On X-Ray Waveguiding in Nanochannels: Channeling Formalism

The question on X-ray extreme focusing (smallest reachable spot size) brings us to the idea for using the wave features of X-ray propagation in media. As known, wave features are revealed at propagation in ultra-narrow collimators as well as at glancing reflection from smooth flat and/or strongly curved surfaces. All these phenomena can be described within the general formalism of X-ray channeling.Comment: by the invited lecture at ISRP-1

Measurement of the Positive Muon Anomalous Magnetic Moment to 0.46 ppm

We present the first results of the Fermilab Muon g-2 Experiment for the positive muon magnetic anomaly $a_\mu \equiv (g_\mu-2)/2$. The anomaly is determined from the precision measurements of two angular frequencies. Intensity variation of high-energy positrons from muon decays directly encodes the difference frequency $\omega_a$ between the spin-precession and cyclotron frequencies for polarized muons in a magnetic storage ring. The storage ring magnetic field is measured using nuclear magnetic resonance probes calibrated in terms of the equivalent proton spin precession frequency ${\tilde{\omega}'^{}_p}$ in a spherical water sample at 34.7$^{\circ}$C. The ratio $\omega_a / {\tilde{\omega}'^{}_p}$, together with known fundamental constants, determines $a_\mu({\rm FNAL}) = 116\,592\,040(54)\times 10^{-11}$ (0.46\,ppm). The result is 3.3 standard deviations greater than the standard model prediction and is in excellent agreement with the previous Brookhaven National Laboratory (BNL) E821 measurement. After combination with previous measurements of both $\mu^+$ and $\mu^-$, the new experimental average of $a_\mu({\rm Exp}) = 116\,592\,061(41)\times 10^{-11}$ (0.35\,ppm) increases the tension between experiment and theory to 4.2 standard deviationsComment: 10 pages; 4 figure

Space charge influence on particles channeling in optical lattice

In this paper the effect of a space charge on the dynamics of relativistic particles in a laser channel has been considered. We derived the expression for effective potential describing the dynamics of charged particles including into the study the interaction of particles with each other. Analysing general concepts on the distribution of a particle beam in a channel, we have formulated the condition, which determines the limits of applicability of the perturbation theory when space charge is taken into account. Keywords: Ponderomotive potential, Lasers, Channeling, Quantum particle, Space charg

Excitation and propagation of X ray fluorescence through thin devices with hollowed ordered structures comparison among experimental and theoretical spectra

The lack of models describing the propagation of X-rays in waveguides and the interference mechanism between incident and reflected radiation waves hamper the understanding and the control of wave propagation phenomena occurring in many real systems. Here, experimental spectra collected at the exit of microchannel plates (MCPs) under the total X-ray reflection condition are presented. The results are discussed in the framework of a theoretical model in which the wave propagation is enhanced by the presence of a transition layer at the surface. The angular distributions of the propagating radiation at the exit of these MCPs with microchannels of ~3 µm diameter will also be presented and discussed. These spectra show contributions associated with the reflection of the primary monochromatic beam and with the fluorescence radiation originating from the excitation of atoms composing the surface of the microchannel. The soft X-ray fluorescence spectra collected at the exit of microcapillaries were analyzed in the framework of a wave approximation while diffraction contributions observed at the exit of these hollow X-ray waveguides have been calculated using the Fraunhofer diffraction model for waves in the far-field domain. Data collected at the Si L-edge show that in glassy MCPs the fluorescence radiation can be detected only when the energy of the primary monochromatic radiation is above the absorption edge for grazing angles higher than half of the critical angle of the total reflection phenomenon. Experimental data and simulations of the propagating radiation represent a clear experimental confirmation of the channeling phenomenon of the excited fluorescence radiation inside a medium and point out that a high transmission can be obtained in waveguide optics for parameters relevant to X-ray imaging

Fine features of parametric X-ray radiation by relativistic electrons and ions

In present work within the frame of dynamic theory for parametric X-ray radiation in two-beam approximation we have presented detailed studies on parametric radiation emitted by relativistic both electrons and ions at channeling in crystals that is highly requested at planned experiments. The analysis done has shown that the intensity of radiation at relativistic electron channeling in Si (110) with respect to the conventional parametric radiation intensity has up to 5% uncertainty, while the error of approximate formulas for calculating parametric X-ray radiation maxima does not exceed 1.2%. We have demonstrated that simple expressions for the Fourier components of Si crystal susceptibility χ0 and χgσ could be reduced, as well as the temperature dependence for radiation maxima in Si crystal (diffraction plane (110)) within Debye model. Moreover, for any types of channeled ions it is shown that the parametric X-ray radiation intensity is proportional to z2−b(Z,z)/z with the function b(Z,z) depending on the screening parameter and the ion charge number z=Z−Ze

Status of the Electron Beam Transverse Diagnostics with Optical Diffraction Radiation at FLASH, DESY.

The characterization of the transverse phase space of electron beams with high charge density and high energy is a fundamental requirement for particle accelerator facilities. The knowledge of characteristics of the accelerated beams is of great importance also for the successful development of the next generation light sources and linear colliders. In order to measure the properties of such beams, development of non-invasive and non-intercepting beam diagnostics techniques is necessary. A promising canditate is Optical Diffraction Radiation (ODR), as testified by the interest of many laboratories all around the world. At this purpose, an experiment using ODR to measure the electron beam transverse parameters has been set up at FLASH (former VUV-FEL) at DESY (Hamburg). Radiation emitted by 620 MeV electron beam passing through a 1 mm slit on a screen made of aluminum deposited on a silicon substrate is detected by a low noise, high sensitivity CCD camera.© (2007) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only

X ray radiation channeling in micro channel plates Spectroscopy with a synchrotron radiation beam

We present here the angular distribution of the radiation propagated inside MultiChannel Plates with micro-channels of $\sim 3 \mu m$ diameter. The spectra collected at the exit of the channels present a complex distribution with contributions that can be assigned to the fluorescence radiation, originated from the excitation of the micro-channel walls. For radiation above the absorption edge, when the monochromatic energy in the region of the Si L-edge hits the micro-channel walls with a grazing angle $\theta \geqslant 5^{\circ}$, or at the O K-edge when $\theta \geqslant 2^{\circ}$ a fluorescence radiation is detected. Additional information associated to the fine structures of the XANES spectra detected at the exit of MCPs are also presented and discussed