36 research outputs found
Synchrotron radiation contributions to optical diffraction radiation measurements
If we try to measure the backward optical diffraction radiation (BODR) of
high energy electrons from a conductive slit or a semi infinitive plate, the
electron beam will pass thru the bending or steering magnets or magnet lenses
before striking the target. The synchrotron radiation (SR) from these magnets
can obscure the BODR measurements. An analysis of the properties of SR from
these magnets is in this paper presented. A model based on the modified Lenar
Wikherd potentials was created, and the SR angular distribution from
relativistic electrons in bending and steering magnets for different conditions
of radiation in the optical region was calculated. The analysis shows, that for
the conditions of the KEK ATF extraction line, the intensity of SR exceeds that
of the backward optical transition radiation (BOTR) from the conducting
targets, and it is much lager than the intensity of the BODR. The SR intensity
from the steering magnets depends on its tuning and may be comparable to BOTR.
Thus, these results it is seen, that the problem of separation of the BODR and
SR in the BODR measurements is important. Two methods resolving of this problem
is in this article suggested
The Measurement of the Asymmetry of Tensor-Polarized Deuteron Electrodisintegration at 180 MeV Electron Energy
The nucleon emission asymmetry in d(e, pn)e' reaction was measured using the tensor-polarized deuterium jet target in the VEPP-2 electron storage ring. At the present experimental accuracy, the results for the proton energy interval Ep= 12-100 MeV do not contradict the nonrelativistic calculations.
Investigation of resonant polarization radiation of relativistic electrons in gratings at small angles
The Resonant Optical Polarization Radiation (ROPR) in the Smith-Purcell
geometry and the one from the inclined grating at the Tomsk synchrotron and
6-MeV microtron have been investigated. The polarization radiation was observed
at 4.2o from the 200 MeV electron beam and at 5o from the 6.2 MeV electron
beam. Two methods of measurement of ROPR maxima in these two cases have been
used. In the first case (the experiment on synchrotron) we have fixed the
wavelength of radiation using an optical filter; the orientation dependence of
this radiation was measured. In this dependence we have observed two peaks of
radiation from electrons in gold foil grating of 0.1 mm period. The first large
peak is a zeroth order peak in direction of specular reflection, and the second
one is the 1-st order peak of resonant polarization radiation. In the
experiment on microtron the spectra of ROPR from aluminum foil strip grating of
0.2 mm period in the Smith-Purcell geometry were measured, and the peak of the
1-st order Smith-Purcell radiation in these spectra was observed. The
comparison of data obtained with the simulation results has been performed
Effect of mesoscopic inhomogeneities on the critical current of bulk melt-textured YBCO
The downsizing 211-inclusions and an increase of their density leads to rise
in mean critical current value in Y-based melt textured material. Very often
211-inclusion are spread in the material volume non-homogeneous, with typical
scale 50 - 100 micrometer. Therefore it is difficult to find the real
correlation between local critical current and the inclusions distribution. We
performed a study of a local critical current using modified magneto-optic
technique on a melt-textured YBaCuO ceramic, found the areas with constant
current and studied the real structure of the material in the areas, inclusions
distribution and their sizes, by scanning electron microscopy and X-ray
microanalysis. The estimation of a pinning in these places, by taking into
account the amount of inclusions and the length of their boundaries, and
comparison with the value of local critical current reveals a strait
correlation between the density of inclusions and the current but shows
remarkable quantitative disagreement.Comment: PDF (8 pages, 4 figures
Modelling and experimental study on β-phase depletion behaviour of HVOF sprayed free-standing CoNiCrA1Y coatings during oxidation
