Search results for "Bremsstrahlung"
showing 10 items of 114 documents
Effect of quantized conductivity on the anomalous photon emission radiated from atomic-size point contacts
2019
We observe anomalous visible to near-infrared electromagnetic radiation emitted from electrically driven atomic-size point contacts. We show that the number of photons released strongly depends on the quantized conductance steps of the contact. Counter-intuitively, the light intensity features an exponential decay dependence with the injected electrical power. We propose an analytical model for the light emission considering an out-of-equilibrium electron distribution. We treat photon emission as bremsstrahlung process resulting from hot electrons colliding with the metal boundary and a find qualitative accord with the experimental data.
Photonuclear reactions with zinc: A case for clinical linacs
2015
WOS: 000365732300003
X-ray emitting hot plasma in solar active regions observed by the SphinX spectrometer
2012
Aims. The detection of very hot plasma in the quiescent corona is important for diagnosing heating mechanisms. The presence and the amount of such hot plasma is currently debated. The SphinX instrument on-board the CORONAS-PHOTON mission is sensitive to X-ray emission of energies well above 1 keV and provides the opportunity to detect the hot plasma component. Methods. We analysed the X-ray spectra of the solar corona collected by the SphinX spectrometer in May 2009 (when two active regions were present). We modelled the spectrum extracted from the whole Sun over a time window of 17 days in the 1.34− 7k eV energy band by adopting the latest release of the APED database. Results. The SphinX …
A model of M87 nuclear emission without ADAF
2007
We present a simple physical model of the central source emission in the M87 galaxy. It is well known that the observed X‐ray luminosity from this galactic nucleus is much lower than the predicted one, if a standard radiative efficiency is assumed. Up to now the main model invoked to explain such a luminosity is the ADAF (Advection‐Dominated‐Accretion‐Flow) model. Our approach supposes only a simple axis‐symmetric adiabatic accretion with a low angular momentum together with the bremsstrahlung emission process in the accreting gas. With no other special hypothesis on the dynamics of the system, this model agrees well enough with the luminosity value measured by Chandra.
A Simple Model of Radiative Emission in M87
2005
We present a simple physical model of the central source emission in the M87 galaxy. It is well known that the observed X-ray luminosity from this galactic nucleus is much lower than the predicted one, if a standard radiative efficiency is assumed. Up to now the main model invoked to explain such a luminosity is the ADAF (Advection-Dominated-Accretion-Flow) model. Our approach supposes only a simple axis-symmetric adiabatic accretion with a low angular momentum together with the bremsstrahlung emission process in the accreting gas. With no other special hypothesis on the dynamics of the system, this model agrees well enough with the luminosity value measured by Chandra.
Atomic physics of positronium with intense slow positron beams
2002
Abstract The theory of quantum electrodynamics has presented a complete calculation of the energy levels of positronium (Ps, e + e − ) up to the order R ∞ α 4 . The annihilation rates for para -Ps (1 1 S 0 ) and ortho -Ps (1 1 S 1 ) are completely known up to the order R ∞ α 5 and R ∞ α 6 , respectively. The present experimental uncertainty for spectroscopic results is 5–100 times larger than the theoretical uncertainty. For the annihilation rates the experimental situation is even worse. The theoretical predictions have presently reached a level of precision which is a challenge to experimentalists! The experimental uncertainty for the fine- and hyperfine transitions in the Ps atom is dete…
The 0.1-100 keV Spectrum of LMC X-4 in the High State: Evidence for a High Energy Cyclotron Absorption Line
2001
We report on the spectral analysis of the X-ray pulsar LMC X-4 in its high state out of eclipse observed by BeppoSAX. During this observation no coherent pulsations are detected. The primary continuum is well described by a power law with a high energy cutoff (E_cutoff ~ E_fold ~ 18 keV). The addition of a cyclotron absorption line at ~100 keV improves the fit significantly. The inferred magnetic moment is 1.1 10^{31} Gauss cm^3, in agreement with the value estimated assuming that the neutron star is at the spin equilibrium, as it has been proposed for this source. The remaining excess at low energies can be fitted by a Comptonization of soft photons by moderately hot electrons (kT ~0.9 keV…
Plasma emission at the laser tripled frequency
2003
The third harmonic generation in the skin-layer of a dense hot plasma due to inverse bremsstrahlung is investigated for regimes having increasing experimental relevance. New analytical dependencies of the radiation flux density at the frequency 3ω on the plasma and fundamental wave parameters are established.
Isobar excitation in proton-proton bremsstrahlung
1978
Abstract The contribution of intermediate nucleon isobars to proton-proton bremsstrahlung is calculated in a relativistic model. Using conventional coupling constants and form factors for the exchange of π - and ρ-mesons we find that for photon energies ω > 100 MeV isobar excitation increases the cross section markedly over the prediction of soft-photon calculations. Our results agree well with recent experiments at incident proton energy T lab =730 MeV.
Efficiency and dynamic range of the photostimulable x-ray storage material KBr:In
1997
By calibrating the photostimulated luminescence (PSL) response with the known intensity of a standard light source, efficiency of the KBr:In powder material to the x- ray bremsstrahlung exposure at room temperature is estimated. At 44 and 85 kV voltages on the x-ray tube, the values of (8 plus or minus 2) multiplied by 10 5 and (18 plus or minus 4) multiplied by 10 5 photons from 1 mm 2 area of the 1 mm thick material are obtained as PSL responses on a 1 mR x-ray exposure, respectively. Under an assumption of the uniform x-ray excitation within the material, the maximum values for the x-ray irradiation dose and the PSL response both corresponding to the upper limit of linearity range are te…