{"created":"2023-06-20T13:20:28.116570+00:00","id":488,"links":{},"metadata":{"_buckets":{"deposit":"4e6c4b54-f8bd-4c7c-b002-9e7285ba089e"},"_deposit":{"created_by":1,"id":"488","owners":[1],"pid":{"revision_id":0,"type":"depid","value":"488"},"status":"published"},"_oai":{"id":"oai:ir.soken.ac.jp:00000488","sets":["2:427:12"]},"author_link":["8635","8633","8634"],"item_1_creator_2":{"attribute_name":"著者名","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"梁, 雲峰"}],"nameIdentifiers":[{}]}]},"item_1_creator_3":{"attribute_name":"フリガナ","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"リャン, ユンフェン"}],"nameIdentifiers":[{}]}]},"item_1_date_granted_11":{"attribute_name":"学位授与年月日","attribute_value_mlt":[{"subitem_dategranted":"2000-09-29"}]},"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（学術）"}]},"item_1_description_12":{"attribute_name":"要旨","attribute_value_mlt":[{"subitem_description":"　　A new technique of soft x-ray imaging with photon counting CCD camera has been applied to measure a shape of magnetic flux surface and two-dimensional electron temperature in magnetically confined high temperature plasma. Various diagnostics for x-ray imaging of plasma have been used especially in tokamaks. Pin diode array has been widely used to reconstruct plasma image with tomography technique for MHD study in most tokamaks. Direct measurement of x-ray image from tangential view by using the micro-channel plate(MCP) detector coupled to video camera has been done in tokamaks in order to measure internal shape of the magnetic flux surfaces and to estimate a current density profile. Two-dimensional hard x-ray image was also measured with a hard x-ray camera to study the distribution of suprathermal electrons during lower hybrid heating in PBX-M tokamak. However, there is no energy resolution in these diagnostics. The energy range measured can be selected only by arranging the Be or AI filter in front of the detector. As a conventional measurement of x-ray with good energy resolution, the pulse height analysis (PHA) has been well developed to measure electron temperature and the concentration of high-Z impurity from the x-ray energy spectra. However, PHA system has a relatively small number of spatial channel and accordingly poor spatial resolution.<br />　　The soft x-ray CCD camera has been widely used in astronomy as an instrument of x-ray imaging because of its good energy and spatial resolution. Recently, the photon counting x-ray CCD camera was applied to inertial confinement fusion (ICF) plasma. However, there is no application of this CCD camera to magnetically confined fusion plasma, because the frame rate has been considered to be too slow to measure x-ray from the short pulse discharge. Recent experiments in the Large Helical Device (LHD) demonstrate the discharge can be sustained for more than a minute, which encourages us to apply the soft x-ray CCD to the measurement of two-dimensional profile of electron velocity distribution as well as a shape of the magnetic flux surface. <br />　　In general, there are two different operation modes in the soft x-ray CCD camera, imaging mode and photon counting mode, depending on the magnitude of photon flux. When the flux of soft x-ray is low enough to the level of one photon per pixel per frame (photon counting mode), an amount of charge in each pixel of CCD created by the individual x-ray photon is proportional to the energy of x-ray. Therefore, the x-ray energy spectra can be obtained by counting the number of photons at given intensity (photon counting mode). When the soft x-ray flux is much higher than the level of photon counting mode, the intensity of each pixel is proportional to the total emission of x-ray (imaging mode). Since the total emission of x-ray is considered to be constant on magnetic flux surface, the shape of magnetic flux can be reconstructed from the soft x-ray image. The magnetic axis moves outward due to the vertical field created by the asymmetric toroidal current (Pfirsch-Schluter current) produced by the plasma pressure gradient in a finite-beta toroidal plasma, which is well known as a Shafranov shift. <br />　　The measurement of Shafranov shift due to the Pfirsch-Schluter currents is important to study equilibrium beta-limit on plasma confinement. The tangential soft x-ray image has been measured by using the soft x-ray CCD camera in the imaging mode with good spatial resolution in the Compact Helical System (CHS). The Shafranov shift of the plasma magnetic axis is derived from the best fit of the intensity contour of soft x-ray emission calculated by using equilibrium code with various pressure profiles to that measured with soft x-ray CCD camera. It is found that the measured Shafranov shifts are larger than those expected from diamagnetic measurements at low-density plasma with tangential NBI, because of a significant fraction of beam pressure parallel to magnetic field. The Shafranov shift (ΔCCD) measured with CCD camera corresponds to the total pressure p including thermal pressure, and parallel (pb//) and perpendicular (pb⊥) beam pressures. The Shafranov shift can be derived from the stored energy measured with diamagnetic loop. However, isotropic pressure profile (i.e. pb// = pb⊥) should be assumed to calculate the Shafranov shift from the stored energy, because the diamagnetic loop detects only the perpendicular pressure. Therefore, anisotropy of plasma pressure can be evaluated from the difference in Shafranov shift measured with CCD camera and that estimated from diamagnetic loop. The pressure anisotropy is found to increase as the electron density is decreased from 4×1019m-3 to 0.5×1019m-3 in the NBI heated plasma. The large anisotropy is consistent with the fact that energy confinement time (〜1ms) is much shorter than the slowing down time (〜0.1s) of neutral beam at low electron density plasma in CHS. Therefore, the pressure anisotropy disappears in ECH plasma even at the low electron density (ne 〜0.5×1019m-3) or high density NBI plasma (ne 〜4.0×1019m-3). On the other hand, there is no anisotropy observed in LHD plasma, where the energy confinement time is comparable to the beam slowing down time of neutral beam.