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[en] Raising the power of X-ray emission from an X-pinch by increasing the pinch current to the megampere level requires the corresponding increase in the initial linear mass of the load. This can be achieved by increasing either the number of wires or their diameter. In both cases, special measures should be undertaken to prevent the formation of a complicated configuration with an uncontrolled spatial structure in the region of wire crossing, because such a structure breaks the symmetry of the neck formed in the crossing region, destabilizes plasma formation, and degrades X-ray generation. To improve the symmetry of the wire crossing region, X-pinch configurations with a regular multilayer arrangement of wires in this region were proposed and implemented. The results of experiments with various symmetric X-pinch configurations on the COBRA facility at currents of ∼1MA are presented. It is shown that an X-pinch with a symmetric crossing region consisting of several layers of wires made of different materials can be successfully used in megampere facilities. The most efficient combinations of wires in symmetric multilayer X-pinches are found in which only one hot spot forms and that are characterized by a high and stable soft X-ray yield.
[en] Measurements of surface scattering from plane mirrors with different degrees of roughness using soft x-rays are reported. Angle resolved distributions of s-polarized light, scattered in the plane of incidence, were obtained with a precise reflectometer for various angles of incidence and different wavelengths. The influence of the sample preparation and the optical constants on the scattering properties is shown
[en] We have been monitoring the supernova remnant (SNR) 1987A with Chandra observations since 1999. Here we report on the latest change in the soft X-ray light curve of SNR 1987A. For the last ∼1.5 yr (since day ∼8000), the soft X-ray flux has significantly flattened, staying (within uncertainties) at fX ∼ 5.7 x 10-12 erg cm-2 s-1 (corresponding to LX ∼ 3.6 x 1036 erg s-1) in the 0.5-2 keV band. This remarkable change in the recent soft X-ray light curve suggests that the forward shock is now interacting with a decreasing density structure, after interacting with an increasing density gradient over ∼10 yr prior to day ∼8000. Possibilities may include the case that the shock is now propagating beyond a density peak of the inner ring. We briefly discuss some possible implications on the nature of the progenitor and the future prospects of our Chandra monitoring observations.
[en] Conventionally, researchers investigated the number distribution of solar flares by univariate analysis using all available data. For the first time, we investigate the bivariate number distribution of peak flux (f) and duration (T) of soft X-ray flares observed by the Geostationary Operational Environmental Satellite during the past 10 years. First, the univariate number distribution of f is found to obey a power law either for each class of flares or for the B or ≥C flares in a certain range of T. But the power-law index of B-class flares is much smaller than those of other higher-class ones. For the ≥C flares, the longer the duration, the smaller the power-law index. The univariate number distribution of T deviates from the power law at shorter durations and is better fitted by a skewed Gaussian function in logarithmic coordinates for almost any given range of f, reflecting the random phenomena in solar flares. Then, based on the univariate analysis, a linear Gaussian function is proposed to describe the bivariate logarithmic number distribution of f and T, from which the local power-law index with respect to either f or T can also be analyzed. The real number distribution of B flares should be in between the observed one and the power-law distribution of stronger flares (≥C). We suggest that nanoflare activity may not be the dominant source of coronal heating.
[en] This paper summarizes the requirement of X-ray pulsar navigation and the development of X-ray detector. The difficulties of pulsar navigation in space environment are pointed out. The lack of detectors in terms of detection efficiency, time resolution and load is discussed. Finally, some suggestions are given for future research in X-ray pulsar navigation. (paper)
[en] We have carried out an extensive X-ray spectral study of the bare Seyfert 1 galaxy MCG –02–58–22 to ascertain the nature of the X-ray reprocessing media using observations from Suzaku (2009) and simultaneous observations from XMM-Newton and NuSTAR (2016). The most significant results of our investigation are as follows. (1) The primary X-ray emission from the corona is constant in these observations, in terms of both the power-law slope (Γ = 1.80) and luminosity (L 2−10 keV = 2.55 × 1044 erg s−1). (2) The soft excess flux decreased by a factor of 2 in 2016, the Compton hump weakened/vanished in 2016, and the narrow FeKα emission line became marginally broad (σ = 0.35 ± 0.08 keV) and its flux doubled in 2016. (3) From physical model fits, we find that the normalization of the narrow component of the FeKα line does not change in the two epochs, although the Compton hump vanishes in the same time span. Since the primary X-ray continuum does not change, we presume that any changes in the reprocessed emission must arise due to changes in the reprocessing media. Our primary conclusions are as follows. (a) The vanishing of the Compton hump in 2016 can probably be explained by a dynamic clumpy torus that is infalling/outflowing or a polar dusty wind. (b) The torus in this active galactic nucleus possibly has two structures: an equatorial toroidal disk (producing the narrow FeKα emission) and a polar component (producing the variable Compton hump). (c) The reduction of the soft excess flux by half and increase in the FeKα flux by a factor of 2 in the same period cannot be adequately explained by an ionized disk reflection model alone.
[en] The experiments had two goals: (1) Better understanding of the dynamics and neutron production of the focus phase and (2) improved scaling of the neutron yield by operating a high-voltage focus. For the first goal, experiments with a 30-kJ/16-kV plasma focus of the Mather type (NESSI) were performed. The simultaneously applied diagnostics include interferometry, X-ray photography with channel plates, magnetic probes and scintillator/photomultiplier detectors for measuring hard X-ray and neutron emission. In the established chronology one can distinguish five phases in the development of the plasma focus: A compression phase is followed by a short (8 ns) very dense phase, where the density peaks at a minimum radius (t=0, authors' chronology). The plasma cylinder expands to a relatively long-lasting (30 to 70 ns) quiescent phase before instabilities occur. This short unstable phase is followed by a decay phase during which the neutron emission peaks. Important correlations between the plasma parameters and the neutron emission are discussed. Secondly, on the assumption that the neutron yield scales with a high power of the current, it was concluded that a high-voltage focus could result in higher neutron yield as compared with a lower voltage device of the same energy. The proper adjustments of the discharge parameters necessary due to the very short current risetime were investigated. (author)
[en] We report the discovery with XMM-Newton of a hard-thermal (T ∼ 130 MK) and variable X-ray emission from the Be star HD 157832, a new member of the puzzling class of γ-Cas-like Be/X-ray systems. Recent optical spectroscopy reveals the presence of a large/dense circumstellar disk seen at intermediate/high inclination. With a B1.5V spectral type, HD 157832 is the coolest γ-Cas analog known. In addition, its non-detection in the ROSAT all-sky survey shows that its average soft X-ray luminosity varied by a factor larger than ∼3 over a time interval of 14 yr. These two remarkable features, 'low' effective temperature, and likely high X-ray variability turn HD 157832 into a promising object for understanding the origin of the unusually high-temperature X-ray emission in these systems.
[en] A preliminary study of synchrotron light sources has been made, primarily oriented toward x-ray lithography. X-ray lithography is being pursued vigorously in several countries, with a goal of manufacturing high-density computer chips (0.25 μm feature sizes), and may attain commercial success in the next decade. Many other applications of soft x-rays appear worthy of investigation as well. The study group visited synchrotron radiation facilities and had discussions with members of the synchrotron radiation community, particularly Canadians. It concluded that accelerator technology for a conventional synchrotron light source appropriate for x-ray lithography is well established and is consistent with skills and experience at Chalk River Nuclear Laboratories. Compact superconducting systems are being developed also. Their technical requirements overlap with capabilities at Chalk River. (32 refs)