scholarly journals Short-wavelength experiments on laser pulse interaction with extended pre-plasma at the PALS-installation

2015 ◽  
Vol 34 (1) ◽  
pp. 94-108 ◽  
Author(s):  
T. Pisarczyk ◽  
S.Yu. Gus'kov ◽  
O. Renner ◽  
R. Dudzak ◽  
J. Dostal ◽  
...  
Keyword(s):  
Shock Wave ◽  
Energy Transfer ◽  
Laser Beam ◽  
Laser Energy ◽  
Laser System ◽  
Radiation Energy ◽  
Point Of View ◽  
Main Beam ◽  
Appreciable Effect ◽  
Fast Electrons

AbstractThe paper is a continuation of research carried out at Prague Asterix Laser System (PALS) related to the shock ignition (SI) approach in inertial fusion, which was carried out with use of 1ω main laser beam as the main beam generating a shock wave. Two-layer targets were used, consisting of Cu massive planar target coated with a thin polyethylene layer, which, in the case of two-beam irradiation geometry, simulate conditions related to the SI scenario. The investigations presented in this paper are related to the use of 3ω to create ablation pressure for high-power shock wave generation. The interferometric studies of the ablative plasma expansion, complemented by measurements of crater volumes and Kα emission, clearly demonstrate the effect of changing the incident laser intensity due to changing the focal radius on efficiency of laser energy transfer to a shock wave and fast electron emission. The efficiency of the energy transfer increases with the radius of the focused laser beam. The pre-plasma does not significantly change the character of this effect. However, it unambiguously results in the increasing temperature of fast electrons, the total energy of which remains very small (<0.1% of the laser energy). This study shows that the optimal radius from the point of view of 3ω radiation energy transfer to the shock wave is the maximal one used in these experiments and equal to 200 µm that corresponds to the minimal effect of two-dimensional (2D)-expansion. Such a result is typical for the ablation process determined by electron conductivity energy transfer under the conditions of one-dimensional or 2D matter expansion without any appreciable effect due to energy transfer by fast electrons. The 2D simulations based on application of the ALANT-HE code and an analytical model that includes generation and transport of hot electrons has been used to support of experimental data.

scholarly journals Pre-plasma effect on laser beam energy transfer to a dense target under conditions relevant to shock ignition

2015 ◽  
Vol 33 (2) ◽  
pp. 221-236 ◽  
Author(s):  
T. Pisarczyk ◽  
S.Yu. Gus'kov ◽  
O. Renner ◽  
N.N. Demchenko ◽  
Z. Kalinowska ◽  
...  
Keyword(s):  
Shock Wave ◽  
Energy Transfer ◽  
Laser Beam ◽  
Inertial Confinement Fusion ◽  
Beam Energy ◽  
Laser Energy ◽  
Line Emission ◽  
Main Beam ◽  
Beam Irradiation ◽  
Shock Ignition

AbstractThis paper reports on properties of a plasma formed by sequential action of two laser beams on a flat target, simulating the conditions of shock-ignited inertial confinement fusion target exposure. The experiments were performed using planar targets consisting of a massive copper (Cu) plate coated with a thin plastic (CH) layer, which was irradiated by the 1ω PALS laser beam (λ = 1.315 μm) at the energy of 250 J. The intensity of the fixed-energy laser beam was scaled by varying the focal spot radius. To imitate shock ignition conditions, the lower-intensity auxiliary 1ω beam created CH-pre-plasma which was irradiated by the main beam with a delay of 1.2 ns, thus generating a shock wave in the massive part of the target. To study the parameters of the plasma treated by the two-beam irradiation of the targets, a set of various diagnostics was applied, namely: (i) Two-channel polaro-interferometric system irradiated by the femtosecond laser (~40 fs), (ii) spectroscopic measurements in the X-ray range, (iii) two-dimensional (2D)-resolved imaging of the Kα line emission from Cu, (iv) measurements of the ion emission by means of ion collectors, and (v) measurements of the volume of craters produced in a massive target providing information on the efficiency of the laser energy transfer to the shock wave. The 2D numerical simulations have been used to support the interpretation of experimental data. The general conclusion is that the fraction of the main laser beam energy deposited into the massive copper at two-beam irradiation decreases in comparison with the case of pre-plasma. The reason is that the pre-formed and expanding plasma deteriorates the efficiency of the energy transfer from the main laser pulse to a solid part of the targets by means of the fast electrons and the wave of an electron thermal conductivity.

scholarly journals Laser-driven ablation through fast electrons in PALS-experiment at the laser radiation intensity of 1–50 PW/cm2

2014 ◽  
Vol 32 (1) ◽  
pp. 177-195 ◽  
Author(s):  
S. Yu. Gus'kov ◽  
N.N. Demchenko ◽  
A. Kasperczuk ◽  
T. Pisarczyk ◽  
Z. Kalinowska ◽  
...  
Keyword(s):  
Shock Wave ◽  
Energy Transfer ◽  
Laser Radiation ◽  
Fast Electron ◽  
Focal Spot ◽  
Laser Energy ◽  
Coupling Parameter ◽  
Laser Radiation Intensity ◽  
Fast Electrons ◽  
Spot Radius

