u003ee\u003c/small\u003e\u003c/i\u003e ~ 2.8 × 10\u003csup\u003e18\u003c/sup\u003e m\u003csup\u003e-3\u003c/sup\u003e. In this case, the\u003cbr /\u003epath integral effect can be almost negligible. On the other hand, the coefficient\u003cbr /\u003eis 1 when T\u003csmall\u003ee\u003c/small\u003e ~ 1 keV and \u003ci\u003en\u003csmall\u003ee\u003c/small\u003e\u003c/i\u003e ~ 1.1 x 10\u003csup\u003e19\u003c/sup\u003e m\u003csup\u003e-3\u003c/sup\u003e, which represent detected beam\u003cbr /\u003efluctuation amplitude is twice as local density fluctuation, and the path integral\u003cbr /\u003eeffect is dominant.\u003cbr /\u003e The ensemble averaged terms can be evaluated if the fluctuations correlation be-\u003cbr /\u003etween two spatial points is assumed as the Gauss function, \u0026fnof;( \u0026Delta;\u003ci\u003ex\u003c/i\u003e) =exp(-0.5(\u0026Delta;/lc)\u003csup\u003e2\u003c/sup\u003e),\u003cbr /\u003ewhere \u003ci\u003elc\u003c/i\u003e is a correlation length. The HIBP of CHS is equipped with three chan-\u003cbr /\u003enels, so that the correlation length \u003ci\u003elc\u003c/i\u003e can be evaluated; the distance between two\u003cbr /\u003e of the channels, \u0026Delta;\u003ci\u003ex\u003c/i\u003e ranges from 3 to 10 mm By substituting the estimated correla-\u003cbr /\u003etion function into Eq. (2), the local electron density fluctuation amplitude profile\u003cbr /\u003ecan be reconstructed. Fig. 5.6(b) shows an example of the reconstruction for the\u003cbr /\u003ecase that the electron density and temperature are ~ 10\u003csup\u003e19\u003c/sup\u003e m\u003csup\u003e-3\u003c/sup\u003e and ~ 1 keV, re-\u003cbr /\u003espectively. Here, the integral equation is solved after several times iteration. The\u003cbr /\u003edetected beam current and the local electron density fluctuation amplitudes are\u003cbr /\u003ewithin the range of error in the outer region (\u003ci\u003ep\u003c/i\u003e \u003e 0.6). However, in the inner\u003cbr /\u003eregion (\u003ci\u003ep\u003c/i\u003e \u003c 0.6), the fluctuation amplitude of detected beam current is a half of\u003cbr /\u003ethe local fluctuation amplitude.\u003cbr /\u003e\u003cbr /\u003e\u003cb\u003e3.2. Reconstruction of local electron density fluctuation spectrum\u003c/b\u003e\u003cbr /\u003e The reconstruction method of local density fluctuation is extended to the esti-\u003cbr /\u003emation of density fluctuation spectra. It is apparent that the power spectra can be\u003cbr /\u003eevaluated simply by appling the above method to the fluctuation power at each\u003cbr /\u003efrequency. However, the integral equation for low frequency (\u003c 50 kHz) cannot be\u003cbr /\u003eoften solved with iteration method. This is caused by the fact that the correlation\u003cbr /\u003elength appears to become longer than the actual value. \u003cbr /\u003e This is considered to result from the path integral effect on the correlation length. \u003cbr /\u003eThe fluctuations of local three channels are strongly affected by the fluctuation\u003cbr /\u003ein the outer plasma regions, and the fluctuations at local three channels become\u003cbr /\u003eto show quite similar behavior. A technique is derived to correct this longer\u003cbr /\u003ecorrelation length. Thanks to the technique, the corrected correlation length is\u003cbr /\u003eevaluated and the spectra of local density fluctuation are successfully obtained. \u003cbr /\u003e Fig. 6.3(b) shows one example of the reconstructed spectrum of local electron\u003cbr /\u003edensity fluctuation, whose position is \u003ci\u003er/a\u003c/i\u003e - 0.26 in the same plasma in Fig. 5.6. \u003cbr /\u003eThe result shows that the path integral effect is larger in low frequency than that\u003cbr /\u003ein high frequency. \u003cbr /\u003e\u003cbr /\u003e\u003cb\u003e3.3. Consideration of the Bolt2;mann Relationship\u003c/b\u003e\u003cbr /\u003e As a result of the estimation of local density, the detected beam fluctuation\u003cbr /\u003ecan be roughly regarded as the local density fluctuation in low density regimes of\u003cbr /\u003en\u003csmall\u003ee\u003c/small\u003e ~ 5 × 10\u003csup\u003e18\u003c/sup\u003e m\u003csup\u003e-3\u003c/sup\u003e. Consequently, the detected beam fluctuation shown in Fig. \u003cbr /\u003e3.9 reflects local density fluctuation. A rough comparison between