Surface Morphology of Refractory Metals Submitted to a Single Laser Pulse

2021 ◽  
Vol 1016 ◽  
pp. 1526-1531
Author(s):  
Pasquale Gaudio ◽  
Roberto Montanari ◽  
Ekaterina Pakhomova ◽  
Maria Richetta ◽  
Alessandra Varone
Keyword(s):  
Laser Pulse ◽  
Central Area ◽  
High Energy ◽  
Heat Propagation ◽  
Refractory Metals ◽  
Surrounding Area ◽  
Microstructural Characteristics ◽  
Plasma Facing Materials ◽  
Transient Thermal ◽  
Specific Metal

The work investigates refractory metals (bulk W, W produced via plasma spraying, W-1% La2O3 and Mo) of interest as plasma facing materials in future nuclear fusion reactors. They have been irradiated by a single Nd:YAG laser pulse to simulate the effects of transient thermal loads of high energy occurring in a tokamak under operative conditions and then examined by SEM observations. In all the materials the laser pulse induces a crater in the central area of laser spot surrounded by a ridge due to movement of molten metal while in a more external area a network of cracks is observed. Diameter and depth of the crater, ablated volume and morphological features of the surrounding area exhibit differences depending on the specific metal, its physical and microstructural characteristics which affect vaporization, melting and heat propagation from the irradiated spot.

scholarly journals Surface Morphological Features of Molybdenum Irradiated by a Single Laser Pulse

Coatings ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 67 ◽  
Author(s):  
Roberto Montanari ◽  
Ekaterina Pakhomova ◽  
Riccardo Rossi ◽  
Maria Richetta ◽  
Alessandra Varone
Keyword(s):  
Laser Pulse ◽  
Thermal Stresses ◽  
High Energy ◽  
Single Laser Pulse ◽  
Critical Aspect ◽  
Surrounding Area ◽  
Glass Laser ◽  
Single Laser ◽  
Lower Viscosity ◽  
Transient Thermal

Molybdenum (Mo) is considered a plasma facing material alternative to tungsten (W) for manufacturing the divertor armours of International Thermonuclear Experimental Reactor (ITER). Transient thermal loads of high energy occurring in a tokamak during the service life have been simulated through a single laser pulse delivered by a Nd:YAG/Glass laser, and the effects have then been examined through scanning electron microscopy (SEM) observations. An erosion crater forms in correspondence with the laser spot due to the vaporization and melting of the metal, while all around a network of cracks induced by thermal stresses is observed. The findings have been compared to results of similar experiments on W and literature data. The morphology of the crater and the surrounding area is different from that of W: the crater is larger and shallower in the case of Mo, while its walls are characterized by long filaments, not observed in W, because the lower viscosity and surface tension of Mo allow an easier flow of the liquid metal. Most importantly, the volume of Mo ablated from the surface by the single laser pulse is about ten times that of W. This critical aspect is of particular relevance and leads us to conclude that W remains the best solution for manufacturing the armours of the ITER divertor.

Laser Pulse Simulation of High Energy Transient Thermal Loads on Bulk and Plasma Sprayed W for NFR

2016 ◽  
Vol 879 ◽  
pp. 1576-1581 ◽  
Author(s):  
Maria Richetta ◽  
Pasquale Gaudio ◽  
Roberto Montanari ◽  
Ekaterina Pakhomova ◽  
Luca Antonelli
Keyword(s):  
Laser Pulse ◽  
Focal Plane ◽  
Focal Spot ◽  
Spot Size ◽  
High Energy ◽  
Fusion Reactors ◽  
Thermal Loads ◽  
Focal Spot Size ◽  
Plasma Sprayed ◽  
Transient Thermal

W is a plasma-facing material candidate for applications in future nuclear fusion reactors (NFR). In this work transient thermal loads of high energy have been simulated by interaction with a single laser pulse. The experiments have been carried out by using the Nd:Glass TVLPS laser working in first harmonic (wavelength λ = 1064 nm); the pulse parameters are: energy E ≈ 8 J, pulse duration ∆t ≈ 15 ns, focal spot size Φ = 200 μm, surface power density on the focal plane I = 1.7 x 1012 W/cm2.The damage produced by the laser pulse on the surface of bulk and plasma sprayed W has been investigated by Scanning Electron Microscopy (SEM) observations. The preliminary results will be presented.

scholarly journals Signatures of the Carrier Envelope Phase in Nonlinear Thomson Scattering

Crystals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 528
Author(s):  
Marcel Ruijter ◽  
Vittoria Petrillo ◽  
Thomas C. Teter ◽  
Maksim Valialshchikov ◽  
Sergey Rykovanov
Keyword(s):  
Laser Pulse ◽  
Radiation Spectrum ◽  
Thomson Scattering ◽  
High Energy ◽  
Phase Changes ◽  
High Energy Radiation ◽  
Carrier Envelope Phase ◽  
High Intensity Laser ◽  
Experimental Parameters ◽  
Intensity Laser

High-energy radiation can be generated by colliding a relativistic electron bunch with a high-intensity laser pulse—a process known as Thomson scattering. In the nonlinear regime the emitted radiation contains harmonics. For a laser pulse whose length is comparable to its wavelength, the carrier envelope phase changes the behavior of the motion of the electron and therefore the radiation spectrum. Here we show theoretically and numerically the dependency of the spectrum on the intensity of the laser and the carrier envelope phase. Additionally, we also discuss what experimental parameters are required to measure the effects for a beamed pulse.

