Bremsstrahlung in a strong laser field

We consider the bremsstrahlung of electrons as they collide with ions in a strong laser field. The bremsstrahlung spectrum has been found to be enriched in sufficiently strong fields. Particular attention is given to the coherent bremsstrahlung component. We propose a qualitative model that explains our results. The possibility of experimentally observing the coherent bremsstrahlung component in a strong field is discussed.     

Bremsstrahlung of nonrelativistic electrons in metals with allowance made for the polarization channel

We theoretically investigate the bremsstrahlung that appears when nonrelativistic electrons are scattered in a metal target with allowance made for the polarization contribution. We take into account the interference of ordinary and polarization bremsstrahlung, the absorption of radiation in the target material, the energy losses and elastic scattering of an electron by atoms of the medium, and the coherent effects when the radiating electron interacts with the target. We analyze the influence of the target thickness on the process and the contribution of polarization bremsstrahlung to the total yield of bremsstrahlung photons as a function of the problem parameters.     

Comparison of the bremsstrahlung absolute probability densities produced by experiment and PENELOPE for low‐energy (keV) electrons incident on solid silver

There has been some recent controversy concerning whether or not polarizational bremsstrahlung (sometimes referred to as ‘atomic bremsstrahlung’) contributes to the total bremsstrahlung spectrum in experiments involving electrons incident on solid targets. We have compared the bremsstrahlung absolute probability density predictions of the widely used Monte Carlo code, PENELOPE, to the results of experiments involving 17.5‐keV and 20‐keV electrons incident on a thick silver target. Comparisons of the results of our experiments to the predictions of the PENELOPE code, which is based on ordinary bremsstrahlung alone, suggest that there were no significant polarizational bremsstrahlung contributions to the total bremsstrahlung spectra in our experiments. Copyright © 2015 John Wiley & Sons, Ltd.     

Beta-induced bremsstrahlung shielding parameters in various types of steels

ABSTRACT

Present work studies the bremsstrahlung efficiency, bremsstrahlung dose rate, probability of energy loss by beta during bremsstrahlung emission and specific bremsstrahlung constant of the beta radionuclide for various steels such as XM-5, 317LM, XM-17216, AL-6XN, JS700, NIROSTA 4565S and stainless steel. We have compared the shielding properties among the studied different steels. From the detailed study, the steel type 317LM is having the highest bremsstrahlung dose rate and specific bremsstrahlung constant values than the other studied steels. This means the steel type 317LM is a good absorber of bremsstrahlung radiation than the other studied steels. Hence it is better to use the steel type 317LM in the nuclear power plants than stainless steels and other steels to avoid the secondary radiation such as bremsstrahlung.     

Bremsstrahlung shielding parameters in polymer concretes

Concretes are used for shielding in nuclear power plants. Beta radiation is emitted during the nuclear reactions. This beta radiation interacts with the concrete and results in secondary radiation such as bremsstrahlung. Shielding parameters of beta-induced bremsstrahlung in concretes are important in the field of radiation protection. We have evaluated the cross section, yield, intensity and dose rate of beta-induced bremsstrahlung by pure beta nuclides of end point energy ranges from 0.4 to 5?MeV in some polymer-based concretes such as sulfur polymer concrete, barium polymer concrete, calcium polymer concrete, fluorine polymer concrete, chlorine polymer concrete and germanium polymer concrete. We have compared the shielding properties among the studied polymer concretes. The efficiency, intensity and dose rate of bremsstrahlung increases with a maximum energy of beta nuclide and modified atomic number of the concrete. From the detailed study, it is clear that the barium polymer concrete is having large bremsstrahlung dose rate and specific bremsstrahlung constant values than the other studied polymer concretes. This means barium polymer concrete is a good absorber of bremsstrahlung radiation than the other studied polymer concretes.     

