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Appearance of a H α Minimumat the Onset of Net Recombination in Hydrogen Plasmas
Author(s) -
Wenzel U.,
Schröder D.,
Fussmann G.
Publication year - 2007
Publication title -
contributions to plasma physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.531
H-Index - 47
eISSN - 1521-3986
pISSN - 0863-1042
DOI - 10.1002/ctpp.200710059
Subject(s) - divertor , plasma , atomic physics , tokamak , asdex upgrade , hydrogen , electron , electron temperature , ionization , electron density , recombination , physics , materials science , ion , nuclear physics , chemistry , biochemistry , quantum mechanics , gene
Hydrogen plasmas out of ionization equilibrium are either ionizing or recombining depending on the electron temperature T e . Within the transition region between these two opposite states a minimum of the H α emission is often experimentally observed. Simple cases were previously analyzed which could be interpreted assuming only a temperature variation, i.e the electron density was constant in the transition region. Here we discuss two examples in which both the density and the temperature vary at the transition. In the linear plasma generator PSI‐II a hydrogen plasma is cooled down by puffing additional gas. We find a minimum at T min ≈ 1.1 eV. A second example is the effect of an ELM(edge localized mode) pulse propagating through a recombining divertor plasma in the tokamak ASDEX Upgrade. The H α response shows a double peak which can be interpreted as a local minimum assuming a simultaneous rise of density and temperature during an ELM. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)