Calculation of the radiative cooling coefficient for krypton in a low density plasma

Fournier, K. B.; May, M. J.; Pacella, D.; Finkenthal, M.; Gregory, B.C.; Goldstein, W. H.

doi:10.1088/0029-5515/40/4/309

Cited by 32 publications

(41 citation statements)

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“…Further details of the model are given in [12]. Both the loss rate L Z and the ionization state of impurities are calculated in coronal equilibrium: ADAS [34], for argon also [35,36], for helium also [37] and for krypton also [38,39]. It is to be noted that there also exist more elaborated current quench models using state-resolved atomic physics [40].…”

Section: Measurements Of the Fuelling Efficiencymentioning

confidence: 99%

Fuelling efficiency of massive gas injection in TEXTOR: mass scaling and importance of gas flow dynamics

et al. 2011

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Abstract.Fuelling efficiency is an important parameter in designing a massive gas injection system for suppression of runaway electrons in ITER. In this work a Z-dependence of the fuelling efficiency is measured for TEXTOR. The dependence covers the following gases: He, Ne, Ar, Kr, Xe and a 10% Ar-D 2 mixture. It is shown that the fuelling efficiency significantly decreases with the gas mass, from above 0.5 for He to below 0.03 for Xe.To explain the variation of the efficiency with the gas mass and pressure a simple model of the gas flow from the valve to the plasma edge is developed. The flow model is validated by using available laboratory flow measurements of a TEXTOR-similar injection system. The unsteady gas flow and a premature plasma disrupting are shown to explain the mass dependence of the efficiency.

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Section: Measurements Of the Fuelling Efficiencymentioning

confidence: 99%

Fuelling efficiency of massive gas injection in TEXTOR: mass scaling and importance of gas flow dynamics

et al. 2011

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“…3(b) is ≈2.4 J. Using the data published in [19], the radiative cooling coefficient at the density of the compressed gas in the shock shell (∼ 10 19 cm −3 ) can be extrapolated to be ∼ 4.6 × 10 −34 Wm 3 , which results in an estimated energy loss rate of ∼ 4 × 10 8 J/s and a cooling time of ∼ 6 ns. Given that cooling function data is only available for astrophysical densities, this is at most an order-ofmagnitude estimate.…”

Section: Pacs Numbers: Valid Pacs Appear Herementioning

confidence: 99%

Observation of a Velocity Domain Cooling Instability in a Radiative Shock

et al. 2010

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We report on experimental investigations into strong, laser-driven, radiative shocks in noble-gas cluster media. Cylindrical shocks launched with several J exhibit strong radiative effects such as increased deceleration and radiative preheat. Using time-resolved propagation data from single-shot streaked Schlieren measurements we observe temporal modulations on shock position and velocity, which we attribute to the thermal cooling instability, an instability which until now has not been observed experimentally. PACS numbers: Valid PACS appear hereShocks are a common phenomenon in astrophysics and high-energy-density (HED) environments in general. A shock forms when material expands with supersonic speed into an ambient medium, faster than the surrounding material can adapt to the expansion. If the energy deposition initially launching the shock is limited in time, the shock is followed by a rarefaction which eventually catches up with the shock front and a blast wave is formed, often consisting of a thin shell containing much of the swept-up material [1].An understanding of shocks and the dynamics of thermal and dynamical instabilities in HED plasmas is vital for numerical models of complex plasma systems. In such environments, radiation can lead to fundamental structural and dynamical changes in the system evolution. A shock becomes radiative if the post-shock conditions lead to an efficient cooling rate through radiative energy losses. The radiation is transmitted through the shock shell and, in an optically thin case, is lost from the system. In contrast, if the upstream material ahead of the shock front is optically thick to parts of the emission spectrum, radiation can be reabsorbed leading to preheat and ionization of the material ahead of the shock front. This modifies the shock propagation dynamics and can lead to growth of instabilities [2,3].The temporal expansion of a shock radius is often described as a power-law type function of the formwhere E 0 denotes the deposited energy per unit length (in cylindrical geometry) and ρ is the mass density. The parameter α is the deceleration parameter determined by the geometry and the energy dissipation in the system, which for cylindrical, adiabatic blast waves is α = 0.5 [4]. Dissipative processes such as radiation or ionization necessarily reduce the polytropic index, γ, of the system, * Electronic address: M.Hohenberger@Imperial.ac.uk and therefore α, to a value below the adiabatic solution and the blast wave decelerates more quickly. In case where radiative losses in the shell are sufficiently large such that the shell cannot support itself any longer, it is pushed by the low-density but high-pressure interior of the shock and collapses to high densities. Specifically the transition to this pressure driven snowplow regime and the associated shell-thinning is thought to make the shock more susceptible to radiation-driven instabilities, one of which we address in detail in this paper. Radiative shocks can be studied experimentally by utilizing the efficient a...

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“…The formulae should only be used for Ar to Ni but no calculations are currently available for heavier elements except for Kr [15]. We have then compared the ISEA rates provided by K. Fournier (hereafter KF [15]) with the data obtained from the AR85 formula extrapolated to Kr. In the T e range of maximum abundance the average ratios of the AR85 rates to the ones from KF are 1.4, 1.2, 1.35, 2.0, 1.6 and 0.8 for S-like to Na-like Kr ions, respectively.…”

Section: Direct Ionization and Excitation-autoionization Ratesmentioning

confidence: 99%

IONIZATION BALANCE FOR OPTICALLY THIN PLASMAS: RATE COEFFICIENTS FOR Cu, Zn, Ga, and Ge IONS

Mazzitelli

Mattioli

2002

Atomic Data and Nuclear Data Tables

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Calculation of the radiative cooling coefficient for krypton in a low density plasma

Cited by 32 publications

References 40 publications

Fuelling efficiency of massive gas injection in TEXTOR: mass scaling and importance of gas flow dynamics

Fuelling efficiency of massive gas injection in TEXTOR: mass scaling and importance of gas flow dynamics

Observation of a Velocity Domain Cooling Instability in a Radiative Shock

IONIZATION BALANCE FOR OPTICALLY THIN PLASMAS: RATE COEFFICIENTS FOR Cu, Zn, Ga, and Ge IONS

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