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.

Nanoparticles and nanowires: synchrotron spectroscopy studies

Abstract: This paper reviews the research in nanomaterials conducted in our laboratory in the last decade using conventional and synchrotron radiation techniques. While preparative and conventional characterisation techniques are described, emphasis is placed on the analysis of nanomaterials using synchrotron radiation. Materials of primary interests are metal nanoparticles and semiconductor nanowires and naonribbons. Synchrotron techniques based on absorption spectroscopy such as X-ray absorption fine structures (XAFS), which includes X-ray absorption near edge structures (XANES) and extended X-ray absorption fine structures (EXFAS), and de-excitation spectroscopy, including X-ray excited optical luminescence (XEOL), time-resolved X-ray excited optical luminescence (TRXEOL) and X-ray emission spectroscopy (XES) are described. We show that the tunability, brightness, polarisation and time structure of synchrotron radiation are providing unprecedented capabilities for nanomaterials analysis. Synchrotron studies of prototype systems such as gold nanoparticles, 1-D nanowires of group IV materials, C, Si and Ge as well as nanodiamond, and compound semiconductors, ZnS, CdS, ZnO and related materials are used to illustrate the power and unique capabilities of synchrotron spectroscopy in the characterisation of local structure, electronic structure and optical properties of nanomaterials.

Investigation of the phase evolution in a super-elastic NiTi shape memory alloy (50.7 at.%Ni) under extensional load with synchrotron radiation

Abstract: Inhomogeneous strain distribution associated with stress induced transformation and shear-band formation in super-elastic NiTi is investigated by diffraction with synchrotron radiation and diffraction imaging. We observe a large displacement of the austenite (1 1 0) diffraction peak as a function of tensile strain. This indicates a significant load transfer on residual austenite grains within the martensite matrix of a Luders-like shear transformation band. A distinct stress state occurs at the interface between the shear-band and the surrounding austenite.

Characterization of a tungsten/gas multislit collimator for microbeam radiation therapy at the European Synchrotron Radiation Facility

Abstract: Clinical microbeam radiation therapy (MRT) will require a multislit collimator with adjustable uniform slit widths to enable reliable Monte Carlo-based treatment planning. Such a collimator has been designed, fabricated of >99% tungsten [W] by Tecomet/Viasys (Woburn, Massachusetts, USA) and installed at the 6GeV electron-wiggler-generated hard x-ray ID17 beamline of the European Synchrotron Radiation Facility. Its pair of 125 parallel, 8mm deep, 0.100mm wide radiolucent slits, 0.400mm on center, are perfused with nitrogen gas [N2] to dissipate heat during irradiation. Major improvements in uniformity of microbeam widths and good peak/valley dose ratios combined with a very high dose rate in targeted tissues have been achieved.

Electron Acceleration by Relativistic Surface Plasmons in Laser-Grating Interaction.

Abstract: The generation of energetic electron bunches by the interaction of a short, ultraintense (I > 10 19 W=cm 2) laser pulse with "grating" targets has been investigated in a regime of ultrahigh pulse-to-prepulse contrast (10 12). For incidence angles close to the resonant condition for surface plasmon excitation, a strong electron emission was observed within a narrow cone along the target surface, with energy spectra peaking at 5-8 MeV and total charge of ∼100 pC. Both the energy and the number of emitted electrons were strongly enhanced with respect to simple flat targets. The experimental data are closely reproduced by three-dimensional particle-in-cell simulations, which provide evidence for the generation of relativistic surface plasmons and for their role in driving the acceleration process. Besides the possible applications of the scheme as a compact, ultrashort source of MeV electrons, these results are a step forward in the development of high-field plasmonics. Surface plasmons [1,2], also named surface waves, are electromagnetic (EM) modes localized at the interface of different media which allow local field confinement and enhancement. Surface plasmons are the core of the vibrant research field of plasmonics [3], with applications ranging from light concentration beyond the diffraction limit [4], to biosensors [5] and plasmonic chips [6]. The extension of plasmonics into the regime of high fields, where nonlinear and relativistic effects arise, is largely unexplored. An example is provided by the multiterawatt laser-driven excitation of unipolar surface plasmons by transient charge separation [7,8], with potential application to the generation of intense THz pulses [8,9]. In the optical or near-infrared frequency range, surface plasmons can be excited by laser light incident on a sharp material interface having a periodic modulation, e.g., a grating, to allow phase matching. However, most experiments so far have been restricted to intensities below 10 16 W=cm 2 [10] because of the prepulses inherent in high-power laser systems which can lead to an early disruption of the target structuring. The development of devices for ultrahigh contrast pulses [11,12] now allows us to explore the interaction with targets structured on a submicrometric scale at laser intensities high enough for the electron dynamics to become relativistic [13,14]. In particular, a strong increase of the cutoff energy of protons accelerated from the rear surface of grating targets was observed and related to surface plasmon-enhanced absorption [15]. While a detailed theory is still lacking for nonlinear and relativistic surface plasmons, numerical simulations also showed surface plasmon-related effects in this regime [16,17], including electron acceleration at weakly relativistic intensities [18] and, more recently, surface plasmon-enhanced high harmonics [19] and synchrotron radiation [20] in gratings. In this Letter, we demonstrate that relativistic surface plasmons accelerate high-energy electrons along a grating surface. The acceleration process is related to two basic surface plasmon properties, i.e., the subluminal phase velocity and the longitudinal field component. The energy and number of electrons in gratings irradiated at an incidence angle close to the resonant value for surface plasmon excitation are strongly enhanced with respect to flat targets. At intensities I ¼ 5 × 10 19 W=cm 2 , corresponding to a relativistic parameter a 0 ≃ 5 [where a 0 ¼ ðIλ 2 =10 18 W cm −2 μm 2 Þ 1=2 and λ isthelaserwavelength]theelectronemissionwasconcentrated in a narrow cone with energy spectra peaking at 5-8 MeVand reaching up to ∼20 MeV. The basics of surface plasmon generation and electron acceleration may be described as follows. At high laser intensities (I > 10 18 W=cm 2) a solid target is ionized within one laser cycle, thus the interaction occurs with a dense plasma. Assuming a dielectric function eðωÞ ¼ 1 − ω 2 p =ω 2 ≡ 1 − α (where ω p is the plasma frequency) the phase velocity of a surface plasmon is v p ¼ ω=k ¼ cðα − 2Þ 1=2 =ðα − 1Þ 1=2 where k is the surface plasmon wave vector PRL 116,