The ATLAS detector as installed in its experimental cavern at point 1 at CERN is described in this paper. A brief overview of the expected performance of the detector when the Large Hadron Collider begins operation is also presented.

The ATLAS Experiment at the CERN Large Hadron Collider

This paper describes the ATLAS experiment as installed in i ts experimental cavern at point 1 at CERN. It also presents a brief overview of the expec ted performance of the detector.

http://absimage.aps.org/image/SES08/MWS_SES08-2008-020010.pdf

Parton distributions with LHC data

A measurement of the Higgs boson mass is presented based on the combined data samples of the ATLAS and CMS experiments at the CERN LHC in the H→γγ and H→ZZ→4l decay channels. The results are obtained from a simultaneous fit to the reconstructed invariant mass peaks in the two channels and for the two experiments. The measured masses from the individual channels and the two experiments are found to be consistent among themselves. The combined measured mass of the Higgs boson is mH=125.09±0.21 (stat)±0.11 (syst)  GeV.

/pdf/combined-measurement-of-the-higgs-boson-mass-in-pp-3ml7f5avlr.pdf

Combined Measurement of the Higgs Boson Mass in pp Collisions at √s=7 and 8 TeV with the ATLAS and CMS Experiments

The simulation software for the ATLAS Experiment at the Large Hadron Collider is being used for large-scale production of events on the LHC Computing Grid. This simulation requires many components, from the generators that simulate particle collisions, through packages simulating the response of the various detectors and triggers. All of these components come together under the ATLAS simulation infrastructure. In this paper, that infrastructure is discussed, including that supporting the detector description, interfacing the event generation, and combining the GEANT4 simulation of the response of the individual detectors. Also described are the tools allowing the software validation, performance testing, and the validation of the simulated output against known physics processes.

/pdf/the-atlas-simulation-infrastructure-gw5d3ea9bf.pdf

The ATLAS Simulation Infrastructure

As part of a collaboration between FNAL and CERN, Nb3Sn Rutherford-type cables made of different wires (MJR and PIT) have been assembled in the sample holder at FNAL and tested at FRESCA (CERN). All cable samples had 28 strands with 1-mm diameter, and a trapezoidal cross-section with 0.9-1 degree keystone angle. All samples were tested at 4.3 and 1.8 K. After the first series of tests both cables were retested with higher prestress. The PIT sample was extensively retested at 1.9 K. During the second run the MJR sample was also tested at constant current in sweeping field in order to characterize its stability. All samples showed signs of instability and several voltage spikes were detected and recorded. Critical current and instability threshold measurements are presented and compared with previous tests and magnet performances

Measurement of Critical Current and Instability Threshold of Rutherford-Type $rm Nb_3rm Sn$ Cables

It is well known that the sextupole (b2) component in superconducting dipole magnets decays during the injection plateau and snaps back rapidly at the start of the ramp. These so-called dynamic effects, which also appear in other magnetic multipoles, were originally discovered in the Tevatron. The chromaticity correctors, distributed around the ring, correct for this effect. Imperfect compensation of the dynamic b2 in the magnets, in particular during injection and snapback, can contribute to beam loss and emittance growth. In the context of recent efforts to improve the Tevatron luminosity, a thorough investigation of the b2 correction in the Tevatron was conducted, including beam chromaticity measurements and extensive offline magnetic measurements on Tevatron dipoles. This study has yielded new information about the effect of the powering history on the dynamic b2 effects. Study findings have also resulted in new proposals for improvement of the sextupole snapback correction in the Tevatron, including a revised functional form for the snapback algorithm and the possibility of eliminating the beam-less pre-cycle. This paper introduces the proposals for an improved b2 correction in the Tevatron and reports on the results of beam studies performed recently to test them. A companion paper describes in detail the results of the magnet measurements [1].

https://epaper.kek.jp/e04/papers/moplt120.pdf

Proposals for improvements of the correction of sextupole dynamic effects in tevatron dipole magnets

The goal of the Fermilab high field magnet (HFM) R&D project is to explore various designs and production technology of a high-field, low-cost Nb/sub 3/Sn accelerator magnet suitable for a future Very Large Hadron Collider (VLHC). The model under fabrication consists of two-layer shell-type coil with 43.5 mm aperture and cold iron yoke. The Fermilab concept of magnet design and fabrication technology involves some specific features such as curing of half-coil with ceramic binder/matrix before reaction, and then simultaneous reaction and impregnation of both half-coils to get a "coil pipe" structure. The coil pipe is mechanically supported by the vertically-split iron yoke locked by two aluminum clamps and a thick stainless steel skin. 2D finite element analysis has been performed to study and optimize the prestress in the coil and in the structural elements at room temperature and at 4.2 K. Model description, material properties and the results of mechanical analysis are reported in this paper.

/pdf/mechanical-design-and-analysis-of-the-fermilab-11-t-nb-sub-3-3zec3lg8xy.pdf

Mechanical design and analysis of the Fermilab 11 T Nb/sub 3/Sn dipole model

As part of the High Field Magnet program at Fermilab three cos(Theta) magnets-two mirror dipole magnets utilizing RRP cable and one dipole magnet utilizing PIT cable-have been designed, fabricated and tested recently. Both mirror magnets with RRP strands only reached ~50-60% of their estimated critical current limit. The PIT conductor based dipole however reached its critical current limit producing over 10 T magnetic field in the bore of the magnet. This paper describes the parameters of superconducting strands and cable, the details of magnet design and fabrication procedure, and reports the results

Development and Test of $rm Nb_3rm Sn rm Cos(theta)$ Magnets Based on RRP and PIT Strands

A dipole magnet based on the common coil design, using prereacted Nb/sub 3/Sn superconductor, is under development at Fermilab, for a future Very Large Hadron Collider. This magnet has some innovative design and technological features such as single layer coils, a 22 mm wide 60-strand Rutherford type cable and stainless steel collars reinforced by horizontal bridges inserted between coil blocks. Both left and right coils are wound simultaneously into the collar structure and then impregnated with epoxy. In order to optimize the design and fabrication techniques an R&D program is underway. The production of cables with the required characteristics was shown possible. Collar laminations were produced, assembled and tested in order to check the effectiveness of the bridges and the validity of the mechanical design. A mechanical model consisting in a 165 mm long section of the magnet straight section was assembled and tested. This paper summarizes the status of the program, and reports the results of fabrication and test of cable, collars and the mechanical model.

Giorgio Ambrosio

Papers

Measurement of Critical Current and Instability Threshold of Rutherford-Type $rm Nb_3rm Sn$ Cables

Proposals for improvements of the correction of sextupole dynamic effects in tevatron dipole magnets

Mechanical design and analysis of the Fermilab 11 T Nb/sub 3/Sn dipole model

Development and Test of $rm Nb_3rm Sn rm Cos(theta)$ Magnets Based on RRP and PIT Strands

R&D for a single-layer Nb/sub 3/Sn common coil dipole using the react-and-wind fabrication technique