scholarly journals FORMALISMS, ANALYSIS, RESULTS AND ACCOMPLISHMENTS WITH POPULATION INVERSION OF MATERIALS

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Milesa Ž. Srećković ◽  
Andrei A. Ionin ◽  
Aco J. Janićijević ◽  
Aleksandar R. Bugarinović ◽  
Stanko M. Ostojić ◽  
...  
Keyword(s):  
Nuclear Physics ◽  
Population Inversion ◽  
Transition Probabilities ◽  
Laser Energy ◽  
Laser System ◽  
Active Material ◽  
Kinetic Equations ◽  
Engineering Application ◽  
State Theory ◽  
Practical Reasons

During six decades of quantum electronics, a vast majority of new types of quantum generators have been developed. Although the principle of population inversion has united different ranges of electromagnetic spectra (and respective quantum generators), the existence of the title laser without the population inversion, makes that the exception had confirmed the rule, i. e. that this title deserves to be discussed further. Developing of formalisms describing the operation of quantum generators, by now have produced several approaches, which must have a quantum mechanics base. For the practical reasons, negative coefficient of absorption is acquired using classic electromagnetics as well, however for the population purposes, quantum representation must be entered. A few levels of formalisms will be set in this paper, linked to quantum generators accenting the optical portion of the spectra. The lowest level descriptions are based on lumped circuits. This could be expanded to equivalents of other physical problems, using program packages developed for the electrical engineering application purposes (Spice, etc.). Schematics are defined at the macro as well as micro equivalent levels (atomic – electronic levels). The kinetic equations with simpler approach will be considered as well as simplified laser equations based on quantum/ semi-quantum approach. The use of Fourier analysis or other appropriate transformations leads to formulating the main five laser equations which serve as the base for various working regimes of quantum generators and amplifiers (free generation regime, Q switch, synchronization, operation with filters, two modes regime, regime with losses, etc.). The Lyapunov stability theorem has to be included here, etc. For some of the chosen types of quantum generator, analytical modeling will be analyzed as well as the results of program packages developed for the lasers dynamics, regimes and parameters. The systems pumped with electronic beams (relativistic) will be considered and the nuclear physics statements discussed which must be included at the beginning, in order to consider further necessary parts of the condensed – solid state theory and laser techniques, after slowing down towards thermal energies. Existing program packages provide fast modeling and visualization of laser energy distribution, temperature, modes, etc. in active material with or without the resonator. A modeling will be performed for the specified geometries and a temperature distribution in active material will be captured during operation of a chosen laser system. Different pump geometries will be compared. Contemporary lasers with the shortest existing pulse durations demand new formalisms. Areas of nonlinear optics and quantum electrody-namics, Glauber states and similar, are areas that have to be included. Two main formalisms thermodynamical and quantum mechanical with transition probabilities using perturbation methods and secondary quantization naturally had to be complemented if the Brillouin, Raman, Compton, soliton, fiber and other lasers are included more generally.

scholarly journals A Personal Reflection of Greenlight 532 nm Laser for BPH Treatment

2014 ◽  
Vol 2014 ◽  
pp. 1-6
Author(s):  
Bilal Chughtai ◽  
Claire Dunphy ◽  
Alexis Te
Keyword(s):  
Surgical Therapy ◽  
Laser Energy ◽  
Laser System ◽  
Prostatic Hyperplasia ◽  
First Line ◽  
Technological Advances ◽  
Urinary Tract Symptoms ◽  
Bothersome Symptom ◽  
532 Nm ◽  
Lower Urinary

Lower urinary tract symptoms (LUTS) secondary to benign prostatic hyperplasia are a bothersome symptom set that affect approximately one in every four males above the age of 50. First line treatment is typically medication, but when medications fail surgical therapy is the next option. Technological advances have made surgical therapy safer and more effective. One area that our group has particular interest and focus in is the application of the 532 nm laser in surgical therapy. The high power 532 nm laser is used to remove obstructive prostatic tissue and the laser energy is selectively absorbed by hemoglobin in the prostate tissue, resulting in effective tissue vaporization and removal. We review our experience with Greenlight laser system and its evolution from the original 60-watt laser to the most recent 180-watt Greenlight system with MoXy fiber.

scholarly journals Characterisation and Modelling of Ultrashort Laser-Driven Electromagnetic Pulses

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Kwinten Nelissen ◽  
Máté Liszi ◽  
Massimo De Marco ◽  
Valeria Ospina ◽  
István Drotár ◽  
...  
Keyword(s):  
Pulse Energy ◽  
Large Scale ◽  
Laser Intensity ◽  
Laser Energy ◽  
Laser System ◽  
Intense Laser ◽  
Electron Interaction ◽  
Laser Target ◽  
Electromagnetic Pulses ◽  
Target Holder

