118899725
Test, Integration and Commissioning of Monitored Drift Tube Chambers for the ATLAS Barrel Muon Spectrometer
c Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. The ATLAS experiment at the Large Hadron Collider (LHC) at CERN is currently being assembled and to be ready for data taking in 2007. In the barrel region of its muon spectrometer, a toroidal air-core magnet is instrumented with three layers of Monitored Drift Tube (MDT) chambers as precision tracking detectors; the middle and outer layers of drift chambers also carry Resistive Plate chambers (RPCs) of the trigger system. The barrel part of the spectrometer consists of a total of 682 muon stations, with sizes ranging from 1 m 2 to 11 m 2. The installation of the muon detectors has started in January 2005. At the of the second largest chamber type—each covering an area of up to 8 m 2 —are being built for the outermost barrel region. The MDT chambers have to pass a series of stringent tests before installation to ensure their proper operation in the experiment. At the production site in Munich, these tests include gas tightness, high voltage stability and measurements of the noise rate, and the response to cosmic muons. In addition, the individual wire positions and electronic time offsets of the drift tubes are determined from the cosmic ray data. After shipment to CERN, a subset of the tests is repeated and the MDT chambers are integrated on a common support frame with the trigger chambers. The completed muon station is is further checked with cosmic rays. All results are stored in the ATLAS commissioning database and constitute an important basis for LHC data taking. We present the test methods and results, an overview on the integration work of the muon detectors and report on the experience with the installation of the first stations in the ATLAS experiment.
120597551
Influence of the magnetic field on the gating of a time projection chamber
A large cylindrical time projection chamber (TPC 90), 60 cm in diameter, a driftlength of 130 cm, as well as a smaller test-chamber of 30 × 30 × 15 cm3 have been used to investigate the effects of the magnetic field on the operation of a gated grid. The magnetic field is found to affect strongly the drifting electrons, but not for the positive ions. The results can be well explained by the specific configuration of the combined EandB fields near the gating grid wires and in the region of the proportional wires.
119295158
Performance of Drift-Tube Detectors at High Counting Rates for High-Luminosity LHC Upgrades
Abstract The performance of pressurized drift-tube detectors at very high background rates has been studied at the Gamma Irradiation Facility (GIF) at CERN and in an intense 20 MeV proton beam at the Munich Van-der-Graaf tandem accelerator for applications in large-area precision muon tracking at high-luminosity upgrades of the Large Hadron Collider (LHC). The ATLAS muon drift-tube (MDT) chambers with 30 mm tube diameter have been designed to cope with γ and neutron background hit rates of up to 500 Hz/cm 2 . Background rates of up to 14 kHz/cm 2 are expected at LHC upgrades. The test results with standard MDT readout electronics show that the reduction of the drift-tube diameter to 15 mm, while leaving the operating parameters unchanged, vastly increases the rate capability well beyond the requirements. The development of new small-diameter muon drift-tube (sMDT) chambers for LHC upgrades is completed. Further improvements of tracking efficiency and spatial resolution at high counting rates will be achieved with upgraded readout electronics employing improved signal shaping for high counting rates.
120421514
GAS SYSTEM FOR ALEPH TPC
Abstract Operation of the time projection chamber of the ALEPH experiment at LEP requires a high-purity argon/methane gas mixture supplied to the detector under stable conditions to ensure minimum signal attenuation throughout the 43 m 3 detector volume (max. 2.2 m drift length) and maintain near-constant electron drift velocity in the gas over extended periods of time. Design considerations for a gas system to fulfil these conditions are presented and details given of the construction, operational aspects and of the achieved performance.
195867117
Construction and test of the precision drift chambers for the ATLAS Muon Spectrometer
The Monitored Drift Tube (MDT) chambers for the muon spectrometer of the ATLAS detector at the Large Hadron Collider (LHC) consist of 3-4 layers of pressurized drift tubes on either side of a space frame carrying an optical deformation monitoring system. The chambers have to provide a track position resolution of 40 /spl mu/m with a single-tube resolution of at least 80 /spl mu/m and a sense wire positioning accuracy of 20 /spl mu/m (rms). The feasibility was demonstrated with the full-scale prototype of one of the largest MDT chambers with 432 drift tubes of 3.8 m length. For the ATLAS muon spectrometer, 88 chambers of this type have to be built. The first chamber has been completed with a wire positioning accuracy of 15 /spl mu/m (rms).