the density\u003cbr /\u003efluctuation and potential fluctuation (normalized by electron temperature) allows\u003cbr /\u003eexamining the validity of the Boltzmann relationship. Fig. 7.1(a) shows the nor-\u003cbr /\u003emalized density fluctuation as a function of normalized potential fluctuations. In\u003cbr /\u003eFig. 7.1(a), the different marks correspond to the different ranges of radial posi-\u003cbr /\u003etion of the plasma; red and green and blue plots are data point in 0 \u003c \u003ci\u003er/a\u003c/i\u003e \u003c 0.3,\u003cbr /\u003e 0.3 \u003c\u003ci\u003e r/a\u003c/i\u003e \u003c 0.6 and\u003ci\u003e r/a \u003e\u003c/i\u003e 0.6, respectively. The lines are fit lines using the least\u003cbr /\u003esquared method. The results show that the Boltzma- relationship should be\u003cbr /\u003e valid, although tendency is found that the normalized density fluctuation should\u003cbr /\u003ebe larger than the normalized potential fluctuation. \u003cbr /\u003e\u003cbr /\u003e\u003cb\u003e4. Summary\u003c/b\u003e\u003cbr /\u003eThe simultaneous measurements of electron density and potential fluctuations\u003cbr /\u003eare successfully made with heavy ion beam probe after the development of a new\u003cbr /\u003eion source. The measurement is achieved in a wide range of radial region with\u003cbr /\u003espatial resolution of 2 mm. A method is proposed to evaluate the path integral\u003cbr /\u003eeffect that is a long-standing problem for density fluctuation measurement with\u003cbr /\u003e the HIBPs. Applying this method on the CHS fluctuation measurements, the local\u003cbr /\u003edensity fluctuation and its power spectrum are successfully evaluated.", "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927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": "2005"}]}, "item_creator": {"attribute_name": "著者", "attribute_type": "creator", "attribute_value_mlt": [{"creatorNames": [{"creatorName": "NAKANO, Haruhisa", "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927_要旨.pdf", "filesize": [{"value": "376.6 kB"}], "format": "application/pdf", "future_date_message": "", "is_thumbnail": false, "licensetype": "license_11", "mimetype": "application/pdf", "size": 376600.0, "url": {"label": "要旨・審査要旨", "url": "https://ir.soken.ac.jp/record/523/files/甲927_要旨.pdf"}, "version_id": "de3f0af3-390e-4cc0-9164-dc82a5440fae"}, {"accessrole": "open_date", "date": [{"dateType": "Available", "dateValue": "2016-02-17"}], "displaytype": "simple", "download_preview_message": "", "file_order": 1, "filename": "甲927_本文.pdf", "filesize": [{"value": "17.6 MB"}], "format": "application/pdf", "future_date_message": "", "is_thumbnail": false, "licensetype": "license_11", "mimetype": "application/pdf", "size": 17600000.0, "url": {"label": "本文", "url": "https://ir.soken.ac.jp/record/523/files/甲927_本文.pdf"}, "version_id": "2374c5ba-3743-46a5-bf5a-91b8462181e9"}]}, "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": "重イオンビームプローブを用いた揺動分布計測と経路積分効果の評価法の確立", "item_titles": {"attribute_name": "タイトル", "attribute_value_mlt": [{"subitem_title": "重イオンビームプローブを用いた揺動分布計測と経路積分効果の評価法の確立"}]}, "item_type_id": "1", "owner": "1", "path": ["12"], "permalink_uri": "https://ir.soken.ac.jp/records/523", "pubdate": {"attribute_name": "公開日", "attribute_value": "2010-02-22"}, "publish_date": "2010-02-22", "publish_status": "0", "recid": "523", "relation": {}, "relation_version_is_last": true, "title": ["重イオンビームプローブを用いた揺動分布計測と経路積分効果の評価法の確立"], "weko_shared_id": 1}
重イオンビームプローブを用いた揺動分布計測と経路積分効果の評価法の確立
https://ir.soken.ac.jp/records/523
https://ir.soken.ac.jp/records/52350cba0d3-58c6-4638-9d84-63599fa13a95
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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 | 重イオンビームプローブを用いた揺動分布計測と経路積分効果の評価法の確立 | |||||
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 |
中野, 治久
× 中野, 治久 |
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フリガナ |
ナカノ, ハルヒサ
× ナカノ, ハルヒサ |
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著者 |
NAKANO, Haruhisa
× NAKANO, Haruhisa |
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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(理学) | |||||
学位記番号 | ||||||
内容記述タイプ | Other | |||||
内容記述 | 総研大甲第927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 | 2006-03-24 | |||||
学位授与年度 | ||||||
2005 | ||||||
要旨 | ||||||
内容記述タイプ | Other | |||||
