Optical systems for high-power laser applications: principles and design aspects

Starting from the optical properties of laser beams, the requirements of optical systems for manipulating laser radiation in industrial applications are derived. The relevant parameters, relations to the diffraction limit and the state-of-the-art design techniques are discussed. The three important types of lasers for use in industrial materials processing operate at wavelengths ranging from the infrared (10.6 μm, CO2 laser; 1.06 μm, Nd:YAG) to the ultraviolet region (excimer lasers). Each wavelength range is associated with specific design challenges. The scarcity of suitable refractive materials for the 10 μm wavelength range and the ultraviolet below 300 nm is a major constraint. Reflective systems are used widely at the longer wavelength, but some designs suffer from coma. The 1.06 μm radiation from the Nd:YAG laser can make use of many well-developed optical means for handling visible light. Energy transport by optical fibres is commonly used. Optical systems for excimer laser applications are specific in that they image a mask onto a workpiece, and use the high photon energy and the high definition possible with the short wavelength for precision micro-machining

Ankle-brachial index as a predictor of coronary disease events in elderly patients submitted to coronary angiography

OBJECTIVES: To correlate the importance of the ankle-brachial index in terms of cardiovascular morbimortalityand the extent of coronary arterial disease amongst elderly patients without clinical manifestations of lowerlimb peripheral arterial disease.METHODS: We analyzed prospective data from 100 patients over 65 years of age with coronary arterial disease,as confirmed by coronary angiography, and with over 70% stenosis of at least one sub-epicardial coronaryartery. We measured the ankle-brachial index immediately after coronary angiography, and a value of ,0.9was used to diagnose peripheral arterial disease.RESULTS: The patients’ average age was 77.4 years. The most prevalent risk factor was hypertension (96%), andthe median late follow-up appointment was 28.9 months. The ankle-brachial index was ,0.9 in 47% of thepatients, and a low index was more prevalent in patients with multiarterial coronary disease compared topatients with uniarterial disease in the same group. Using a bivariate analysis, only an ankle-brachial index of,0.9 was a strong predictive factor for cardiovascular events, thereby increasing all-cause deaths and fatal andnon-fatal acute myocardial infarctions two- to three-fold.CONCLUSION: In elderly patients with documented coronary disease, a low ankle-brachial index (,0.9) wasassociated with the severity and extent of coronary arterial disease, and in late follow-up appointments, a lowindex was correlated with an increase in the occurrence of major cardiovascular events

Ankle-brachial index as a predictor of coronary disease events in elderly patients submitted to coronary angiography

OBJECTIVES: To correlate the importance of the ankle-brachial index in terms of cardiovascular morbimortality and the extent of coronary arterial disease amongst elderly patients without clinical manifestations of lower limb peripheral arterial disease.METHODS: We analyzed prospective data from 100 patients over 65 years of age with coronary arterial disease, as confirmed by coronary angiography, and with over 70% stenosis of at least one sub-epicardial coronary artery. We measured the ankle-brachial index immediately after coronary angiography, and a value of <0.9 was used to diagnose peripheral arterial disease.RESULTS: the patients' average age was 77.4 years. the most prevalent risk factor was hypertension (96%), and the median late follow-up appointment was 28.9 months. the ankle-brachial index was <0.9 in 47% of the patients, and a low index was more prevalent in patients with multiarterial coronary disease compared to patients with uniarterial disease in the same group. Using a bivariate analysis, only an ankle-brachial index of,0.9 was a strong predictive factor for cardiovascular events, thereby increasing all-cause deaths and fatal and non-fatal acute myocardial infarctions two-to three-fold.CONCLUSION: in elderly patients with documented coronary disease, a low ankle-brachial index (<0.9) was associated with the severity and extent of coronary arterial disease, and in late follow-up appointments, a low index was correlated with an increase in the occurrence of major cardiovascular events.Univ Fed Estado São Paulo, Dept Cardiol, São Paulo, BrazilHosp Israelita Albert Einstein, Dept Cardiol, São Paulo, BrazilDuke Univ, Sch Med, Dept Med, Durham, NC 27706 USAUniv Fed Estado São Paulo, Dept Cardiol, São Paulo, BrazilWeb of Scienc

