Diagnosing ions and neutrals via n=2 excited hydrogen atoms in plasmas with high electron density and low electron temperature
- FOM-Institute for Plasma Physics Rijnhuizen, Association EURATOM-FOM, Trilateral Euregio Cluster, Nieuwegein (Netherlands)
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{approx}T{sub e}) are obtained from analysis of H{alpha} 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 {approx}0.6) and yield an ionization degree >85% and dissociation degree in the residual gas of {approx}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.
- OSTI ID:
- 21560075
- Journal Information:
- Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics (Print), Vol. 83, Issue 3; Other Information: DOI: 10.1103/PhysRevE.83.036402; (c) 2011 American Institute of Physics; ISSN 1539-3755
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ATOMS
CONFINEMENT
DISSOCIATION
ELECTRON DENSITY
ELECTRON TEMPERATURE
EV RANGE
EXCITATION
FLUORESCENCE
HYDROGEN
IONIZATION
ITER TOKAMAK
LASERS
MOLECULES
NEUTRAL PARTICLES
PLASMA
SENSITIVITY
SIMULATION
THICKNESS
CLOSED PLASMA DEVICES
DIMENSIONS
ELEMENTS
EMISSION
ENERGY RANGE
ENERGY-LEVEL TRANSITIONS
LUMINESCENCE
NONMETALS
PHOTON EMISSION
THERMONUCLEAR DEVICES
THERMONUCLEAR REACTORS
TOKAMAK DEVICES
TOKAMAK TYPE REACTORS