scholarly journals Tokamak Plasmas: A Paradigm for Coronal Equilibrium and Disequilibrium

1990 ◽  
Vol 115 ◽  
pp. 57-62
Author(s):  
Richard D. Petrasso
Keyword(s):  
Electron Density ◽  
Direct Consequence ◽  
High Electron ◽  
Tokamak Plasmas ◽  
Edge Region ◽  
Plasma Region ◽  
Astrophysical Plasmas ◽  
Central Plasma ◽  
Electron Density And Temperature ◽  
Ion Species

AbstractTokamaks operate over a wide parameter space, allowing access to plasma conditions relevant to astrophysical plasmas. For high electron density discharges, for example, the central electron density and temperature are ~ 3 × 1014cm-3 and ~ 1.5 keV, and the central plasma region is in coronal equilibrium. Towards the edge of the plasma, however, many ion species will be far out of coronal equilibrium. A novel feature of the edge region is the seemingly contradictory property that it is, simultaneously, both a strongly recombining and a strongly ionizing plasma. Recent tokamak observations of strongly recombining plasmas also show that the G parameter (the ratio of forbidden plus intercombination to resonance lines) is larger by a factor of 3 than the ratio of statistical weights of the triplet-singlet series. Such observations can be of direct consequence to the interpretation of non-equilibrium astrophysical plasmas.

scholarly journals Application of Thomson scattering to helicon plasma sources

2020 ◽  
Vol 86 (3) ◽  
Author(s):  
R. Agnello ◽  
Y. Andrebe ◽  
H. Arnichand ◽  
P. Blanchard ◽  
T. De Kerchove ◽  
...  
Keyword(s):  
Electron Density ◽  
Electric Fields ◽  
Plasma Column ◽  
Coherent Scattering ◽  
Thomson Scattering ◽  
High Electron ◽  
Plasma Diagnostic ◽  
Ion Temperature ◽  
Helicon Plasma ◽  
Electron Density And Temperature

The possibility of performing electron density and temperature measurements in a high power helicon plasma is a crucial issue in the framework of the AWAKE (Advanced WAKefield Experiment) project, which demonstrates acceleration of particles using $\text{GeV}~\text{m}^{-1}$ electric fields in plasmas. For AWAKE, a helicon is currently envisaged as a candidate plasma source due to its capability for low electron and ion temperature, high electron density and production of an elongated plasma column. A plasma diagnostic to accurately determine the electron density in AWAKE regimes would be a valuable supporting tool. A demonstration Thomson scattering (TS) diagnostic was installed and successfully tested on the resonant antenna ion device (RAID) at the Swiss Plasma Center of Ecole Polytechnique Fédérale de Lausanne. RAID produces a helicon plasma column with characteristics similar to those of the AWAKE helicon source, and is therefore an optimal testbed for application to the AWAKE device. The spectrometer employed in RAID is based on polychromators which collect the light scattered by plasma electrons in spectrally filtered wavelength regions. Results from TS on RAID demonstrate conditions of electron density and temperature respectively of $n_{e}=1.10\,(\pm 0.19)\times 10^{19}~\text{m}^{-3}$ and $T_{e}=2.3\,(\pm 0.6)~\text{eV}$ in a steady-state discharge in an Ar plasma with 5 kW of RF power. If the same polychromator system is used for AWAKE, where the electron density attained is $2\times 10^{20}~\text{m}^{-3}$ , the contribution to measurement error due to coherent scattering is ${\sim}2.5\,\%$ . Presented here are details of the TS diagnostic and the first tests in RAID, and the expectations for the system when employed on the AWAKE device.

