Anastassiya Suslova - Academia.edu (original) (raw)

Papers by Anastassiya Suslova

Submitted for the DPP17 Meeting of The American Physical Society Multi-dimensional simulation pac... more Submitted for the DPP17 Meeting of The American Physical Society Multi-dimensional simulation package for ultrashort pulse lasermatter interactions 1 ANASTASSIYA SUSLOVA, AHMED HASSANEIN, Purdue Univ-Advanced simulation models recently became a popular tool of investigation of ultrashort pulse lasers (USPLs) to enhance understanding of the physics and allow minimizing the experimental costs for optimization of laser and target parameters for various applications. Our research interest is focused on developing multi-dimensional simulation package FEMTO-2D to investigate the USPL-matter interactions and laser induced effects. The package is based on solution of two heat conduction equations for electron and lattice subsystems enhanced two temperature model (TTM). We have implemented theoretical approach based on the collision theory to define the thermal dependence of target material optical properties and thermodynamic parameters. Our approach allowed elimination of fitted parameters commonly used in TTM based simulations. FEMTO-2D is used to simulated the light absorption and interactions for several metallic targets as a function of wavelength and pulse duration for wide range of laser intensity. The package has capability to consider different angles of incidence and polarization. It has also been used to investigate the damage threshold of the gold coated optical components with the focus on the role of the film thickness and substrate heat sink effect.

Journal of Laser Applications, 2018

The properties of laser ablation of metallic targets with ultrashort single and double pulses wit... more The properties of laser ablation of metallic targets with ultrashort single and double pulses with a similar total energy were investigated for two target materials: silver and copper. The numerical analysis was performed using the developed FEMTO-2D computer package developed by the authors based on the solution of a two-temperature model. The thermal dependence of the target optical and thermodynamic processes and their role in the overall target response to dual pulse laser irradiation were carefully considered. The ablation rate for a dual pulse laser machining at the optimal pulse separation time was found to be similar (for silver) or above (for copper) the ablation rate for a single pulse machining for the same total fluence. The advantages of using dual pulse laser micromachining are reduced maximum electron temperature and increased lattice temperature in the ablated region predicted by the model developed by the authors.

Laser and Particle Beams, 2018

Integrated simulation results of femtosecond laser ablation of copper were compared with new expe... more Integrated simulation results of femtosecond laser ablation of copper were compared with new experimental data. The numerical analysis was performed using our newly developed FEMTO-2D computer package based on the solution of the two-temperature model. Thermal dependence of target optical and thermodynamic processes was carefully considered. The experimental work was conducted with our 40 fs 800 nm Ti:sapphire laser in the energy range from 0.14 mJ to 0.77 mJ. Comparison of measured ablation profiles with simulation predictions based on phase explosion criterion has demonstrated that more than one ablation mechanisms contribute to the total material removal even in the laser intensity range where explosive boiling is dominating. Good correlation between experimental and simulation results was observed for skin depth and hot electron diffusion depth – two parameters commonly considered to identify two ablation regimes in metal. Analysis of the development dynamics for electron–lattic...

Applied Surface Science, 2017

Highlights  FEMTO-2D simulation code developed for 2-dimensional 2-layered target configuration.... more Highlights  FEMTO-2D simulation code developed for 2-dimensional 2-layered target configuration.  Thermal dependent optical properties for Au calculated based on collision theory.  Thermal dependent thermal physical properties calculated based on collision theory.  The minimum and maximum Au film thickness determined for substrate heat sink effect.  10% damage threshold improvement found for Ni and Cu substrates for 50 nm Au film.

Laser and Particle Beams, 2017

The interaction of femtosecond laser with initially cold solid metallic targets (Al, Au, Cu, Mo, ... more The interaction of femtosecond laser with initially cold solid metallic targets (Al, Au, Cu, Mo, Ni) was investigated in a wide range of laser intensity with focus on the laser energy absorption efficiency. Our developed simulation code (FEMTO-2D) is based on two-temperature model in two-dimensional configuration, where the temperature-dependent optical and thermodynamic properties of the target material were considered. The role of the collisional processes in the ultrashort pulse laser–matter interaction has been carefully analyzed throughout the process of material transition from the cold solid state into the dense plasma state during the pulse. We have compared the simulation predictions of the laser pulse absorption with temperature-dependent reflectivity and optical penetration depth to the case of constant optical parameters. By considering the effect of the temporal and spatial (radial) distribution of the laser intensity on the light absorption efficiency, we obtained a go...

