Validation of 2D and measurements made with Helium imaging spectroscopy in the volume of the TCV divertor

Nuclear Fushion

article

B.L. Linehan¹  A. Perek²  B.P. Duval²  F. Bagnato²  P. Blanchard²  C. Colandrea²  H. De Oliveira²  O. Février²  E. Flom⁴  S. Gorno²  M. Goto⁵  E. Marmar¹  L. Martinelli²  A. Mathews¹  J. Muñoz-Burgos⁶  D. Mykytchuk²  N. Offeddu²  D.S. Oliveira²  H. Reimerdes²  D. Reiter⁷  O. Schmitz⁴  J.L. Terry¹  C. Theiler²  C.K. Tsui⁸  B. Vincent²  T. Wijkamp³  C. Wüthrich²  W. Zholobenko⁹ 

[1] Massachusetts Institute of Technology;Ecole Polytechnique Fédérale de Lausanne ,(EPFL), Swiss Plasma Center;DIFFER-Dutch Institute for Fundamental Energy Research;University of Wisconsin Madison;National Institute for Fusion Science;Astro Fusion Spectre LLC;Institut für Laser- und Plasmaphysik, Heinrich-Heine-Universität;Center for Energy Research ,(CER), University of California-San Diego;Max-Planck-Institut für Plasmaphysik

关键词: scrape-off layer;    multi-spectral imaging;    TCV;    helium collisional radiative modeling;    plasma boundary physics;    tokamak divertor;    tokamak diagnostics;   

DOI  :  10.1088/1741-4326/acb5b0

来源: Institute of Physics Publishing Ltd.

【 摘 要 】

Multi-spectral imaging of helium atomic emission (HeMSI) has been used to create 2D poloidal maps of {{T}}_{mathrm{e}}and {{n}}_{mathrm{e}}in TCV's divertor. To achieve these measurements, TCV's MANTIS multispectral cameras (Pereket al2019Rev. Sci. Instrum.90123514) simultaneously imaged four He I lines (two singlet and two triplet) and a He II line (468 nm) from passively present He and He⁺. The images, which were absolutely calibrated and covered the whole divertor region, were inverted through the assumption of toroidal symmetry to create emissivity profiles and, consequently, line-ratio profiles. A collisional-radiative model (CRM) was applied to the line-ratio profiles to produce 2D poloidal maps of {{T}}_{mathrm{e}}and {{n}}_{mathrm{e}} . The collisional-radiative modeling was accomplished with the Goto helium CRM code (Zholobenkoet al2018Nucl. Fusion58126006, Zholobenkoet al2018Technical Report , Goto 2003J. Quant. Spectrosc. Radiat. Transfer76331–44) which accounts for electron-impact excitation (EIE) and deexcitation, and electron–ion recombination (EIR) with {extrm{He}}^{+} . The HeMSI {{T}}_{mathrm {e}}and {{n}}_{mathrm{e}}measurements were compared with co-local Thomson scattering measurements. The two sets of measurements exhibited good agreement for ionizing plasmas: ({5 ,{extrm{eV}} leqslant {{T}}_{mathrm{e}} leqslant 60 ,{extrm{eV}}} , and {2 imes 10^{18}, {extrm{m}}^{-3} leqslant{{n}}_{mathrm{e}} leqslant 3 imes 10^{19},{extrm{m}}^{-3}})in the case of majority helium plasmas, and ({10 ,{extrm{eV}} leqslant {{T}}_{mathrm{e}} leqslant 40 ,{extrm{eV}}},{2 imes 10^{18},{extrm{m}}^{-3} leqslant{{n}}_{mathrm{e}} leqslant 3 imes 10^{19} ,{extrm{m}}^{-3}})in the case of majority deuterium plasmas. However, there were instances where HeMSI measurements diverged from Thomson scattering. When {{T}}_{mathrm{e}} leqslant 10 ,{extrm{eV}}in majority deuterium plasmas, HeMSI deduced inaccurately high values of {{T}}_{mathrm{e}}{} . This disagreement cannot be rectified within the CRM's EIE and EIR framework. Second, on sporadic occasions within the private flux region, HeMSI produced erroneously high measurements of {{n}}_{mathrm{e}} . Multi-spectral imaging of Helium emission has been demonstrated to produce accurate 2D poloidal maps of {{T}}_{mathrm{e}}and {{n}}_{mathrm{e}}within the divertor of a tokamak for plasma conditions relevant to contemporary divertor studies.

【 授权许可】

Unknown