AbstractRecent advances on laser technology have enabled the generation of ultrashort (fs) high power (PW) laser systems. For such large scale laser facilities there is an imperative demand for high repetition rate operation in symbiosis with beamlines or end-stations. In such extreme conditions the generation of electromagnetic pulses (EMP) during high intense laser target interaction experiments can tip the scale for the good outcome of the campaign. The EMP effects are several including interference with diagnostic devices and actuators as well as damage of electrical components. The EMP issue is quite known in the picosecond (ps) pulse laser experiments but no systematic study on EMP issues at multi-Joule fs-class lasers has been conducted thus far. In this paper we report the first experimental campaign for EMP-measurements performed at the 200 TW laser system (VEGA 2) at CLPU laser center. EMP pulse energy has been measured as a function of the laser intensity and energy together with other relevant quantities such as (i) the charge of the laser-driven protons and their maximum energy, as well as (ii) the X-ray Kα emission coming from electron interaction inside the target. Analysis of experimental results demonstrate (and confirm) a direct correlation between the measured EMP pulse energy and the laser parameters such as laser intensity and laser energy in the ultrashort pulse duration regime. Numerical FEM (Finite Element Method) simulations of the EMP generated by the target holder system have been performed and the simulations results are shown to be in good agreement with the experimental ones.

scholarly journals Scanning electron microscope studies on laser ablation of solids

2019 ◽  
Vol 37 (01) ◽  
pp. 101-109 ◽  
Author(s):  
Mohamed E. Shaheen ◽  
Joel E. Gagnon ◽  
Brian J. Fryer
Keyword(s):  
Pulse Width ◽  
Laser Energy ◽  
Laser System ◽  
Picosecond Laser ◽  
Laser Pulses ◽  
Ablation Rate ◽  
Laser Wavelength ◽  
High Laser Fluence ◽  
Electron Imaging ◽  
Scanning Electron

AbstractThis study investigates the interaction of picosecond laser pulses with sapphire and brass in air using scanning electron microscopy. A picosecond laser system operating at a wavelength of 785 nm, pulse width of 110 ps, and variable repetition rate (1–1000 Hz) was used in this study. The pulse width applied in this work was not widely investigated as it lies in the gap between ultrashort (femtosecond) and long (nanosecond) pulse width lasers. Different surface morphologies were identified using secondary electron and backscattered electron imaging of the ablated material. Thermal ablation effects were more dominant in brass than in sapphire. Exfoliation and fractures of sapphire were observed at high laser fluence. Compared with brass, multiple laser pulses were necessary to initiate ablation in sapphire due to its poor absorption to the incident laser wavelength. Ablation rate of sapphire was lower than that of brass due to the dissipation of a portion of the laser energy due to heating and fracturing of the surface.

A Laser Decontamination Technology for Radioactive Contaminated Metals

2020 ◽  
Author(s):  
Zhao Wan ◽  
Cao Junjie ◽  
Wang Shuai ◽  
Chen Xumin ◽  
Zhang Yongling
Keyword(s):  
Nuclear Power ◽  
Laser Scanning ◽  
Laser System ◽  
Research Result ◽  
Engineering Application ◽  
Scanning Speed ◽  
Decontamination Factor ◽  
Nuclear Facilities ◽  
Laser Scanning Speed ◽  
Deposit Layer

Abstract A large number of radioactive contaminated metals will be produced during the operation and decommissioning of nuclear facilities. Laser ablation is a clean and efficient surface decontamination method for radioactive metals. This study presents experiments to select laser decontamination parameters including laser power, laser pulse width, laser scanning speed and laser focal shift, as well as the construction of a laser decontamination prototype based on a fiber laser system of high power density, which can automatically ablate the radioactive deposit layer, oxide layer and shallow surface layer of metals to get an excellent decontamination result. Depending on this equipment, some engineering application tests were conducted in a nuclear power factory to verify the technology research result and equipment. Decontamination results which evaluate by decontamination factor show that the laser decontamination technology has a good result on the decontamination of radioactive surface contaminated metals.

scholarly journals High-energy hybrid femtosecond laser system demonstrating 2 × 10 PW capability

2020 ◽  
Vol 8 ◽  
Author(s):  
François Lureau ◽  
Guillaume Matras ◽  
Olivier Chalus ◽  
Christophe Derycke ◽  
Thomas Morbieu ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Repetition Rate ◽  
Nuclear Physics ◽  
Laser System ◽  
Output Pulse ◽  
High Energy ◽  
Barium Borate ◽  
Femtosecond Pulses ◽  
Chirped Pulse ◽  
Pulse Amplifier

Abstract We report on a two-arm hybrid high-power laser system (HPLS) able to deliver 2 × 10 PW femtosecond pulses, developed at the Bucharest-Magurele Extreme Light Infrastructure Nuclear Physics (ELI-NP) Facility. A hybrid front-end (FE) based on a Ti:sapphire chirped pulse amplifier and a picosecond optical parametric chirped pulse amplifier based on beta barium borate (BBO) crystals, with a cross-polarized wave (XPW) filter in between, has been developed. It delivers 10 mJ laser pulses, at 10 Hz repetition rate, with more than 70 nm spectral bandwidth and high-intensity contrast, in the range of 1013:1. The high-energy Ti:sapphire amplifier stages of both arms were seeded from this common FE. The final high-energy amplifier, equipped with a 200 mm diameter Ti:sapphire crystal, has been pumped by six 100 J nanosecond frequency doubled Nd:glass lasers, at 1 pulse/min repetition rate. More than 300 J output pulse energy has been obtained by pumping with only 80% of the whole 600 J available pump energy. The compressor has a transmission efficiency of 74% and an output pulse duration of 22.7 fs was measured, thus demonstrating that the dual-arm HPLS has the capacity to generate 10 PW peak power femtosecond pulses. The reported results represent the cornerstone of the ELI-NP 2 × 10 PW femtosecond laser facility, devoted to fundamental and applied nuclear physics research.

