2,294 research outputs found
Experimental Observation of Energy Modulation in Electron Beams Passing Through Terahertz Dielectric Wakefield Structures
We report observation of a strong wakefield induced energy modulation in an
energy-chirped electron bunch passing through a dielectric-lined waveguide.
This modulation can be effectively converted into a spatial modulation forming
micro-bunches with a periodicity of 0.5 - 1 picosecond, hence capable of
driving coherent THz radiation. The experimental results agree well with
theoretical predictions.Comment: v3. Reviewers' suggestions incorporated. Accepted by PR
High pressure effects in fluorinated HgBa2Ca2Cu3O(8+d)
We have measured the pressure sensitivity of Tc in fluorinated
HgBa2Ca2Cu3O(8+d) (Hg-1223) ceramic samples with different F contents, applying
pressures up to 30 GPa. We obtained that Tc increases with increasing pressure,
reaching different maximum values, depending on the F doping level, and
decreases for a further increase of pressure. A new high Tc record (166 K +/- 1
K) was achieved by applying pressure (23 GPa) in a fluorinated Hg-1223 sample
near the optimum doping level. Our results show that all our samples are at the
optimal doping, and that fluorine incorporation decreases the crystallographic
-parameter concomitantly increasing the maximum attainable Tc. This effect
reveals that the compression of the axes is one of the keys that controls
the Tc of high temperature superconductors.Comment: 4 pages, 4 figures, submitted to Phys. Rev.
Synthesis of Single Phase Hg-1223 High Tc Superconducting Films With Multistep Electrolytic Process
We report the multistep electrolytic process for the synthesis of high Tc
single phase HgBa2Ca2Cu3O8+ (Hg-1223) superconducting films. The
process includes : i) deposition of BaCaCu precursor alloy, ii) oxidation of
BaCaCu films, iii) electrolytic intercalation of Hg in precursor BaCaCuO films
and iv) electrochemical oxidation and annealing of Hg-intercalated BaCaCuO
films to convert into Hg1Ba2Ca2Cu3O8+ (Hg-1223). Films were
characterized by thermo-gravimetric analysis (TGA) and differential thermal
analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM).
The electrolytic intercalation of Hg in BaCaCuO precursor is proved to be a
novel alternative to high temperature-high pressure mercuration process. The
films are single phase Hg-1223 with Tc = 121.5 K and Jc = 4.3 x 104 A/cm2.Comment: 17 Pages, 10 Figures. Submitted to Superconductor Science and
Technolog
Chiral Anomaly and
Measurement of the process has revealed a possible conflict
with what should be a solid prediction generated by the chiral anomaly. We show
that inclusion of appropirate energy-momentum dependence in the matrix element
reduces the discrepancy.Comment: 8 page standard Latex fil
Phenomenological study of light (anti)nuclei, (anti)hypertriton and di-Lambda production at RHIC
We present the production of light (anti)nuclei, (anti)hypertriton and
di-Lambda based on coalescence model in central Au+Au collisions at
. The invariant yields of \He(\Hebar),
\hypert(\hypertbar), \Hee(\Heebar) obtained is found to be consistent with the
STAR measurements. The integrated yields for di-Lambda
, and is not strongly dependent
on the parameter employed for coalescence process. Relative particle ratios of
light anti(nuclei) and (anti)hypertriton are explored, and agree with
experimental data and thermal model predictions quite well. An exponential
reducion behavior is presented for the differential invariant yields with
increased baryon number. The production rate reduces by a factor of 1692 (1285)
for each additional antinucleon (nucleon) added to antinuclei (nuclei), and the
production rate of \Libar is predicted to be which is consistent
with STAR result.Comment: 4 pages, 3 figures parallel talk delivered by L. Xue at the 14th
national conference on nuclear structure, April 12nd - 16th, 2012, Huzhou,
Chin
Structure and propertties of ball milled utrahigh-molecular weight Polyethylene - clay composite
In this work the composite material based on polymer matrix filled with clay is studied. The preparation of powder composition consists of mechanical activation of substances and further common ball milling of polymer and clay in a high energy planetary ball mill. The process is divided into two stages; the first stage involves crushing of clay to obtain a nanosized powder, and in the second stage preparation of powdered nanocomposite is carried out. New clay-polymer composite shows considerable increase in modulus of elasticity and a decrease in coefficient of friction
The Longitudinal Polarimeter at HERA
The design, construction and operation of a Compton back-scattering laser
polarimeter at the HERA storage ring at DESY are described. The device measures
the longitudinal polarization of the electron beam between the spin rotators at
the HERMES experiment with a fractional systematic uncertainty of 1.6%. A
measurement of the beam polarization to an absolute statistical precision of
0.01 requires typically one minute when the device is operated in the
multi-photon mode. The polarimeter also measures the polarization of each
individual electron bunch to an absolute statistical precision of 0.06 in
approximately five minutes. It was found that colliding and non-colliding
bunches can have substantially different polarizations. This information is
important to the collider experiments H1 and ZEUS for their future
longitudinally polarized electron program because those experiments use the
colliding bunches only.Comment: 21 pages (Latex), 14 figures (EPS
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