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[en] X-ray microscopies using polarized x-rays allow for imaging magnetic microstructures down to a 20 nm lateral resolution with chemical sensitivity. Utilizing the pulsed time structure of synchrotron radiation a sub-ns time resolution can be implemented by performing stroboscopic pump-and-probe experiments. The temporal evolution of the magnetization in a 50 nm thin circular permalloy element with a diameter of 2 (micro)m could be imaged with magnetic transmission x-ray microscopy. The magnetic pump pulse to the sample was generated electronically with a rise time of less than 100 ps up to 150 Oe by a microcoil. The probe pulse is the flash of the circularly polarized x-ray beam with a pulse width of about 70 ps at a frequency of 3 MHz. Images were recorded at varying delay times between pump and probe pulse up to 2000 ps. Fast detection schemes utilizing avalanche photo diodes are capable to pick individual bunches from the storage ring
[en] Nanoparticles of Ag-Pt and Ag-Pd with high aspect ratios were synthesized using a radiolysis method. Gamma rays at dose rates below 0.5 kGy/h were used for irradiation. The nanoparticles were characterized by transmission electron microscopy (TEM), optical absorption spectroscopy and x-ray Absorption Fine Structure (XAFS) spectroscopy. Bright field micrographs show that Ag-Pt nanowires are composed of large particles with diameters ranging from 20-30 nm and joined by filaments of diameter between 2-5 nm. The Ag-Pd nanowires have diameters of 20-25 nm and lengths of 1.5 (micro)m. For XAFS measurements, the Pt L3 edge (11.564 keV), Ag K-edge (25.514 keV) and Pd K-edge (24.350 keV) were excited to determine the local structure around the respective atoms in the cluster. The Ag-Pt particles were found to possess a distinct core-shell structure with Pt in the core surrounded by Ag shell, with no indication of alloy formation. However, nanorods of Ag-Pd have formed an alloy for all the alloy compositions.
[en] Ground configuration and low-lying levels of Al-like ions contribute to a variety of laboratory and solar spectra, but the available information in databases are neither complete not necessarily correct. We have performed multireference Moeller-Plesset perturbation theory calculations that approach spectroscopic accuracy in order to check the information that databases hold on the 40 lowest levels of Al-Like ions of iron group elements (K through Ge), and to provide input for the interpretation of concurrent experiments. Our results indicate problems of the database holdings on the levels of the lowest quartet levels in the lighter elements of the range studied. The results of our calculations of the decay rates of five long-lived levels (3s23p 2po3/2, 3s3p24Po J and 3s3p3d 4Fo9/2) are compared with lifetime data from beam-foil, electron beam ion trap and heavy-ion storage ring experiments.
[en] A strong effect of a moderately elevated surface temperature on net carbon deposition and deuterium co-deposition in the DIII-D divertor was observed under detached conditions. A DiMES sample with a gap 2 mm wide and 18 mm deep was exposed to lower-single-null (LSN) L-mode plasmas first at room temperature, and then at 200 C. At the elevated temperature, deuterium co-deposition in the gap was reduced by an order of magnitude. At the plasma-facing surface of the heated sample net carbon erosion was measured at a rate of 3 nm/s, whereas without heating net deposition is normally observed under detachment. In a related experiment three sets of molybdenum mirrors recessed 2 cm below the divertor floor were exposed to identical LSN ELMy H-mode discharges. The first set of mirrors exposed at ambient temperature exhibited net carbon deposition at a rate of up to 3.7 nm/s and suffered a significant drop in reflectivity. In contrast, two other mirror sets exposed at elevated temperatures between 90 C and 175 C exhibited virtually no carbon deposition
[en] We give an overview of atomic spectroscopy performed on electron beam ion traps at various locations throughout the world. Spectroscopy at these facilities contributes to various areas of science and engineering, including but not limited to basic atomic physics, astrophysics, extreme ultraviolet lithography, and the development of density and temperature diagnostics of fusion plasmas. These contributions are accomplished by generating, for example, spectral surveys, making precise radiative lifetime measurements, accounting for radiative power emitted in a given wavelength band, illucidating isotopic effects, and testing collisional-radiative models. While spectroscopy with electron beam ion traps had originally focused on the x-ray emission from highly charged ions interacting with the electron beam, the operating modes of such devices have expanded to study radiation in almost all wavelength bands from the visible to the hard x-ray region; and at several facilities the ions can be studied even in the absence of an electron beam. Photon emission after charge exchange or laser excitation has been observed, and the work is no longer restricted to highly charged ions. Much of the experimental capabilities are unique to electron beam ion traps, and the work performed with these devices cannot be undertaken elsewhere. However, in other areas the work on electron beam ion traps rivals the spectroscopy performed with conventional ion traps or heavy-ion storage rings. The examples we present highlight many of the capabilities of the existing electron beam ion traps and their contributions to physics.
[en] This paper is concerned with the general (inclusive) characteristics of 24Mg interactions with different components of emulsion nuclei. Reaction cross sections, number of interacting projectile protons and shower particle multiplicity distributions are studied. An extended Glauber model in which higher order eclipse corrections are included is found to reproduce correctly the experimental results. (orig.)
[en] The 2s2p22S12 and 2P1/2 levels in the boronlike ions are strongly affected by spin-orbit interaction, which leads to intermediate coupling, and the degree of the deviation from pure LS coupling varies with the nuclear charge of the ions. We have measured the relative intensities of the decays from the nominal 2s2p22S1/2 level to the 2s22p 2P01/2,3/2 fine structure levels of the ground term, for all elements from O to Cl. This ratio would be 1 / 2 for pure LS states, but it clearly deviates from this value in the range of our study. We also discuss the measured relative intensities of the 2s2p22P1/2,3/2 decays. We compare our results with predictions from various calculations involving configuration mixing with electrons up to the n = 3 shell. Our own MCHF calculations indicate that an additional inclusion of n = 4 electrons has no significant effect on the transitions of interest. (orig.)
[en] A new kind of magnetoacoustic wave which is different from the usual compressional hydromagnetic wave (fast Alfven wave) is shown to exist in a magnetized, three component dusty plasma. The ''dust-magnetoacoustic mode'' arises due essentially to the effects which account for the departures from the frozen-in-field approximation for the ion dynamics. Other normal modes in a magnetized dusty plasma are also pointed out. (orig.)