Highly-Resolved Numerical Simulation of the Turbulent Combustion Process in Experimental Burners

This paper presents investigations of experimentally well-characterised turbulent flames with highly-resolved Large Eddy Simulations (LES) and Direct Numerical Simulations (DNS). The combustion process is modelled with a flamelet-based approach, which assumes that the local turbulent flame structure can be described by an ensemble of wrinkled laminar flames. Good agreements between the simulation results and experimental measurement data is achieved. The governing equations are discretised with the Finite Volume Method (FVM). The numerical implementation is tailored for massively parallel simulations on a large number of grid cells. The computational efficiency benefits from the applied simple grid structure and the use of non-blocking Message Passing Interface (MPI) parallelisation

The CARE accelerator R&D programme in Europe

Published online on JACoWCARE, an ambitious and coordinated programme of accelerator research and developments oriented towards high energy physics projects, has been launched in January 2004 by the main European laboratories and the European Commission. This project aims at improving existing infrastructures dedicated to future projects such as linear colliders, upgrades of hadron colliders and high intensity proton drivers. We describe the CARE R&D plans, mostly devoted to advancing the performance of the superconducting technology, both in the fields of RF cavities for electron or proton acceleration and of high field magnets, as well as to developing high intensity electron and proton injectors. We highlight some results and progress obtained so far

Plasma dynamically induced frequency shifts in high-order harmonic generation in nitrogen

Experiments and theoretical calculations on high-harmonic generation in nitrogen are presented in the regime of laser pulses of a 300-ps duration, where the plasma dynamics following the ionization of the medium plays a decisive role. The experiments are performed with similar to 4-GW Ti:sapphire laser pulses, giving rise to fully saturated ionization. The shifts between the exact harmonic frequency in the extreme ultraviolet and the integer multiple of the fundamental frequency are caused by the self-phase modulation of the laser pulse due to the time-dependent free-electron density in the plasma generated in the focal zone. Well-calibrated atomic resonances in the extreme ultraviolet measured through absorption in a secondary gas jet are used as frequency markers in the extreme ultraviolet for the accurate determination of the sign and magnitude of the frequency shifts. A theoretical model including both plasma dynamics and harmonic generation from atoms and ions has previously been developed, and successfully applied to explain the frequency red shift observed in xenon [Phys. Rev. Lett. 96, 123904 (2006)]. The plasma-dynamical model is extended and applied to the results of the harmonic generation in nitrogen, fully explaining the observed harmonic frequency shifts in the 9th and 13th harmonic

First Observation of Self-Amplified Spontaneous Emission in a Free-Electron Laser at 109 nm Wavelength

We present the first observation of Self-Amplified Spontaneous Emission (SASE) in a free-electron laser (FEL) in the Vacuum Ultraviolet regime at 109 nm wavelength (11 eV). The observed free-electron laser gain (approx. 3000) and the radiation characteristics, such as dependency on bunch charge, angular distribution, spectral width and intensity fluctuations all corroborate the existing models for SASE FELs.Comment: 6 pages including 6 figures; e-mail: [email protected]

Characterisation of the dip-bump structure observed in proton-proton elastic scattering at root s=8 TeV

The TOTEM collaboration at the CERN LHC has measured the differential cross-section of elastic proton-proton scattering at root s = 8 TeV in the squared four-momentum transfer range 0.2 GeV2 < vertical bar t vertical bar < 1.9 GeV2. This interval includes the structure with a diffractive minimum ("dip") and a secondary maximum ("bump") that has also been observed at all other LHC energies, where measurements were made. A detailed characterisation of this structure for root s = 8 TeV yields the positions, vertical bar t vertical bar(dip) = (0.521 +/- 0.007) GeV2 and vertical bar t vertical bar(bump) = (0.695 +/- 0.026) GeV2, as well as the cross-section values, d sigma/dt vertical bar(dip) = (15.1 +/- 2.5) mu b/GeV2 and d sigma/dt vertical bar(bump) = (29.7 +/- 1.8) mu b/Ge-2, for the dip and the bump, respectively

The Decentralization Tradeoff for Complementary Spillovers

We examine a symmetric two-district setting with spillovers of local public spending where a spill-in from the foreign spending is not a substitute, but a complement to domestic spending. Specifically, we assume production of two district-specific public goods out of two complementary district-specific inputs. We compare equilibria in non-cooperative decentralization and cooperative centralization for different spillovers, complementarities and cost-division rules, and control for the effects of strategic delegation and the feasibility of voluntary contributions to the input in the foreign district. We find that centralization welfare-dominates decentralization in most institutional settings and for a wide range of parameters, yet we can also identify necessary and sufficient conditions for decentralization to welfare-dominate centralization. The setup features three novelties: In the absence of transfers, welfare in decentralization increases in spillovers, strategic delegation in decentralization improves welfare, and centralized provision may be non-monotonic in spillovers