Laser Ignition of Metalized Solid Propellants

2018 ◽  
pp. 79-99
Author(s):  
Igor G. Assovskiy
Keyword(s):  
Laser Pulse ◽  
Energetic Material ◽  
Critical Density ◽  
Thermal Relaxation ◽  
Resonant Interaction ◽  
Maximum Temperature ◽  
Optimal Size ◽  
Solid Propellants ◽  
Metallic Particles ◽  
Size Of Particles

This Chapter presents a theoretical analysis of radiation interaction with a semi-transparent metalized energetic material. Main regularities of the laser pulse interaction with metalized compositions are considered within the framework of non-resonant interaction of radiation with matter. The large variety of metalized composite propellants with different properties of the components, their ratio and dispersion can be divided into two classes, depending on the ratio of the laser irradiation's characteristic time (tr) and the thermal relaxation time of the propellant characteristic cell containing one metal particle (tm). Analysis of the role of metallic particles shape shows that in the case of spherical metal particles, duration of the laser pulse corresponds to the optimal size of particles, heated to a maximum temperature. In the case of flat metallic particles and constant pulse duration, the critical radiation flux and the critical density of ignition energy significantly decrease with decreasing thickness of the particle.

Increase of magnetic hyperthermia efficiency due to optimal size of particles: theoretical and experimental results

2020 ◽  
Vol 22 (9) ◽  
Author(s):  
L. H. Nguyen ◽  
V. T. K. Oanh ◽  
P. H. Nam ◽  
D. H. Doan ◽  
N. X. Truong ◽  
...  
Keyword(s):  
Magnetic Hyperthermia ◽  
Experimental Results ◽  
Optimal Size ◽  
Size Of Particles

Laser Encapsulation of Metallic Films in SiO2

1995 ◽  
Vol 397 ◽  
Author(s):  
A. J. Pedraza ◽  
S. Cao ◽  
D. H. Lowndes ◽  
L. F. Allard
Keyword(s):  
Energy Density ◽  
Laser Pulse ◽  
Laser Energy ◽  
Substrate Material ◽  
Laser Energy Density ◽  
Cross Sectional ◽  
Metallic Particles ◽  
Transmission Electron ◽  
Encapsulation Process ◽  
Deposited Film

ABSTRACTThin films of gold, copper and iron deposited on silica were driven into the substrate by a laser pulse. This transport takes place only when the irradiation is performed at a laser energy density of 0.7 J/cm2 or lower. Cross sectional transmission electron microscopy (TEM) of the irradiated specimens reveals two distinctive stages in the encapsulation process. In the first, the film melts and clusters into small particles and in the second one the particles are driven into the substrate by the laser pulse. The particle size of encapsulated metal varies from 5 to 50 nm. Selected area diffraction of the large particles and lattice fringe images of the smaller particles reveal pure metals, e.g., gold, copper or iron. Titanium films laser irradiated are not encapsulated in silica; instead, these films react with silica forming an amorphous compound. Apparently, one of the conditions required for encapsulation is that the metal should not react with the substrate material. On subsequent irradiation at a laser energy density of 1.5 J/cm2, ablation of silica partially exposes the metallic particles. Strong bonding between a new film deposited after irradiation and the substrate is obtained because these particles anchor the freshly deposited film. Anchoring is clearly revealed by cross sectional TEM. The mechanisms of encapsulation are discussed using results from TEM and adhesion testing.

scholarly journals Intense local plasma heating by stopping of ultrashort ultraintense laser pulse in dense plasma

2007 ◽  
Vol 25 (4) ◽  
pp. 631-638 ◽  
Author(s):  
W. Yu ◽  
M. Y. Yu ◽  
H. Xu ◽  
Y. W. Tian ◽  
J. Chen ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Plasma Oscillation ◽  
Plasma Heating ◽  
Critical Density ◽  
Deposition Process ◽  
Particle In Cell ◽  
Linearly Polarized ◽  
Plasma Slab ◽  
Cell Simulation ◽  
Channel Boundary

AbstractSelf-trapping, stopping, and absorption of an ultrashort ultraintense linearly polarized laser pulse in a finite plasma slab of near-critical density is investigated by particle-in-cell simulation. As in the underdense plasma, an electron cavity is created by the pressure of the transmitted part of the light pulse and it traps the latter. Since the background plasma is at near-critical density, no wake plasma oscillation is created. The propagating self-trapped light rapidly comes to a stop inside the slab. Subsequent ion Coulomb explosion of the stopped cavity leads to explosive expulsion of its ions and formation of an extended channel having extremely low plasma density. The energetic Coulomb-exploded ions form shock layers of high density and temperature at the channel boundary. In contrast to a propagating pulse in a lower density plasma, here the energy of the trapped light is deposited onto a stationary and highly localized region of the plasma. This highly localized energy-deposition process can be relevant to the fast ignition scheme of inertial fusion.

