Research

5 pages, 328 KiB

Open AccessCommunication

X-ray Spectroscopy Based Diagnostic of GigaGauss Magnetic Fields during Relativistic Laser-Plasma Interactions

by Elisabeth Dalimier and Eugene Oks

Atoms 2018, 6(4), 60; https://doi.org/10.3390/atoms6040060 - 06 Nov 2018

Cited by 4 | Viewed by 2482

GigaGauss (GG), and even multi-GG magnetic fields are expected to be developed during relativistic laser-plasma interactions. Sub-GG magnetic fields were previously measured by a method using the self-generated harmonics of the laser frequency, and the fact that the magnetized plasma is birefringent and/or [...] Read more.

GigaGauss (GG), and even multi-GG magnetic fields are expected to be developed during relativistic laser-plasma interactions. Sub-GG magnetic fields were previously measured by a method using the self-generated harmonics of the laser frequency, and the fact that the magnetized plasma is birefringent and/or optically active depending on the propagation direction of the electromagnetic wave. In the present short communication, we outline an idea for a method of measuring GG magnetic fields based on the phenomenon of Langmuir-wave-caused dips (L-dips) in X-ray line profiles. The L-dips were observed in several experimental spectroscopic studies of relativistic laser-plasma interactions. Ultrastrong magnetic fields affect the separation of the L-dips from one another, so that this relative shift can be used to measure such fields. Full article

(This article belongs to the Special Issue Stark Broadening of Spectral Lines in Plasmas)

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6 pages, 4435 KiB

Open AccessArticle

Plasma Expansion Dynamics in Hydrogen Gas

by Ghaneshwar Gautam and Christian G. Parigger

Atoms 2018, 6(3), 46; https://doi.org/10.3390/atoms6030046 - 20 Aug 2018

Cited by 2 | Viewed by 3549

Abstract

Micro-plasma is generated in ultra-high-pure hydrogen gas, which fills the inside of a cell at a pressure of (1.08 ± 0.033) × 10⁵ Pa by using a Q-switched neodymium-doped yttrium-aluminum-garnet (Nd:YAG) laser device operated at a fundamental wavelength of 1064 nm and [...] Read more.

Micro-plasma is generated in ultra-high-pure hydrogen gas, which fills the inside of a cell at a pressure of (1.08 ± 0.033) × 10⁵ Pa by using a Q-switched neodymium-doped yttrium-aluminum-garnet (Nd:YAG) laser device operated at a fundamental wavelength of 1064 nm and a pulse duration of 14 ns. The micro-plasma emission spectra of the hydrogen Balmer alpha line, H_α, are recorded with a Czerny–Turner type spectrometer and an intensified charge-coupled device. The spectra are calibrated for wavelength and corrected for detector sensitivity. During the first few tens of nanoseconds after the initiation of optical breakdown, the significant Stark-broadened and Stark-shifted H_α lines mark the well-above hypersonic outward expansion. The vertical diameters of the spectrally resolved plasma images are measured for the determination of expansion speeds, which were found to decrease from 100 to 10 km/s for time delays of 10 to 35 ns. For time delays of 0.5 µs to 1 µs, the expansion speed of the plasma decreases to the speed of sound of 1.3 km/s in the near ambient temperature and pressure of the hydrogen gas. Full article

(This article belongs to the Special Issue Stark Broadening of Spectral Lines in Plasmas)

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9 pages, 2191 KiB

Open AccessArticle

Measurement of Electron Density from Stark-Broadened Spectral Lines Appearing in Silver Nanomaterial Plasma

by Ashraf M. EL Sherbini, Ahmed E. EL Sherbini and Christian G. Parigger

Atoms 2018, 6(3), 44; https://doi.org/10.3390/atoms6030044 - 13 Aug 2018

Cited by 8 | Viewed by 5058

Abstract

This work communicates results from optical emission spectroscopy following laser-induced optical breakdown at or near nanomaterial. Selected atomic lines of silver are evaluated for a consistent determination of electron density. Comparisons are presented with Balmer series hydrogen results. Measurements free of self-absorption effects [...] Read more.

