{"created":"2023-06-20T13:20:26.720660+00:00","id":464,"links":{},"metadata":{"_buckets":{"deposit":"a8fe494b-24f7-4ae9-892d-9e6edfbc6292"},"_deposit":{"created_by":1,"id":"464","owners":[1],"pid":{"revision_id":0,"type":"depid","value":"464"},"status":"published"},"_oai":{"id":"oai:ir.soken.ac.jp:00000464","sets":["2:427:12"]},"author_link":["8574","8575","8573"],"item_1_creator_2":{"attribute_name":"著者名","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"西村, 伸"}],"nameIdentifiers":[{}]}]},"item_1_creator_3":{"attribute_name":"フリガナ","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"ニシムラ, シン"}],"nameIdentifiers":[{}]}]},"item_1_date_granted_11":{"attribute_name":"学位授与年月日","attribute_value_mlt":[{"subitem_dategranted":"1998-03-24"}]},"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":"The radial electric fields in magnetically confined toroidal plasmas are
considered to play an important role in plasma confinements. For
example, they change the neoclassical ripple loss in the low collisionality
regime in helical devices, and they are considered to be the important
parameter to determine the L/H transition and the anomalous transport
characteristics of L/H-modes in tokamak plasmas. Therefore many efforts
to study the radial electric fields experimentally have been performed.
One method for this study is the spectroscopic measurements of the
rotations of impurity ions. However, toroidal effects on the plasma
rotations have never been studied experimentally. The coupling of
toroidal and poloidal rotations caused by the toroidal effect to satisfy the
poloidal flow conservation condition is the most important basis of
neoclassical transport theory and is also important for understanding the
supersonic (with Mp～1 where Mp is the poloidal Mach number) plasma
flows in tokamak H-mode plasmas. Therefore many related theoretical
studies have been made.
To study this problem experimentally is to compare poloidal flux on
the inside and outside of the magnetic surfaces. In the poloidal rotation
measurements in many tokamaks, the poloidal rotation velocities only in
the outside were measured, since it is difficult to install the observation
chords viewing vertically the inside of the torus. Another severe
difficulty is the calibration of mechanical wavelength offset～0.5 Å) of
spectrometers with the accuracy for the plasma rotation measurements.
The study of the inside/outside asymmetry of poloidal rotation velocity requires
the accuracy of absolute wavelength of ～0.01 Å. To measure
the absolute value of the rotation velocity canceling this offset, it needs
the observation along opposite viewing directions. In past plasma rotation
measurements using the observation from one direction only, some
assumptions or approximations about the plasma rotation velocity profiles
were used. For example, the average of the poloidal rotation velocities in
the inside and the outside was used as poloidal rotation 'velocity' in
Heliotron E.
In the present work, I have carried out the measurement of the profiles
of the poloidal rotation velocity, the temperature and the density of
impurity ions using bidirectional charge exchange spectroscopy (CXS) in
the Compact Helical System (CHS). For the purpose mentioned above, this
measurement system uses two fiber arrays to view vertically the beam
line from up and down sides simultaneously at one vertically elongated
section. In Heliotron/Torsatron devices like CHS, the strong parallel
viscosity reduces the parallel ion flow velocity which is necessary for
incompressible flow conservation when the perpendicular ion flow exists
in low aspect ratio tori. This damping is strong in peripheral region
where the helical ripple becomes large. However, the poloidal rotation of
impurity tons mainly driven by radial electric field determined by the
ambipolar condition of the electron and ion fluxes is also large in this
peripheral region. Therefore the compensation of the asymmetry of
inside and outside perpendicular flows by the parallel flows becomes
difficult in this region. When the electrostatic potential is the surface
quantity and the poloial rotation of ions is mainly the E×B drift, the
flow, especially of the impurity ions having low pressure, should be
compressible. Otherwise the electrostatic potential is not the surface
quantity or the poloidal rotation of impurity ions is not E × B drift.
Investigating this problem is easier in low aspect ratio devices. Therefore
this measurement in CHS with the lowest aspect ratio R0/a=5 in helical
devices will give the new information about the plasma rotations.