AbstractThe paper is directed to the study of high-temperature plasma and ablation plasma formation as well as efficiency of the laser energy transfer to solid targets irradiated by laser pulses with intensities of 1–50 PW/cm2 and duration of 200–300 ps, i.e., at conditions corresponding to the characteristics of the laser spike designed to generate the igniting shock wave in the shock ignition concept. The experiments have been performed at Prague Asterix Laser System. The iodine laser delivered 250 ps (full width at half maximum) pulses with the energy in the range of 100–600 J at the first (λ1 = 1.315 µm) and third (λ3 = 0.438 µm) harmonic frequencies. The focal spot radius of the laser beam on the surface of Al or Cu targets made was gradually decreased from 160 to 40 µm. The diagnostic data collected using three-frame interferometry, X-ray spectroscopy, and crater replica technique were interpreted by two-dimensional numerical and analytical modeling which included generation and transport of fast electrons. The coupling parameter Iλ2 was varied in the range of 1 × 1014−8 × 1016 Wμm2/cm2 covering the regimes of weak to intense fast electron generation. The dominant contribution of fast electron energy transfer into the ablation process and shock wave generation was found when using the first harmonic laser radiation, the focal spot radius of 40–100 µm, and the laser energy of 300–600 J.

Interferometric studies of the pre-plasma influence on the laser energy transfer to the shock wave with the use of two-layer planar targets

2014 ◽  
Vol T161 ◽  
pp. 014023
Author(s):  
Zofia Kalinowska ◽  
Tadeusz Pisarczyk ◽  
Jan Badziak ◽  
Stefan Borodziuk ◽  
Tomasz Chodukowski ◽  
...  
Keyword(s):  
Shock Wave ◽  
Energy Transfer ◽  
Laser Energy

Pre-plasma effect on energy transfer from laser beam to shock wave generated in solid target

2014 ◽  
Vol 21 (1) ◽  
pp. 012708 ◽  
Author(s):  
T. Pisarczyk ◽  
S. Yu. Gus'kov ◽  
Z. Kalinowska ◽  
J. Badziak ◽  
D. Batani ◽  
...  
Keyword(s):  
Shock Wave ◽  
Energy Transfer ◽  
Laser Beam ◽  
Solid Target ◽  
Plasma Effect

scholarly journals New techniques for laser beam atmospheric extinction measurements from manned and unmanned aerospace vehicles

2013 ◽  
Vol 3 (1) ◽  
Author(s):  
Roberto Sabatini ◽  
Mark Richardson
Keyword(s):  
Laser Beam ◽  
Near Infrared ◽  
Laser Energy ◽  
Laser System ◽  
Direct Determination ◽  
Atmospheric Conditions ◽  
Atmospheric Extinction ◽  
Laser Systems ◽  
Non Linear Propagation ◽  
Nir Laser

AbstractNovel techniques for laser beam atmospheric extinction measurements, suitable for several air and space platform applications, are presented in this paper. Extinction measurements are essential to support the engineering development and the operational employment of a variety of aerospace electro-optical sensor systems, allowing calculation of the range performance attainable with such systems in current and likely future applications. Such applications include ranging, weaponry, Earth remote sensing and possible planetary exploration missions performed by satellites and unmanned flight vehicles. Unlike traditional LIDAR methods, the proposed techniques are based on measurements of the laser energy (intensity and spatial distribution) incident on target surfaces of known geometric and reflective characteristics, by means of infrared detectors and/or infrared cameras calibrated for radiance. Various laser sources can be employed with wavelengths from the visible to the far infrared portions of the spectrum, allowing for data correlation and extended sensitivity. Errors affecting measurements performed using the proposed methods are discussed in the paper and algorithms are proposed that allow a direct determination of the atmospheric transmittance and spatial characteristics of the laser spot. These algorithms take into account a variety of linear and non-linear propagation effects. Finally, results are presented relative to some experimental activities performed to validate the proposed techniques. Particularly, data are presented relative to both ground and flight trials performed with laser systems operating in the near infrared (NIR) at λ= 1064 nm and λ= 1550 nm. This includes ground tests performed with 10 Hz and 20 KHz PRF NIR laser systems in a large variety of atmospheric conditions, and flight trials performed with a 10 Hz airborne NIR laser system installed on a TORNADO aircraft, flying up to altitudes of 22,000 ft.

scholarly journals Hydrodynamic evolution of laser driven diverging shock waves

1990 ◽  
Vol 8 (1-2) ◽  
pp. 247-252 ◽  
Author(s):  
M. A. Harith ◽  
V. Palleschi ◽  
A. Salvetti ◽  
D. P. Singh ◽  
G. Tropiano ◽  
...  
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Temporal Evolution ◽  
Laser Energy ◽  
Appreciable Effect ◽  
Density Jump ◽  
Hydrodynamic Evolution ◽  
Self Similar Solution ◽  
Glass Cell ◽  
Strong Explosion

