Synchrotron radiation

About: Synchrotron radiation is a research topic. Over the lifetime, 14639 publications have been published within this topic receiving 244775 citations. The topic is also known as: magnetobremsstrahlung radiation & Synchrotron Radiation.

BACH, the beamline for advanced dichroic and scattering experiments at ELETTRA

Abstract: A beamline for advanced dichroism (BACH), to perform light polarization dependent experiments in the 35–1600 eV photon energy range is under construction at the ELETTRA Synchrotron Radiation Source in Trieste, Italy. The radiation source, based on two APPLE-II helical undulators, is designed for high photon flux and high resolving powers. The photons dispersion system is based on a Padmore variable angle spherical grating monochromator with a typical resolving power of 20 000–6000, 20 000–6000, and 15 000–5000 in the energy ranges 35–200 eV, 200–500 eV, and 500–1600 eV, respectively. Two separate branches after the monochromator allow setting two independent experimental chambers. The photon flux in the experimental chamber(s), calculated at the best resolutions achievable and with the aperture of the slits set at 10 μm, is expected to be above 1011 photons’s with linearly or circularly polarized light. In addition, a fourth grating operates in the 400–1600 eV range to provide a higher flux, 1012 photons’...

On the origin of spectral states in accreting black holes

Abstract: The origin of dramatically different electron distributions responsible for Comptonization in black hole X-ray binaries (BHBs) in their various states is discussed. We solve the coupled kinetic equations for photons and electrons without approximations on the relevant cross-sections accounting for Compton scattering, synchrotron radiation, and Coulomb collisions. In the absence of external soft photons, the electrons are efficiently thermalized by synchrotron self-absorption and Coulomb scattering even for pure nonthermal electron injection. The resulting quasi-thermal synchrotron self-Compton spectra have very stable slopes and electron temperatures similar to the hard states of BHBs. The observed hard X-ray spectral slopes, the cutoff at 100 keV, and the MeV tail together require low magnetic fields, ruling out the magnetic dissipation mechanism. The motion of the accretion disk toward the black hole results in larger Compton cooling and lower equilibrium electron temperature. Our self-consistent simulations show that in this case both electron and photon distributions attain a power-law-dominated shape similar to what is observed in the soft state. The electron distribution in the Cyg X-1 soft state might require a strong magnetic field, being consistent with the magnetically dominated corona.

Illuminating the dark corridor in graphene: polarization dependence of angle-resolved photoemission spectroscopy on graphene

Abstract: We have used s- and p-polarized synchrotron radiation to image the electronic structure of epitaxial graphene near the (K) over bar point by angle-resolved photoemission spectroscopy (ARPES). Part of the experimental Fermi surface is suppressed due to the interference of photoelectrons emitted from the two equivalent carbon atoms per unit cell of graphene's honeycomb lattice. Here we show that, by rotating the polarization vector, we are able to illuminate this dark corridor giving access to the complete experimental Fermi surface. Our measurements are supported by first-principles photoemission calculations, which reveal that the observed effect persists in the low-photon-energy regime.

Zone-plate X-ray microscopy.

Abstract: The scope of this article is to describe a transmission X-ray microscope, possible biological applications of soft X-ray microscopy and preliminary results.For soft X-ray microscopy of biological specimens the wavelength range of 1–10 nm is best suited. Microscopy in this wavelength range requires intense X-ray sources as well as high-resolution X-ray lenses. Intense X-radiation is provided by the synchrotron radiation of electron and positron storage rings. Suited X-ray lenses are zone plates.A theoretical treatment of the contrast mechanism and the radiation damage as well as first experiments yield the following results. Firstly, relatively thick (1–10 μm) biological specimens can be investigated. This means that unsectioned dried and even wet cells and cell organelles in a natural state can be examined. Second, it will be possible to resolve cellular aggregates in live cells with a resolution in the region of ≤10nm.