@article{7472,
  author = {A. E. Shumack and D.C. Schram and J. Biesheuvel and W. J. Goedheer and G. J. van Rooij},
  title = {Diagnosing ions and neutrals via n=2 excited hydrogen atoms in plasmas with high electron density and low electron temperature},
  abstract = {Ion and neutral parameters are determined in the high electron density, magnetized, hydrogen plasma beam of an ITER divertor relevant plasma via measurements of the n = 2 excited neutrals. Ion rotation velocity (up to 7 km/s) and temperature (2-3 eV similar to T-e) are obtained from analysis of Ha spectra measured close to the plasma source. The methodology for neutral density determination is explained whereby measurements in the linear plasma beam of Pilot-PSI are compared to modeling. Ground-state atomic densities are obtained via the production rate of n = 2 and the optical thickness of the Lyman-alpha transition (escape factor similar to 0.6) and yield an ionization degree > 85% and dissociation degree in the residual gas of similar to 4%. A 30% proportion of molecules with a rovibrational excitation of more than 2 eV is deduced from the production rate of n = 2 atoms. This proportion increases by more than a factor of 4 for a doubling of the electron density in the transition to ITER divertor relevant electron densities, probably because of a large increase in the production and confinement of ground-state neutrals. Measurements are made using laser-induced fluorescence (LIF) and absorption, the suitability of which are evaluated as diagnostics for this plasma regime. Absorption is found to have a much better sensitivity than LIF, mainly owing to competition with background emission.
},
  year = {2011},
  journal = {Physical Review E},
  volume = {83},
  number = {3},
  pages = {036402},
  month = {Mar},
  isbn = {1539-3755},
  url = {https://pure.tue.nl/ws/files/3129688/Metis251310.pdf},
  doi = {10.1103/PhysRevE.83.036402},
  note = {ISI Document Delivery No.: 728ZJTimes Cited: 0Cited Reference Count: 24Part 1},
  language = {English},
}