Search results for "SB"
showing 10 items of 1841 documents
Switching Reciprocity On and Off in a Magneto-Optical X-Ray Scattering Experiment Using Nuclear Resonance ofα−Fe57Foils
2012
Reciprocity is when the scattering amplitude of wave propagation satisfies a symmetry property, connecting a scattering process with an appropriate reversed one. We report on an experiment using nuclear resonance scattering of synchrotron radiation, which demonstrates that magneto-optical materials do not necessarily violate reciprocity. The setting enables us to switch easily between reciprocity and its violation. In the latter case, the exhibited reciprocity violation is orders of magnitude larger than achieved by previous wave scattering experiments.
A common optical algorithm for the evaluation of specular spin polarized neutron and Mössbauer reflectivities
2001
Using the general approach of Lax for multiple scattering of waves a 2x2 covariant expression for the reflectivity of polarized slow neutrons of a magnetic layer structure of arbitrary complexity is given including polarization effects of the external magnetic field. The present formalism is identical to the earlier published one for the (nuclear) resonant X-ray (Mossbauer) reflectivity and properly takes the effect of the external magnetic field of arbitrary direction on the neutron beam into account. The form of the reflectivity matrix allows for an efficient numerical calculation.
A portable readout system for silicon microstrip sensors
2010
Abstract This system can measure the collected charge in one or two microstrip silicon sensors by reading out all the channels of the sensor(s), up to 256. The system is able to operate with different types (p- and n-type) and different sizes (up to 3 cm 2 ) of microstrip silicon sensors, both irradiated and non-irradiated. Heavily irradiated sensors will be used at the Super Large Hadron Collider, so this system can be used to research the performance of microstrip silicon sensors in conditions as similar as possible to the Super Large Hadron Collider operating conditions. The system has two main parts: a hardware part and a software part. The hardware part acquires the sensor signals eith…
Problems of electron detection in Depth-Selective Conversion Electron Mössbauer Spectroscopy
1992
Applications of Depth-Selective Conversion Electron Mossbauer Spectroscopy (DCEMS) are limited by the long measuring times needed for collecting sufficient data statistics. To shorten the recording time, the background should be reduced and the detection efficiency for conversion electrons should be improved. For57Co/57Fe DCEMS, systematic studies were performed to investigate the origin, shape, and structure of the background components in DCEMS data distributions for various samples using channeltrons and low-noise scintillation counters as electron detectors.
A time-differential Mössbauer emission spectrometer with high efficiency and high time resolution
1986
A high-efficiency, high rate-capability, computer-based measuring setup for Time-Differential Mossbauer Spectroscopy was constructed. Applying NaI(Tl) and plastic scintillators for the detection of the 14.4 keV and 122 keV γ-radiation respectively, a superior timing (2, 3 ns FWHM) was achieved by a “fast-fast-ultra fast” timing method developed for that purpose.
Magnetic hyperfine anomaly in muonic193Ir
1977
The nuclear decay of the 5/2+ 139 keV state to the 3/2+ ground state was observed in muonic193Ir. The hyperfine splitting of the 3/2+ state and 5/2+ state was determined to be 640±100 eV and 1280±160 eV, respectively. The ground state splitting is about twice that of a point nucleus, an anomaly never observed this large. This is mainly due to the different radial distribution of spin and orbital magnetization of a d3/2 proton configuration for which these contributions nearly cancel to zero in the magnetic moment. But calculations including configuration mixing and coupling to a vibrating or a deformed core show deviations. The groundstate anomaly is in line with that observed by the Mossba…
The Electric Field Gradient and the Quadrupole Interaction
1984
The Mossbauer effect has become a popular method in analytical chemistry. In contrast to other techniques such as x-ray spectroscopy, NMR, EPR, and MCD where highly sophisticated evaluation procedures are applied to obtain reliable information on the chemical compound, the Mossbauer effect is generally used on a low level concerning the evaluation of quadrupole split spectra. This procedure on a low level is favored by the structure of the spectra especially the simple doublet of the 3/2 → 1/2 nuclear transitions in paramagnetic and diamagnetic compounds. The separation of the two absorption lines, the quadrupole splitting ΔE Q and the center of the two lines, the isomer shift, are easily d…
The structure of the accretion disk in the lensed quasar SBS 0909+532
2011
We derive the size and temperature profile of the accretion disk of the lensed quasar SBS 0909+532 by measuring the wavelength dependence (chromaticity) of the microlensing magnification produced by the stars in the lens galaxy. After correcting for extinction using the flux ratios of 14 emission lines, we observe a marked change in the B-A flux ratio with wavelength, varying from -0.67 ± 0.05 mag at (rest frame) ∼1460 Åto -0.24 ± 0.07 mag at ∼6560 Å. For λ ≳ 7000 both effects, extinction and microlensing, look minimal. Simulations indicate that image B rather than A is strongly microlensed. If we model the change in disk size from 1460 Å to 6560 Å using a Gaussian source (I exp(-R 2/2r 2 s…
Instantaneous root mean squire value of the acoustic emission as a means of measuring partial discharges
2003
The author presents the measurement results of the parameter A/sub RMS/ for three types of partial discharges (PDs) generated in a typical high-voltage system: on pressboard, on resin, and on glass. A typical run of A/sub RMS/ on an X-Y register is shown. It manifests a relatively stable instantaneous root mean square value of the electric signal converted from the acoustic signal as a function of time. Results obtained for the three surfaces demonstrate that the parameter A/sub RMS/ is perfectly suitable for characterizing PDs measured by the acoustic method. It is univocally connected with the energy of the generated PD. >
Density of Phonon States in Superconducting FeSe as a Function of Temperature and Pressure
2010
The temperature and pressure dependence of the partial density of phonon states (phonon-DOS) of iron atoms in superconducting ${\text{Fe}}_{1.01}\text{Se}$ was studied by $^{57}\text{F}\text{e}$ nuclear inelastic scattering. The high-energy resolution allows for a detailed observation of spectral properties. A sharpening of the optical phonon modes and shift of all spectral features toward higher energies by $\ensuremath{\sim}4\mathrm{%}$ with decreasing temperature from 296 to 10 K was found. However, no detectable change at the tetragonal--orthorhombic phase transition around 100 K was observed. Application of a pressure of 6.7 GPa, connected with an increase in the superconducting temper…