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.

140 W Cr:ZnSe laser system

Abstract: We report a significant breakthrough in the development of fiber-pumped high-power CW laser systems based on Cr2+:ZnS and Cr2+:ZnSe gain media. We demonstrate output power levels of up to 140 W near 2500 nm, and 32 W at 2940 nm with corresponding optical efficiencies of 62% and 29%. Our novel approach is based on rapid simultaneous scanning of the collinear laser mode and pump beam across the Cr:ZnS/Se gain element which allows us to virtually eliminate thermal lensing effects and obtain unprecedented levels of output power with very high optical-to-optical efficiency.

Dehydration and partial melting in subduction zones: Constraints from U-series disequilibria

Abstract: [1] We present a critical reappraisal of U-series data from arc volcanoes to constrain slab dehydration and melting processes using a global subduction zone data set. There is no clear evidence for significant mobilization of Th or Pa in dehydration fluids while the source region of arc rocks is relatively oxidized and mobility of U is strongly enhanced. It is argued that along-arc U/Th and U/Pa isotope data reflect time-integrated addition of U from the slab to the mantle wedge. The presence of large Ra-Th disequilibrium correlated with Ba/Th ratios provides evidence for some very recent fluid addition and fast magma ascent. This is consistent with radiogenic Os isotope signatures in arc lavas that can only be preserved if there is no melt-peridotite equilibration during melt transport. The 231Pa excesses found in most arc lavas provide clear evidence for a melting signature and require that the timescale of melt production cannot be as short as the timescale of melt migration (<100 annum). We propose a dynamic model in which melting is initiated by fluid fluxing and where melt is rapidly extracted out of the mantle via high-velocity channels while 231Pa excess is produced at melting rates consistent with literature estimates of melt productivity. An alternative model with continuous flux melting would require a long melting timescale (1–5 Ma), a large melting region and the mobility of Th and Pa in fluids. A model with a time lag between melting and initial dehydration is more consistent with a thermal structure where the wet solidus is not reached before an intermediate depth.

Low Z elements (Mg, Al, and Si) K-edge X-ray absorption spectroscopy in minerals and disordered systems

Abstract: Soft X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy have been performed at the Mg-, Al- and Si-K edges in order to establish the ability of this spectroscopy to derive structural information in disordered solids such as glasses and gels. Mg- and Al-K XANES are good structural probes to determine the coordination state of these elements in important minerals, glasses and gels. In a CaO MgO 2SiO2 glass Mg XANES spectra differ from that found in the crystalline equivalent, with a significant shift of the edge maxima to lower energy, consistent with a CN lower than 6. Mg-EXAFS on the same sample are in agreement and indicate the presence of 5-coordinated Mg with Mg O distances of 2.01A. In aluminosilicate gels, Al K XANES has been used to investigate the [4]Al/Altotal ratios. These ratios increase as the Al/Si ratios decrease. Aluminosilicate and ferric-silicate gels were studied by using Si K edge XANES. XANES spectra differ significantly among the samples studied. Aluminosilicate gels with Al/Si= 1 present a different Al and Si local environment from that known in clay minerals with the same Al/Si ratio. The gel-to-mineral transformation thus implies a dissolution-recrystallization mechanism. On the contrary, ferric-silicate gel presents a Si local environment close to that found in nontronite which may be formed by a long range ordering of the initial gels.

Structural environments around molybdenum in silicate glasses and melts. i. influence of composition and oxygen fugacity on the local structure of molybdenum

Abstract: The coordination chemistry of molybdenum was investigated in nine series of synthetic silicate glasses, including sodium disilicate (NS2), sodium trisilicate (NS3), albite (Ab), anorthite (An), Ab50An50, Ab30An70, diopside (DI), rhyolite (RH), and basalt (BA), using electron paramagnetic resonance (EPR) and X-ray absorption fine structure (XAFS) spectroscopies. The Mo content of these glasses ranges from 300 ppm to 3 wt.%. On the basis of results derived from high-resolution X-ray absorption near-edge structure (XANES) spectroscopy, molybdenum is present primarily as molybdate moieties [Mo(VI)O42−] in most of the glass compositions prepared at f (O2) values ranging from 1 atm to 10−12 atm (temperatures ranging from 1100 to 1700°C, i.e., from air to IW+4). Analysis of extended XAFS (EXAFS) spectra of these glasses indicates an average Mo–O distance of ~1.76(1) A. No evidence for second-neighbor Si or Al around Mo was found in any of the glasses, confirming that molybdate moieties are not connected to the tetrahedral framework, in agreement with Pauling bond-valence predictions. The presence of molybdate moieties in regions of these glasses enriched in network modifiers helps explain why crystalline molybdates can nucleate easily in silicate glasses (and, by extension, in the corresponding melts). In the highly polymerized glass compositions (such as “Ab” or “RH”), Mo(VI)O66− moieties also exist, but at minor levels (<20% of the total Mo). In glasses prepared at low f (O2) (near IW), reduced species of Mo occur, such as molybdenyl [Mo(V) and Mo(IV)]. In glasses prepared at even lower f (O2) (near IW+4), Mo is present as a metallic precipitate. The prevalence of molybdate moieties in silicate glasses until relatively low oxygen fugacities (IW) are achieved appears to be at variance with the fact that molybdenite, Mo(IV)S2, is the dominant Mo-bearing mineral in the Earth’s crust. In a companion paper, we re-examine the speciation of molybdenum in more complex systems that are closer to geochemical reality, such as high-temperature melts, densified (high-pressure) glasses, and silicate glass compositions enriched in volatiles.