The preliminary measurements of plasma rotations using this system
clarified some technical problems in multi-channel CXS. The most
important problem was the apparent wavelength shift caused by
the spectral fine structure of hydrogen-like ions used in CXS. This structure
is the red-side/blue-side asymmetric splitting of the lines due to a
relativistic effect and thus cause the red-side/blue-side asymmetry of the
Doppler broadened spectral profile. Because of this asymmetry, the
wavelength given by single Gaussian least square fitting shows the
apparent shifts which depends on Doppler widths. The observed apparent
shifts of CVI lines, not due to plasma rotation, in the plasma peripheral
region (Ti～100eV) and in the after-glow recombining phase (Ti～
30eV) are always red-shifts regardless the direction of plasma rotation.
The magnitude corresponds to the velocity error of a few km/s. This
direction and magnitude are consistent with the calculation using the
collisional l-mixing model. This value is not negligible in CHS plasmas,
and thus should be corrected.
The density profile of the fully ionized impurity ions can be measured
using the intensity of the charge exchange spectral lines. For this purpose,
the initial beam density profile without attenuation was also measured in
the torus using H α from the beam. The measured density profile was a
broad and inside shifted profile compared with the calculated one. This
result means the possibility to measure the parameters on inside of the
torus with CXS. However, the calculation of the beam attenuation
required that the average electron densities should be less than 2 ×
1013 cm-3 to avoid the ambiguity of beam attenuation calculation and the
degradation of signal level on the inside.
The measurements of the asymmetry of the poloidal flux of fully
ionized carbon tons on the inside and outside of the torus were carried
out for the magnetic surface configurations with different magnetic axis
positions. In inward shifted configurations, the gradients of surface
function (dψ/dR) on the inside and outside of the section are almost
symmetric. It becomes asymmetric in outward shifted configurations
and the strength of the radial electric field will become asymmetric in
these configuration.
The asymmetry of the Doppler shifts of the CVI line(Δn=8-7, λ
=5290 Å) on the inside and outside of the torus was successfully
measured. In outward shifted configurations, the electrostatic potential
calculated from this velocity using the momentum balance equation is the
surface quantity. The measured density of impurity ions has a hollow
profile and is higher on the inside of the magnetic surfaces compared
with that on the outside. This inside/outside asymmetry of the density profile
can be explained by the poloidal flow conservation on both sides
under the damping of toroidal rotation.
In the inward shifted configurations, the density profile is a flat or
peaking profile and the inside/outside asymmetry is not clear. The
quantitative comparison or the electrostatic potential and the poloidal flow
on both sides is difficult in inward shifted configurations because of
the intense back and radiation at the inside of the magnetic axis. It
causes the degradation of signal/noise ratio of spectrum after subtracting
background spectrum. However, this change in the density asymmetry is
consistent with the past measurement of the toroidal rotation damping and
suggests the poloidal rotation accompanying the inside/outside asymmetric
toroidal flow. Therefore the measurement of inside/outside asymmetry of
the toroidal rotation velocity is an interesting future theme.","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322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":"1997"}]},"item_creator":{"attribute_name":"著者","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"NISHIMURA, Shin","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322_要旨.pdf","filesize":[{"value":"384.3 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/464/files/甲322_要旨.pdf"},"version_id":"acb09859-3027-45c6-92c2-b9356e39f01b"},{"accessrole":"open_date","date":[{"dateType":"Available","dateValue":"2016-02-17"}],"displaytype":"simple","filename":"甲322_本文.pdf","filesize":[{"value":"8.2 MB"}],"format":"application/pdf","licensetype":"license_11","mimetype":"application/pdf","url":{"label":"本文","url":"https://ir.soken.ac.jp/record/464/files/甲322_本文.pdf"},"version_id":"8a953942-a466-4e4a-9cd3-1f7d3814b380"}]},"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":"Observation of the Non-uniform Poloidal Flow of Impurity Ion on Magnetic Surfaces using Bidirectional Charge Exchange Spectroscopy in CHS","item_titles":{"attribute_name":"タイトル","attribute_value_mlt":[{"subitem_title":"Observation of the Non-uniform Poloidal Flow of Impurity Ion on Magnetic Surfaces using Bidirectional Charge Exchange Spectroscopy in CHS"},{"subitem_title":"Observation of the Non-uniform Poloidal Flow of Impurity Ion on Magnetic Surfaces using Bidirectional Charge Exchange Spectroscopy in CHS","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":"464","relation_version_is_last":true,"title":["Observation of the Non-uniform Poloidal Flow of Impurity Ion on Magnetic Surfaces using Bidirectional Charge Exchange Spectroscopy in CHS"],"weko_creator_id":"1","weko_shared_id":1},"updated":"2023-06-20T14:53:53.573808+00:00"}