<br />　　When the soft x-ray CCD camera is operated with photon counting mode, the full image area of CCD detector is divided to 512 zones (32x16), which gives two-dimensional spatial channels. One energy spectrum corresponding to one spatial channel is derived by counting the number of photons in one zone (32x32 pixels). The energy calibration of soft x-ray CCD detector has been done with Fe K-alpha and K-beta lines from iron target soft x-ray source. The energy resolution of each pixel is calibrated to be 16eV/ADC count, and the instrumental width, full width of half maximum (FWHM), is 0.21keV at 6.4keV. It is very important to optimize the level of x-ray flux good for photon counting mode, since the number of pixels in one zone (32x32 pixels) is only 1024 and the number of photons acceptable is limited. The number of x-ray photon should be adjusted just below the critical photon number for &quot;pile-up&quot;. The ratio of photon number to pixel number (η≡Nphoton/Npixel) should be below 1/ √N pixel to avoid &quot;pile-up&quot;. Since the one zone consists to 1024 pixels in our measurements, the critical η for the pile-up is 0.03. In our experiment, the energy spectra measured with CCD camera agree with those estimated from electron temperature and density profiles measured with YAG Thomson scattering, when the ratio η is below the critical value (0.03). Two-dimensional energy spectra of x-ray emission have been measured by using x-ray CCD camera with photon counting mode in CHS. The energy spectrum measured with CCD camera agrees with that estimated from electron temperature and density profiles measured with YAG Thomson scattering in the energy region of 2〜8keV. The two-dimensional electron temperature profiles (32x16 channels) are derived from the slopes of x-ray continuum with 512 spatial channels (32x16).<br />　　The two-dimensional intensity profiles of titanium (Ti), chromium (Cr) and iron (Fe) K-alpha lines have been measured with x-ray CCD camera as well as the two-dimensional electron temperature when the electron temperature is high enough (〜3keV) with additional ECH to NBI plasma. The source of Ti impurity is Ti gettering, while the source of Cr and Fe impurities is stainless steel of vacuum vessel. The radial profiles of impurity line intensity can be reconstructed from the best fit of the contour of impurity line intensity calculated using equilibrium code to that measured with CCD camera. The reconstructed radial profiles of Ti, Cr and Fe K-alpha line intensity are localized at ρ<0.4, where the electron temperature exceeds 1.0keV as predicted by the temperature dependence of emission cross section of Ti, Cr and Fe, The concentrations of Ti, Cr and Fe measured with CCD camera are 0.2%, 0.07% and 0.06%, respectively. The radial intensity profiles of Ti K-alpha and Fe K-alpha lines agree with those calculated with the assumption of constant impurity concentration(nFe/ne=0.06%, nCr/ne=0.07%; nTi/ne=0.2%).","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493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":"数物科学研究科"}]},"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":"2000"}]},"item_creator":{"attribute_name":"著者","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"LIANG, Yunfeng","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493_要旨.pdf","filesize":[{"value":"591.2 kB"}],"format":"application/pdf","licensetype":"license_11","mimetype":"application/pdf","url":{"label":"要旨・審査要旨 / Abstract, Screening Result","url":"https://ir.soken.ac.jp/record/488/files/甲493_要旨.pdf"},"version_id":"727740f2-f5e4-4280-9319-3991098529bf"},{"accessrole":"open_date","date":[{"dateType":"Available","dateValue":"2016-02-17"}],"displaytype":"simple","filename":"甲493_本文.pdf","filesize":[{"value":"3.8 MB"}],"format":"application/pdf","licensetype":"license_11","mimetype":"application/pdf","url":{"label":"本文","url":"https://ir.soken.ac.jp/record/488/files/甲493_本文.pdf"},"version_id":"61aeaf33-db55-4925-ac5a-782792366741"}]},"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":"Soft x-ray Imaging with CCD Camera for Magnetically Confined High Temperature Plasma","item_titles":{"attribute_name":"タイトル","attribute_value_mlt":[{"subitem_title":"Soft x-ray Imaging with CCD Camera for Magnetically Confined High Temperature Plasma"},{"subitem_title":"Soft x-ray Imaging with CCD Camera for Magnetically Confined High Temperature Plasma","subitem_title_language":"en"}]},"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":"488","relation_version_is_last":true,"title":["Soft x-ray Imaging with CCD Camera for Magnetically Confined High Temperature Plasma"],"weko_creator_id":"1","weko_shared_id":1},"updated":"2023-06-20T14:53:24.580477+00:00"}