Optical diagnostics for density measurement in high-quality laser-plasma electron accelerators

Brandi, F.; Gizzi, L. A.

doi:10.1017/hpl.2019.11

Cited by 18 publications

(18 citation statements)

References 68 publications

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“…The method used for evaluation of the wave-front distortion of the probe beam caused by the gas was shearing interferometry using a Wollaston prism. Shearing interferometry 13 employed with our method benefits from not requiring a reference beam, which simplifies the setup, as the beam path of the multi-pass probing setup becomes rather long. The gas jet was imaged by a biconvex lens with a 300 mm focal length on a CMOS camera with resolution 2048 × 2048 and pixel size of 5.5 µm with 1.15 magnification.…”

Section: Methodsmentioning

confidence: 99%

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Multi-pass probing for high-sensitivity tomographic interferometry

Karatodorov

Lera

Raclavský

et al. 2021

Sci Rep

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Optical probing is an indispensable tool in research and development. In fact, it has always been the most natural way for humankind to explore nature. However, objects consisting of transparent materials with a refractive index close to unity, such as low-density gas jets, are a typical example of samples that often reach the sensitivity limits of optical probing techniques. We introduce an advanced optical probing method employing multiple passes of the probe through the object to increase phase sensitivity, and relay-imaging of the object between individual passes to preserve spatial resolution. An interferometer with four-passes was set up and the concept was validated by tomographic characterization of low-density supersonic gas jets. The results show an evident increase of sensitivity, which allows for the accurate quantitation of fine features such as a shock formed by an obstacle or a barrel shock on the jet boundary in low ambient gas pressures. Despite its limitations in temporal resolution, this novel method has demonstrated an increase in phase sensitivity in transmission, however, it can also be employed to boost the absorption or polarization contrast of weakly interacting objects in both transmission and reflection setups, thus, upgrading the sensitivity of various optical characterization methods.

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Section: Methodsmentioning

confidence: 99%

“…Interferometry is the most popular method for assessing the density distribution of gas jets 13 , 14 . Lately, the research on interferometric techniques for neutral gas jet density characterization focuses on the improvement of interferometric sensitivity, e.g.…”

mentioning

confidence: 99%

Multi-pass probing for high-sensitivity tomographic interferometry

Karatodorov

Lera

Raclavský

et al. 2021

Sci Rep

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“…Since the long vortex was designed for plasma-based laser-guiding applications, it was important to estimate the absolute gas density inside the vortex channel. Interferometry, however, can provide only the information about the relative density [10]. To get the absolute gas density we inserted a thin probe into the gas vortex as shown in Figure 1a (green tube).…”

Section: Methodsmentioning

confidence: 99%

Vortex dynamics and applications to gaseous optical elements

Kaganovich,

Hafizi,

Johnson

et al. 2020

Preprint

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Experimental studies of the optical properties of compressible, viscous and rapidly-rotating gas flows (vortices) are presented. Gas vortices can function as optical elements such as lenses or waveguides. The optical properties are determined from direct interferometric phase measurements and beam propagation analysis. Output beams are analyzed in terms of Zernike polynomials for a range of gas flow parameters, including choked flow. The absolute radial gas density distribution is measured and a technique for adjusting it is demonstrated.

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“…Liquid n-octane, a component of industrial gasoline, is a colorless and transparent combustible organic compound fuel. At present, this liquid fuel is widely used in theoretical and experimental spray combustion research on the combustion chambers of internal combustion engines and aerospace engines [45][46][47]. It is, therefore, essential to determine the temperature-dependent optical constants and radiative properties of liquid n-octane and n-octane droplets.…”

Section: Introductionmentioning

confidence: 99%

Spectral Radiative Properties of a Liquid n-Octane Droplet in the Midinfrared Region

Zhao

Jing

et al. 2020

Journal of Spectroscopy

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The optical constants of a liquid hydrocarbon such as liquid n-octane are basic material properties that may be used to evaluate their thermal radiation transfer capabilities. In this study, the ellipsometry method was used to measure the optical constants of liquid n-octane in the midinfrared wavelength range of 2.0–16.0 μm at temperatures of 20, 50, and 80°C. Experimental analyses indicate the significant effect of temperature on the refractive index, although it has little effect on the absorption index. With increasing temperature, the refractive index shows a linear decrease, and reduced density leads to weaker absorption intensities. The radiative properties of n-octane droplets, including the absorption and scattering efficiency factors of single droplets with droplet radii r = 10, 20, 50, and 100 μm and the absorption and scattering coefficients in a droplets-air system of droplet volume fractions fv = 2%, 3%, and 4%, were calculated using Mie theory. The numerical results indicate that, with increasing temperature, the absorption efficiency factor slightly decreases, and the variation trend of the scattering efficiency factor is more complicated. With increasing droplet radius, the absorption efficiency factor increases within the studied wavelength range, except for certain absorption peaks, but the scattering efficiency factor tends to decrease. While the absorption is greater, the scattering is weaker for a given droplet radius. With an increasing volume fraction of n-octane droplets, the absorption and scattering coefficients increase linearly within the studied wavelength range.

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Optical diagnostics for density measurement in high-quality laser-plasma electron accelerators

Cited by 18 publications

References 68 publications

Multi-pass probing for high-sensitivity tomographic interferometry

Multi-pass probing for high-sensitivity tomographic interferometry

Vortex dynamics and applications to gaseous optical elements

Spectral Radiative Properties of a Liquid n-Octane Droplet in the Midinfrared Region

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