Beam Performance and Luminosity Limitations in the High-Energy Storage Ring (HESR)

The High-Energy Storage Ring (HESR) of the future International Facility for Antiproton and Ion Research (FAIR) at GSI in Darmstadt is planned as an antiproton synchrotron and storage ring in the momentum range from 1.5 to 15 GeV/c. An important feature of this new facility is the combination of phase space cooled beams with dense internal targets (e.g. pellet targets), resulting in demanding beam parameter of two operation modes: high luminosity mode with peak luminosities up to 2*10^32 cm-2 s-1, and high resolution mode with a momentum spread down to 10^-5, respectively. To reach these beam parameters very powerful phase space cooling is needed, utilizing high-energy electron cooling and high-bandwidth stochastic cooling. The effect of beam-target scattering and intra-beam interaction is investigated in order to study beam equilibria and beam losses for the two different operation modes.Comment: 8 pages, based on a talk presented at COULOMB'05, Accepted for publication by Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipmen

Strangeness Production at COSY

The paper gives an overview of strangeness-production experiments at the Cooler Synchrotron COSY. Results on kaon-pair and phi meson production in pp, pd and dd collisions, hyperon-production experiments and Lambda p final-state interaction studies are presented.Comment: Proceedings of the 12th Int. Conf. on Meson-Nucleon Physics and the Structure of the Nucleon (MENU2010) in Williamsburg (USA

Feminism and the Politics of Representation: Towards a Critical and Ethical Encounter with “Others”

This essay begins from the position that a speaking subject in feminism occupies a place of power and authority which requires a commitment to an ethical involvement in the representation of ‘others.’ Specifically, this essay will address feminist concerns of speaking for others and the concerns raised by the dangers of representing across differences of race, sexuality, gender and cultures. First, it will critique feminist claims to political effectivity as a solution to ethical representation. Second, it will look at how hierarchies of oppression and privileged ontological positions are inconsistently represented in feminist discussions. Lastly, it will briefly examine how differences between ‘others’ are increasingly being represented as cultural in potentially problematic ways. The essay will argue that feminist discussions of representation must be self-critical, but at the same time not abandon the task of working towards an ethical involvement with ‘others.

Ion optics with electrostatic lenses

Ion optics with electrostatic lenses is presented using the standard matrix formalism of magnetic ion optics. We introduce the paraxial ray equation which is appropriate to systems with rotational symmetry. The rst-order solutions of the paraxial ray equation are derived. The resulting transport matrices can be used to study systems with acceleration tube lenses, aperture lenses, einzel lenses and dc accelerators. The analogy with geometrical optics is discussed. Beam transport and phase ellipses are described using the so-called matrices. The equations of the longitudinal transport matrix are derived. Besides rotational symmetric elements, electrostatic quadrupoles and electrostatic de- ectors are also presented. The effect of space charge forces is discussed

Electrostatic accelerators

The principle of electrostatic accelerators is presented. We consider Cockcroft Walton, Van de Graaff and Tandem Van de Graaff accelerators. We resume high voltage generators such as cascade generators, Van de Graaff band generators, Pelletron generators, Laddertron generators and Dynamitron generators. The speci c features of accelerating tubes, ion optics and methods of voltage stabilization are described. We discuss the characteristic beam properties and the variety of possible beams. We sketch possible applications and the progress in the development of electrostatic accelerators

Regularisations of Irregularly Staying Migrants in the EU: A Comparative Legal Analysis of Austria, Germany and Spain