This work communicates results from optical emission spectroscopy following laser-induced optical breakdown at or near nanomaterial. Selected atomic lines of silver are evaluated for a consistent determination of electron density. Comparisons are presented with Balmer series hydrogen results. Measurements free of self-absorption effects are of particular interest. For several silver lines, asymmetries are observed in the recorded line profiles. Electron densities of interest range from 0.5 to 3 × 10¹⁷ cm⁻³ for five nanosecond Q-switched Nd:YAG radiation at wavelengths of 1064 nm, 532 nm, and 355 nm and for selected silver emission lines including 328.06 nm, 338.28 nm, 768.7 nm, and 827.3 nm and the hydrogen alpha Balmer series line at 656.3 nm. Line asymmetries are presented for the 328.06-nm and 338.28-nm Ag I lines that are measured following generation of the plasma due to multiple photon absorption. This work explores electron density variations for different irradiance levels and reports spectral line asymmetry of resonance lines for different laser fluence levels. Full article

(This article belongs to the Special Issue Stark Broadening of Spectral Lines in Plasmas)

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15 pages, 4164 KiB

Open AccessArticle

Automodel Solutions of Biberman-Holstein Equation for Stark Broadening of Spectral Lines

by Alexander B. Kukushkin, Vladislav S. Neverov, Petr A. Sdvizhenskii and Vladimir V. Voloshinov

Atoms 2018, 6(3), 43; https://doi.org/10.3390/atoms6030043 - 13 Aug 2018

Cited by 6 | Viewed by 2988

Abstract

The accuracy of approximate automodel solutions for the Green’s function of the Biberman-Holstein equation for the Stark broadening of spectral lines is analyzed using the distributed computing. The high accuracy of automodel solutions in a wide range of parameters of the problem is [...] Read more.

The accuracy of approximate automodel solutions for the Green’s function of the Biberman-Holstein equation for the Stark broadening of spectral lines is analyzed using the distributed computing. The high accuracy of automodel solutions in a wide range of parameters of the problem is shown. Full article

(This article belongs to the Special Issue Stark Broadening of Spectral Lines in Plasmas)

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9 pages, 1645 KiB

Open AccessFeature PaperArticle

Interaction of Ultrashort Laser Pulses with Atoms in Plasmas

by V. A. Astapenko and V. S. Lisitsa

Atoms 2018, 6(3), 38; https://doi.org/10.3390/atoms6030038 - 11 Jul 2018

Cited by 3 | Viewed by 2800

Abstract

The paper is devoted to the investigation of the absorption of ultrashort laser pulses on atoms in plasmas, accounting for the different broadening mechanisms of atomic resonant transitions. The analysis is made in terms of the absorption probability during the entire interaction between [...] Read more.

The paper is devoted to the investigation of the absorption of ultrashort laser pulses on atoms in plasmas, accounting for the different broadening mechanisms of atomic resonant transitions. The analysis is made in terms of the absorption probability during the entire interaction between the laser pulse and atom. Attention is mainly given to dependence of probability upon the pulse duration and the carrier frequency of the pulse. The results are presented via dimensionless parameters and functions describing the effect of finite pulse duration on atomic spectra for different broadening mechanisms, namely Doppler, Voigt, Holtsmark and their combinations, as well as the Stark line broadening of Rydberg atomic lines. Full article

(This article belongs to the Special Issue Stark Broadening of Spectral Lines in Plasmas)

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9 pages, 308 KiB

Open AccessFeature PaperArticle

Improving the Method of Measuring the Electron Density via the Asymmetry of Hydrogenic Spectral Lines in Plasmas by Allowing for Penetrating Ions

by Paul Sanders and Eugene Oks

Atoms 2018, 6(2), 21; https://doi.org/10.3390/atoms6020021 - 18 Apr 2018

Cited by 1 | Viewed by 2417

Abstract

There was previously proposed and experimentally implemented a new diagnostic method for measuring the electron density N_e using the asymmetry of hydrogenic spectral lines in dense plasmas. Compared to the traditional method of deducing N_e from the experimental widths of spectral [...] Read more.

