{"created":"2023-06-20T13:20:29.892596+00:00","id":523,"links":{},"metadata":{"_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":["2:427:12"]},"author_link":["0","0","0"],"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_12":{"attribute_name":"要旨","attribute_value_mlt":[{"subitem_description":"<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>&xi;</i> <sup>2</sup>(<i>p</i><sub>*</sub>)<br />　　　　　　　－2<font size=\"5\">&Sigma;　</font><font size=\"5\"><i>&int;</i> </font> <sub><i>li</i></sub> ＜<i>&xi;</i> (<i>p<sub>*</i></sub>)<i>&xi;</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\">&Sigma;</font>　<font size=\"5\">&Sigma;</font> <font size=\"5\">　<i>&int;</i> </font>  <sub><i>li</i></sub> <font size=\"5\"><i>&int;</i> </font><sub><i>lj</i></sub> ＜<i>&xi;</i> (<i>p<sub>i</i></sub>)&xi; (<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>&xi;</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>&xi;</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, &fnof;( &Delta;<i>x</i>) =exp(－0.5(&Delta;/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, &Delta;<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.","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","filename":"甲927_要旨.pdf","filesize":[{"value":"376.6 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/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","filename":"甲927_本文.pdf","filesize":[{"value":"17.6 MB"}],"format":"application/pdf","licensetype":"license_11","mimetype":"application/pdf","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"],"pubdate":{"attribute_name":"公開日","attribute_value":"2010-02-22"},"publish_date":"2010-02-22","publish_status":"0","recid":"523","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_creator_id":"1","weko_shared_id":1},"updated":"2023-06-20T16:01:35.357965+00:00"}