The role of the polarization mechanism for emission of radiation by atoms over a broad photon frequency range

This paper develops an effective method for calculating the bremsstrahlung cross section with allowance for the polarization mechanism. We calculate the cross section of bremsstrahlung produced in the scattering of electrons and positrons by H and Kr atoms. We also demonstrate the important role of polarization bremsstrahlung in the formation of the total emission spectrum over the entire frequency range. Zh. éksp. Teor. Fiz. 114, 458–473 (August 1998)     

Bremsstrahlung in heavy-ion reactions

We investigate bremsstrahlung processes induced by heavy ions: nuclear dipole and quadrupole radiation, radiation from bound target electrons into the continuum and secondary electron bremsstrahlung (SEB), which contribute to the background of the X-ray spectra. A comparison with experiment is presented.     

电子储存环直线节中的轫致辐射的剂量率的计算

电子储存环的电子束流与环中的残余气体碰撞会产生轫致辐射,这也是造成储存环中束流损失的主要原因之一.一直以来,由于各种原因,人们在辐射防护上并没有给予它足够的重视.本文通过一些经验公式对该轫致辐射进行了分析和计算:(1)该轫致辐射会导致较高的剂量率,尤其是在直线节;(2)影响剂量率的几个主要因素;(3)轫致辐射中的高能粒子占有很大的比例.     

Photon emission from bare quark stars

We investigate the photon emission from the electrosphere of a quark star. We show that at temperatures T ≈ 0.1–1 MeV, the dominating mechanism is the bremsstrahlung due to bending of electron trajectories in the mean Coulomb field of the electrosphere. The radiated energy for this mechanism is much larger than that for the Bethe-Heitler bremsstrahlung. The energy flux from the mean field bremsstrahlung also exceeds the one from the tunnel e ⁺ e ^? pair creation. We demonstrate that the LPM suppression of the photon emission is negligible.     

Bremsstrahlung in the nuclear medium: Search for coherence phenomena

Photon angular distributions and energy spectra up to the kinematical limit have been measured in proton reactions with light and heavy targets. For the first time the dependence of photon spectra on scattered protons has been measured to investigate the influence of multiple-scattering processes on the photon production. A strong suppression of bremsstrahlung relative to a quasi-free production model using the free pn bremsstrahlung cross section is observed in the low-energy regime of the photon spectrum in p+nucleus reactions. We attribute this effect to modifications of the bremsstrahlung amplitude in the nuclear medium and to interference of photon amplitudes due to multiple scattering of nucleons.     

Stabilization effect of Weibel modes due to inverse bremsstrahlung absorption in laser fusion plasma using Krook collisions model

In this work, the Weibel instability due to inverse bremsstrahlung absorption in laser fusion plasma has been investigated. The stabilization effect due to the coupling of the self-generated magnetic field by Weibel instability with the laser wave field is explicitly showed. The main result obtained in this work is that the inclusion of self-generated magnetic field due to Weibel instability to the inverse bremsstrahlung absorption causes a stabilizing effect of excited Weibel modes. We found a decrease in the spectral range of Weibel unstable modes. This decrease is accompanied by a reduction of two orders in the growth rate of instability or even stabilization of these modes. It has been shown that the previous analyses of the Weibel instability due to inverse bremsstrahlung have overestimated the values of the generated magnetic fields. Therefore, the generation of magnetic fields by the Weibel instability due to inverse bremsstrahlung should not affect the experiences of an inertial confinement fusion.     

Influence of acoustic waves on coherent bremsstrahlung from 20 MeV electrons

We investigate coherent bremsstrahlung from electrons with the energy 20 MeV incident at small angles to crystallographic planes of quartz crystal periodically deformed by acoustic waves. Depending on the parameters of the acoustic wave and on the incidence angle, the presence of deformation can either enhance or reduce the bremsstrahlung cross-section.     

Photon formation length in Hanbury-Brown and Twiss interferometry of bremsstrahlung photons

We study the effect of the photon formation length on the interference of two bremsstrahlung photons in the simplest case of radiation emitted by only two charged particles. Most of interference patterns obtained can be interpreted in terms of the photon formation length. After having analyzed the simplest situations we discuss the interference of bremsstrahlung photons in more realistic and more complicated situations. A possibility of studying the effect in synchrotron radiation is briefly sketched.     