2014 IEEE 41st International Conference on Plasma Sciences (ICOPS) held with 2014 IEEE International Conference on High-Power Particle Beams (BEAMS), 2014

Tungsten (W) has been selected as a plasma-facing component (PFC) material in the activated phase... more Tungsten (W) has been selected as a plasma-facing component (PFC) material in the activated phase of ITER. High melting point and thermal conductivity and low erosion rate and low tritium inventory are the major advantages of W material, which makes it suitable for plasma fusion technology. However, ductile-to-brittle transition is also a major drawback of W, which could produce large macroscopic particles as well as small dust particles. The emission of dust particles from W are found to persist for longer duration compared to plasma lifetime with velocities of several tens m/s. The lifetime of the PFCs also depends on ELMs, VDEs, disruptions and runaway electrons.

Nuclear Fusion, 2015

ABSTRACT We investigated the effect of edge-localized mode like transient heat events on pristine... more ABSTRACT We investigated the effect of edge-localized mode like transient heat events on pristine samples for two different grades of deformed tungsten with ultrafine and nanocrystalline grains as potential candidates for plasma-facing components. Pulses from a laser beam with durations ~1 ms and operating in the near infrared wavelength were used for simulating transient heat loading in fusion devices. We specifically focused on investigating and analysis of different mechanisms for material removal from the sample surface under repetitive transient heat loads. Several techniques were applied for analysing different mechanisms leading to material removal from the W surface under repetitive transient heat loads which include witness plates for collected ejected material, and subsequent analysis using x-ray photoelectron spectroscopy and scanning electron microscopy, visible imaging using fast-gated camera, and evaluating thermal emission from the particles using optical emission spectroscopy. Our results show a significantly improved performance of polycrystalline cold-rolled tungsten compared to tungsten produced using an orthogonal machining process under repetitive transient loads for a wide range of the power densities.

Materials Characterization, 2015

Plasma facing components for future fusion applications will experience heliumand neutron-induced... more Plasma facing components for future fusion applications will experience heliumand neutron-induced structural damage. Direct observation of the in-situ dynamic response of such components during particle beam exposure assists in fundamental understanding of the physical phenomena that give rise to their irradiation resistance. We investigated the response of ultrafine and nanocrystalline-grained tungsten to 3 MeV heavy ion irradiations (Si 2+ , Cu 3+ and W 4+) for the simulation of neutron-induced damage through transmutation reactions via in-situ ion irradiation-transmission electron microscopy experiments. Defect densities as a function of irradiation dose (displacement per atom) and fluence were studied. Four stages of defect densities evolution were observed, as a function of irradiation dose: 1) increase in defect density at lower doses 2) higher defect production rate at the intermediate doses (before saturation), 3) reaching the maximum value, and 4) drop of the defect density in the case of W 4+ , possibly due to defect coalescence and grain boundary absorption of small defect clusters. The effect of grain size on defect densities were investigated and found that defect densities were

MRS Proceedings, 2014

ABSTRACTMany theoretical predictions have suggested that the confined length scales and increased... more ABSTRACTMany theoretical predictions have suggested that the confined length scales and increased interface density of various nanostructured materials may result in desired thermal, mechanical, and radiation properties. An important aspect of this for next generation nuclear reactors is understanding the change in swelling resulting from helium evolution in tungsten alloys, as a function of grain size and grain boundary type. This study investigated this using a new ion irradiation transmission electron microscope (TEM) facility that has been developed at Sandia National Laboratories and is capable of ion implanting helium at energies up to 20 keV. It was demonstrated in this feasibility study that helium could be implanted into an ultrafine grained tungsten TEM sample produced by severe plastic deformation. The size and density of the helium bubbles formed during the experiment appear nearly constant; while the larger voids formed appear to be dependent on the local microstructure...

