Analysis of D
                    <sub>α</sub>
                    (H
                    <sub>α</sub>
                    ) spectrum emitted in front of the limiter in HT-7

,

doi:10.1088/1674-1056/17/12/038

Cited by 4 publications

(1 citation statement)

References 12 publications

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“…In particular, the mechanisms for the dissociation of molecules into atomic species within the plasma edge need to be both qualitatively and quantitatively understood. These processes are likely responsible for the large number of slow hydrogen atoms with kinetic energies less than 0.5 eV detected in the plasma edge layer of tokamaks (Mertens et al 2001, Huang et al 2008. A recent investigation by Hollmann et al (2006) in the DIII-D plasma edge has revealed highly excited D 2 , with an X 1 + g rotational temperature up to 10 000 K and vibrational temperature up to 30 000 K. Their analysis has also shown that collisonal excitation and ionization of D 2 and the dissociative recombination of D + 2 with electrons are major mechanisms for the production of D atoms.…”

Section: Introductionmentioning

confidence: 99%

Electron and photon dissociation cross sections of the D₂singlet ungerade continua

Liu¹,

Shemansky²,

Johnson³

et al. 2012

J. Phys. B: At. Mol. Opt. Phys.

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The dissociation of H2 and its isotopologues through excitation to the singlet ungerade continua is one of the major channels for the production of slow hydrogen atoms at high temperature (T > 10 000 K) and electron energy >25 eV. State-specific photodissociation cross sections and oscillator strengths for molecular deuterium from the X 1Σ+g(vi, Ji) levels to the continuum levels of the B 1Σ+u, C 1Πu, B′ 1Σ+u, D 1Πu, B, D′ 1Πu and 5pσ 1Σ+u states have been calculated. The corresponding (vi, Ji) state-specific electron impact dissociation cross sections have been obtained for the first time over a wide energy range using calculated continuum oscillator strengths along with previously published excitation functions of the Lyman and Werner bands. Estimated cross sections to the higher (n ⩾ 5) npσ 1Σ+u and npπ 1Πu continua are also provided. Both photon and electron impact excitation cross sections show strong dependences on the initial (vi, Ji) quantum numbers. Thermally averaged electron impact cross sections of all singlet ungerade states increase monotonically with temperature. While excitation to the B′ 1Σ+u continuum is the dominant dissociation channel at room temperature, the C 1Πu and B 1Σ+u continua become more important at high temperature (>5000 K). The large increase of the C 1Πu and B 1Σ+u cross sections with (vi, Ji) is primarily responsible for making the continuum dissociation from a minor break-up channel at room temperature into a major one at high temperature. The electron dissociation cross section of D2 via the singlet ungerade continua is smaller than its H2 counterpart, although this difference decreases with temperature. This work, along with the previous calculations of H2 by Liu et al (2009, 2012), provides the complete electron impact dissociation cross sections of H2 and D2 through the singlet ungerade continua. Thermally averaged electron dissociation cross sections are provided at various temperatures for applications in plasma physics.

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Section: Introductionmentioning

confidence: 99%

Electron and photon dissociation cross sections of the D₂singlet ungerade continua

Liu¹,

Shemansky²,

Johnson³

et al. 2012

J. Phys. B: At. Mol. Opt. Phys.

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A Dip Structure in the Intrinsic Toroidal Rotation Near the Edge of the Ohmic Plasmas in EAST

Xu¹,

Wan²,

Guo³

et al. 2011

Plasma Sci. Technol.

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Ion's toroidal velocity, vt, in both the outermost 4 cm of the confined region and the scrap-off layer of Ohmic L-mode plasmas in EAST was measured using Mach probes. At about 1 cm inside the separatrix a local minimum in vt was observed, from which a cocurrent rotation increased both inwards and outwards. The radial width of the vt dip was 1 cm to 2 cm, and both the density and electron temperature profiles exhibited steep gradients at this dip position. It was observed in both divertor and limiter configurations. To find out its origin, the toroidal torques induced by neutral friction, neoclassical viscosity, collisional perpendicular shear viscosity, ion orbit loss and turbulent Reynolds stress were estimated using the measured parameters. Our results indicate that in this particular parameter regime the neutral friction was the dominant damping force. The calculated cocurrent toroidal torque by the neoclassical viscosity dominates over those from the collisional perpendicular shear viscosity, ion orbit loss and turbulent Reynolds stress. These results are potentially important for the understanding of boundary conditions for the intrinsic toroidal momentum in tokamak plasmas.

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Spectroscopic Measurement of Neutral Particle Influx Ratio on EAST

Shi

et al. 2013

Plasma Sci. Technol.

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The spectra of HeI (587.6 nm), Hα (656.28 nm) and Dα (656.1 nm) of the helium discharges as well as the normal deuterium discharges have been measured with two optical spectroscopic multi-channel analysis (OMA) systems on the experimental advanced superconducting tokamak (EAST). The influx ratio of the sum of H and D to He spectral lines and the influx ratio of H to D are given. In this way the ratio of hydrogen/deuterium ion (S/XB) H/D to (S/XB)He as well as (S/XB) H/D is not very sensitive to the variation in the edge density and temperature. The low-density helium discharges are operated in order to reduce the recycling hydrogen fluxes; however, the effect is not obvious. The possible reason is that the number of helium discharges is not enough and the content of hydrogen in the wall is still very abundant, which is caused by frequent wall conditionings and the vacuum leakage. The H/(H+D) ratio decreases quickly after one lithium coating and reduces to less than 10% using several accumulated lithium wall conditioning. It is found that the deposited He atoms on the carbon wall will remain at a low level after several D2 discharges.

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Analysis of D _α (H _α ) spectrum emitted in front of the limiter in HT-7

Cited by 4 publications

References 12 publications

Electron and photon dissociation cross sections of the D₂singlet ungerade continua

Electron and photon dissociation cross sections of the D₂singlet ungerade continua

A Dip Structure in the Intrinsic Toroidal Rotation Near the Edge of the Ohmic Plasmas in EAST

Spectroscopic Measurement of Neutral Particle Influx Ratio on EAST

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Analysis of D α (H α ) spectrum emitted in front of the limiter in HT-7

Cited by 4 publications

References 12 publications

Electron and photon dissociation cross sections of the D2singlet ungerade continua

Electron and photon dissociation cross sections of the D2singlet ungerade continua

A Dip Structure in the Intrinsic Toroidal Rotation Near the Edge of the Ohmic Plasmas in EAST

Spectroscopic Measurement of Neutral Particle Influx Ratio on EAST

Contact Info

Product

Resources

About

Analysis of D _α (H _α ) spectrum emitted in front of the limiter in HT-7

Electron and photon dissociation cross sections of the D₂singlet ungerade continua

Electron and photon dissociation cross sections of the D₂singlet ungerade continua