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X-ray Illumination (x-ray + illumination)
Selected AbstractsIn situ investigation of the non-linear optical crystal rubidium titanyl arsenate, RbTiOAsO4, under applied electric field using X-ray imagingJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3 2007P. A. Thomas Recent work on the non-linear optical single-crystal rubidium titanyl arsenate (RbTiOAsO4, RTA) has shown that it exhibits behaviour consistent with a ferroelectric semiconductor under large applied electric fields, with the development of a non-uniform field in the near-surface region. To confirm aspects of the proposed model, the behaviour of 001 slices of initially single-domain RTA, patterned with periodic Ag electrodes of spacing 38,µm, as for periodic poling in non-linear optics, were investigated using synchrotron X-ray section topography with the electric field applied in situ while under X-ray illumination at the ID19 topography beamline of the ESRF, Grenoble. The results of white-beam section topography as both a function of crystal to film distance, and under DC voltage are reported, confirming that there is a bending of the planes in the near-surface region. The strain in the near-surface region was examined directly using high-resolution monochromatic X-ray section topography. This revealed an extensive strain of 3,(±1) × 10,4 at 1,kV, indicating that the electrostrictive coefficient, ,3333, in RTA is positive in sign. [source] Measurement of the speed of X-raysJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2002E. Zolotoyabko X-ray pulses from the Advanced Photon Source at Argonne National Laboratory were used to measure the speed of X-rays in the energy range between 21 and 60,keV. An LiNbO3 -based 0.58,GHz surface acoustic wave device served as a temporal analyzer in the stroboscopic time-resolved diffraction measurements. By synchronizing the surface acoustic wave excitation and periodic X-ray illumination of the LiNbO3 crystal, the temporal modifications in the LiNbO3 diffraction profiles could be followed and the time points of X-ray arrivals at the analyzer position for different analyzer to storage ring distances determined. The speed of the X-rays was determined as the ratio of measured spacings and corresponding delay time intervals. Within the experimental error bars, the obtained X-ray velocities converged to the tabulated constant for the speed of light in a vacuum. [source] An additional soft X-ray component in the dim low/hard state of black hole binariesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2010C. Y. Chiang ABSTRACT We test the truncated disc models using multiwavelength (optical/ultraviolet/X-ray) data from the 2005 hard state outburst of the black hole Swift J1753.5,0127. This system is both fairly bright and has fairly low interstellar absorption, so gives one of the best data sets to study the weak, cool disc emission in this state. We fit these data using models of an X-ray illuminated disc to constrain the inner disc radius throughout the outburst. Close to the peak, the observed soft X-ray component is consistent with being produced by the inner disc, with its intrinsic emission enhanced in temperature and luminosity by reprocessing of hard X-ray illumination in an overlap region between the disc and corona. This disc emission provides the seed photons for Compton scattering to produce the hard X-ray spectrum, and these hard X-rays also illuminate the outer disc, producing the optical emission by reprocessing. However, the situation is very different as the outburst declines. The optical is probably cyclo-synchrotron radiation, self-generated by the flow, rather than tracing the outer disc. Similarly, limits from reprocessing make it unlikely that the soft X-rays are directly tracing the inner disc radius. Instead they appear to be from a new component. This is seen more clearly in a similarly dim low/hard state spectrum from XTE J1118+480, where the 10 times lower interstellar absorption allows a correspondingly better view of the ultraviolet/extreme ultraviolet (EUV) emission. The very small emitting area implied by the relatively high temperature soft X-ray component is completely inconsistent with the much larger, cooler, ultraviolet component which is well fit by a truncated disc. We speculate on the origin of this component, but its existence as a clearly separate spectral component from the truncated disc in XTE J1118+480 shows that it does not simply trace the inner disc radius, so cannot constrain the truncated disc models. [source] Optical spectroscopy of GX 339,4 during the high,soft and low,hard states , II.MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2001Line ionization, emission region We have carried out observations of the X-ray transient GX 339,4 during its high,soft and low,hard X-ray spectral states. Our high-resolution spectroscopic observation in 1999 April suggests that the H, line has a single-peaked profile in the low,hard state as speculated in our previous paper. The He ii,4686 line, however, has a double-peaked profile in both the high,soft and low,hard states. This suggests that the line-emission mechanism is different in the two states. Our interpretation is that double-peaked lines are emitted from a temperature-inversion layer on the accretion disc surface when it is irradiatively heated by soft X-rays. Single-peaked lines may be emitted from outflow/wind matter driven by hard X-ray heating. We have constructed a simple plane-parallel model and we use it to illustrate that a temperature-inversion layer can be formed at the disc surface under X-ray illumination. We also discuss the conditions required for the formation of temperature inversion and line emission. Based on the velocity separations measured for the double-peaked lines in the high,soft state, we propose that GX 339,4 is a low-inclination binary system. The orbital inclination is about 15° if the orbital period is 14.8 h. [source] | ||||||||||