Scientific Reports, 2014

Tungsten has been chosen as the main candidate for plasma facing components (PFCs) due to its sup... more Tungsten has been chosen as the main candidate for plasma facing components (PFCs) due to its superior properties under extreme operating conditions in future nuclear fusion reactors such as ITER. One of the serious issues for PFCs is the high heat load during transient events such as ELMs and disruption in the reactor. Recrystallization and grain size growth in PFC materials caused by transients are undesirable changes in the material, since the isotropic microstructure developed after recrystallization exhibits a higher ductile-to-brittle transition temperature which increases with the grain size, a lower thermal shock fatigue resistance, a lower mechanical strength, and an increased surface roughening. The current work was focused on careful determination of the threshold parameters for surface recrystallization, grain growth rate, and thermal shock fatigue resistance under ELM-like transient heat events. Transient heat loads were simulated using long pulse laser beams for two different grades of ultrafine-grained tungsten. It was observed that cold rolled tungsten demonstrated better power handling capabilities and higher thermal stress fatigue resistance compared to severely deformed tungsten. Higher recrystallization threshold, slower grain growth, and lower degree of surface roughening were observed in the cold rolled tungsten. T ungsten was selected as the main candidate for plasma facing components (PFCs) in the magnetic confinement nuclear fusion reactors of the International Thermonuclear Experimental Reactor (ITER), due to its high thermal conductivity 1 , low tritium retention 2,3 , low sputtering yield 4,5 , low erosion rate 5,6 , and high neutron load capacity 7 , which all together can result in longer component lifetime 8. Tungsten was also proposed as a promising structural material candidate for the Demonstration Power Plant (DEMO) reactor for the high temperature wall operation regime using helium cooled design 3. Significant research efforts were focused on detailed investigations of issues and concerns resulting from plasma-tungsten interactions, and the limitations to use tungsten in future fusion reactors. The list of issues includes erosion by energetic ions and neutral atoms from the plasma 6 , helium bubble formation 9 , blistering, swelling 10 , crack formation, tritium retention 2 , and etc. 8. One of the serious issues for PFCs is the heat load accompanied by transient events such as edge-localized-modes (ELMs) and disruptions in the reactor. These transient events lead to a significant temperature rise above the normal operating temperature of the reactor and cause high thermal stresses in PFCs. High temperature gradient and high thermal stresses developed during transients can lead to material recrystallization and grain growth, formation of a melt layer, material erosion, and crack formation. Therefore, can limit the power handling capacity of PFCs, decrease their lifetime, and lead to plasma contamination that affects subsequent operations. In order to study the effect of ELMs on PFCs, plasma guns 4,11,12 , quasi-steady-state plasma accelerators 13,14 , electron beams 15-17 , and long pulse lasers 18,19 have been used to simulate transient reactor conditions. The mechanisms leading to material erosion, crack formation and surface melting under ELMs-like transient heat events in different tungsten grades were investigated in detail by several groups 19-22. However, limited information is available about recrystallization and grain growth processes under ELMs-like transient heat events. Recrystallization and grain size growth in PFC materials can be a critical issue, since the isotropic microstructure developed after recrystallization exhibits a higher ductile-to-brittle transition temperature (DBTT) which increases with the grain size 23 , a lower thermal shock fatigue resistance, a lower mechanical strength, and an increased surface roughening 21,22. The goal of this work was to examine the performance of two types of ultrafinegrained tungsten materials to high ELMs-like transient heat events. The use of ultrafine-grained materials as a

MRS Proceedings, 2011

ABSTRACTIon-beam sputtering (IBS) has been studied as a means for scalable, mask-less nanopattern... more ABSTRACTIon-beam sputtering (IBS) has been studied as a means for scalable, mask-less nanopatterning of surfaces. Patterning at the nanoscale has been achieved for numerous types of materials including: semiconductors, metals and insulators. Although much work has been focused on tailoring nanopatterning by systematic ion-beam parameter manipulation, limited work has addressed elucidating on the underlying mechanisms for self-organization of multi-component surfaces. In particular there has been little attention to correlate the surface chemistry variation during ion irradiation with the evolution of surface morphology and nanoscale self-organization. Moreover the role of surface impurities on patterning is not well known and characterization during the time-scale of modification remains challenging. This work summarizes an in-situ approach to characterize the evolution of surface chemistry during irradiation and its correlation to surface nanopatterning for a variety of multi-compo...

