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Register a new userBroad angular anisotropy of multiple scattering in a Si crystal
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We observed reduction of multiple Coulomb scattering of 855 MeV electrons within a Si crystalline plate w.r.t. an amorphous plate with the same mass thickness. The reduction owed to complete or partial suppression of the coherent part of multiple scattering in a crystal vs crystal orientation with the beam. Experimental data were collected at Mainz Mikrotron and critically compared to theoretical predictions and Monte Carlo simulations. Our results highlighted maximal 7 % reduction of the r.m.s. scattering angle at certain beam alignment with the [100] crystal axes. However, partial reduction was recorded over a wide range of alignment of the electron beam with the crystal up to 15 deg. This evidence may be relevant to refine the modelling of multiple scattering in crystals for currently used software, which is interesting for detectors in nuclear, medical, high energy physics.
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In this paper, we discuss an experimental layout for the two-crystals scenario at the Super Proton Synchrotron (SPS) accelerator. The research focuses on a fixed target setup at the circulating machine in a frame of the Physics Beyond Colliders (PBC) project at CERN. The UA9 experiment at the SPS serves as a testbench for the proof of concept, which is planning to be projected onto the Large Hadron Collider (LHC) scale. The presented in the text configuration was used for the quantitative characterization of the deflected particle beam by a pair of bent silicon crystals. For the first time in the double-crystal configuration, a particle deflection efficiency by the second crystal of $0.188 pm 3 cdot 10^{-5}$ and $0.179 pm 0.013$ was measured on the accelerator by means of the Timepix detector and Beam Loss Monitor (BLM) respectively. In this setup, a wide range angular scan allowed a possibility to textit{in situ} investigate different crystal working regimes (channeling, volume reflection, etc.), and to measure a bent crystal torsion.
The real-space multiple-scattering (RSMS) approach is applied to model non-resonant inelastic scattering from deep core electron levels over a broad energy spectrum. This approach is applicable to aperiodic or periodic systems alike and incorporates ab initio, self-consistent electronic structure and final state effects. The approach generalizes to finite momentum transfer a method used extensively to model x-ray absorption spectra (XAS), and includes both near edge spectra and extended fine structure. The calculations can be used to analyze experimental results of inelastic scattering from core-electrons using either x-ray photons (NRIXS) or electrons (EELS). In the low momentum transfer region (the dipole limit), these inelastic loss spectra are proportional to those from XAS. Thus their analysis can provide similar information about the electronic and structural properties of a system. Results for finite momentum transfer yield additional information concerning monopole, quadrupole, and higher couplings. Our results are compared both with experiment and with other theoretical calculations.
We present general algorithms to convert scattering data of linear and area detectors recorded in various scattering geometries to reciprocal space coordinates. The presented algorithms work for any goniometer configuration including popular four-circle, six-circle and kappa goniometers. We avoid the use of commonly employed approximations and therefore provide algorithms which work also for large detectors at small sample detector distances. A recipe for determining the necessary detector parameters including mostly ignored misalignments is given. The algorithms are implemented in a freely available open-source package.
Laser-cleaning of the electrodes in a planar micro-fabricated ion trap has been attempted using ns pulses from a tripled Nd:YAG laser at 355nm. The effect of the laser pulses at several energy density levels has been tested by measuring the heating rate of a single 40Ca+ trapped ion as a function of its secular frequency. A reduction of the electric-field noise spectral density by ~50% has been observed and a change in the frequency dependence also noticed. This is the first reported experiment where the anomalous heating phenomenon has been reduced by removing the source as opposed to reducing its thermal driving by cryogenic cooling. This technique may open the way to better control of the electrode surface quality in ion microtraps.
The temperature evolution of spin relaxation time, {tau}sf, in degenerate silicon (Si)-based lateral spin valves is investigated by means of the Hanle effect measurements. {tau}sf at 300 K is estimated to be 1.68+-0.03 ns and monotonically increased with decreasing temperature down to 100 K. Below 100 K, in contrast, it shows almost a constant value of ca. 5 ns. The temperature dependence of the conductivity of the Si channel shows a similar behavior to that of the {tau}sf, i.e., monotonically increasing with decreasing temperature down to 100 K and a weak temperature dependence below 100 K. The temperature evolution of conductivity reveals that electron scattering due to magnetic impurities is negligible. A comparison between {tau}sf and momentum scattering time reveals that the dominant spin scattering mechanism in the Si is the Elliott-Yafet mechanism, and the ratio of the momentum scattering time to the {tau}sf attributed to nonmagnetic impurities is approximately 3.77*10^-6, which is more than two orders of magnitude smaller than that of copper.
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