Pion bremsstrahlung and critical phenomena in relativistic nuclear collisions

We investigate the dependence of pion bremsstrahlung on the deceleration of the nuclei in relativistic heavy ion collisions. The vicinity of an abnormal phase in nuclear matter can lead - owing to critical N-N scattering - to faster deceleration or decreasing transparency of the nuclei. This would result in a threshold enhancement of the pion bremsstrahlung cross section, which in turn can be used to search for abnormal nuclear states experimentally.     

Photon Production in a Chemically Equilibrating Quark-Gluon Plasma at Finite Baryon Density： Complete Leading Order Results

We investigate hard photon production of the near-collinear bremsstrahlung and a new process called the inelastic pair annihilation, fully including the LPM effect, in a chemically equilibrating quark-gluon plasma at finite baryon density, and find that the effect of the system evolution on the photon production and large contribution of the bremsstrahlung make the total photon yield of the two processes as a strongly increasing function of the initial quark chemical potential.     

Absolute doubly differential cross sections for electron bremsstrahlung from rare gas atoms at 28 and 50 keV

Absolute doubly differential bremsstrahlung cross sections from Xe, Kr, Ar, and Ne have been measured for electron bombarding energies of 28 and 50 keV. Bremsstrahlung photons have been detected at 90 degrees to the incident electron beam at energies ranging from 5 keV up to the kinematic end point. The results are compared with predictions of ordinary bremsstrahlung and of total bremsstrahlung that include polarizational bremsstrahlung from the target atom calculated in the stripping approximation. All previous absolute cross sections have been from thin-film solid targets and have not shown any polarizational bremsstrahlung contribution. The present results, the first from free atoms, provide definitive evidence for the contribution of polarizational bremsstrahlung to the photon spectrum from electron bremsstrahlung.     

Comparison of atomic potentials and bremsstrahlung Gaunt factors in dense aluminum plasmas

We determine and compare high temperature high density atomic potentials for dense aluminum plasmas. We then evaluate bremsstrahlung Gaunt factors from these potentials utilizing various methods. The potentials considered are obtained from density functional theory, from the hypernetted chain/Poisson model and from the Thomas-Fermi model. The bremsstrahlung spectra obtained for these three potentials, with the partial wave expansion method and for incident electrons of about 1 keV, are in qualitative agreement. We indicate in which circumstances and with what precision bremsstrahlung Gaunt factors can also be estimated from much simpler potentials, such as the Debye or ion sphere model, and from much simpler calculations of the spectrum, such as the Born-Elwert approximation or a simple classical mechanics approach. The aluminum plasmas considered have temperatures of 0.5-1 keV and electron densities of 10²⁵, 10²⁴, 10²³cm^-3.     

Time Evolution of High-Energy Bremsstrahlung and Argon Ion Production in Electron Cyclotron Resonance Ion-Source Plasma

Bremsstrahlung radiation measurement is one of the most commonly used plasma-diagnostics methods. Most of the bremsstrahlung measurements with electron cyclotron resonance ion sources (ECRISs) have been performed in continuous-operation mode yielding information only on the steady-state bremsstrahlung emission. This paper describes results of bremsstrahlung and argon ion-current measurements with the JYFL 14-GHz ECRIS operated in a pulsed mode. The bremsstrahlung radiation was studied as a function of neutral-gas pressure and radio frequency power. The timescale of ECRIS bremsstrahlung production is compared to ion-production timescale for different charge states of argon for the first time. It was observed, for example, that the ion currents of different charge states reach the steady state before the bremsstrahlung emission rate saturates.      

Suppression of the polarization bremsstrahlung from a fast charged particle in an amorphous medium

Based on a consistent quantum-mechanical approach, we calculate and analyze the suppression of the polarization bremsstrahlung (PB) from a fast charged particle moving in an amorphous medium. The suppression effect is attributable to destructive interference between the contributions from atoms of condensed material to the bremsstrahlung due to their finite sizes and chaotic arrangement. We calculate the spectral and angular PB dependences on various targets that demonstrate characteristic features of the phenomenon under consideration. We have established the region of the clearest manifestation of the suppression effect. The results obtained by various methods of calculation are compared.