Radioactive Ion Sources

This chapter provides an overview of the basic requirements for ion sources designed and operated in radioactive ion beam facilities. The facilities where these sources are operated exploit the isotope separation online (ISOL) technique, in which a target is combined with an ion source to maximize the secondary beam intensity and chemical element selectivity. Three main classes of sources are operated, namely surface-type ion sources, arc discharge-type ion sources, and finally radio-frequency-heated plasma-type ion sources.Comment: 19 pages, contribution to the CAS-CERN Accelerator School: Ion Sources, Senec, Slovakia, 29 May - 8 June 2012, edited by R. Bailey, CERN-2013-00

Exercises in equivariant cohomology and topological theories

Equivariant cohomology is suggested as an alternative algebraic framework for the definition of topological field theories constructed by E. Witten circa 1988. It also enlightens the classical Faddeev Popov gauge fixing procedure.Comment: 17 pages, LaTeX with sprocl.sty, also available at http://lapphp0.in2p3.fr/preplapp/psth/ENSLAPP604.ps.g

Influence of bioturbation on denitrification activity in Mediterranean coastal sediments:an in situ experimental approach

An in situ experiment was conducted in the French Mediterranean littoral (Gulf of Fos) from July 1993 to January 1994 using controls without macrofauna or natural sediments. After 1, 4 and 6 mo, sediment reworking and denitrification activities (natural and potential rates) were studied. The bacterial processes were stimulated by the bioturbating activity of the autochthonous infauna. The natural and potential denitrification rates were 160 and 280% higher, respectively, than in the controls. The increase of denitrification, occurring at different depths in the sediment with respect to time, was directly dependent on the macrofaunal activity

Quantizing Yang-Mills Theory: From Parisi-Wu Stochastic Quantization to a Global Path Integral

Based on a generalization of the stochastic quantization scheme we recently proposed a generalized, globally defined Faddeev-Popov path integral density for the quantization of Yang-Mills theory. In this talk first our approach on the whole space of gauge potentials is shortly reviewed; in the following we discuss the corresponding global path integral on the gauge orbit space relating it to the original Parisi-Wu stochastic quantization scheme.Comment: 4 pages, Latex, uses espcrc2.sty; talk by Helmuth Huffel at the Third Meeting on Constrained Dynamics and Quantum Gravity, Villasimius, Sardinia, Italy, Sept. 13-17, 199

Renormalization of Massless Feynman Amplitudes in Configuration Space

A systematic study of recursive renormalization of Feynman amplitudes is carried out both in Euclidean and in Minkowski configuration space. For a massless quantum field theory (QFT) we use the technique of extending associate homogeneous distributions to complete the renormalization recursion. A homogeneous (Poincare covariant) amplitude is said to be convergent if it admits a (unique covariant) extension as a homogeneous distribution. For any amplitude without subdivergences - i.e. for a Feynman distribution that is homogeneous off the full (small) diagonal - we define a renormalization invariant residue. Its vanishing is a necessary and sufficient condition for the convergence of such an amplitude. It extends to arbitrary - not necessarily primitively divergent - Feynman amplitudes. This notion of convergence is finer than the usual power counting criterion and includes cancellation of divergences.Comment: LaTeX, 64 page

Effects of population density on the sediment mixing induced by the gallery-diffusor Hediste (Nereis) diversicolor O.F. Müller, 1776

The aim of this work was to quantify the intensity of sediment mixing induced by the gallery-diffusor (functional bioturbation group) Hediste diversicolor as a function of density, using particles tracers (luminophores). In order to assess the impact of density on sediment reworking, a 1-D model was used to obtain sediment reworking coefficients such as Db (biodiffusion-like) and r (biotransport). Densities used in this experiment corresponded to population densities observed in the sampling area (Saint-Antoine Canal, Gulf of Fos, France): 144, 288, 577, 1153 indiv/m2. At first, results showed that neither luminophore maximum burying depth nor the more marked tracer accumulation areas were influenced by density. Thus density did not seem to have any influence on size of galleries or complexity of structure. Then, density-dependent relations with Db (biodiffusion-like mixing) and r (biotransport) were highlighted with an observed process intensity rate twice as high at highest worm density. On the other hand, Db and r per capita coefficients were negatively influenced by density. Db and r per capita at highest density were equal to ∼20% of individual Db and r obtained at the lowest density. Finally, this study showed the importance of density which appears to be a key parameter in the functioning of the sedimentary ecosystem

Comparison between the Nereis diversicolor and Nereis virens marine worms in the transformation of ingested hydrocarbons

A feeding experiment was conducted on the marine worm Nereis diversicolor to compare the fate of a hydrocarbon mixture during the gut passage in this species with the hydrocarbon breakdown process demonstrated for Nereis virens. Hydrocarbon dissolution/solubilization processes in the gut of N. diversicolor were found to have similar qualitative and quantitative importance in the hydrocarbon transformation as those observed in N. virens

Exercises in equivariant cohomology

Equivariant cohomology is a mathematical framework particularly well adapted to a kinematical understanding of topological gauge theories of the cohomological type. It also sheds some light on gauge fixing, a necessary field theory operation connected with the non compactness of the gauge group. The respective roles of fields and observables are emphasized throughout.Equivariant cohomology is a mathematical framework particularly well adapted to a kinematical understanding of topological gauge theories of the cohomological type. It also sheds some light on gauge fixing, a necessary field theory operation connected with the non compactness of the gauge group. The respective roles of fields and observables are emphasized throughout

BRST Cohomology of N=2 Super-Yang-Mills Theory in 4D

The BRST cohomology of the N=2 supersymmetric Yang-Mills theory in four dimensions is discussed by making use of the twisted version of the N=2 algebra. By the introduction of a set of suitable constant ghosts associated to the generators of N=2, the quantization of the model can be done by taking into account both gauge invariance and supersymmetry. In particular, we show how the twisted N=2 algebra can be used to obtain in a straightforward way the relevant cohomology classes. Moreover, we shall be able to establish a very useful relationship between the local gauge invariant polynomial $tr\phi^2$ and the complete N=2 Yang-Mills action. This important relation can be considered as the first step towards a fully algebraic proof of the one-loop exactness of the N=2 beta function.Comment: 22 pages, LaTeX, final version to appear in Journ. Phys.