This paper investigates the β-phase depletion behaviour during oxidation of free-standing CoNiCrA1Y (Co-31.7%Ni-20.8%Cr-8.1%A1-0.5%Y, all in wt%) bond coats prepared by high velocity oxy-fuel (HVOF) thermal spraying. The microstructure of the coatings was characterised using scanning electron microscopy with energy dispersive X-ray (EDX) analysis and electron backscatter diffraction (EBSD). It comprises a two phase structure of fcc γ-Ni and bcc β-NiA1, with grain sizes varying largely from 0.5 to 2 μm for both phases. Isothermal oxidation tests of the free-standing coatings were carried out at 1100 °C for times up to 250 h. The β phase depletion behaviour at the surface was measured and was also simulated using Thermo-Calc and DICTRA software. An A1 flux function derived from an oxide growth model was employed as the boundary condition in the diffusion model. The diffusion calculations were performed using the TTNi7 thermodynamic database together with the MOB2 mobility database. Reasonable agreement was achieved between the measured and the predicted element concentration and phase fraction profiles after various time periods. Grain boundary diffusion is likely to be important to element diffusion in this HVOF sprayed CoNiCrA1Y coating due to the sub-micron grains
Rapid and highly variable warming of lake surface waters around the globe
In this first worldwide synthesis of in situ and satellite-derived lake data, we find that lake summer surface water temperatures rose rapidly (global mean = 0.34°C decade−1) between 1985 and 2009. Our analyses show that surface water warming rates are dependent on combinations of climate and local characteristics, rather than just lake location, leading to the counterintuitive result that regional consistency in lake warming is the exception, rather than the rule. The most rapidly warming lakes are widely geographically distributed, and their warming is associated with interactions among different climatic factors—from seasonally ice-covered lakes in areas where temperature and solar radiation are increasing while cloud cover is diminishing (0.72°C decade−1) to ice-free lakes experiencing increases in air temperature and solar radiation (0.53°C decade−1). The pervasive and rapid warming observed here signals the urgent need to incorporate climate impacts into vulnerability assessments and adaptation efforts for lakes.Peer reviewe
A global database of lake surface temperatures collected by in situ and satellite methods from 1985–2009
Peer reviewe
A new SPS programme
A new experiemntal program to study hadron production in hadron-nucleus and nucleus-nucleus collisions at the CERN SPS has been recently proposed by the NA49-future collaboration. The physics goals of the program are: (i) search for the critical point of strongly interacting matter and a study of the properties of the onset of deconfinemnt in nucleus-nucleus collisions, (ii) measurements of correlations, fluctuations and hadron spectra at high transverse momentum in proton-nucleus collisions needed as for better understanding of nucleus-nucleus results, (iii) measurements of hadron production in hadron-nucleus interactions needed for neutrino (T2K) and cosmic-ray (Pierre Auger Observatory and KASCADE) expriments. The physics of the nucleus-nucleus program is reviewed in this presentation
Search for the QCD critical point at SPS energies
Lattice QCD calculations locate the QCD critical point at energies accessible at the CERN Super Proton Synchrotron (SPS). We present average transverse momentum and multiplicity fluctuations, as well as baryon and anti-baryon transverse mass spectra which are expected to be sensitive to effects of the critical point. The future CP search strategy of the NA61/SHINE experiment at the SPS is also discussed.Lattice QCD calculations locate the QCD critical point at energies accessible at the CERN Super Proton Synchrotron (SPS). We present average transverse momentum and multiplicity fluctuations, as well as baryon and anti-baryon transverse mass spectra which are expected to be sensitive to effects of the critical point. The future CP search strategy of the NA61/SHINE experiment at the SPS is also discussed
Rapid and highly variable warming of lake surface waters around the globe
peer reviewedIn this first worldwide synthesis of in situ and satellite-derived lake data, we find that lake summer surface water temperatures rose rapidly (global mean = 0.34°C decade-1) between 1985 and 2009. Our analyses show that surface water warming rates are dependent on combinations of climate and local characteristics, rather than just lake location, leading to the counterintuitive result that regional consistency in lake warming is the exception, rather than the rule. The most rapidly warming lakes are widely geographically distributed, and their warming is associated with interactions among different climatic factors - from seasonally ice-covered lakes in areas where temperature and solar radiation are increasing while cloud cover is diminishing (0.72°C decade-1) to ice-free lakes experiencing increases in air temperature and solar radiation (0.53°C decade-1). The pervasive and rapid warming observed here signals the urgent need to incorporate climate impacts into vulnerability assessments and adaptation efforts for lakes. © 2015. American Geophysical Union. All Rights Reserved