IPG Photonics

About: IPG Photonics is a based out in . It is known for research contribution in the topics: Laser & Fiber laser. The organization has 903 authors who have published 1241 publications receiving 63339 citations.

Fiber lasers for material processing

Abstract: Low power fiber lasers began entering the commercial markets in the early 1990s. Since their introduction, fiber lasers have rapidly progressed in power levels level with greatly improved beam quality to the point where they now exceed any other commercial material processing laser. These lasers, with single mode operation to 1 kilowatt and multi-mode operation to beyond 20 kilowatts, have high wall plug efficiency, an extremely compact footprint, are maintenance free and have a predicted diode life beyond 100,000 hours of continuous operation. Fiber lasers are making inroads into the scientific, medical, government, and in particular, material processing markets. These lasers have greatly expanded the application umbrella due to their unparallel performance combined with the ability to operate at different wavelengths, address remote applications and be propagated great distances in fiber. In the material processing markets, fiber lasers are rapidly gaining share in the automotive, microelectronic, medical device and marking markets, to name a few. The single mode lasers are redefining process parameters that have been accepted for decades. The high brightness multimode-kilowatt class lasers are achieving speeds and depths greater than comparable powered conventional lasers while providing the only commercial material processing lasers operating beyond 6 kilowatts at the 1 micron region.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Cations in glasses under ambient and non-ambient conditions

Abstract: Structural data on the short-and medium-range structure of multicomponent oxide glasses may be obtained by taking advantage of the chemical selectivity of X-ray Absorption Spectroscopy (XAS). Ni K edge XAS in silicate glasses shows that this element occurs in 4- and 5-coordination, the ratio between the two coordination states being composition dependent. [4] Ni is bound to the silicate network, with large alkalis completing charge-compensation. Coordination changes from [6] Ni to [5] Ni and [4] Ni are also observed in borate glasses with increasing potassium content. Low alkali glasses show a medium-range structure consistent with the grafting of nickel octahedra onto boroxol rings. Zirconium is another element which shows a coordination change from [6] Zr to [8] Zr as a function of glass composition. The structural environment of glass components may be modeled using the interatomic distances derived from EXAFS and a bond valence model derived from the Pauling rules. XAS experiments may also be performed in situ at high pressure or high temperature using synchrotron radiation. High pressure EXAFS spectra on germanate glasses show a coordination change of germanium from 4 to 6 with increasing pressure. These modifications are reversible in glasses, which illustrates the need for in situ measurements. High temperature EXAFS and XANES show also a coordination change of Ni during the melting of sodium silicate glass, with an increase of the [4] Ni content in the melt.

Podzolisation and exportation of organic matter in black waters of the Rio Negro (upper Amazon basin, Brazil)

Abstract: In the Rio Negro basin, podzols develop at the expense of clay-depleted laterites through localized and spectacular weathering fronts. This natural process leads to the remobilization of previously accumulated organic matter (OM) which is redistributed within soil profiles and exported towards rivers, hence their typical black coloration. We investigate the fate of OM in the soil–water continuum in the Rio Negro basin through description of the composition of OM potentially mobile at different stages of podzol development and exploration of evidence for contributions from different soil horizons to the exportation of OM into waters. OM was water-extracted from seven key soil samples from a sequence representative of the transition between latosol and podzol on the low elevation plateaux of the Rio Negro basin, thus enabling following both vertical and lateral differentiations. The chemical structure of freeze-dried samples, investigated using 13C nuclear magnetic resonance and thermally assisted hydrolysis and methylation (THM), shows contrasting features depending on the horizon considered. The bulk features of water extracts were first compared with samples collected in the water-tables and rivers draining the soil sequence. A molecular level comparison was then performed with groundwater draining the well-developed podzol. This approach evidenced a contribution from deep horizons of well-developed podzols. It highlights that OM is certainly remobilised after being accumulated in Bh horizons during the development of podzols through accumulation of OM redistributed from surface horizons. The identification of specific compounds opens new perspective to trace a “podzolic origin” of OM in drainage networks.