Jets and energy flow in photon-proton collisions at HERA

Properties of the hadronic final state in photoproduction events with large transverse energy are studied at the electron-proton collider HERA. Distributions of the transverse energy, jets and underlying event energy are compared to \overline{p}p data and QCD calculations. The comparisons show that the \gamma p events can be consistently described by QCD models including -- in addition to the primary hard scattering process -- interactions between the two beam remnants. The differential jet cross sections d\sigma/dE_T^{jet} and d\sigma/d\eta^{jet} are measured

Разработка интерактивной моделирующей системы технологии низкотемпературной сепарации газа

We present a study of J ψ meson production in collisions of 26.7 GeV electrons with 820 GeV protons, performed with the H1-detector at the HERA collider at DESY. The J ψ mesons are detected via their leptonic decays both to electrons and muons. Requiring exactly two particles in the detector, a cross section of σ(ep → J ψ X) = (8.8±2.0±2.2) nb is determined for 30 GeV ≤ W γp ≤ 180 GeV and Q 2 ≲ 4 GeV 2 . Using the flux of quasi-real photons with Q 2 ≲ 4 GeV 2 , a total production cross section of σ ( γp → J / ψX ) = (56±13±14) nb is derived at an average W γp =90 GeV. The distribution of the squared momentum transfer t from the proton to the J ψ can be fitted using an exponential exp(− b ∥ t ∥) below a ∥ t ∥ of 0.75 GeV 2 yielding a slope parameter of b = (4.7±1.9) GeV −2

A Measurement of the Proton Structure Function F ⁣2(x,Q2)F_{\!2}(x,Q^2)

A measurement of the proton structure function $F_{\!2}(x,Q^2)$ is reported for momentum transfer squared $Q^2$ between 4.5 $GeV^2$ and 1600 $GeV^2$ and for Bjorken $x$ between $1.8\cdot10^{-4}$ and 0.13 using data collected by the HERA experiment H1 in 1993. It is observed that $F_{\!2}$ increases significantly with decreasing $x$, confirming our previous measurement made with one tenth of the data available in this analysis. The $Q^2$ dependence is approximately logarithmic over the full kinematic range covered. The subsample of deep inelastic events with a large pseudo-rapidity gap in the hadronic energy flow close to the proton remnant is used to measure the "diffractive" contribution to $F_{\!2}$.Comment: 32 pages, ps, appended as compressed, uuencoded fil

High-power CO2 laser with coaxial waveguide and diffusion cooling

A diffusion-cooled CO2 laser using a coaxial waveguide is analyzed theoretically and experimentally. The resonator extracting the laser beam consists of two annular plane mirrors enclosing the two ends of the waveguide. The beam exits through an aperture in one of these annular mirrors. The mirror tilt is shown to provide efficient beam extraction through this aperture. A theoretical resonator model based on the vector modes of propagation in a dielectric coaxial waveguide is presented. Experimental data show the feasibility of coaxial waveguide lasers and their ability to supply beams of high power and quality. Experimental data are discussed with respect to the presented theory

Diffusion-cooled CO2-laser with coaxial high frequency excitation and internal axicon

A report on the design and performance of a coaxial laser system with a stable resonator with internal axicon is given. Efficient diffusion cooling is obtained by using an annular transverse high- frequency excited discharge. Experimental results are compared with the results of a loaded resonator model that takes tilted mirrors into account. The agreement between theory and experiment for extraction efficiency, alignment sensitivity, polarization and mode structure is very good

Anordnung zur Formung des geometrischen Querschnitts eines Strahlungsfeldes eines oder mehrerer Gaslaser(s): Anordnung und Verfahren zur Formung und Fuehrung eines Strahlungsfelds eines oder mehrerer Gaslaser(s) (III) (A1)

The device includes a reflection block (8) onto which the outputs (7) of an array of gas laser elements (1) are incident parallel to each other. The laser outputs, separated into at least two parts, are directed downwards at angle to respective corresponding reflecting surfaces of the block. The surface of the reflector is formed with a series of stepped sections that each receive one or more of the laser element emissions. A number of different reflection geometries may be used. The angle of incidence of the array relative to the block determines the grouping (10) and orientation of the reflected beams and this can be varied both vertically and horizontally. USE/ADVANTAGE - Allows laser array output to be easily and cheaply focussed and orientated into e.g. either single line or single point