'Combatting' irregular migration is one of the key challenges to migration management at EU level. The present book addresses one of the most pressing structural problems regarding the EU’s return policy: the low return rate of irregularly staying migrants. In this regard the EU Return Directive obliges Member States to issue a return decision, yet only 40% of such decisions are enforced annually. Moreover, despite the political and legal efforts, the EU is not making any significant progress in enforcing the rules it has laid down in the Return Directive. The legislation of EU Member States may, however, serve as a source for possible solutions to 'combat' the problem of irregularly staying migrants. It is for this reason that the book compares the system of regularisations in Austria, Germany and Spain. Regularisations constitute an effective alternative to returns because they terminate the irregular residence of migrants, not through deportation, but rather by granting a right of residence. Regularisation is therefore understood as each legal decision that awards legal residency to irregularly staying migrants. As is shown by the examination and comparison of regularisations in Austria, Germany and Spain, differentiated systems of regularisation exist at national level. However, EU regularisations supplementing the present return policy would be more effective at 'combatting' irregular migration at EU level.Eine zentrale Herausforderung der Migrationssteuerung auf Unionsebene ist die "Bekämpfung" irregulärer Einwanderung. Die vorliegende Arbeit widmet sich einem der drängendsten Probleme der EU-Rückführungspolitik, in concreto der niedrigen Rückführungsrate irregulär aufhältiger Migrant:innen. Die Rückführungsrichtlinie der EU erlegt den Mitgliedstaaten in diesem Zusammenhang die Pflicht auf, gegen jede drittstaatsangehörige Person, die sich irregulär in der EU aufhält, eine Rückkehrentscheidung zu erlassen, wobei jährlich nur rund 40% aller Rückkehrentscheidungen auch tatsächlich vollzogen werden. Die EU schafft es insgesamt aber trotz der rechtlichen und politischen Bemühungen kaum, Fortschritte im Hinblick auf die Vorgaben der Rückführungsrichtlinie zu machen. Mögliche Lösungsansätze finden sich in den Rechtsordnungen ausgewählter Mitgliedstaaten. Deshalb wird die österreichische, deutsche und spanische Rechtslage in einem Rechtsvergleich analysiert. Die drei Mitgliedstaaten "bekämpfen" den irregulären Aufenthalt von Migrant:innen mithilfe eines differenzierten Systems von Regularisierungen. Regularisierungen, verstanden als Rechtsinstrument, stellen eine Alternative zu Rückführungen dar und umschreiben jede rechtliche Entscheidung, die irregulär aufhältigen Migrant:innen ein Aufenthaltsrecht gewährt. Sie beenden den irregulären Aufenthalt von Migrant:innen, allerdings nicht durch eine Rückführung im Sinne einer Außerlandesbringung, sondern durch die Gewährung eines Aufenthaltsrechts. Anhand dieser Untersuchung wird die folgende These entwickelt: Durch unionsrechtlich normierte Regularisierungen, die die derzeitige Rückführungspolitik der EU ergänzen, wird die irreguläre Einwanderung auf Unionsebene wirksamer "bekämpft"

Study of the Λp\Lambda p Interaction Close to the Σ+n\Sigma^+n and Σ0p\Sigma^0p Thresholds

The $\Lambda p$ interaction close to the $\Sigma N$ threshold is considered. Specifically, the pronounced structure seen in production reactions like $K^-d \to \pi^- \Lambda p$ and $pp\to K^+ \Lambda p$ around the $\Sigma N$ threshold is analyzed. Modern interaction models of the coupled $\Lambda N - \Sigma N$ systems generate such a structure either due to the presence of a (deuteron-like) unstable bound state or of an inelastic virtual state. % A determination of the position of the prominent peak as observed in various experiments for the two aforementioned reactions leads to values that agree quite well with each other. Furthermore, the deduced mean value of $2128.7\pm 0.3$ MeV for the peak position coincides practically with the threshold energy of the $\Sigma^+ n$ channel. This supports the interpretation of the structure as a genuine cusp, signaling an inelastic virtual state in the $^3S_1-^3D_1$ partial wave of the $\Sigma N$ isospin 1/2 channel. % There is also evidence for a second peak (or shoulder) in the data sets considered which appears at roughly 10-15 MeV above the $\Sigma N$ threshold. However, its concrete position varies significantly from data set to data set and, thus, a theoretical interpretation is difficult.Comment: accepted for publication Nucl. Phys.

B7/CD28 in Central Tolerance: Costimulation Promotes Maturation of Regulatory T Cell Precursors and Prevents Their Clonal Deletion

According to the “two-step model,” the intrathymic generation of CD4+ regulatory T (Treg) cells segregates into a first, T cell receptor (TCR)-driven phase and a second, cytokine-dependent phase. The initial TCR stimulus gives rise to a CD25+Foxp3− developmental intermediate. These precursors subsequently require cytokine signaling to establish the mature CD25+Foxp3+ Treg cell phenotype. In addition, costimulation via CD28/B7 (CD80/86) axis is important for the generation of a Treg cell repertoire of normal size. Recent data suggest that CD28 or B7 deficient mice lack CD25+Foxp3− Treg cell progenitors. However, these data leave open whether costimulation is also required at subsequent stages of Treg differentiation. Also, the fate of “presumptive” Treg cells carrying a permissive TCR specificity in the absence of costimulation remains to be established. Here, we have used a previously described TCR transgenic model of agonist-driven Treg differentiation in order to address these issues. Intrathymic adoptive transfer of Treg precursors indicated that costimulation is dispensable once the intermediate CD25+Foxp3− stage has been reached. Furthermore, lack of costimulation led to the physical loss of presumptive Treg cells rather than their escape from central tolerance and differentiation into the conventional CD4+ T cell lineage. Our findings suggest that CD28 signaling does not primarily operate through enhancing the TCR signal strength in order to pass the threshold intensity required to initiate Treg cell specification. Instead, costimulation seems to deliver unique and qualitatively distinct signals that coordinately foster the developmental progression of Treg precursors and prevent their negative selection