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 new powder diffractometer for synchrotron radiation with a multiple-detector system.

Abstract: A new powder diffractometer for synchrotron radiation with six detector arms has been constructed. Five detector arms are attached radially at intervals of 25° to the 2θ axis and form a multiple-detector system. Five scintillation counters coupled with flat Ge(111) crystal analyzers on the respective arms can simultaneously record the whole powder pattern divided into five segments, each with an equal 2θ span. The optics design is based on flat-specimen reflection geometry using a parallel beam. The intensity data are collected using a 2θ step-scan technique in asymmetric diffraction at a fixed incident angle. A sixth multi-purpose detector arm can be used in the conventional single-arm scan mode. It can be equipped with various kinds of analyzers such as long horizontal parallel slits, a fiat or channel-cut crystal analyzer, a receiving slit and a solid-state detector. Test operations of the multiple-detector system, conducted at the Photon Factory in Tsukuba, recorded a full width at half maximum of 0.022° and a peak maximum intensity of more than 40000 counts s−1 for the (111) reflection from Si powder. The whole powder pattern of Mg2SiO4 over a 2θ range of 130° could be step-scanned at a step interval of 0.004° (2θ) in just 4 h. Results of whole-powder-pattern decomposition and Rietveld refinement of the Mg2SiO4 pattern are given.

General description of electromagnetic radiation processes based on instantaneous charge acceleration in `endpoints'

Abstract: We present a methodology for calculating the electromagnetic radiation from accelerated charged particles. Our formulation - the 'endpoint formulation' - combines numerous results developed in the literature in relation to radiation arising from particle acceleration using a complete, and completely general, treatment. We do this by describing particle motion via a series of discrete, instantaneous acceleration events, or 'endpoints', with each such event being treated as a source of emission. This method implicitly allows for particle creation and destruction, and is suited to direct numerical implementation in either the time or frequency domains. In this paper we demonstrate the complete generality of our method for calculating the radiated field from charged particle acceleration, and show how it reduces to the classical named radiation processes such as synchrotron, Tamm's description of Vavilov-Cherenkov, and transition radiation under appropriate limits. Using this formulation, we are immediately able to answer outstanding questions regarding the phenomenology of radio emission from ultra-high-energy particle interactions in both the earth's atmosphere and the moon. In particular, our formulation makes it apparent that the dominant emission component of the Askaryan effect (coherent radio-wave radiation from high-energy particle cascades in dense media) comes from coherent 'bremsstrahlung' from particle acceleration, rathermore » than coherent Vavilov-Cherenkov radiation.« less

Synchrotron-radiation-operated cryogenic electrical-substitution radiometer as the high-accuracy primary detector standard in the ultraviolet, vacuum-ultraviolet, and soft-x-ray spectral ranges.

Abstract: The accuracy of detector calibration in the UV, vacuum-ultraviolet, and soft-x-ray spectral ranges could be significantly improved by the use of the synchrotron radiation electrical substitution radiometer (SYRES) as the primary detector standard. The SYRES radiometer is optimized for use with spectrally dispersed synchrotron radiation as supplied by two monochromator beam lines in the radiometry laboratory of the Physikalisch-Technische Bundesanstalt at the Berlin electron-storage ring (BESSY). Wavelength ranges from 0.8 to 25 nm and from 35 to 400 nm are covered. The typically available radiant power of approximately 1-10 microW can be measured with the SYRES radiometer with a standard relative uncertainty of less than 0.2%. The spectral responsivity of qualified photodiodes for use as secondary detector standards is determined by direct comparison with the primary detector standard at an arbitrary wavelength. At present, the scale of spectral responsivity is realized with a standard relative uncertainty of well below 1% in the spectral ranges 0.8-3.5 nm, 5-25 nm, and 120-400 nm. We provide a comprehensive description of the SYRES radiometer and of the two facilities for detector calibration in the UV and vacuum-ultraviolet spectral ranges and in the soft-x-ray spectral range, respectively, and we discuss the achievable uncertainties in the calibration of detectors.

The JLab high power ERL light source

Abstract: A new THz/IR/UV photon source at Jefferson Lab is the first of a new generation of light sources based on an Energy-Recovered, (superconducting) Linac (ERL). The machine has a 160 MeV electron beam and an average current of 10 mA in 75 MHz repetition rate hundred femtosecond bunches. These electron bunches pass through a magnetic chicane and therefore emit synchrotron radiation. For wavelengths longer than the electron bunch the electrons radiate coherently a broadband THz ∼ half cycle pulse whose average brightness is >5 orders of magnitude higher than synchrotron IR sources. Previous measurements showed 20 W of average power extracted [Carr, et al., Nature 420 (2002) 153]. The new facility offers simultaneous synchrotron light from the visible through the FIR along with broadband THz production of 100 fs pulses with >200 W of average power. The FELs also provide record-breaking laser power [Neil, et al., Phys. Rev. Lett. 84 (2000) 662]: up to 10 kW of average power in the IR from 1 to 14 μm in 400 fs pulses at up to 74.85 MHz repetition rates and soon will produce similar pulses of 300–1000 nm light at up to 3 kW of average power from the UV FEL. These ultrashort pulses are ideal for maximizing the interaction with material surfaces. The optical beams are Gaussian with nearly perfect beam quality. See www.jlab.org/FEL for details of the operating characteristics; a wide variety of pulse train configurations are feasible from 10 ms long at high repetition rates to continuous operation. The THz and IR system has been commissioned. The UV system is to follow in 2005. The light is transported to user laboratories for basic and applied research. Additional lasers synchronized to the FEL are also available. Past activities have included production of carbon nanotubes, studies of vibrational relaxation of interstitial hydrogen in silicon, pulsed laser deposition and ablation, nitriding of metals, and energy flow in proteins. This paper will present the status of the system and discuss some of the discoveries we have made concerning the physics performance, design optimization, and operational limitations of such a first generation high power ERL light source.

Dots, Clumps, and Filaments: The Intermittent Images of Synchrotron Emission in Random Magnetic Fields of Young Supernova Remnants

Abstract: Nonthermal X-ray emission in some supernova remnants originates from synchrotron radiation of ultrarelativistic particles in turbulent magnetic fields. We address the effect of a random magnetic field on synchrotron emission images and spectra. A random magnetic field is simulated to construct synchrotron emission maps of a source with a steady distribution of ultrarelativistic electrons. Nonsteady localized structures (dots, clumps, and filaments), in which the magnetic field reaches exceptionally high values, typically arise in the random field sample. These magnetic field concentrations dominate the synchrotron emission (integrated along the line of sight) from the highest energy electrons in the cutoff regime of the distribution, resulting in an evolving, intermittent, clumpy appearance. The simulated structures resemble those observed in X-ray images of some young supernova remnants. The lifetime of X-ray clumps can be short enough to be consistent with that observed even in the case of a steady particle distribution. The efficiency of synchrotron radiation from the cutoff regime in the electron spectrum is strongly enhanced in a turbulent field compared to emission from a uniform field of the same magnitude.