Electron microscope study of the secretory activity of epithelial cells in embryonic thymus

1990 ◽  
Vol 48 (3) ◽  
pp. 382-383
Author(s):  
H. Alasam
Keyword(s):  
Cell Differentiation ◽  
T Cell ◽  
Epithelial Cells ◽  
Electron Density ◽  
Secretory Activity ◽  
T Cell Differentiation ◽  
High Electron ◽  
Transmission Electron ◽  
Medullary Epithelial Cells ◽  
Thymic Factor

The possibility that intrathymic T-cell differentiation involves stem cell-lymphoid interactions in embryos led us to study the ultrastructure of epithelial cell in normal embryonic thymus. Studies in adult thymus showed that it produces several peptides that induce T-cell differentiation. Several of them have been chemically characterized, such as thymosin α 1, thymopoietin, thymic humoral factor or the serum thymic factor. It was suggested that most of these factors are secreted by populations of A and B-epithelial cells.Embryonic materials were obtained from inbred matings of Swiss Albino mice. Thymuses were disected from embryos 17 days old and prepared for transmission electron microscopy. Our studies showed that embryonic thymus at this stage contains undifferentiated and differentiated epithelial cells, large lymphoblasts, medium and few small lymphocytes (Fig. 5). No differences were found between cortical and medullary epithelial cells, in contrast to the findings of Van Vliet et al,. Epithelial cells were mostly of the A-type with low electron density in both cytoplasm and nucleus. However few B-type with high electron density were also found (Fig. 7).

THEORETICAL ELECTRON DENSITY AND TEMPERATURE SENSITIVE EMISSION LINE RATIOS FOR HELIUM-LIKE Si XIII COMPARED TO DITE TOKAMAK OBSERVATIONS

1989 ◽  
Vol 50 (C1) ◽  
pp. C1-559-C1-564
Author(s):  
F. P. KEENAN ◽  
R. BARNSLEY ◽  
J. DUNN ◽  
K. D. EVANS ◽  
S. M. McCANN ◽  
...  
Keyword(s):  
Emission Line ◽  
Electron Density ◽  
Temperature Sensitive ◽  
Electron Density And Temperature

Effective Dielectric Function of Porous Silicon: the Transverse Component

1994 ◽  
Vol 358 ◽  
Author(s):  
G. Gumbs
Keyword(s):  
Absorption Spectrum ◽  
Absorption Coefficient ◽  
Electron Density ◽  
Quantum Wires ◽  
Interband Transition ◽  
Incident Light ◽  
Transverse Component ◽  
Effect Of Temperature ◽  
High Electron ◽  
Confining Potential

ABSTRACTA self-consistent many-body theory is developed to study the effect of temperature and electron density on the interband absorption coefficient and the frequency-dependent refractive index for an array of isolated quantum wires. The peaks in the absorption coefficient correspond to interband transitions resulting in the resonant absorption of light. The oscillations in the derivative spectrum are due to the quantization of the energy levels related to the in-plane confining potential for such reduced dimensional systems. There are appreciable changes in the absorption spectrum when the electron density or temperature is increased. One interband transition peak is suppressed in the high electron density limit and the thermal depopulation effect on the electron subbands can be easily seen when the temperature is high. We also find that the exciton coupling weakens the shoulder features in the absorption spectrum. This study is relevant to optical characterization of the confining potential and the areal density of electrons using photoreflectance. By using incident light with tunable frequencies in the interband excitation regime, contactless photoreflectance measurements may be carried out and the data compared with our calculations. By fitting the numerical results to the peak positions of the photoreflectance spectrum, the number of electrons in each wire may be extracted.

Impurity effects on trapped electron modes in tokamak plasmas with inverted electron density profile

2021 ◽  
Vol 28 (5) ◽  
pp. 052510
Author(s):  
X. R. Zhang ◽  
J. Q. Dong ◽  
H. R. Du ◽  
J. Y. Liu ◽  
Y. Shen ◽  
...  
Keyword(s):  
Electron Density ◽  
Density Profile ◽  
Electron Density Profile ◽  
Tokamak Plasmas ◽  
Impurity Effects ◽  
Trapped Electron

scholarly journals Measurement of Electron Density and Temperature of Laser-Induced Copper Plasma

2013 ◽  
Vol 25 (4) ◽  
pp. 2192-2198 ◽  
Author(s):  
M.A. Naeem ◽  
M. Iqbal ◽  
N. Amin ◽  
M. Musadiq ◽  
Y. Jamil ◽  
...  
Keyword(s):  
Electron Density ◽  
Electron Density And Temperature ◽  
Copper Plasma
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