内容記述 | <b>1. Research Purpose</b><br /> An anomalous transport in torus magnetic confinement plasma is expressed as<br /> a product of electron density and potential fluctuations. In order to elucidate the<br />anomalous transport experimentally, it is necessary to measure simultaneosly lo-<br />cal electron density and potential fluctuation. A heavy ion beam probe (HIBP)<br />is only a diagnostics device to be able to measure electron density and potential<br />simultaneously with high temporal (~ μs) and spatial resolution (~ mm) in high<br />temperature plasma (1 keV ~). In the HIBP diagnostics, electron density and<br />potential fluctuations are measured as the fluctuations of detected beam current<br />and change of beam energy, respectively. However, such simultaneous measure<br />ments in high temperature plasma have never been performed except ISX-B [l],<br />TEXT(-U) [2] tokamaks.<br /> In Compact Helical System (CHS), the HIBP has been used to measure mainly<br />the potential profile and its dynamics, which is much larger displacement than<br />fluctuation, and density fluctuations. The first purpose of this thesis is to extend<br />the potential ability of the HIBP and to achieve the simultaneous measurements<br /> of electron density and potential fluctuations in all radial positions in CHS plasma<br />by improving its ion source of a part of the ion gun of HIBP. The second pur-<br />pose of this thesis is to evaluate path integral effect, which is a well-known and<br /> long-standing problem for the HIBP diagnostics, and to reconstruct local density<br />fluctuation. The detected beam current fluctuation of HIBP contains information<br />of local electron density fluctuation at ionization point and fluctuations along pri-<br />mary and secondary beam trajectories. The latter effect of beam trajectory is<br />called a path integral effect. Several previous articles l3-6] exist on simulating<br />influences of its effect, assuming electron density and temperature and electron the<br />density fluctuation profiles. In this thesis, a method is proposed to eliminate the<br />path integral effect in real <i>" experimental data "</i> and to evaluate " actual" local elec-<br />tron density fluctuation profile.<br /><br /><b>2. Simultaneous measurements of electron density and po-tential fluctuation<br />2.1. Improvement oHon Source </b><br /> In CHS an ion source of alkali zeolite emitter type is used for the HIBP; the<br />cesium ions are released from the high temperature zeolite heated up to ~1000 ℃.<br />Previously, in an old socket, the cesium zeolite is indirectly heated through the<br />ceramic case heated by a filament (Fig. 3.1(a)). The indirect heating of the<br />socket of this type may prevent the zeolite, from attaining the sufficiently high<br />temperature. Then, the structure of the ion source is newly developed to increase<br />the higher beam current by direct heatly heating the zeolite.<br />The new socket structure is shown in Fig. 3.1(b). This socket allows heating<br />directly the zeolite, by setting the filament inside the zeolite. Using this socket of<br />direct heating, ten times higher beam current compared with the old is extracted<br />from the present ion source.<br /><br /><b>2.2. Simultaneous measurements</b><br /> Using the direct heating socket, simultaneous measurements of electron density<br />(detected beam current of HIBP) and potential fluctuations are successfully per-<br />formed in low density (<i>n<small>e</small></i> ~ 5 x 10<sup>18</sup> m<sup>-3</sup>) high temperature (<i>T<small>e</small></i> = 1.0 ~ 1.5 keV)<br />plasma in CHS. The major and minor radii of the CHS plasma <i>R</i>=1 m and minor <br />radius <i>α</i> = 0.2 m.<br /> The fluctuation distribution measurements were done with 2 mm resolution over<br />the whole radius form center to near the last closed field surface (LCFS) [7], as <br />is shown in Fig. 3.9. It is the first achievement as the simultaneous fluctuation<br />measurements for all radial positions in high temperature torus plasma, because<br />the previous works did not measure them simultaneously in center region because<br />of insufficient beam energy and/or detected beam current. The fluctuation spectra<br />measured in CHS shows broad bands characteristics to indicate turbulence nature.