Mathematical Simulation of the Distribution of the Electron Beam Current during Pulsed Heating of a Metal Target

Journal of Applied and Industrial Mathematics - We study a model of the current distribution during heating of the surface of a tungsten sample under pulsed exposure to an electron beam. The model...     

Decay of the compound nucleus179Au formed in the cold fusion reaction90Zr+89Y

For the compound nucleus¹⁷⁹Au formed at an excitation energy of 26 MeV in the fusion reaction⁹⁰Zr+⁸⁹Y, the energy spectra of promptly emitted protons,α particles andγ rays were measured in concidence with the evaporation residues. On the basis of the measured total decay energy, the 1p and 1α decay channels were separated from all other evaporation-residue channels. The energy spectra and absolute cross sections, together with previously measured excitation functions for various decay channels, are successfully described by statisticalmodel calculations with the Monte Carlo code CODEX.     

Organocatalytic asymmetric aldol reactions mediated by a cysteine-derived prolinamide

In this Letter, a cysteine-derived prolinamide is described to act as a robust and effective organocatalyst for enantioselective aldol reactions.     

Prospects for electron cooling of antiprotons at low energies

The motivation of using electron cooling in low-energy antiproton storage rings and the expected cooling performance are discussed. Results obtained recently, during the first operation of electron cooling in LEAR at CERN with a 50 MeV proton beam, are summarized, concerning in particular the equilibrium beam properties, the recombination between cooling electrons and cooled protons, and the deceleartion of acceleration of protons by friction in the electron beam. Conclusions are drawn for the formation of antihydrogen with the cooled antiproton beam, and for the deceleration of antiprotons to energies close to or below 1 MeV.     

Element 107

A new and transparent method for the analysis of recoil distance Doppler shift data is presented, which we call thedifferentialdecay curve method (DDCM). The DDCM can be used for singles as well as for coincidence plunger data and systematic errors can be discovered with it much easier than in the conventional analysis. In addition we propose a modification of the normal plunger which we call the differential plunger. With the differential plunger in principle it is possible to determine lifetimes from quantities measured at only one target to stopper distance. The DDCM was tested with lifetime data for¹²⁰Xe and¹²⁸Ba.     

Evidence for nuclear shape coexistence in180Hg

Theγ decay in the radiative fusion reaction⁹⁰Zr+⁹⁰Zr→¹⁸⁰Hg+xγ has been observed in an array of NaI detectors. States up to 6⁺ in the yrast sequence of¹⁸⁰Hg are tentatively assigned and suggest the coexistence of weakly oblate and strongly prolate nuclear shapes. The difference in potential energy between the two inferred shapes has dropped to about 200 keV, continuing the downward trend observed in the heavier even isotopes^188–182Hg.     

Study of the out-of-plane emission of protons and light fragments in symmetric heavy-ion collisions

Midrapidity protons from²⁰⁹Bi+²⁰⁹Bi collisions were measured with the Kaon Spectrometer at SIS at incident energies of E _Lab /A=400, 700 and 1000 MeV. Additionally, light fragments were analysed at 400 MeV. We have investigated the azimuthal emission pattern of the particles relative to the reaction plane as function of transverse momentum, bombarding energy and impact parameter. We observe an enhanced emission of particles perpendicular to the reaction plane at all bombarding energies. The ratio of the number of particles emitted out-of-plane/in-plane increases strongly with the particles transverse momentum. The anisotropy decreases with increasing beam energy. Composite particles show a much stronger effect than protons.