The effects of the atmosphere on the surface modification of alumina by pulsed-laser-irradiation

1997 ◽  
Vol 12 (7) ◽  
pp. 1747-1754 ◽  
Author(s):  
Siqi Cao ◽  
A. J. Pedraza ◽  
L. F. Allard ◽  
D. H. Lowndes
Keyword(s):  
Energy Density ◽  
Laser Pulse ◽  
Thin Layer ◽  
Amorphous Phase ◽  
Laser Energy ◽  
Pulsed Laser ◽  
Laser Pulses ◽  
Near Surface ◽  
Metallic Particles ◽  
Cellular Microstructure

A near-surface thin layer is melted when alumina is pulsed-laser-irradiated in an Ar–4% H2 atmosphere or in air. A thin layer of amorphous phase forms when the substrates are irradiated in Ar–4% H2 at 1 to 1.3 J/cm2 with multiple laser pulses. Amorphous phase is also found in samples laser-irradiated in air and oxygen. After a laser pulse at an energy density of 1.6 J/cm2 or higher the melt solidifies epitaxially from the unmelted substrate with a cellular microstructure. There is a decrease in the cooling rate of the melt as the laser energy density is increased because more heat must be dissipated. The amorphous phase forms when the heat input due to the laser pulse produces a superheated melt that cools down sufficiently fast to avoid crystallization. Very small particles of aluminum in the laser-melted and subsequently solidified layer are observed only in samples laser-irradiated in an Ar–4% H2 atmosphere. In this reducing atmosphere, the alumina is possibly reduced to metallic aluminum which is mixed into the melt by the turbulence provoked by the laser pulses. The effects of these metallic particles on copper deposition when the irradiated substrates are immersed in an electroless bath are discussed.

Enhancement of brightness of high-order harmonics with elliptical polarization from near-critical density plasmas irradiated by an ultraintense laser pulse

2020 ◽  
Vol 27 (8) ◽  
pp. 083101
Author(s):  
Yan Jiang ◽  
Qing Wang ◽  
Lihua Cao ◽  
Zhanjun Liu ◽  
Chunyang Zheng ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Critical Density ◽  
High Order ◽  
Elliptical Polarization

scholarly journals Proton acceleration in a laser-induced relativistic electron vortex

2019 ◽  
Vol 85 (4) ◽  
Author(s):  
L. Q. Yi ◽  
I. Pusztai ◽  
A. Pukhov ◽  
B. F. Shen ◽  
T. Fülöp
Keyword(s):  
Laser Pulse ◽  
Relativistic Electron ◽  
Density Gradient ◽  
Incidence Angle ◽  
Grazing Angle ◽  
Critical Density ◽  
Intense Laser ◽  
Plasma Parameters ◽  
Analytical Estimate ◽  
Background Density

We show that when a solid plasma foil with a density gradient on the front surface is irradiated by an intense laser pulse at a grazing angle, ${\sim}80^{\circ }$ , a relativistic electron vortex is excited in the near-critical-density layer after the laser pulse depletion. The vortex structure and dynamics are studied using particle-in-cell simulations. Due to the asymmetry introduced by non-uniform background density, the vortex drifts at a constant velocity, typically $0.2{-}0.3$ times the speed of light. The strong magnetic field inside the vortex leads to significant charge separation; in the corresponding electric field initially stationary protons can be captured and accelerated to twice the velocity of the vortex (100–200 MeV). A representative scenario – with laser intensity of $10^{21}~\text{W}~\text{cm}^{-2}$ – is discussed: two-dimensional simulations suggest that a quasi-monoenergetic proton beam can be obtained with a mean energy 140 MeV and an energy spread of ${\sim}10\,\%$ . We derive an analytical estimate for the vortex velocity in terms of laser and plasma parameters, demonstrating that the maximum proton energy can be controlled by the incidence angle of the laser and the plasma density gradient.

scholarly journals Thermal Relaxation of Port-Wine Stain Vessels Probed In Vivo: The Need for 1-10-Millisecond Laser Pulse Treatment.

1995 ◽  
Vol 105 (5) ◽  
pp. 709-714 ◽  
Author(s):  
Christine C Dierickx ◽  
J. Michael Casparian ◽  
Vasan Venugopalan ◽  
William A. Farinelli ◽  
R. Rox Anderson
Keyword(s):  
Laser Pulse ◽  
Thermal Relaxation ◽  
Pulse Treatment ◽  
Port Wine Stain ◽  
Port Wine ◽  
Millisecond Laser
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