<br />It is found that fluctuation amplitudes become larger toward the plasma edge as<br />is similar to the observations of ISX-B and TEXT(-U).<br /><br /><b>3. Reconstruction local electron density fluctuation<br />3.1. Reconstruction local electron density fluctuation profiIe<br /></b> The average of the detected beam fluctuation amplitude is written by,<br /><br /> <i>η<sup>2</sup></i>(<i>p</i><sub>*</sub>)= <i>ξ</i> <sup>2</sup>(<i>p</i><sub>*</sub>)<br /> -2<font size="5">Σ </font><font size="5"><i>∫</i> </font> <sub><i>li</i></sub> <<i>ξ</i> (<i>p<sub>*</i></sub>)<i>ξ</i> (<i>p<sub>i</sub></i>)>><small>E</small><i>S<small>i</small></i>(<i>p<sub>i</i></sub>) w<small>i</small>(<i>p<sub>i</i></sub>)d<i>p<sub>i</sub></i> (1)<br /> <sup><i>i</i>=1,2</sup><br /> + <font size="5">Σ</font> <font size="5">Σ</font> <font size="5"> <i>∫</i> </font> <sub><i>li</i></sub> <font size="5"><i>∫</i> </font><sub><i>lj</i></sub> <<i>ξ</i> (<i>p<sub>i</i></sub>)ξ (<i>p<sub>j</i></sub>)><small>E</small>S<small>i</small>(<i>p<sub>i</i></sub>) S<small>j</small>(<i>p<sub>j</i></sub>) w<small>i</small>(<i>p<sub>i</i></sub>) w<small>j</small>(<i>p<sub>i</i></sub>)d<i>p<small>i</i></small>d<i>p<small>j</small></i><br /> <small><i>i</i>=1,2 <i> j</i>=1,2</small><br />where, <i>η</i>=δ<i>I<small>d</small>/I<small>d</small></i>, <i>ξ</i> = <i>δn<small>e</small>/n<small>e</small>, S </i>and <i>w<small>i</small></i> are detected beam current fluctuation<br />rate and local electron density fluctuation rate point, ionization rate and integral<br />weight, respectively.Where <i>I<small>d</small>, n<small>e</small></i> represents detected beam current, local elec-<br />tron density, respectively, andδindicates fluctuation. The ionization rate can be<br />estimated as a function of electron density and temperature from Lotz's empirical<br />formula [8]. The electron density and temperature can be given with Thomson<br />scattering measurement. The bracket with subscript E, < ><small>E</small>, represents the en-<br />semble average,and the terms including the bracket are the correlations between<br /> density fluctuations at two spatial points. If the correlation terms of fluctuations<br />are evaluated, local electron density fluctuation is estimated by solving the above<br />integral equation. <br /> On the right-hand-side of Eq. (1), the second and third terms are effects around<br />ionization point and along the beam trajectories, respectively. They are under-<br />stood if assuming a limiting case that the fluctuation should have the infinitesimal<br />short correlation length and the ensemble averaged terms should be expressed as<br />theδ-function. In addition to this, several simplification makes the Eq. (1) take<br />the followlng form, as<br /><br /> <i>η</i><sup>2</sup> = (1-〓<small>c</small>+〓<small>c</small>)<i>ξ</i><sup>2</sup> (2)<br /><br />where the first , second and third terms represent the local density fluctuation, the<br />screening effect and the accumulating effect. From this simplification, the path<br />integral effect is found to be composed of the screening and accumulating effects.<br />The degree of the path integral effect, whose coefficient ζ, is estimated from the<br />sum of the second and third terms in Eq. (2).<br /> Fig. 4.2(a) shows the dependence of the coefficient on electron density and<br />temperature, using cesium ion beam. The coefficient is calculated for our HIBP<br />geometry and CHS plasma assuming that the correlation length is 1 cm and the<br />used beam is cesium ion. Here, the primary and secondary beam trajectory lengths<br />are 0.2 m, corresponding to the CHS plasma radius. In this calculation, the<br />coefficient is 0.1 when <i>T<small>e</small></i> ~ 1 keV is 0.1 in <i>n<small>e</small></i> ~ 2.8 × 10<sup>18</sup> m<sup>-3</sup>. In this case, the<br />path integral effect can be almost negligible. On the other hand, the coefficient<br />is 1 when T<small>e</small> ~ 1 keV and <i>n<small>e</small></i> ~ 1.1 x 10<sup>19</sup> m<sup>-3</sup>, which represent detected beam<br />fluctuation amplitude is twice as local density fluctuation, and the path integral<br />effect is dominant.