To maintain gain in the proposed 100 m long linac-driven Linac Coherent Light Source (LCLS) Free Electron Laser (FEL) undulator, the electron and photon beams must propagate colinearly to within -5 urn rms over distances comparable to the 11.7 m FEL gain length in the 6 mm diameter undulator vacuum chamber. We have considered a variety of intercepting and non-intercepting position monitor techn...

Context: Numerical simulations of MHD accretion flows in the vicinity of a supermasssive black hole provide important insights to the problem of why and how systems – such as the Galactic Center – are underluminous and variable. In particular, the simulations indicate that low angular momentum accretion flow is strongly variable both quantitatively and qualitatively. This variability and a rela...

Recently it has been suggested that thermal bremsstrahlung emission, when decouples prior to recombination, creates an excess over the Planck cosmic microwave background spectrum at sub-GHz frequencies. Remarkable by itself, this would also explain a long-standing unexplained deficit in predictions of extragalactic radio background. In brief note we reiterate no such non-thermal component can a...

Traditionally, lead has been used for field shaping in megavoltage electron beams in radiation therapy. In this study, we analyze the dosimetric parameters of a nontoxic, high atomic number (Z = 83), bismuth-loaded material called Gamma Putty that is malleable and can be easily molded to any desired shape. First, we placed an ionization chamber at different depths in a solid water phantom under...

Final state medium-induced gluon radiation in ultradense nuclear matter is shown to favor large angle emission when compared to vacuum bremsstrahlung due to the suppression of collinear gluons. In a simple model of momentum transfers from the medium to the jet+gluon system the phase space distribution of non-Abelian bremsstrahlung is examined to first order in opacity. Perturbative expression f...

The long-term transitions of the black hole candidate Cygnus X-1 (between the states γ1, γ2, and γ3) include the occasional appearance of a strong ∼ MeV bump (γ1), whose strength appears to be anti-correlated with the continuum flux (<∼ 400 keV) due to the Compton upscattering of cold disk photons by the inner, hot corona. We develop a self-consistent disk picture that accounts naturally for th...

X-ray and γ-ray emissions, observed in correlation with negative leaders of lightning and long sparks of high-voltage laboratory experiments, are conventionally connected with the bremsstrahlung of high-energy runaway electrons (REs). Here we extend a focusing mechanism, analyzed in our previous paper, which allows the electric field to reach magnitudes, required for a generation of significant...

An economic technique for calculation of polarized bremsstrahlung process is proposed, assuming typical atomic momentum transfer q ≪ m. The adopted approach is based on the natural reduction of the matrix element to the form V γ + A5γ . Polarization distribution in the fully differential cross-section is analyzed. It is found that at a given momentum transfer to the atom polarization in the pla...