Search results for "edge"
showing 10 items of 3866 documents
A Hard Tail in the Broad Band Spectrum of the Dipper XB 1254-690
2001
We report on the results of spectral analysis of the dipping source XB 1254-690 observed by the BeppoSAX satellite. We find that the X-ray dips are not present during the BeppoSAX observation, in line with recent RXTE results. The broad band (0.1-100 keV) energy spectrum is well fitted by a three-component model consisting of a multicolor disk blackbody with an inner disk temperature of ~0.85 keV, a comptonized spectrum with an electron temperature of ~2 keV, and a bremsstrahlung at a temperature of ~20 keV. Adopting a distance of 10 kpc and taking into account a spectral hardening factor of ~1.7 (because of electron scattering which modifies the blackbody spectrum emitted by the disk) we e…
Numerical study of a multiscale expansion of the Korteweg de Vries equation and Painlev\'e-II equation
2007
The Cauchy problem for the Korteweg de Vries (KdV) equation with small dispersion of order $\e^2$, $\e\ll 1$, is characterized by the appearance of a zone of rapid modulated oscillations. These oscillations are approximately described by the elliptic solution of KdV where the amplitude, wave-number and frequency are not constant but evolve according to the Whitham equations. Whereas the difference between the KdV and the asymptotic solution decreases as $\epsilon$ in the interior of the Whitham oscillatory zone, it is known to be only of order $\epsilon^{1/3}$ near the leading edge of this zone. To obtain a more accurate description near the leading edge of the oscillatory zone we present a…
Temperature and pressure dependence of the optical absorption in hexagonal MnTe
2000
The absorption edge of hexagonal (NiAs structure) antiferromagnetic MnTe has been measured by means of light transmission experiments carried out at different temperatures in the range 16--420 K $(P=1\mathrm{bar})$ and hydrostatic pressures up to 9 GPa $(T=295\mathrm{K}).$ An indirect band gap has been found, in agreement with previous band-structure calculations, with an energy of ${E}_{\mathrm{ig}}=1.272\ifmmode\pm\else\textpm\fi{}0.013\mathrm{eV}$ at room temperature and pressure. The temperature dependence of the absorption edge is linear above the N\'eel temperature ${T}_{N}=310\mathrm{K},$ with a temperature coefficient $dE/dT=\ensuremath{-}(3.5\ifmmode\pm\else\textpm\fi{}0.1)\ifmmode…
Operation of transition-edge sensors with excess thermal noise
2006
The superconducting transition-edge sensor (TES) is currently one of the most attractive choices for ultra-high resolution calorimetry in the keV x-ray band, and is being considered for future ESA and NASA missions. We have performed a study on the noise characteristics of Au/Ti bilayer TESs, at operating temperatures around ~100 mK, with the SQUID readout at 1.5 K. Experimental results indicate that without modifications the back-action noise from the SQUID chip degrades the noise characteristics significantly. We present a simple and effective solution to the problem: by installing an extra shunt resistor which absorbs the excess radiation from the SQUID input, we have reduced the excess …
Improving the Performance of Quasi-Hemispherical CdZnTe Detectors Using Infrared Stimulation
2012
The influence of monochromatic optical stimulation with wavelengths from 400 to 1100 nm on the characteristics of CdZnTe quasi-hemispherical detectors was studied. It was found that illumination with infrared (IR) light with wavelengths of 870-900 nm close to the absorption edge of the CdZnTe significantly improves the performance of the detector at room temperature. Improvement can be achieved with low-intensity IR illumination at 1-300 μW depending on the chosen wavelength of illumination. Higher intensity illumination was observed to lead to the degradation of the detector's spectrometric characteristics. IR radiation was noted to influence the detector's sensitivity, changing the equili…
Optimizing the operating temperature of a transition edge sensor
2006
We discuss the theory for optimizing the operating temperature of a voltage biased superconducting transition edge sensor (TES) in terms of energy resolution and speed, considering only internal detector noise sources. The noise processes included in the modeling are the unavoidable Johnson and phonon noise. The phonon noise is calculated for the case of ballistic transport. If other external and excess internal noise sources are not dominant, an optimal operating temperature can be found to minimize the energy resolution. The detector slows down by approximately a factor of two at the optimal energy resolution point.
Search for excited leptons in Z0 decay
1990
Due to the severity of system-wide power outages, though their probability of occurrence is slight, regulatory authorities require that a system restoration plan be drawn up and kept up to date at all times. The power outage that affected northeastern North America in 2003 proved the need for such a requirement. The particular structure of Hydro-Quebec's power system requires the use of a highly specific system restoration procedure. The daily preparation of the system restoration plan is based on a strategy whose application requires that a restoration sequence be drawn up that uses available equipment, the electrical behavior of which has been validated using appropriate studies. Over the…
The response of (95,97)Mo to supernova neutrinos
2011
Knowledge about nuclear responses to neutrinos is essential for both astrophysical applications and studies of neutrino properties. We perform in this paper calculations of the cross sections for neutral-current neutrino scattering off the odd A = 95,97 Mo isotopes for energies appropriate for the detection of supernova neutrinos. Both the incoherent and coherent contributions to the cross sections are evaluated. The prominently contributing nuclear final states are identified and analysed. We employ the microscopic quasiparticle-phonon model (MQPM) to construct the wave functions of the initial and final nuclear states. The response of the aforementioned nuclei to supernova neutrinos are c…
A BeppoSAX study of the Galactic Z-source GX 340+0
2004
Abstract We present the results of a BeppoSAX broad band (0.1–200 keV) observation of the Z-source GX 340+0. The 1.8–30 keV continuum is well described by a blackbody ( kT BB ∼0.5 keV) plus a Comptonized component with seed photons temperature ∼ 1 keV and electron temperature ∼ 3 keV. A hard tail dominates the spectrum above 30 keV. It can be fitted using a bremsstrahlung component or, equivalently, a powerlaw (with a low-energy cutoff). We detect also a Gaussian line at ∼6.8 keV and an absorption edge at ∼9.2 keV. A low-energy (∼1 keV) unresolved feature needs further investigations.
Optical investigations of TlBr detector crystals
2004
Shift of fundamental absorption edge, the position of main luminescence bands, the luminescence decay and transient absorption spectra in three TlBr crystals were studied. The γ-quanta detector made from TlBr crystals with similar transient absorption and luminescence parameters shows similar detector properties. The iodine impurity in TlBr was detected by optical methods. The role of impurities and crystal defects in γ-quanta detectors manufactured is discussed.