Calculation of the variable-profile electron beam for electron coolers

Interaction of an electron beam with a cooled ion beam makes it possible to reduce its phase volume, perform accumulation of particles, and suppress various “heating” effects. The electron beam can also be used as a target for an electron-ion recombination reaction, which offers a chance to carry out atomic physics experiments and ensure slow uniform extraction of the ion beam from the storage ring. A high-perveance electron beam with a variable profile is required for effective cooling, while a high current density and a low energy of transverse motion of electrons in the beam is needed for extraction by means of recombination. It is shown that a convex cathode placed in a magnetic field can be used to form such a beam. A high current density can be attained with this shape of the cathode, but additional efforts must be focused on optimizing the gun’s optics in order to obtain a low energy of transverse motion of particles. Since ions repeatedly pass through the cooling section during their lifetime at different values of the betatron oscillation phase, the rates of recombination and cooling are dependent on the rms electron velocity averaged over the volume in which the beam interaction occurs. The proposed design of the gun with a convex cathode 10.2 mm in diameter ensures formation of a variable-profile electron beam with a nominal current of 1 A and a current density of 1.2 A/cm². The rms energy of Larmor gyration of electrons at the exit from the gun, averaged over the beam cross section (the “transverse” temperature) is 1 eV. A focusing electrode that forms the Pierce optics near the edge of the cathode, an electrode controlling the beam profile, and an anode are included in the optics of the electron gun.     

Vacuum pumping with an electron beam

The results of preliminary vacuum tests of an electron cooler with an electron beam that was designed for the LEIR lead-ion storage device (currently being built at CERN) are presented. The tests were performed at the Budker Institute of Nuclear Physics, Siberian Division, Russian Academy of Sciences (Novosibirsk, Russia). It has been shown that, after degassing the collector, injection of an electron beam improves the vacuum level in the setup.     

Sorption properties of multilayer carbon nanotubes produced from cotton

The sorption capacity of multilayer carbon nanotubes that have been synthesized by the mechanical activation of amorphous carbon produced from cotton is investigated. The sorptional efficiency of the carbon nanotubes depends on the storage time. The use of carbon materials derived from cotton as chelators is considered.     

Tin- and copper-based electrochemical coatings for sliding bearings

Copper- and tin-based electrochemical coatings are obtained. The results of disk-shoe couple tests show the wear and wear rate of the coatings; their structure is studied demonstrating that bi- and tricomponental electrochemical coatings boost considerably the copper and bronze wear resistance, making them useful for the manufacture of sliding bearings.     

Mechanochemical Synthesis of Hafnium Carbide using Amorphous Carbon from Plant Materials

Metallurgist - The paper presents the results of studying mechanochemical synthesis of hafnium carbide in the process of vibration treatment of the mixture of powders of hafnium and amorphous...     

A new approach to the design of a sequence with the highest affinity for a molecular surface

We describe an algorithm to design the primary structures forpeptides which must have the strongest binding to a given molecularsurface. This problem cannot be solved by a direct combinatorialsorting, because of an enormous number of possible primary andspatial structures. The approach to solve this problem is todescribe a state of each residue by two variables: (i) aminoacid type and (ii) 3-D coordinate, and to minimize binding energyover all these variables simultaneously. For short chains whichhave no long-range interactions within themselves, this minimizationcan be done easily and efficiently by dynamic programming. Wealso discuss the problem of how to estimate specificity of bindingand how to deduce a sequence with maximal specificity for agiven surface. We show that this sequence can be deduced bythe same algorithm after some modification of energetic parameters.