Beam-beam-induced orbit effects at LHC

For high bunch intensities the long-range beam-beam interactions are strong enough to provoke effects on the orbit. As a consequence the closed orbit changes. The closed orbit of an unperturbed machine with respect to a machine where the beam-beam force becomes more and more important has been studied and the results are presented in this paper.Comment: 5 pages, contribution to the ICFA Mini-Workshop on Beam-Beam Effects in Hadron Colliders, CERN, Geneva, Switzerland, 18-22 Mar 201

The role of interfaces in CoFe/IrMn exchange biased systems

A trilayer system consisting of an IrMn layer exchanged coupled to two CoFe layers of equal thickness has been studied. A single stage reversal was observed over a wide range of temperatures. Two bilayers with the same thicknesses of the pinning layer but different ferromagnetic thicknesses were also studied. By comparing the magnetic properties of these three stacks the effect of the interfacial area on the exchange field and the coercivity has been determined. We find that the interfacial area has a very minor effect on the exchange field H-ex and the blocking temperature (T-B) but causes a doubling of the coercivity (H-c). This indicates that H-c is dominated by the interface whereas the exchange bias is controlled by volumetric effects

Impact of single-particle compressibility on the fluid-solid phase transition for ionic microgel suspensions

We study ionic microgel suspensions composed of swollen particles for various single-particle stiffnesses. We measure the osmotic pressure $\pi$ of these suspensions and show that it is dominated by the contribution of free ions in solution. As this ionic osmotic pressure depends on the volume fraction of the suspension $\phi$, we can determine $\phi$ from $\pi$, even at volume fractions so high that the microgel particles are compressed. We find that the width of the fluid-solid phase coexistence, measured using $\phi$, is larger than its hard-sphere value for the stiffer microgels that we study and progressively decreases for softer microgels. For sufficiently soft microgels, the suspensions are fluid-like, irrespective of volume fraction. By calculating the dependence on $\phi$ of the mean volume of a microgel particle, we show that the behavior of the phase-coexistence width correlates with whether or not the microgel particles are compressed at the volume fractions corresponding to fluid-solid coexistence.Comment: 5 pages, 3 figure

Effects of percentage of blockage and flameholder downstream counterbores on lean combustion limits of premixed, prevaporized propane-air mixture

Lean combustion limits were determined for a premixed prevaporized propane air mixture with flat plate flame stabilizers. Experiments were conducted in a constant area flame tube combustor utilizing flameholders of varying percentages of blockage and downstream counterbores. Combustor inlet air velocity at ambient conditions was varied from 4 to 9 meters per second. Flameholders with a center hole and four half holes surrounding it were tested with 63, 73, and 85 percent blockage and counterbore diameters of 112 and 125 percent of the thru hole diameter, in addition to the no counterbore configuration. Improved stability was obtained by using counterbore flameholders and higher percentages of blockage. Increases in mixture velocity caused the equivalence ratio at blowout to increase in all cases