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.

A high-energy-resolution resonant inelastic X-ray scattering spectrometer at ID20 of the European Synchrotron Radiation Facility.

Abstract: An end-station for resonant inelastic X-ray scattering and (resonant) X-ray emission spectroscopy at beamline ID20 of ESRF - The European Synchrotron is presented. The spectrometer hosts five crystal analysers in Rowland geometry for large solid angle collection and is mounted on a rotatable arm for scattering in both the horizontal and vertical planes. The spectrometer is optimized for high-energy-resolution applications, including partial fluorescence yield or high-energy-resolution fluorescence detected X-ray absorption spectroscopy and the study of elementary electronic excitations in solids. In addition, it can be used for non-resonant inelastic X-ray scattering measurements of valence electron excitations.

Particle Acceleration and Non-Thermal Emission in Pulsar Outer Magnetospheric Gap

Abstract: A two-dimensional electrodynamic model is used to study particle acceleration and non-thermal emission mechanisms in the pulsar magnetospheres. We solve distribution of the accelerating electric field with the emission process and the pair-creation process in meridional plane, which includes the rotational axis and the magnetic axis. By solving the evolutions of the Lorentz factor, and of the pitch angle, we calculate spectrum in optical through $\gamma$-ray bands with the curvature radiation, synchrotron radiation, and inverse-Compton process not only for outgoing particles, but also for ingoing particles, which were ignored in previous studies. We apply the theory to the Vela pulsar. We find that the curvature radiation from the outgoing particles is the major emission process above 10 MeV bands. In soft $\gamma$-ray to hard X-ray bands, the synchrotron radiation from the ingoing primary particles in the gap dominates in the spectrum. Below hard X-ray bands, the synchrotron emissions from both outgoing and ingoing particles contribute to the calculated spectrum. The calculated spectrum is consistent with the observed phase-averaged spectrum of the Vela pulsar. We show that the observed five-peak pulse profile in the X-ray bands of the Vela pulsar is reproduced by the inward and outward emissions, and the observed double-peak pulse profile in $\gamma$-ray bands is explained by the outward emissions.

Imaging of magnetic structures by photoemission electron microscopy

Abstract: Photoemission electron microscopy (PEEM) has proven to be a powerful analytical tool in surface science. In this contribution, a status report is given on the application of the PEEM technique in the investigation of surface and interface magnetism. Owing to its fast parallel image acquisition and its wide zoom range, allowing fields of view from almost 1 mm down to a few micrometres, combined with a high base resolution of the order of 20 nm, the method offers a unique access to many aspects in surface and thin-film magnetism on the mesoscopic length scale. There are three basically different modes of magnetic imaging using PEEM. The first one exploits the magnetic x-ray circular dichroism (MXCD) for contrast formation. It offers the important advantage of selecting the magnetic contrast of a certain element via the corresponding x-ray absorption edges using a tuneable x-ray source such as synchrotron radiation. This mode gives access to magnetic structures and coupling phenomena with a sensitivity in the submonolayer range and the capability to image the signal of buried layers with an information depth up to more than 5 nm. The two other modes work with simple UV light sources and are therefore highly attractive for standard laboratory applications. The magnetic stray-field-induced changes of the electron trajectories close to the sample surface lead to a Lorentz-type contrast. A third type of contrast arises as a consequence of the Kerr rotation of the dielectric vector inside a magnetic material, a phenomenon which is also responsible for the well known magneto-optical Kerr effect. Examples and typical applications of magnetic imaging using PEEM are discussed.

Constraints on particle acceleration sites in the Crab nebula from relativistic magnetohydrodynamic simulations

Abstract: The Crab Nebula is one of the most efficient accelerators in the Galaxy and the only galactic source showing direct evidence of PeV particles. In spite of this, the physical process behind such effective acceleration is still a deep mystery. While particle acceleration, at least at the highest energies, is commonly thought to occur at the pulsar wind termination shock, the properties of the upstream flow are thought to be non-uniform along the shock surface, and important constraints on the mechanism at work come from exact knowledge of where along this surface particles are being accelerated. Here we use axisymmetric relativistic MHD simulations to obtain constraints on the acceleration site(s) of particles of different energies in the Crab Nebula. Various scenarios are considered for the injection of particles responsible for synchrotron radiation in the different frequency bands, radio, optical and X-rays. The resulting emission properties are compared with available data on the multi wavelength time variability of the inner nebula. Our main result is that the X-ray emitting particles are accelerated in the equatorial region of the pulsar wind. Possible implications on the nature of the acceleration mechanism are discussed.

Spectral and morphological analysis of the remnant of Supernova 1987A with ALMA and ATCA

Abstract: We present a comprehensive spectral and morphological analysis of the remnant of supernova (SN) 1987A with the Australia Telescope Compact Array (ATCA) and the Atacama Large Millimeter/submillimeter Array (ALMA). The non-thermal and thermal components of the radio emission are investigated in images from 94 to 672 GHz (λ 3.2 mm to 450 μm), with the assistance of a high-resolution 44 GHz synchrotron template from the ATCA, and a dust template from ALMA observations at 672 GHz. An analysis of the emission distribution over the equatorial ring in images from 44 to 345 GHz highlights a gradual decrease of the east-to-west asymmetry ratio with frequency. We attribute this to the shorter synchrotron lifetime at high frequencies. Across the transition from radio to far infrared, both the synchrotron/dust-subtracted images and the spectral energy distribution (SED) suggest additional emission beside the main synchrotron component (Sν∝ν−0.73) and the thermal component originating from dust grains at T ~ 22 K. This excess could be due to free–free flux or emission from grains of colder dust. However, a second flat-spectrum synchrotron component appears to better fit the SED, implying that the emission could be attributed to a pulsar wind nebula (PWN). The residual emission is mainly localized west of the SN site, as the spectral analysis yields −0.4 lesssim α lesssim −0.1 across the western regions, with α ~ 0 around the central region. If there is a PWN in the remnant interior, these data suggest that the pulsar may be offset westward from the SN position.