Target geometrical effects on the stagnation layer formed by colliding a pair of laser produced copper plasmas

Fallon, C.; Hayden, P.; Walsh, N.; Kennedy, E. T.; Costello, J. T.

doi:10.1063/1.4930204

Cited by 19 publications

(10 citation statements)

References 33 publications

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“…Accretion and compression of the material within the SL leads to a local increase in density and temperature. The degree of stagnation can be described by a collisionality parameter ξ = d/λ ii , where d is the distance between the two plasmas and λ ii is the ion-other ion mean free path, given by, [65,66]…”

Section: Discussionmentioning

confidence: 99%

“…Accretion and compression of the material within the SL leads to a local increase in density and temperature. The degree of stagnation can be described by a collisionality parameter ξ = d / λ ii , where d is the distance between the two plasmas and λ ii is the ion-other ion mean free path, given by, [ 65 , 66 ]

where ε 0 is the permittivity of free space, m i is the ion mass,

is the relative ion flow velocity (prior to impact), q is the elementary charge, Z is the average ionisation state, n i is the plasma density at the collision plane and ln (Λ 1–2 ) is the Coulomb Logarithm, a slowly varying function, with a value O (10–20) [ 67 ]. The parameter ξ is very sensitive to the relative plasma velocity term

4 while only linearly dependent on separation d. If used in ambient air, this description is more complex than in vacuum due to the presence of shock waves and rapid plasma deceleration due to collisions with the air.…”

Section: Discussionmentioning

confidence: 99%

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Backward Flux Re-Deposition Patterns during Multi-Spot Laser Ablation of Stainless Steel with Picosecond and Femtosecond Pulses in Air

et al. 2021

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We report on novel observations of directed re-deposition of ablation debris during the ultrafast laser micro-structuring of stainless steel in the air with multi-beams in close proximity on the surface. This interesting phenomenon is observed with both 10 ps and 600 fs NIR laser pulses at 5 kHz repetition rate. Ablation spot geometries could be altered with the use of beam splitting optics or a phase-only Spatial Light modulator. At low fluence (F ~ 1.0 J cm−2) and pulse exposure of a few hundred pulses, the debris appears as concentrated narrow “filaments” connecting the ablation spots, while at higher fluence, (F ~ 5.0 J cm−2) energetic jets of material emanated symmetrically along the axes of symmetry, depositing debris well beyond the typical re-deposition radius with a single spot. Patterns of backward re-deposition of debris to the surface are likely connected with the colliding shock waves and plasma plumes with the ambient air causing stagnation when the spots are in close proximity. The 2D surface debris patterns are indicative of the complex 3D interactions involved over wide timescales during ablation from picoseconds to microseconds.

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Section: Discussionmentioning

confidence: 99%

“…Accretion and compression of the material within the SL leads to a local increase in density and temperature. The degree of stagnation can be described by a collisionality parameter ξ = d / λ ii , where d is the distance between the two plasmas and λ ii is the ion-other ion mean free path, given by, [ 65 , 66 ]

where ε 0 is the permittivity of free space, m i is the ion mass,

Section: Discussionmentioning

confidence: 99%

Backward Flux Re-Deposition Patterns during Multi-Spot Laser Ablation of Stainless Steel with Picosecond and Femtosecond Pulses in Air

et al. 2021

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“…of different target geometries ( lateral collision, orthogonal collision etc.) and also different laser pulse durations (femtosecond to nanosecond) [11][12][13][14][15]. Stagnation layer and its properties attract the curiosity of many researchers and it still requires further investigation to understand the complex physical processes underlying in it.…”

Section: Introductionmentioning

confidence: 99%

Study of stagnation layer of laterally colliding laser produced aluminium plasmas

Shilpa

Gopinath

2022

IOP Conf. Ser.: Mater. Sci. Eng.

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When two dense laser produced plasmas collide, a layer of plasma stagnates at the collision front exhibiting special properties, is called stagnation layer. The characteristics of stagnation layer formed due to the collision of two laser produced aluminium plasmas were studied using spectroscopic and the fast imaging techniques. Time gated Intensified Charge Coupled Device (ICCD) imaging was used to study the temporal evolution of stagnation region and time resolved spectroscopy was used to obtain information about the distribution of neutral as well as the ionic species in collision process of laterally colliding aluminum plasmas. Electron density and temperature of the stagnation layer were also calculated from the emission spectra. The overall experiment results clearly depict the peculiar properties of stagnation layer which is more advantageous than the conventional laser produced plasma.

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“…To specifically investigate the effect of increased collisional mean-free paths in plasma collisions, dedicated experiments have been designed, aiming at reproducing that interaction in a more controllable way [9][10][11][12][13][14]. To specifically study the interaction of the ablator and hohlraum case materials, an experimental setup has recently been used [15], which involves the ablative expansion of a carbon plasma and a gold plasma facing each other, initially separated by an adjustable amount of helium gas.…”

Section: Introductionmentioning

confidence: 99%

An extended hydrodynamics model for inertial confinement fusion hohlraums

Larroche

2021

Preprint

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In some inertial confinement fusion hohlraum designs, the inside plasma is not sufficiently collisional to be satisfactorily described by the Euler equations implemented in hydrodynamic simulation codes, particularly in converging regions of the expanding plasma flow. To better treat that situation, this paper presents an extended hydrodynamics model including higher moments of the particle velocity distribution function, together with physically justified closure assumptions and relaxation terms. A preliminary one-dimensional numerical implementation of the model is shown to give satisfactory results in a test case involving a high-velocity collision of two plasma flows. Paths to extend that model to three dimensions as needed for an actual hohlraum geometry are briefly discussed.

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Target geometrical effects on the stagnation layer formed by colliding a pair of laser produced copper plasmas

Cited by 19 publications

References 33 publications

Backward Flux Re-Deposition Patterns during Multi-Spot Laser Ablation of Stainless Steel with Picosecond and Femtosecond Pulses in Air

Backward Flux Re-Deposition Patterns during Multi-Spot Laser Ablation of Stainless Steel with Picosecond and Femtosecond Pulses in Air

Study of stagnation layer of laterally colliding laser produced aluminium plasmas

An extended hydrodynamics model for inertial confinement fusion hohlraums

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