A New Beam Delivery System (BDS) for the TESLA Linear Collider

An overview of the proposed new BDS for the TESLA linear collider is presented. Several major changes have been incorporated since the publication of the TESLA Conceptual Design Report (CDR) [1]. The most notable of these modifications are: incorporation of the photonbasedpositron source upstream of the interaction point (IP), i.e. at the exit of the electron linac; a new concept for the collimation system, including integration of the emittance measurement section; an increase in the length of the final telescope, which, together with a new spent beam extraction line, allows for cleaner extraction of both the spent electron (positron) beam and the beamstrahlung photons

The 2mrad horizontal crossing angle IR layout for a TeV ILC

The current status of the 2mrad crossing angle layout for the ILC is reviewed. The scheme developed in the UK and France is described and the performance discussed for a TeV machine. Secondly, the scheme developed at SLAC and BNL is then studied and modified for a TeV machine. We find that both schemes can handle the higher energy beam with modifications, and share many common features.Comment: The proceedings of the 2005 International Linear Collider Workshop, March 2005. 4 pages, 5 figure

Non linear flux flow in TiN superconducting thin film

We have studied the superconducting behavior of 100 nm Titanium Nitride (TiN) thin film in a perpendicular magnetic field. We found a zero field transition temperature of 4.6 K and a slope in the H-T plane of -0.745 T/K. At 4.2 K, we have performed careful transport measurements by measuring both the differential resistivity and voltage as a function of a DC current. Our results are analyzed in the framework of linear and non linear flux flow behavior. In particular, we have observed an electronic instability at high vortex velocities and from its dependence with respect to the applied magnetic field, we can exctract the inelastic scattering time and diffusion length of the quasiparticles

Evaluation of Luminosity Reduction in the ILC Head-on Scheme from Parasitic Collisions

online : http://cern.ch/AccelConf/p07/PAPERS/THPMN008.PDFInternational audienceAn interaction region with head-on collisions is being developed for the ILC as an alternative to the base line 14 mrad crossing angle design, motivated by simpler beam manipulations upstream of the interaction point (IP) and a more favourable configuration for the detector and physics analysis. The design of the post-collision beam line in this scheme involves however a number of technological challenges, one of which is the strength requirement for the electrostatic separators (ES) placed immediately after the final doublet to extract the spent beam. In this paper, we examine in detail the main mechanism behind this requirement, the multi-beam kink instability, which results from the long-range beam-beam forces at the parasitic crossings after the bunches have been extracted. Our analysis uses realistic bunch distributions, the Guinea-Pig program to treat beam-beam effects at the interaction point and the DIMAD program to track the disrupted beam distributions in the postcollision beam line

Model for the on-site matrix elements of the tight-binding hamiltonian of a strained crystal: Application to silicon, germanium and their alloys

We discuss a model for the on-site matrix elements of the sp3d5s* tight-binding hamiltonian of a strained diamond or zinc-blende crystal or nanostructure. This model features on-site, off-diagonal couplings between the s, p and d orbitals, and is able to reproduce the effects of arbitrary strains on the band energies and effective masses in the full Brillouin zone. It introduces only a few additional parameters and is free from any ambiguities that might arise from the definition of the macroscopic strains as a function of the atomic positions. We apply this model to silicon, germanium and their alloys as an illustration. In particular, we make a detailed comparison of tight-binding and ab initio data on strained Si, Ge and SiGe.Comment: Submitted to Phys. Rev.

Optical studies for the super separator spectrometer S3

International audienceS3 (Super Separator Spectrometer) [1] is a future device designed for experiments with the high intensity heavy ion stable beams of SPIRAL2 [2] at GANIL (Caen, France). It will include a target resistant to these very high intensities, a first stage momentum achromat for primary beam extraction and suppression, a second stage mass spectrometer and a dedicated detection system. This spectrometer includes large aperture quadrupole triplets with embedded multipolar corrections. To enable the primary beam extraction one triplet has to be opened on one side, which requires an appropriate design of such a multipolar magnet. The final mass separation power required for S3 needs a careful design of the optics with a high level of aberration correction. Multiple symmetric lattices were studied for this purpose. A 4-fold symmetric lattice and the achieved results are described in this paper

Design of an interaction region with head-on collisions for the ILC

An interaction region (IR) with head-on collisions is considered as an alternative to the baseline configuration of the International Linear Collider (ILC) which includes two IRs with finite crossing-angles (2 and 20 mrad). Although more challenging for the beam extraction, the head-on scheme is favoured by the experiments because it allows a more convenient detector configuration, particularly in the forward region. The optics of the head-on extraction is revisited by separating the e+ and e- beams horizontally, first by electrostatic separators operated at their LEP nominal field and then using a defocusing quadrupole of the final focus beam line. In this way the septum magnet is protected from the beamstrahlung power. Newly optimized final focus and extraction optics are presented, including a first look at post-collision diagnostics. The influence of parasitic collisions is shown to lead to a region of stable collision parameters. Disrupted beam and beamstrahlung photon losses are calculated along the extraction elements

Radio emission of extensive air shower at CODALEMA: Polarization of the radio emission along the v*B vector

Cosmic rays extensive air showers (EAS) are associated with transient radio emission, which could provide an efficient new detection method of high energy cosmic rays, combining a calorimetric measurement with a high duty cycle. The CODALEMA experiment, installed at the Radio Observatory in Nancay, France, is investigating this phenomenon in the 10^17 eV region. One challenging point is the understanding of the radio emission mechanism. A first observation indicating a linear relation between the electric field produced and the cross product of the shower axis with the geomagnetic field direction has been presented (B. Revenu, this conference). We will present here other strong evidences for this linear relationship, and some hints on its physical origin.Comment: Contribution to the 31st International Cosmic Ray Conference, Lodz, Poland, July 2009. 4 pages, 8 figures. v2: Typo fixed, arxiv references adde