Measurement of Interface Strength by Laser Pulse induced Spallation

1990 ◽  
Vol 188 ◽  
Author(s):  
V. Gupta ◽  
A. S. Argon
Keyword(s):  
Free Surface ◽  
Laser Pulse ◽  
Pressure Pulse ◽  
Stress Amplitude ◽  
Threshold Level ◽  
High Energy ◽  
Piezoelectric Crystal ◽  
Critical Amplitude ◽  
Laser Spallation ◽  
Simulation Process

ABSTRACTThe strength of planar interfaces between a substrate and a thin coating (1–2 µm) can be measured quite effectively by a laser spallation technique. In this technique a laser pulse of a high energy and a predetermined length is converted into a pressure pulse of a critical amplitude and width that is sent through the substrate toward the free surface with the coating. The compressive pressure pulse is reflected into a tension pulse from the free surface of the coating and loads the coating/substrate interface in tension. The laser flux is tuned to a threshold level at which the interface comes apart. The critical stress amplitude that accomplishes the removal of the coating is determined from a computer simulation process. The simulation itself is verified by means of a piezoelectric crystal probe which is capable of mapping out the profile of the stress pulse generated by the laser pulse.

scholarly journals Focusing of intense laser pulse by a hollow cone

2010 ◽  
Vol 28 (2) ◽  
pp. 293-298 ◽  
Author(s):  
Wei Yu ◽  
Lihua Cao ◽  
M.Y. Yu ◽  
A.L. Lei ◽  
Z.M. Sheng ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Strong Field ◽  
High Energy ◽  
Plasma Boundary ◽  
High Energy Density ◽  
Intense Laser ◽  
Intense Laser Pulse ◽  
Hollow Cone ◽  
Conical Channel ◽  
Boundary Plasma

AbstractIt is shown that an intense laser pulse can be focused by a conical channel. This anomalous light focusing can be attributed to a hitherto ignored effect in nonlinear optics, namely that the boundary response depends on the light intensity: the inner cone surface is ionized and the laser pulse is in turn modified by the resulting boundary plasma. The interaction creates a new self-consistently evolving light-plasma boundary, which greatly reduces reflection and enhances forward propagation of the light pulse. The hollow cone can thus be used for attaining extremely high light intensities for applications in strong-field and high energy-density physics and other areas.

scholarly journals Large area high efficiency broad bandwidth 800 nm dielectric gratings for high energy laser pulse compression

2009 ◽  
Vol 17 (26) ◽  
pp. 23809 ◽  
Author(s):  
D. H. Martz ◽  
H. T. Nguyen ◽  
D. Patel ◽  
J. A. Britten ◽  
D. Alessi ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Pulse Compression ◽  
High Efficiency ◽  
High Energy ◽  
Large Area ◽  
Broad Bandwidth ◽  
Dielectric Gratings ◽  
Energy Laser ◽  
High Energy Laser

The Doppler Aerosol Wind (DAWN) Airborne, Wind-Profiling Coherent-Detection Lidar System: Overview and Preliminary Flight Results

2014 ◽  
Vol 31 (4) ◽  
pp. 826-842 ◽  
Author(s):  
Michael J. Kavaya ◽  
Jeffrey Y. Beyon ◽  
Grady J. Koch ◽  
Mulugeta Petros ◽  
Paul J. Petzar ◽  
...  
Keyword(s):  
Laser Pulse ◽  
High Energy ◽  
Coherent Detection ◽  
Lidar System ◽  
Airborne Measurements ◽  
Secondary Mirror ◽  
Wind Measurements ◽  
Wind Lidar ◽  
Aerosol Backscatter ◽  
Flight Measurements

Abstract The first airborne wind measurements of a pulsed, 2-μm solid-state, high-energy, wind-profiling lidar system for airborne measurements are presented. The laser pulse energy is the highest to date in an eye-safe airborne wind lidar system. This energy, the 10-Hz laser pulse rate, the 15-cm receiver diameter, and dual-balanced coherent detection together have the potential to provide much-improved lidar sensitivity to low aerosol backscatter levels compared to earlier airborne-pulsed coherent lidar wind systems. Problems with a laser-burned telescope secondary mirror prevented a full demonstration of the lidar’s capability, but the hardware, algorithms, and software were nevertheless all validated. A lidar description, relevant theory, and preliminary results of flight measurements are presented.

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