Electron density dependence of intensity ratio for FeXXII extreme ultraviolet emission lines arising from different ground levels in electron beam ion trap and large helical device

Journal Article · Fri Apr 01 00:00:00 EDT 2011 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.3549707· OSTI ID:21538212

Sakaue, H A; Morita, S; Kato, D; Murakami, I ^[1]; Yamamoto, N ^[2]; Nakamura, N; Kikuchi, H; Ohtani, S ^[3]; Chen, C ^[4]; Tanuma, H ^[5]; Watanabe, T ^[6]; Tawara, H ^[7]

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1. National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan)
2. Institute of Laser Engineering, Osaka University, Suita, Osaka 565-0871 (Japan)
3. Institute for Laser Science, The University of Electro-Communications, Chofu, Tokyo 182-8585 (Japan)
4. Institute of Modern Physics, Fudan University, Shanghai 200433 (China)
5. Tokyo Metropolitan University, Hachioji, Tokyo 192-0397 (Japan)
6. National Astronomical Observatory of Japan, Mitaka, Tokyo, 181-8588 (Japan)
7. Max Planck Institute for Nuclear Physics, Saupfercheckweg 1, 69117 Heidelberg (Germany)

Extreme ultraviolet (EUV) spectra of highly charged iron ions in a wavelength range of 100-300 A have been observed from two different plasma sources of the Tokyo Electron Beam Ion Trap (Tokyo-EBIT) with a monoenergetic electron beam and a Large Helical Device (LHD) with Maxwellian electron energy. The excitation process of the spectral lines is compared between the two plasmas, and it is found that the excitation process for Fe XIX - Fe XXII ions is clearly different. Namely, the EUV emission lines from the EBIT plasma are only dominated by electron impact excitation connected to the ground state, but the excitation mechanism is not so simple in the LHD plasma. The difference in the excitation process is studied by measuring the intensity ratio of EUV emission lines (114.412 A [1s{sup 2}2s2p{sup 2} {sup 2}P{sub 3/2}{yields}1s{sup 2}2s{sup 2}2p {sup 2}P{sub 3/2}]/117.144 A [1s{sup 2}2s2p{sup 2} {sup 2}P{sub 1/2}{yields}1s{sup 2}2s{sup 2}2p {sup 2}P{sub 1/2}]) arising from different ground levels in the Fe XXII ions. The line intensity ratio has an extremely small value of 0.2 in the EBIT plasma with a low beam current of 30 mA and a beam energy of 2 keV, while the ratio varies with the electron density n{sub e} in the LHD plasmas, i.e., 0.35 for n{sub e} = 1 x 10{sup 13} cm{sup -3} and 0.65 for n{sub e} = 4 x 10{sup 13} cm{sup -3}. Here, the electron density of the EBIT plasma is estimated to be smaller than 10{sup 12} cm{sup -3} and the electron temperature of the LHD plasmas is 2 keV. The dependence of the line intensity ratio on the observed electron density is analyzed for both the EBIT and the LHD plasmas using several collisional-radiative (CR) models. The present experimental data can easily be reproduced by the analysis when the thermal proton impact excitation is taken into account. The importance of the proton impact excitation is also experimentally verified by injecting an iron pellet into the LHD plasmas and changing the ratio of the proton density to the electron density.

• OSTI ID: 21538212
• Journal Information: Journal of Applied Physics, Vol. 109, Issue 7; Other Information: DOI: 10.1063/1.3549707; (c) 2011 American Institute of Physics; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BEAM CURRENTS
CATIONS
ELECTRON BEAMS
ELECTRON DENSITY
ELECTRON TEMPERATURE
EMISSION
EXCITATION
EXTREME ULTRAVIOLET RADIATION
GROUND LEVEL
ION SOURCES
ION TEMPERATURE
IRON
IRON IONS
LHD DEVICE
MULTICHARGED IONS
PLASMA
PLASMA DENSITY
PROTON DENSITY
TRAPS
ULTRAVIOLET SPECTRA
BEAMS
CHARGED PARTICLES
CLOSED PLASMA DEVICES
CURRENTS
ELECTROMAGNETIC RADIATION
ELEMENTS
ENERGY-LEVEL TRANSITIONS
IONS
LEPTON BEAMS
LEVELS
METALS
PARTICLE BEAMS
RADIATIONS
SPECTRA
THERMONUCLEAR DEVICES
TRANSITION ELEMENTS
ULTRAVIOLET RADIATION