Search results for "electron density"
showing 10 items of 428 documents
Development of an array of calorimetric low-temperature detectors for heavy ion physics
2006
Abstract Calorimetric low-temperature detectors have been investigated for several applications in heavy ion physics within the last 15 years. The detectors used consist of sapphire absorbers of 2×3×0.33 mm 3 and superconducting aluminum transition edge sensors operated at T ≈1.5 K. To fully exploit the potential of such detectors for heavy ion physics, a detector array is developed. For this purpose, a specially adapted 4 He bath cryostat with a base temperature of 1.2 K, which allows an active detector area of 30×80 mm 2 , was constructed. As different detectors have different transition temperatures, each detector pixel has to be adjusted to its specific working point and temperature sta…
Density of Phonon States in Superconducting FeSe as a Function of Temperature and Pressure
2010
The temperature and pressure dependence of the partial density of phonon states (phonon-DOS) of iron atoms in superconducting ${\text{Fe}}_{1.01}\text{Se}$ was studied by $^{57}\text{F}\text{e}$ nuclear inelastic scattering. The high-energy resolution allows for a detailed observation of spectral properties. A sharpening of the optical phonon modes and shift of all spectral features toward higher energies by $\ensuremath{\sim}4\mathrm{%}$ with decreasing temperature from 296 to 10 K was found. However, no detectable change at the tetragonal--orthorhombic phase transition around 100 K was observed. Application of a pressure of 6.7 GPa, connected with an increase in the superconducting temper…
The influence of topological phase transition on the superfluid density of overdoped copper oxides
2017
We show that a topological quantum phase transition, generating flat bands and altering Fermi surface topology, is a primary reason for the exotic behavior of the overdoped high-temperature superconductors represented by $\rm La_{2-x}Sr_xCuO_4$, whose superconductivity features differ from what is described by the classical Bardeen-Cooper-Schrieffer theory [J.I. Bo\^zovi\'c, X. He, J. Wu, and A. T. Bollinger, Nature 536, 309 (2016)]. We demonstrate that 1) at temperature $T=0$, the superfluid density $n_s$ turns out to be considerably smaller than the total electron density; 2) the critical temperature $T_c$ is controlled by $n_s$ rather than by doping, and is a linear function of the $n_s$…
Resolution of Weighted Homogeneous Surface Singularities
2000
The purpose of this article is to review the method of Orlik and Wagreich to resolve normal singularities on weighted homogeneous surfaces X. Moreover, we explain the description of such surfaces by automorphy factors due to Dolgachev and Pinkham.
High Energy, High Resolution X-Ray Spectroscopy: Microcalorimeters For Nuclear Line Astrophysics
2005
We introduce focusing optics and microcalorimeter spectroscopy to nuclear line emission astrophysics with a balloon payload concept called, B‐MINE. It is designed to probe the deepest regions of a supernova explosion by detecting 44Ti emission at 68 keV with spatial and spectral resolutions that are sufficient to determine the velocity distribution of the 44Ti emitting region. B‐MINE has a thin plastic foil telescope multilayered to maximize the reflectivity in a 20 keV band centered at 68 keV and a microcalorimeter array optimized for the same energy band. This combination provides a reduced background, an energy resolution of 50 eV and a 3σ sensitivity in 106 s of 6 × 10−8 ph cm−2 s−1 at …
Variable zoom digital in-line holographic microscopy
2020
Abstract We report on a novel layout providing variable zoom in digital in-line holographic microscopy (VZ-DIHM). The implementation is in virtue of an electrically tunable lens (ETL) which enables to slightly shift the illumination source axial position without mechanical movement of any system component. Magnifications ranging from ~15X to ~35X are easily achievable using the same layout and resulting in a substantial variation of the total field of view (FOV). The performance of the proposed setup is, first, validated using a resolution test target where the main parameters are analyzed (theoretically and experimentally) and, second, corroborated analyzing biological sample (prostate can…
Multi-illumination single-holographic-exposure lensless Fresnel (MISHELF) microscopy using 4 channels
2021
MISHELF microscopy is generalized by considering 4 illumination/detection channels while retaining single-shot working principle, twin image mitigation and noise averaging. Proof of principle validation is included considering a resolution test target.
Cubic optical nonlinearity of
1999
We perform angular non-critical phase-matching third-harmonic generation (THG) experiments in (KTP). From these experiments, we determine the magnitude and sign of the two phase-matched nonlinear coefficients of by a complete analysis of phase-matching properties of the cascaded quadratic and pure cubic processes, the resolution of the coupled propagation equations and by the calculation of the quadratic and cubic dielectric susceptibility tensor by an extended bond charge model; we find: and . We also demonstrate that the two studied THG are mainly governed by the cubic interaction.
PEEM with high time resolution—imaging of transient processes and novel concepts of chromatic and spherical aberration correction
2006
The potential of time-resolved photoemission electron microscopy (PEEM) for imaging ultrafast processes and for aberration correction in full-field imaging is discussed. In particular, we focus on stroboscopic imaging of precessional magnetic excitations via XMCD-PEEM exploiting the time structure of synchrotron radiation (magnetic field pulse pump–X-ray probe). In a special bunch-compression mode at BESSY, a time resolution of about 15 ps has been obtained. Further, we discuss an all-optical pump–probe technique using femtosecond laser excitation. A highly promising alternative to stroboscopic imaging is an approach using time-resolved image detection. As a second application of time-resol…
Elastic constants in RbI, determined by inelastic neutron scattering
1978
Long-wavelength acoustic phonons have been studied in the whole (100)-plane of RbI at 295 K by means of inelastic neutron scattering. The raw data have been corrected for resolution effects taking into account the curvature of the dispersion surface and variations of the mode eigenvectors. The shifts of the neutron groups due to these resolution effects are discussed in detail. The analysis of the experimental results gives for the zero sound elastic constantsc11=28.15±0.5,c12=3.7±0.5 andc44=2.85±0.1 1010 dyn/cm2. A comparison with first sound elastic constants taken from ultrasonic measurements yields significant differences between the high and low frequency elastic constantsc11 andc″=(c1…