Natural As-Sb alloys: texture types, thermal behaviour and mechanism of formation

1987 ◽  
Vol 51 (360) ◽  
pp. 295-304 ◽  
Author(s):  
G. P. Bernardini ◽  
C. Cipriani ◽  
F. Corsini ◽  
G. G. T. Guarini ◽  
G. Mazzetti ◽  
...  
Keyword(s):  
Solid Solution ◽  
Thermal Behaviour ◽  
Diffusion Mechanism ◽  
Kinetic Equations ◽  
State Theory ◽  
Mechanism Of Formation ◽  
Constant Composition ◽  
Rate Determining Step ◽  
Dta Studies ◽  
Annealing Experiments

AbstractThe thermal behaviour and mechanism of formation of different texture types of intergrown As-Sb alloys have been studied by DTA and annealing experiments performed on natural samples. The constant composition of the As-rich component and of the stibarsen in the intergrowths, and the large compositional range of the homogeneous solid solution obtained after heating in the DTA cycle, have been established using the linear relationship between cell volume and composition. The high-temperature features detected in the DTA studies of the natural samples confirm previously published phase relations for the synthetic As-Sb system. The low-temperature features can be correlated with the homogenization reaction which leads to the formation of a complete solid solution. Study of TTT plots based on the annealing experiments clearly shows that a diffusion mechanism is involved in the homogenization reaction. This has been further substantiated by fitting the experimental data to kinetic equations for diffusion-controlled processes. The kinetic parameters evaluated from the ending time for the 520, 480, and 420 °C annealing experiments, using both the Arrhenius and the transition state theory formalisms, suggests a rather rigid activated complex for the rate-determining step of the process.

The Resonant Faraday Effect

1972 ◽  
Vol 50 (22) ◽  
pp. 2866-2880 ◽  
Author(s):  
D. M. Camm ◽  
F. L. Curzon
Keyword(s):  
Faraday Effect ◽  
Transition Probabilities ◽  
Active Material ◽  
Argon Plasma ◽  
Absorption Lines ◽  
Doppler Width ◽  
Voigt Profile ◽  
Lorentzian Width ◽  
Relative Transition ◽  
Lorentzian Component

The resonant Faraday effect occurs for radiation at frequencies close to the absorption lines of a magneto-active material. In the paper we present a theory for isolated absorption lines with Voigt profiles. The background source is also assumed to have a Voigt profile. The theory shows how the resonant Faraday effect can be used to determine relative transition probabilities, as well as the magnitude of the Lorentzian component of the line profiles.Experimental results for an argon plasma are presented and show that the relative transition probabilities of atomic transitions with a common lower level can be measured to an accuracy of ± 1%. For strong absorption lines, the Voigt "a" parameter can also be determined to an accuracy of 10%, even when the Doppler width is 14 times larger than the Lorentzian width.

The award of medals by the President, Sir George Porter, at the Anniversary Meeting, 1 December 1986

1987 ◽  
Vol 230 (1259) ◽  
pp. 101-105
Keyword(s):  
Nuclear Physics ◽  
Nuclear Power ◽  
State Theory ◽  
Theoretical Physics ◽  
Chain Reactions ◽  
Power Stations ◽  
Resonance Reactions ◽  
Rudolf Peierls ◽  
Wide Range ◽  
A Chain

The Copley Medal is awarded to Sir Rudolf Peierls, C. B. E., F. R. S., in recognition of his fundamental contributions to a very wide range of theoretical physics, and signal advances in proposing the probable existence of nuclear chain reactions in fissile materials. Peierls's earliest work was in solid-state theory, where he made the fundamental advances in our understanding of thermal conductivity and the transport of phonons. His contributions to nuclear physics included, with Bethe, aspects of the two-body problem and, with Kapur, a quantitative treatment of nuclear resonance reactions. In 1940, in work with O. R. Frisch, he predicted the near-certainty of an explosion through multiplication of neutrons in 235 U and made accurate estimates of the critical size for a chain reaction. He also advocated the use of gaseous diffusion for separating 235 U from 238 U. His work laid the basis for the development of nuclear weapons and nuclear power stations. Following the Second World War, Peierls built up and led one of the premier schools of theoretical physics in the U. K., which numbered among its members many who were to achieve high distinction.

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.

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