Short-pulse laser opacity measurements

Experimental measurements of the opacity of plasmas at densities close to solid state and temperatures ∼ 60 -300 eV using a probing X-ray laser are presented. Utilizing thin targets, opacities of iron have been measured using x-ray lasers of photon energy 89 eV created by pumping with the VULCAN RAL laser. The thin targets are separately heated by spot focus laser pulses. We have demonstrated that X-ray laser brightness is sufficient to overcome the self-emission of hot plasma so that useful opacity measurements can be made. Due to their high brightness, x-ray lasers can fulfill a useful niche in measuring opacity and other phenomena associated with laser-plasma interactions. Quantities such as opacity measured in laser-plasmas are useful elsewhere. For example, plasma opacity is important in understanding radiative transfer in the sun.

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“…The use of short pulse lasers to create uniform plasmas from buried layer targets has been discussed widely in the literature (see e.g. [20]). …”

Section: Interpretation Of Opacitymentioning

confidence: 99%

Hot dense plasma opacity measurements using x-ray lasers

et al. 2005

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“…Various statistical mechanics models [18][19][20] differ by factors of several in the predicted electron-ion collisionality in this regime. Material properties such as electrical [21][22][23][24] and thermal conductivity [25,26], opacity [27][28][29][30], and equation-of-state (EOS) [31,32] have been studied in this regime to attempt to resolve theoretical and calculational uncertainties. However, the usefulness of such measurements has been impaired because of the lack of an independent measurement of temperature and density.…”

Section: Motivationmentioning

confidence: 99%

Dense matter characterization by X-ray Thomson scattering

Landen

Glenzer

Edwards

et al. 2001

Journal of Quantitative Spectroscopy and Radiative Transfer

103

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We discuss the extension of the powerful technique of Thomson scattering to the x-ray regime for providing an independent measure of plasma parameters for dense plasmas. By spectrallyresolving the scattering, the coherent (Rayleigh) unshifted scattering component can be separated from the incoherent Thomson component, which is both Compton and Doppler shifted. The free electron density and temperature can then be inferred from the spectral shape of the high frequency Thomson scattering component. In addition, as the plasma temperature is dcreased, the electron velocity distribution as measured by incoherent Thomson scattering will make a transition from the traditional Gaussian Boltzmann distribution to a density-dependent parabolic Fermi distribution to. We also present a discussion for a proof-of-principle experiment appropriate for a high energy laser facility.

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“…Subsequently a number of other experiments in this category have been undertaken by, for example, Eidmann et al (2000) who studied the emission spectroscopy of an aluminium buried layer. Davidson et al (2000) presented improvements to the target design and diagnostics used by Nazir et al (1996). The second class of experiment does not heat a thin layer buried just below the surface by electron thermal conduction but rather uses higher intensities (up to 10 21 W cm −2 ) to produce electrons that have sufficient energy (typically many megaelectronvolts) to heat a layer of material that is buried deep (tens of micrometres) beneath the surface.…”

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confidence: 99%

New experimental possibilities for measuring radiative opacity under conditions in the Sun's interior

Rose¹

2005

Plasma Phys. Control. Fusion

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Opacity experiments that have been conducted to date using long-pulse (nanosecond) high-power lasers have reached conditions similar in density and temperature to those found in the outer part of the radiative flow region of the Sun. Experiments using short-pulse (picosecond) lasers are beginning to give access to conditions halfway to the Sun's centre. In this paper we describe a preliminary design of an opacity experiment that uses a combination of long and short-pulse laser beams to compress and heat the plasma and thereby access conditions similar to those at the centre of the Sun.

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Short-pulse laser opacity measurements

Cited by 11 publications

References 8 publications

Hot dense plasma opacity measurements using x-ray lasers

Hot dense plasma opacity measurements using x-ray lasers

Dense matter characterization by X-ray Thomson scattering

New experimental possibilities for measuring radiative opacity under conditions in the Sun's interior

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