Microscopy and Microanalysis, 2012

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, ... more Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Journal of Applied Physics, 2011

A systematic study is conducted in order to elucidate the underlying mechanism(s) for nanopattern... more A systematic study is conducted in order to elucidate the underlying mechanism(s) for nanopatterning with low-energy irradiation of GaSb (100) under normal incidence. Ion energies between 50 and 1000 eV of Arþ and ion fluences of up to 10 18 cm À2 were employed. Characterization of the shallow (e.g., 1 to 6 nm) amorphous phase region induced by irradiation and the subsurface crystalline phase region is accomplished with low-energy ion scattering spectroscopy and x-ray photoelectron spectroscopy, respectively. In situ studies are conducted due to the strong chemical affinity for oxygen of GaSb. The studies conclude that at energies below 200 eV, the native oxide layer hampers nanopatterning until it becomes removed at a fluence of approximately 5 Â 10 16 cm À2. At this energy and threshold fluence, the surface is enriched with Ga atoms during irradiation. At energies above 200 eV, the native oxide layer is efficiently removed in the early irradiation stages, and thus the detrimental effects from the oxide on nanopatterning are negligible. In situ surface concentration quantification indicates that the surface enrichment with Sb atoms in the amorphous phase layer increases with the incident ion energy. Post-air exposure characterization reveals that the measured enrichment of the surface with gallium is due to oxygen reduction by Ga atoms segregated from both the amorphous and the crystalline phase regions as a result of air exposure. V

Journal of Applied Physics, 2013

We investigated the effect of silicide formation on ion-induced nanopatterning of silicon with va... more We investigated the effect of silicide formation on ion-induced nanopatterning of silicon with various ultrathin metal coatings. Silicon substrates coated with 10 nm Ni, Fe, and Cu were irradiated with 200 eV argon ions at normal incidence. Real time grazing incidence small angle x-ray scattering (GISAXS) and x-ray fluorescence (XRF) were performed during the irradiation process and real time measurements revealed threshold conditions for nanopatterning of silicon at normal incidence irradiation. Three main stages of the nanopatterning process were identified. The real time GISAXS intensity of the correlated peaks in conjunction with XRF revealed that the nanostructures remain for a time period after the removal of the all the metal atoms from the sample depending on the binding energy of the metal silicides formed. Ex-situ XPS confirmed the removal of all metal impurities. In-situ XPS during the irradiation of Ni, Fe, and Cu coated silicon substrates at normal incidence demonstrated phase separation and the formation of different silicide phases that occur upon metal-silicon mixing. Silicide formation leads to nanostructure formation due the preferential erosion of the non-silicide regions and the weakening of the ion induced mass redistribution. V

Applied Physics Letters, 2012

We have investigated the influence of native oxides on ion-sputtering-induced nanostructure forma... more We have investigated the influence of native oxides on ion-sputtering-induced nanostructure formation on GaSb using in situ low energy ion scattering spectroscopy (LEISS) and X-ray photoelectron spectroscopy (XPS). Comparing an oxygen-free sample with a native oxide sample, LEISS and XPS reveal the effect of oxygen in generating higher surface Ga fractions during early stages (fluences of 1 Â 10 15-1 Â 10 16 cm À2) of low energy (<100 eV) Arþ irradiation. Enhanced surface Ga and Ga 2 O 3 fractions were also observed on "oxide free" samples exposed to air following irradiation. The results suggest preferential Ga oxidation and segregation on the top of the amorphous layer if oxygen is present on the surface. In addition, the native oxide also increases the fluence threshold for nanopatterning of GaSb surfaces by almost a factor of four during low energy irradiation. V

Journal of Applied Physics, 2018

The role of ballistic electrons generated during ultrashort pulse laser (USPL) absorption in meta... more The role of ballistic electrons generated during ultrashort pulse laser (USPL) absorption in metallic targets was investigated in a wide range of laser intensities using our developed simulation package FEMTO-2D. The simulation package is based on the numerical solution of the two-temperature model with the assumption of local thermal equilibrium for electron and lattice subsystems within the simulation cell at any time step. Electron thermodynamic parameters were calculated through the processes of material transition from the cold solid state into the dense plasma state during and after the pulse based on the collision theory. The appropriate model for temperature dependent thermodynamic parameters allows defining the heat transport during an early stage of the USPL-matter interaction directly, without relying on the effective absorption depth model. The study investigated, for the first time, using integrated computer simulation the role of ballistic electrons in energy transfer and heat conduction during USPL deposition. The simulation predictions of the electron heat transport dynamics during and shortly after the laser pulse were benchmarked for the gold target against available experimental data and were able to confirm the dominant role of the ballistic electrons in the initial heat propagation within 100-120 nm of the target at laser intensities below 10 13 W/cm 2 .