Spherically symmetric shock waves have been produced via Nd3+ laser induced break-down in helium, nitrogen and air at pressures ranging from 760 Torr to 2300 Torr. The measurements are performed at different absorbed laser energies (E0 = 0.05 J to 2 J) at the center of the experimental spherical glass cell where the breakdown of the gas takes place. The temporal evolution of the shock wave followed by a double-pulse, doublewavelength holographic technique is described hydrodynamically well by the point strong explosion theory. The ambient gas counterpressure plays a negligible role in determining the shock wave motion even at low laser energy absorption (E0 ≤, 0.5 J), whereas it has an appreciable effect on the gas density jump at the shock wave itself. The experimental data on temporal evolution of the density jump of the gas and the corresponding theoretical profiles obtained adopting a non-self-similar solution at the same laser absorbed energy are found to be in good mutual agreement.

The atomic-force microscope and its future in biology

1993 ◽  
Vol 51 ◽  
pp. 704-705
Author(s):  
Jean-Paul Revel
Keyword(s):  
Silicon Nitride ◽  
Laser Beam ◽  
Atomic Force Microscope ◽  
Scanning Tunneling Microscope ◽  
Point Of View ◽  
Scanning Tunneling ◽  
Close Relative ◽  
Tunneling Microscope ◽  
Atomic Force ◽  
Sharp Point

The last few years have been marked by a series of remarkable developments in microscopy. Perhaps the most amazing of these is the growth of microscopies which use devices where the place of the lens has been taken by probes, which record information about the sample and display it in a spatial from the point of view of the context. From the point of view of the biologist one of the most promising of these microscopies without lenses is the scanned force microscope, aka atomic force microscope.This instrument was invented by Binnig, Quate and Gerber and is a close relative of the scanning tunneling microscope. Today's AFMs consist of a cantilever which bears a sharp point at its end. Often this is a silicon nitride pyramid, but there are many variations, the object of which is to make the tip sharper. A laser beam is directed at the back of the cantilever and is reflected into a split, or quadrant photodiode.

Relativistic self-focusing of a rippled laser beam in a plasma

1999 ◽  
Vol 62 (4) ◽  
pp. 389-396 ◽  
Author(s):  
M. V. ASTHANA ◽  
A. GIULIETTI ◽  
DINESH VARSHNEY ◽  
M. S. SODHA
Keyword(s):  
Refractive Index ◽  
Laser Beam ◽  
The Self ◽  
Laser Beams ◽  
Radial Dependence ◽  
Main Beam ◽  
Gaussian Laser Beam ◽  
Self Focusing ◽  
Saturation Effects ◽  
Paraxial Ray

This paper presents an analysis of the relativistic self-focusing of a rippled Gaussian laser beam in a plasma. Considering the nonlinearity as arising owing to relativistic variation of mass, and following the WKB and paraxial-ray approximations, the phenomenon of self-focusing of rippled laser beams is studied for arbitrary magnitude of nonlinearity. Pandey et al. [Phys. Fluids82, 1221 (1990)] have shown that a small ripple on the axis of the main beam grows very rapidly with distance of propagation as compared with the self-focusing of the main beam. Based on this analogy, we have analysed relativistic self-focusing of rippled beams in plasmas. The relativistic intensities with saturation effects of nonlinearity allow the nonlinear refractive index in the paraxial regime to have a slower radial dependence, and thus the ripple extracts relatively less energy from its neighbourhood.

scholarly journals 1178 J, 527 nm near diffraction limited laser based on a complete closed-loop adaptive optics controlled off-axis multi-pass amplification laser system

2021 ◽  
Vol 9 ◽  
Author(s):  
Deen Wang ◽  
Xin Zhang ◽  
Wanjun Dai ◽  
Ying Yang ◽  
Xuewei Deng ◽  
...  
Keyword(s):  
Laser Beam ◽  
Adaptive Optics ◽  
Closed Loop ◽  
Focal Spot ◽  
Beam Quality ◽  
Laser System ◽  
Diffraction Limit ◽  
Kdp Crystal ◽  
Main Amplifier

Abstract A 1178 J near diffraction limited 527 nm laser is realized in a complete closed-loop adaptive optics (AO) controlled off-axis multi-pass amplification laser system. Generated from a fiber laser and amplified by the pre-amplifier and the main amplifier, a 1053 nm laser beam with the energy of 1900 J is obtained and converted into a 527 nm laser beam by a KDP crystal with 62% conversion efficiency, 1178 J and beam quality of 7.93 times the diffraction limit (DL). By using a complete closed-loop AO configuration, the static and dynamic wavefront distortions of the laser system are measured and compensated. After correction, the diameter of the circle enclosing 80% energy is improved remarkably from 7.93DL to 1.29DL. The focal spot is highly concentrated and the 1178 J, 527 nm near diffraction limited laser is achieved.

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