Neutral cluster debris dynamics in droplet-based laser-produced plasma sources

Hudgins, Duane; Gambino, N.; Rollinger, Bob; Abhari, Reza S.

doi:10.1088/0022-3727/49/18/185205

Cited by 29 publications

(22 citation statements)

References 48 publications

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“…The thermodynamic and radiation transport properties, particularly of high-Z laser-produced plasmas (LPPs), are extremely challenging to measure because of the transient nature of these plasmas, combined with complex equations of state and atomic plasma processes. One thermodynamic variable -the pressure -can however be elegantly obtained by measuring the propulsion velocity of metallic liquid microdroplets as a result of a laserpulse impact 11,12 . In an industrially relevant setting for EUV light production such droplets are irradiated by relatively long (∼ 10-100 ns) laser pulses at modest intensities (∼ 10 9 -10 12 W/cm 2 ), where the laser absorption takes place mostly through the inverse bremsstrahlung mechanism.…”

Section: Introductionmentioning

confidence: 99%

Power-law scaling of plasma pressure on laser-ablated tin microdroplets

et al. 2018

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The measurement of the propulsion of metallic microdroplets exposed to nanosecond laser pulses provides an elegant method for probing the ablation pressure in dense laser-produced plasma. We present the measurements of the propulsion velocity over three decades in the driving Nd:YAG laser pulse energy, and observe a near-perfect power law dependence. Simulations performed with the RALEF-2D radiation-hydrodynamic code are shown to be in good agreement with the power law above a specific threshold energy. The simulations highlight the importance of radiative losses which significantly modify the power of the pressure scaling. Having found a good agreement between the experiment and the simulations, we investigate the analytic origins of the obtained power law and conclude that none of the available analytic theories is directly applicable for explaining our power exponent.

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Section: Introductionmentioning

confidence: 99%

Power-law scaling of plasma pressure on laser-ablated tin microdroplets

et al. 2018

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“…With the intensity profile at R eff at hand, we now obtain an expression for the plasma ablation pressure p a acting on this surface. A power-law dependence between this pressure and the impinging laser pulse energy has been established in previous work 8,11,16 , and experimentally shown to be valid to excellent accuracy over three orders of magnitude in laser energy 8,16 ,…”

Section: Modelmentioning

confidence: 71%

“…Our approach differs from the one presented in Ref. [11] as we include the full pressure distribution on the surface of the droplet, see Eqs. (3).…”

Section: Modelmentioning

confidence: 99%

“…Maximizing the conversion efficiency (CE) of laser light into the required EUV light of such sources requires a careful control over the target shape. This shape is very sensitive to the precise alignment of the prepulse laser to the initially spherical droplet 10,11 . Any deviation from the optimum location for laser impact will produce a suboptimal target tilt and decrease the target radial expansion, as shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, reflections of the laser light from the incorrectly tilted surface of the target back towards the laser itself may be detrimental to laser operation stability. In spite of its obvious relevance, the precise relation between such laser-to-droplet (L2D) alignment and the resulting target tilt has so far remained poorly explored aside from activities by Tsygvintsev et al 12 and the recent work by Hudgins et al 11 who combine modeling with experimental efforts. Due to experimental constraints, however, their model predictions for the tilt sensitivity could not be validated under conditions of controlled misalignment.…”

Section: Introductionmentioning

confidence: 99%

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Laser-to-droplet alignment sensitivity relevant for laser-produced plasma sources of extreme ultraviolet light

Reijers

Kurilovich

Torretti

et al. 2018

Journal of Applied Physics

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We present and experimentally validate a model describing the sensitivity of the tilt angle, expansion and propulsion velocity of a tin micro-droplet irradiated by a 1 µm Nd:YAG laser pulse to its relative alignment. This sensitivity is particularly relevant in industrial plasma sources of extreme ultraviolet light for nanolithographic applications. Our model has but a single parameter: the dimensionless ratio of the laser spot size to the effective size of the droplet, which is related to the position of the plasma critical density surface. Our model enables the development of straightforward scaling arguments in turn enabling precise control the alignment sensitivity.

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Acceleration of metal drops in a laser beam

et al. 2020

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Different processes require the detachment of metal drops from a solid material using a laser beam as the heat source, for instance laser drop generation or cyclam. These techniques imply that the drops enter the laser beam, which might affect their trajectory. Also, many laser processes such as laser welding or additive manufacturing generate spatters that can be accelerated by the laser beam during flight and create defects on the material. This fundamental study aims at investigating the effects of a continuous power laser beam on the acceleration of intentionally detached drops and unintentionally detached spatters. Two materials were studied: 316L steel and AlSi5 aluminium alloy. High-speed imaging was used to measure the position of the drops and calculate their acceleration to compare it to theoretical models. Accelerations up to 11.2 g could be measured. The contributions of the vapor pressure, the recoil pressure, and the radiation pressure were investigated. The recoil pressure was found to be the main driving effect but other phenomena counteract this acceleration and reduce it by an order of magnitude of one to two. In addition, two different vaporization regimes were observed, resulting respectively in a vapor plume and in a vapor halo around the drop.

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Neutral cluster debris dynamics in droplet-based laser-produced plasma sources

Cited by 29 publications

References 48 publications

Power-law scaling of plasma pressure on laser-ablated tin microdroplets

Power-law scaling of plasma pressure on laser-ablated tin microdroplets

Laser-to-droplet alignment sensitivity relevant for laser-produced plasma sources of extreme ultraviolet light

Acceleration of metal drops in a laser beam

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