Proof-of-principle laser-induced fluorescence measurements of gas distributions from supersonic nozzles

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We have developed a 12-cm-diameter Ar gas Z-pinch load, which produces two annular gas shells and a center gas jet. The two-dimensional (2-D) gas density profiles of the load, in -and -planes, were measured with submillimeter spatial resolutions using the planar-laser-induced fluorescence (PLIF) method, for conditions used in Z-pinch experiments. Due to interactions between the shells, the net gas density profile differs from the superposition of the individual shell profiles. Narrow density peaks are observed both at smaller and larger radii than the radius where the shells come in contact with each other. Two-dimensional flow velocity distributions are determined from the displacements between the fluorescence and later time phosphorescence images. The measured stream velocities of argon gas puffs are 650 20 m/s, higher than the ideal gas velocity due to the formation of clusters in the supersonic gas flow. Indeed, clusters were observed in earlier Rayleigh scattering experiments. The gas measurements of the initial phase using the PLIF will be combined with other density measurements of the implosion and pinch phases to better understand the implosion dynamics and to provide initial conditions for simulation codes.Index Terms-Argon gas puff, laser-induced fluorescence, plasma radiation source, Z-pinch.

“…We determined the puff gas densities from this ratio. A detailed description of these procedures was reported in an earlier publication [12].…”

Section: Experiments Details and Resultsmentioning

confidence: 99%

Section: Experiments Details and Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Two-dimensional gas density and velocity distributions of a 12-cm-diameter, triple-nozzle argon Z-pinch load

Failor

Banister

et al. 2005

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“…The properties of the gas-puff loads for these nozzles are listed in Table I along with the peak current (I o ), the implosion time (τ imp ), and the total K-shell yield (from calorimeters) including the FB continuum for the seven shots. The initial radial and axial gas distributions and the average initial linear mass density (m l ) were obtained using a laser-induced fluorescence technique for nozzle A [22], [23] and near-IR interferometry for nozzle B [16].…”

Section: A Z-pinch Sourcementioning

confidence: 99%

Measurement and Analysis of Continuum Radiation From a Large-Diameter Long Implosion Time Argon Gas Puff$Z$-Pinch at 6 MA

Young

Commisso

Murphy

et al. 2006

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Time-resolved measurements of the absolute freebound (FB) continuum spectrum emitted from a 12-cm-diameter argon gas-puff Z-pinch driven at ∼6-MA peak current with 220-to 260-ns implosion times are reported. A crystal spectrometer is used with silicon diode detectors to provide kiloelectronvolt spectral resolution. The energy and absolute-intensity calibration procedures for the spectrometer are described. The slope of the FB continuum is well represented by a decaying exponential spectrum with a single electron temperature from which spatially averaged, time-resolved (T e (t)), and time-integrated ( T e ) electron temperatures are inferred. An expression for the absolute FB continuum, which takes into account recombination onto bare as well as H-like species, is presented and used to infer time-integrated spatially averaged ion densities n i . The values of T e and n i are in general agreement with the values of these quantities obtained by using the conventional K-shell line-ratio method. Values of T e (t) peak on the rise of the continuum radiation pulse and gradually decrease during the pulse. The fraction of the total energy radiated in the K-shell that resides in the FB continuum is 6%-10%, and this fraction increases with n i . Calculated continuum spectra are in agreement with measured spectra.Index Terms-Electron temperature, free-bound continuum spectrum, ion density, Z-pinch.

“…The initial distribution of neutral atoms in the load was measured off-line in a separate test chamber using a laser-induced-fluorescence (LIF) technique [16]. For these measurements, a trace amount of acetone (5%) was added to the Ar in the plenum.…”

Section: Experimental Systemmentioning

confidence: 99%

Interferometric measurement of physical phenomena during the implosion phase of a puff-on-puff Z-pinch load on double-EAGLE

Hazelton¹,

Yadlowsky²,

Moschella³

et al. 2003

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Theoretical studies have predicted that the disruptive role of the Rayleigh-Taylor (R-T) instability on the current conduction and implosion characteristics of annular Z-pinch loads will be mitigated by mass accretion if uniform fill or multiple annular shell loads are used. Holographic interferometry was used to study these physical processes during the implosion phase of puff-on-puff loads on a terawatt accelerator. Both axial (r-z) density perturbation and azimuthal ( ) filamentation modes of the R-T instability were observed. Significant ionization ( 3 10) of the inner gas puff atoms was observed below the anode grid before the outer puff had imploded to this radial position. Radiation hydrodynamic calculations indicate that photoionization by radiation from the outer current carrying shell could not account for this ionization. Current flowing on the inner gas puff could be the source of this ionization. The effect of these physical processes on the radiation yield from z-pinches warrants further investigation. Index Terms-Holographic interferometry, phase-step reconstruction, Rayleigh-Taylor (R-T) instability, z-pinch.