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The long-distance stable transport of relativistic electron beams (REBs) in plasmas is studied by full three-dimensional particle-in-cell simulations. Theoretical analysis shows that the beam transport is mainly influenced by three transverse instabilities, where the excitation of self-modulation instability, and the suppression of the filamentation instability and the hosing instability are important to realize the beam stable transport. By modulating the transport parameters such as the electron density ratio, the relativistic Lorentz factor, the beam envelopes and the density profiles, the relativistic bunches having a smooth density profile and a length of several plasma wave periods can suppress the beam-plasma instabilities and propagate in plasmas for long distances with small energy losses. The results provide a reference for the research of long-distance and stable transport of REBs, and would be helpful for new particle beam diagnosis technology and space active experiments.
Europium-doped lutetium oxide (Lu2O3:Eu3+) nanophosphors were synthesized via modified combustion technique using urea as the fuel and metal nitrates as oxidants. The pellets prepared from the calcined nanocrystalline powders were vacuum sintered up to 1750 °C leading to very translucent ceramic. The products were characterized by x-ray diffraction to ascertain phase purity. The microstructures reveal the nanocrystalline nature of the powders. We have illustrated the crystallite size dependence and the influence of Eu3+ activation of Lu2O3:Eu3+ nanophosphors on Raman scattering. We have also demonstrated the particle size dependence of emission characteristics of nanophosphors and ceramics. Our results suggest that although the processed ceramics display superior emission characteristics, the nanocrystalline phosphor powders calcined at 1100 °C also display reasonably good emission characteristics, illustrating the possibility of their applications in display technology.
This Comm. 20 triennial report is prepared as a short summary of the scientific progress in the fields of interest, where, by necessity, only a few highlights are to be mentioned. On the Comm. 20 webpage, the interested reader may find a more complete list of recent references to the relevant literature. Its URL at the time of writing (October 1999) is www.astro.uu.se/IAU/c20/, but mirror sites are expected to have been set up at the time of appearance of these Transactions.
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