Measurement of the radiative cooling rates for high-ionization species of krypton using an electron beam ion trap

We describe a measurement of the radiative cooling rate for krypton made at the Berlin electron beam ion trap (EBIT). The EBIT was tuned to a charge-state distribution approaching the ionization balance of a plasma at a temperature of about 5 keV. To determine the cooling rate, we made use of EBIT's capabilities to sample a wide range of electron-beam energies and distinguish between different radiation channels. We have measured the x-ray emission from bremsstrahlung, radiative recombination, dielectronic recombination, and line radiation following electron-impact excitation. The dominant contribution to the cooling rate is made by the n=3-2, n=4-2, ellipsis x rays of the L-shell spectra of krypton, which produce more than 75% of the total radiation loss. A difference with theoretical calculations is noted for the measured total cooling rate. The predicted values are lower by a factor of 1.5-2, depending on the theoretical model. For our measurement of the cooling rate, we estimate an uncertainty interval of 22-30 %.     

Can shadowing mimic the QCD phase transition?

The directed flow of protons is studied in the quark-gluon string model as a function of the impact parameter for S+S and Pb+Pb reactions at 160 AGeV/c. A significant reduction of the directed flow in midrapidity range, which can lead to the development of the antiflow, is found due to the absorption of early emitted particles by massive spectators (shadowing effect). This effect can mimic the formation of the quark-gluon plasma (QGP). However, in the absorption scenario the antiflow is stronger for the system of light colliding nuclei than for the heavy ones, while in the case of the plasma creation the effect should be opposite.     

Ueber lineare homogene Differentialgleichungen,zwischen deren Integralen homogene Relationen höheren als ersten Grades bestehen

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Structural investigation of icosahedral Pd58.8U20.6Si20.6

The structure factors of the amorphous, icosahedral and crystalline Pd_58.8U_20.6Si_20.6 were measured with X-rays and neutrons. By comparing the radial distribution functions of the three phases, we find a similar short range order in the amorphous and icosahedral phase, but a different atomic arrangement in the crystalline phase. A magnetic long range order observed in the crystalline material is absent in the icosahedral phase.Dedicated to Professor Harry Thomas on the occasion of his 60th birthday     

On quantitative aspects of the unit sum number problem

We investigate the function u _K,S (n; q) which counts the number of representations of algebraic integers α with |N_{K/\mathbb Q}(a)| ￡ q{|N_{K/{\mathbb Q}}(\alpha)| \leq q} for some real positive q that can be written as sums of exactly n S-units of the number field K.     

Untersuchung von Mehl

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Jodzahl

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