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Title: Temperature and impurity transport studies of heated tokamak plasmas by means of a collisional-radiative model of x-ray emission from Mo{sup 30+} to Mo{sup 39+}

Abstract

This work presents and interprets, by means of detailed atomic calculations, observations of L-shell (n=3{yields}n=2) transitions in highly ionized molybdenum, the main intrinsic heavy impurity in the Frascati tokamak upgrade plasmas. These hot plasmas were obtained by additional electron cyclotron resonance heating (ECRH), at the frequency of 140 Ghz, during the current ramp-up phase of the discharge. Injecting 400 kW on axis and 800 kW slightly off axis, the peak central electron temperature reached 8.0 and 7.0 keV, respectively, for a time much longer than the ionization equilibrium time of the molybdenum ions. X-ray emissions from rarely observed high charge states, Mo{sup 30+} to Mo{sup 39+}, have been studied with moderate spectral resolution ({lambda}/{delta}{lambda}{approx}150) and a time resolution of 5 ms. A sophisticated collisional-radiative model for the study of molybdenum ions in plasmas with electron temperature in the range 4-20 keV is presented. The sensitivity of the x-ray emission to the temperature and to impurity transport processes is discussed. This model has been then used to investigate two different plasma scenarios. In the first regime the ECRH heating occurs on axis during the current ramp up phase, when the magnetic shear is evolving from negative to zero up to themore » half radius. The spectrum is well reproduced with the molybdenum ions in coronal equilibrium and with a central impurity peaking. In the second regime, at the beginning of the current flat top when magnetic shear is monotonic and sawtoothing activity is appearing, the lowest charge states (Mo{sup 33+} to Mo{sup 30+}), populated off axis, are affected by anomalous transport and the total molybdenum profile is found to be flat up to the half radius. We conclude with the presentation of ''synthetic spectra'' computed for even higher temperature plasmas that are expected in future experiments with higher ECRH power input. (c) 2000 The American Physical Society.« less

Authors:
 [1];  [1];  [2];  [1];  [1];  [2];  [1];  [1];  [1]
  1. Associazione EURATOM-ENEA sulla Fusione, 00044 Frascati, Rome, (Italy)
  2. (United States)
Publication Date:
OSTI Identifier:
20216394
Resource Type:
Journal Article
Journal Name:
Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics
Additional Journal Information:
Journal Volume: 61; Journal Issue: 5; Other Information: PBD: May 2000; Journal ID: ISSN 1063-651X
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; TOKAMAK DEVICES; PLASMA IMPURITIES; TRANSPORT THEORY; MOLYBDENUM IONS; ELECTRON CYCLOTRON-RESONANCE; HOT PLASMA; L SHELL; COLLISIONAL PLASMA; ELECTRON TEMPERATURE; EXPERIMENTAL DATA; THEORETICAL DATA

Citation Formats

Pacella, D., Fournier, K. B., Lawrence Livermore National Laboratory, P.O. Box 808, L-41, Livermore, California 94550, Zerbini, M., Finkenthal, M., Applied Physics Laboratory, The Johns Hopkins University, Johns Hopkins Road, Laurel, Maryland 20723, Mattioli, M., May, M. J., and Goldstein, W. H. Temperature and impurity transport studies of heated tokamak plasmas by means of a collisional-radiative model of x-ray emission from Mo{sup 30+} to Mo{sup 39+}. United States: N. p., 2000. Web. doi:10.1103/PhysRevE.61.5701.
Pacella, D., Fournier, K. B., Lawrence Livermore National Laboratory, P.O. Box 808, L-41, Livermore, California 94550, Zerbini, M., Finkenthal, M., Applied Physics Laboratory, The Johns Hopkins University, Johns Hopkins Road, Laurel, Maryland 20723, Mattioli, M., May, M. J., & Goldstein, W. H. Temperature and impurity transport studies of heated tokamak plasmas by means of a collisional-radiative model of x-ray emission from Mo{sup 30+} to Mo{sup 39+}. United States. doi:10.1103/PhysRevE.61.5701.
Pacella, D., Fournier, K. B., Lawrence Livermore National Laboratory, P.O. Box 808, L-41, Livermore, California 94550, Zerbini, M., Finkenthal, M., Applied Physics Laboratory, The Johns Hopkins University, Johns Hopkins Road, Laurel, Maryland 20723, Mattioli, M., May, M. J., and Goldstein, W. H. Mon . "Temperature and impurity transport studies of heated tokamak plasmas by means of a collisional-radiative model of x-ray emission from Mo{sup 30+} to Mo{sup 39+}". United States. doi:10.1103/PhysRevE.61.5701.
@article{osti_20216394,
title = {Temperature and impurity transport studies of heated tokamak plasmas by means of a collisional-radiative model of x-ray emission from Mo{sup 30+} to Mo{sup 39+}},
author = {Pacella, D. and Fournier, K. B. and Lawrence Livermore National Laboratory, P.O. Box 808, L-41, Livermore, California 94550 and Zerbini, M. and Finkenthal, M. and Applied Physics Laboratory, The Johns Hopkins University, Johns Hopkins Road, Laurel, Maryland 20723 and Mattioli, M. and May, M. J. and Goldstein, W. H.},
abstractNote = {This work presents and interprets, by means of detailed atomic calculations, observations of L-shell (n=3{yields}n=2) transitions in highly ionized molybdenum, the main intrinsic heavy impurity in the Frascati tokamak upgrade plasmas. These hot plasmas were obtained by additional electron cyclotron resonance heating (ECRH), at the frequency of 140 Ghz, during the current ramp-up phase of the discharge. Injecting 400 kW on axis and 800 kW slightly off axis, the peak central electron temperature reached 8.0 and 7.0 keV, respectively, for a time much longer than the ionization equilibrium time of the molybdenum ions. X-ray emissions from rarely observed high charge states, Mo{sup 30+} to Mo{sup 39+}, have been studied with moderate spectral resolution ({lambda}/{delta}{lambda}{approx}150) and a time resolution of 5 ms. A sophisticated collisional-radiative model for the study of molybdenum ions in plasmas with electron temperature in the range 4-20 keV is presented. The sensitivity of the x-ray emission to the temperature and to impurity transport processes is discussed. This model has been then used to investigate two different plasma scenarios. In the first regime the ECRH heating occurs on axis during the current ramp up phase, when the magnetic shear is evolving from negative to zero up to the half radius. The spectrum is well reproduced with the molybdenum ions in coronal equilibrium and with a central impurity peaking. In the second regime, at the beginning of the current flat top when magnetic shear is monotonic and sawtoothing activity is appearing, the lowest charge states (Mo{sup 33+} to Mo{sup 30+}), populated off axis, are affected by anomalous transport and the total molybdenum profile is found to be flat up to the half radius. We conclude with the presentation of ''synthetic spectra'' computed for even higher temperature plasmas that are expected in future experiments with higher ECRH power input. (c) 2000 The American Physical Society.},
doi = {10.1103/PhysRevE.61.5701},
journal = {Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics},
issn = {1063-651X},
number = 5,
volume = 61,
place = {United States},
year = {2000},
month = {5}
}