There was previously proposed and experimentally implemented a new diagnostic method for measuring the electron density N_e using the asymmetry of hydrogenic spectral lines in dense plasmas. Compared to the traditional method of deducing N_e from the experimental widths of spectral lines, the new method has the following advantages. First, the traditional method requires measuring widths of at least two spectral lines (to isolate the Stark broadening from competing broadening mechanisms), while for the new diagnostic method it is sufficient to obtain the experimental profile of just one spectral line. Second, the traditional method would be difficult to implement if the center of the spectral lines was optically thick, while the new diagnostic method could still be used even in this case. In the theory underlying this new diagnostic method, the contribution of plasma ions to the spectral line asymmetry was calculated only for configurations where the perturbing ions were outside the bound electron cloud of the radiating atom/ion (non-penetrating configurations). In the present paper, we take into account the contribution to the spectral line asymmetry from penetrating configurations, where the perturbing ion is inside the bound electron cloud of the radiating atom/ion. We show that in high-density plasmas, the allowance for penetrating ions can result in significant corrections to the electron density deduced from the spectral line asymmetry. Full article

(This article belongs to the Special Issue Stark Broadening of Spectral Lines in Plasmas)

4 pages, 207 KiB

Open AccessFeature PaperArticle

Correcting the Input Data for Calculating the Asymmetry of Hydrogenic Spectral Lines in Plasmas

by Paul Sanders and Eugene Oks

Atoms 2018, 6(1), 9; https://doi.org/10.3390/atoms6010009 - 06 Mar 2018

Cited by 2 | Viewed by 2604

Abstract

We provide corrections to the data in Sholin’s tables from his paper in Optics and Spectroscopy 26 (1969) 27. Since his data was used numerous times by various authors to calculate the asymmetry of hydrogenic spectral lines in plasmas, our corrections should motivate [...] Read more.

We provide corrections to the data in Sholin’s tables from his paper in Optics and Spectroscopy 26 (1969) 27. Since his data was used numerous times by various authors to calculate the asymmetry of hydrogenic spectral lines in plasmas, our corrections should motivate revisions of the previous calculations of the asymmetry and its comparison with the experimental asymmetry, and thus should have a practical importance. Full article

(This article belongs to the Special Issue Stark Broadening of Spectral Lines in Plasmas)

Review

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69 pages, 6410 KiB

Open AccessReview

Review of Recent Advances in the Analytical Theory of Stark Broadening of Hydrogenic Spectral Lines in Plasmas: Applications to Laboratory Discharges and Astrophysical Objects

by Eugene Oks

Atoms 2018, 6(3), 50; https://doi.org/10.3390/atoms6030050 - 03 Sep 2018

Cited by 11 | Viewed by 3389

Abstract

There is presented an overview of the latest advances in the analytical theory of Stark broadening of hydrogenic spectral lines in various types of laboratory and astrophysical plasmas. They include: (1) advanced analytical treatment of the Stark broadening of hydrogenic spectral lines by [...] Read more.

There is presented an overview of the latest advances in the analytical theory of Stark broadening of hydrogenic spectral lines in various types of laboratory and astrophysical plasmas. They include: (1) advanced analytical treatment of the Stark broadening of hydrogenic spectral lines by plasma electrons; (2) center-of-mass effects for hydrogen atoms in a nonuniform electric field: applications to magnetic fusion, radiofrequency discharges, and flare stars; (3) penetrating-ions-caused shift of hydrogenic spectral lines in plasmas; (4) improvement of the method for measuring the electron density based on the asymmetry of hydrogenic spectral lines in dense plasmas; (5) Lorentz–Doppler broadening of hydrogen/deuterium spectral lines: analytical solution for any angle of observation and any magnetic field strength, and its applications to magnetic fusion and solar physics; (6) Revision of the Inglis-Teller diagnostic method; (7) Stark broadening of hydrogen/deuterium spectral lines by a relativistic electron beam: analytical results and applications to magnetic fusion; (8) Influence of magnetic-field-caused modifications of the trajectories of plasma electrons on shifts and relative intensities of Zeeman components of hydrogen/deuterium spectral lines: applications to magnetic fusion and white dwarfs; (9) Influence of magnetic-field-caused modifications of trajectories of plasma electrons on the width of hydrogen/deuterium spectral lines: applications to white dwarfs; (10) Stark broadening of hydrogen lines in plasmas of electron densities up to or more than N_e~10²⁰ cm⁻³; and, (11) The shape of spectral lines of two-electron Rydberg atoms/ions: a peculiar Stark broadening. Full article