<br /> The ensemble averaged terms can be evaluated if the fluctuations correlation be-<br />tween two spatial points is assumed as the Gauss function, ƒ( Δ<i>x</i>) =exp(-0.5(Δ/lc)<sup>2</sup>),<br />where <i>lc</i> is a correlation length. The HIBP of CHS is equipped with three chan-<br />nels, so that the correlation length <i>lc</i> can be evaluated; the distance between two<br /> of the channels, Δ<i>x</i> ranges from 3 to 10 mm By substituting the estimated correla-<br />tion function into Eq. (2), the local electron density fluctuation amplitude profile<br />can be reconstructed. Fig. 5.6(b) shows an example of the reconstruction for the<br />case that the electron density and temperature are ~ 10<sup>19</sup> m<sup>-3</sup> and ~ 1 keV, re-<br />spectively. Here, the integral equation is solved after several times iteration. The<br />detected beam current and the local electron density fluctuation amplitudes are<br />within the range of error in the outer region (<i>p</i> > 0.6). However, in the inner<br />region (<i>p</i> < 0.6), the fluctuation amplitude of detected beam current is a half of<br />the local fluctuation amplitude.<br /><br /><b>3.2. Reconstruction of local electron density fluctuation spectrum</b><br /> The reconstruction method of local density fluctuation is extended to the esti-<br />mation of density fluctuation spectra. It is apparent that the power spectra can be<br />evaluated simply by appling the above method to the fluctuation power at each<br />frequency. However, the integral equation for low frequency (< 50 kHz) cannot be<br />often solved with iteration method. This is caused by the fact that the correlation<br />length appears to become longer than the actual value. <br /> This is considered to result from the path integral effect on the correlation length. <br />The fluctuations of local three channels are strongly affected by the fluctuation<br />in the outer plasma regions, and the fluctuations at local three channels become<br />to show quite similar behavior. A technique is derived to correct this longer<br />correlation length. Thanks to the technique, the corrected correlation length is<br />evaluated and the spectra of local density fluctuation are successfully obtained. <br /> Fig. 6.3(b) shows one example of the reconstructed spectrum of local electron<br />density fluctuation, whose position is <i>r/a</i> - 0.26 in the same plasma in Fig. 5.6. <br />The result shows that the path integral effect is larger in low frequency than that<br />in high frequency. <br /><br /><b>3.3. Consideration of the Bolt2;mann Relationship</b><br /> As a result of the estimation of local density, the detected beam fluctuation<br />can be roughly regarded as the local density fluctuation in low density regimes of<br />n<small>e</small> ~ 5 × 10<sup>18</sup> m<sup>-3</sup>. Consequently, the detected beam fluctuation shown in Fig. <br />3.9 reflects local density fluctuation. A rough comparison between the density<br />fluctuation and potential fluctuation (normalized by electron temperature) allows<br />examining the validity of the Boltzmann relationship. Fig. 7.1(a) shows the nor-<br />malized density fluctuation as a function of normalized potential fluctuations. In<br />Fig. 7.1(a), the different marks correspond to the different ranges of radial posi-<br />tion of the plasma; red and green and blue plots are data point in 0 < <i>r/a</i> < 0.3,<br /> 0.3 <<i> r/a</i> < 0.6 and<i> r/a ></i> 0.6, respectively. The lines are fit lines using the least<br />squared method. The results show that the Boltzma- relationship should be<br /> valid, although tendency is found that the normalized density fluctuation should<br />be larger than the normalized potential fluctuation. <br /><br /><b>4. Summary</b><br />The simultaneous measurements of electron density and potential fluctuations<br />are successfully made with heavy ion beam probe after the development of a new<br />ion source. The measurement is achieved in a wide range of radial region with<br />spatial resolution of 2 mm. A method is proposed to evaluate the path integral<br />effect that is a long-standing problem for density fluctuation measurement with<br /> the HIBPs. Applying this method on the CHS fluctuation measurements, the local<br />density fluctuation and its power spectrum are successfully evaluated. | |||||
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