548 research outputs found
Resonant Diffusive Radiation in Random Multilayered Systems
We have theoretically shown that the yield of diffuse radiation generated by
relativistic electrons passing random multilayered systems can be increased
when a resonant condition is met. Resonant condition can be satisfied for the
wavelength region representing visible light as well as soft X-rays. The
intensity of diffusive soft X-rays for specific multilayered systems consisting
of two components is compared with the intensity of Cherenkov radiation. For
radiation at photon energy of , the intensity of Resonant Diffusive
Radiation (RDR) generated by electrons passing a multilayer
exceeds the intensity of Cherenkov radiation by a factor of for
electrons with the same energy passing a foil. For a photon energy of
and electrons passing multilayer generate RDR exceeding
Cherenkov radiation generated by electrons passing a foils by a factor
.Comment: Talk presented at the RC2005, Frascati, Ital
Cherenkov radiation in the soft X-ray region : towards a compact narrowband source
IX+125hlm.;24c
Transverse self-fields within an electron bunch moving in an arc of a circle
As a consequence of motions driven by external forces, self-fields (which are
different from the static case) originate within an electron bunch. In the case
of magnetic external forces acting on an ultrarelativistic beam, the
longitudinal self-interactions are responsible for CSR (Coherent Synchrotron
Radiation)-related phenomena, which have been studied extensively. On the other
hand, transverse self-interactions are present too. At the time being, existing
theoretical analysis of transverse self-forces deal with the case of a bunch
moving along a circular orbit only, without considering the situation of a
bending magnet with a finite length. In this paper we propose an
electrodynamical analysis of transverse self-fields which originate, at the
position of a test particle, from an ultrarelativistic electron bunch moving in
an arc of a circle. The problem will be first addressed within a two-particle
system. We then extend our consideration to a line bunch with a stepped density
distribution, a situation which can be easily generalized to the case of an
arbitrary density distribution. Our approach turns out to be also useful in
order to get a better insight in the physics involved in the case of simple
circular motion and in order to address the well known issue of the partial
compensation of transverse self-force.Comment: 23 pages, 14 figure
T lymphocytes and cytokines in graft-versus-host disease : a study in mice with emphasis on prevention and treatment.
This thesis describes the results of experiments aimed to improve the insight into
this complex disease using a murine model. Based on previous work from our
laboratory we investigated the possibilities to prevent GVHD in a specific manner,
namely by pretreatment of prospective donors with a recipient-specific blood transfusion.
Furthermore, we assessed the role of (subsets of) T lymphocytes and of cytokines in
GVHD. Cytokines are factors that can be produced a.o. by T cells and play a central
role in immune and inflammatory reactions. Recent data from the literature indicate
that cytokines might be involved in the development of GVHD. We studied the
therapeutic effect of in vivo administration of anti-T cell (subset), anti-cytokine and
anti-cytokine receptor monoclonal antibodies (mAb) on GVH
High-brightness, compact soft x-ray source based on Cherenkov radiation
Cherenkov radiation in the soft x-ray region is generated in narrowband regions at inner-shell absorption edges. Mainly low-Z elements are suitable Cherenkov sources, which emit in a photon energy range from 30 eV to 1 keV and require moderate electron energies up to 25 MeV. Generally, in the soft x-ray region materials are highly absorbing and therefore the Cherenkov radiation theory is discussed for absorbing media. A detailed description includes transition radiation that is generated at the interface when the relativistic electron exits the material. We show that the transition radiation yield equation, when it is adopted for an absorbing medium, includes Cherenkov radiation. Based on this approach it is shown that the spectral intensity of Cherenkov radiation in the soft x-ray region is large compared to transition radiation for moderate electron energies. First measurements of soft x-ray Cherenkov radiation in the water-window spectral region, generated in titanium and vanadium foils, are discussed in detail. The measured spectral and angular distribution of the radiation, and the measured total yield (â 10 -4 photon per electron) are in agreement with theoretical predictions based on the refractive index data. We show that the brightness that can be achieved using a small electron accelerator is sufficient for practical x-ray microscopy in the water window.</p
High-brightness, narrowband, compact soft x-ray Cherenkov sources in the water window
Narrowband, soft x-ray Cherenkov radiation at energies of 453 and 512 eV has been generated by 10 MeV electrons in, respectively, titanium and vanadium foils. The measured spectral and angular distribution of the radiation, and the measured total yield (10â4 photon per electron) are in agreement with theoretical predictions based on refractive index data. We show that the brightness that can be achieved using a small electron accelerator is sufficient for practical x-ray microscopy in the water-window spectral region
A tabletop soft X-ray source based on 5-10 MeV LINACs
We are investigating the feasibility of a novel, tabletop, high-brightness soft X-ray source
Comparison of modelled and monitored deposition fluxes of sulphur and nitrogen to ICP-forest sites in Europe
The EMEP MSC-W Eulerian chemical transport model, and its predictions of deposition of acidifying and eutrophying pollutants over Europe, play a key role in the development of emission control strategies for Europe. It is important that this model is tested against observational data. Here we compare the results of the EMEP model with measured data from 160 sites of the European Union/ICP Forest (Level II) monitoring network, for the years 1997 and 2000. This comparison comprises: (a) Precipitation amount, (b) Total deposition of SO42- to coniferous and deciduous forests, (c) Wet deposition of SO42-, NO3- and NH4+ in open field sites, and (d) Concentrations of SO42-, NO3- and NH4+ in precipitation. Concerning precipitation, the EMEP model and ICP network showed very similar overall levels (within 4% for 1997 and 11% for 2000). The correlation was, however, poor (r2=0.15-0.23). This can be attributed largely to the influence of a few outliers, combined with a small range of rainfall amounts for most points. Correlations between modelled and observed deposition values in this study were rather high (r2 values between 0.4-0.8 for most components and years), with mean values across all sites being within 30%. The EMEP model tends to give somewhat lower values for SO42-, NO3- and NH4+ wet deposition to ICP, but differences in mean values were within 20% in 1997 and 30% in 2000. Modelled and observed concentrations of SO 42-, NO3- and NH4+ in precipitation are very similar on average (differences of 0-14%), with good correlation between modelled and observed data (r 2=0.50-0.78). Differences between the EMEP model and ICP measurements are thought to arise from a mixture of problems with both the observations and model. However, the overall conclusion is that the EMEP model performs rather well in reproducing patterns of S and N deposition to European forests
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