(This article belongs to the Special Issue Stark Broadening of Spectral Lines in Plasmas)

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15 pages, 2631 KiB

Open AccessReview

Mini-Review of Intra-Stark X-ray Spectroscopy of Relativistic Laser–Plasma Interactions

by Elisabeth Dalimier, Tatiana A. Pikuz and Paulo Angelo

Atoms 2018, 6(3), 45; https://doi.org/10.3390/atoms6030045 - 16 Aug 2018

Cited by 7 | Viewed by 2941

Abstract

Intra-Stark spectroscopy (ISS) is the spectroscopy within the quasi-static Stark profile of a spectral line. The present paper reviews the X-ray ISS-based studies recently advanced for the diagnostics of the relativistic laser–plasma interactions. By improving experiments performed on the Vulcan Petawatt (PW) laser [...] Read more.

Intra-Stark spectroscopy (ISS) is the spectroscopy within the quasi-static Stark profile of a spectral line. The present paper reviews the X-ray ISS-based studies recently advanced for the diagnostics of the relativistic laser–plasma interactions. By improving experiments performed on the Vulcan Petawatt (PW) laser facility at the Rutherford Appleton Laboratory (RAL), the simultaneous production of the Langmuir waves and of the ion acoustic turbulence at the surface of the relativistic critical density gave the first probe by ISS of the parametric decay instability (PDI) predicted by PIC simulations. The reliable reproducibility of the experimental signatures of PDI—i.e., the Langmuir-wave-induced dips—allowed measurements of the fields of the Langmuir and ion acoustic waves. The parallel theoretical study based on a rigorous condition of the dynamic resonance depending on the relative values of the ion acoustic and the Langmuir fields could explain the disappearance of the Langmuir dips as the Langmuir wave field increases. The ISS used for the diagnostic of the PDI process in relativistic laser–plasma interactions has reinforced the reliability of the spectral line shape while allowing for all broadening mechanisms. The results can be used for a better understanding of intense laser–plasma interactions and for laboratory modelling of physical processes in astrophysical objects. Full article

(This article belongs to the Special Issue Stark Broadening of Spectral Lines in Plasmas)

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17 pages, 2985 KiB

Open AccessFeature PaperReview

Laboratory Hydrogen-Beta Emission Spectroscopy for Analysis of Astrophysical White Dwarf Spectra

by Christian G. Parigger, Kyle A. Drake, Christopher M. Helstern and Ghaneshwar Gautam

Atoms 2018, 6(3), 36; https://doi.org/10.3390/atoms6030036 - 01 Jul 2018

Cited by 26 | Viewed by 6689

Abstract

This work communicates a review on Balmer series hydrogen beta line measurements and applications for analysis of white dwarf stars. Laser-induced plasma investigations explore electron density and temperature ranges comparable to white dwarf star signatures such as Sirius B, the companion to the [...] Read more.

This work communicates a review on Balmer series hydrogen beta line measurements and applications for analysis of white dwarf stars. Laser-induced plasma investigations explore electron density and temperature ranges comparable to white dwarf star signatures such as Sirius B, the companion to the brightest star observable from the earth. Spectral line shape characteristics of the hydrogen beta line include width, peak separation, and central dip-shift, thereby providing three indicators for electron density measurements. The hydrogen alpha line shows two primary line-profile parameters for electron density determination, namely, width and shift. Both Boltzmann plot and line-to-continuum ratios yield temperature. The line-shifts recorded with temporally- and spatially-resolved optical emission spectroscopy of hydrogen plasma in laboratory settings can be larger than gravitational redshifts that occur in absorption spectra from radiating white dwarfs. Published astrophysical spectra display significantly diminished Stark or pressure broadening contributions to red-shifted atomic lines. Gravitational redshifts allow one to assess the ratio of mass and radius of these stars, and, subsequently, the mass from cooling models. Full article

(This article belongs to the Special Issue Stark Broadening of Spectral Lines in Plasmas)

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