Magma flow, exsolution processes and rock metasomatism in the Great Messejana-Plasencia dyke (Iberian Peninsula)

Abstract: Magma flow in dykes is still not well understood; some reported magnetic fabrics are contradictory and the potential effects of exsolution and metasomatism processes on the magnetic properties are issues open to debate. Therefore, a long dyke made of segments with different thickness, which record distinct degrees of metasomatism, the Messejana–Plasencia dyke (MPD), was studied. Oriented dolerite samples were collected along several cross-sections and characterized by means of microscopy and magnetic analyses. The results obtained show that the effects of metasomatism on rock mineralogy are important, and that the metasomatic processes can greatly influence anisotropy degree and mean susceptibility only when rocks are strongly affected by metasomatism. Petrography, scanning electron microscopy (SEM) and bulk magnetic analyses show a high-temperature oxidation-exsolution event, experienced by the very early Ti-spinels, during the early stages of magma cooling, which was mostly observed in central domains of the thick dyke segments. Exsolution reduced the grain size of the magnetic carrier (multidomain to single domain transformation), thus producing composite fabrics involving inverse fabrics. These are likely responsible for a significant number of the ‘abnormal’ fabrics, which make the interpretation of magma flow much more complex. By choosing to use only the ‘normal’ fabric for magma flow determination, we have reduced by 50 per cent the number of relevant sites. In these sites, the imbrication angle of the magnetic foliation relative to dyke wall strongly suggests flow with end-members indicating vertical-dominated flow (seven sites) and horizontal-dominated flow (three sites).

A study of transient variations in the Earth's electromagnetic field at equatorial electrojet latitudes in western Africa (Mali and the Ivory Coast)

Abstract: . In the framework of the French-Ivorian participation to the IEEY, a network of 10 electromagnetic stations were installed at African longitudes. The aim of this experiment was twofold: firstly, to study the magnetic signature of the equatorial electrojet on the one hand, and secondly, to characterize the induced electric field variations on the other hand. The first results of the magnetic field investigations were presented by Doumouya and coworkers. Those of the electric field experiment will be discussed in this study. The electromagnetic experiment will be described. The analysis of the electromagnetic transient variations was conducted in accordance with the classical distinction between quiet and disturbed magnetic situations. A morphological analysis of the recordings is given, taking into consideration successively quiet and disturbed magnetic situations, with the results interpreted in terms of the characterization of external and internal sources. Particular attention was paid to the effects of the source characteristics on the induced field of internal origin, and to the bias they may consequently cause to the results of electromagnetic probing of the Earth; the source effect in electromagnetic induction studies. During quiet magnetic situations, our results demonstrated the existence of two different sources. One of these, the SRE source, was responsible for most of the magnetic diurnal variation and corresponded to the well-known magnetic signature of the equatorial electrojet. The other source (the SR*E source) was responsible for most of the electric diurnal variation, and was also likely to be an ionospheric source. Electric and magnetic diurnal variations are therefore related to different ionospheric sources, and interpreting the electric diurnal variation as induced by the magnetic field diurnal variation is not relevant. Furthermore, the magnetotelluric probing of the upper mantle at dip equator latitudes with the electromagnetic diurnal variation is consequently impossible to perform. In the case of irregular variations, the source effect related to the equatorial electrojet is also discussed. A Gaussian model of equatorial electrojet was considered, and apparent resistivities were computed for two models of stratified Earth corresponding to the average resistive structure of the two tectonic provinces crossed by the profile: a sedimentary basin and a cratonic shield. The apparent resistivity curves were found to depend significantly on both the model used and the distance to the center of the electrojet. These numerical results confirm the existence of a daytime source effect related to the equatorial electrojet. Furthermore, we show that the results account for the observed differences between daytime and night-time apparent resistivity curves. In particular, it was shown that electromagnetic probing of the Earth using the classical Cagniard-Tikhonov magnetotelluric method is impossible with daytime recordings made at dip latitude stations. Key words. Electromagnetics (Transient and time do- main) Geomagnetism and paleomagnetism (geomagne- tic induction) Ionosphere (equatorial ionosphere)