108271361
Concepts for the readout of time projection chambers
While the use of CCD’s for the readout of TPC’s offers a reliable and ever more of the digitization concept. The problem of precision of currently available FADC’s is discussed together with two proposals for a solution.
67778447
A fast readout using switched current techniques for a DEPFET-pixel vertex detector at TESLA
Abstract A fully depleted silicon detector with a first amplifying transistor integrated in every pixel (DEPFET) is a promising proposal for the pixel-based vertex detector at TESLA. The DEPFET offers good spatial resolution, an excellent signal-to-noise ratio and low power consumption in a row-wise operation mode. A readout concept for a DEPFET pixel array matching the requirements at TESLA is described. In order to meet the operation specifications at TESLA ( 50 MHz row rate), a readout architecture based on current mode techniques (Switched Current) is presented. It contains stand alone zero suppression offering a triggerless operation. The core of the readout chip, a fast operating current memory cell, is discussed in detail. The results of a first prototype chip, CURO I (CUrrent ReadOut), show that the requirements for TESLA are achievable.
110363376
Design and test of radiation hard p'n silicon strip detectors for the ATLAS SCT
Strip detectors covering radiation hardness and large-scale production ability are developed and produced for the ATLAS experiment at the Large Hadron Collider (LHC) at CERN (Switzerland). Capacitively coupled p‘n detectors (p-type strips on n-type substrate) were developed with implanted bias resistors in order to simplify the detector processing addressing the requirements of large-scale production. The detectors were irradiated with 24 GeV protons up to 3]1014 cm~2 in order to simulate a 10 years operation scenario at LHC. The presented static and signal measurements demonstrate the function of the device concept before and after irradiation. ( 2000 Elsevier Science B.V. All rights reserved.
15731595
Stringy Instantons and Yukawa Couplings in MSSM-like Orientifold Models
Type IIA orientifold constructions with intersecting D6-branes and their IIB duals in terms of magnetized D9/D7-branes constitute one of the most promising avenues for the construction of semirealistic MSSM-like compactifications. One generic problem with these constructions is that there are many Yukawa couplings, which vanish due to additional U(1) symmetries in the theory. In this paper, we consider a number of such settings and study under what conditions stringy instanton effects can give rise to non-perturbative contributions to the Yukawa couplings, so that all perturbatively forbidden terms are induced. We find specific settings in which Yukawa couplings for all fermions are indeed obtained. For some cases we provide specific local examples of rigid O(1) instantons within the T6/2 × 2' toroidal orientifold with torsion that gives rise to the required amplitudes. A potential problem in these settings is that the same instantons, providing for Yukawa coupling contributions, may give rise to too large μ-terms for the Higgs multiplets. We show how this problem may be overcome in explicit models with a doubled Higgs system.
118634238
Development of muon drift-tube detectors for high-luminosity upgrades of the Large Hadron Collider
Abstract The muon detectors of the experiments at the Large Hadron Collider (LHC) have to cope with unprecedentedly high neutron and gamma ray background rates. In the forward regions of the muon spectrometer of the ATLAS detector, for instance, counting rates of 1.7 kHz / cm 2 are reached at the LHC design luminosity. For high-luminosity upgrades of the LHC, up to 10 times higher background rates are expected which require replacement of the muon chambers in the critical detector regions. Tests at the CERN Gamma Irradiation Facility showed that drift-tube detectors with 15 mm diameter aluminum tubes operated with Ar : CO 2 ( 93 : 7 ) gas at 3 bar and a maximum drift time of about 200 ns provide efficient and high-resolution muon tracking up to the highest expected rates. For 15 mm tube diameter, space charge effects deteriorating the spatial resolution at high rates are strongly suppressed. The sense wires have to be positioned in the chamber with an accuracy of better than 50 μ m in order to achieve the desired spatial resolution of a chamber of 50 μ m up to the highest rates. We report about the design, construction and test of prototype detectors which fulfill these requirements.
6594228
Scattering of gauge, matter, and moduli fields from intersecting branes
Abstract We calculate various tree-level (disk) scattering amplitudes involving gauge, matter and moduli fields in IIB toroidal orbifold/orientifold backgrounds with D9-, D5- respectively D7-, D3-branes or via T -duality D6-branes in type IIA compactifications. In type IIB the D-branes may have non-vanishing fluxes on their world-volume. From these results we extract the moduli and flux dependence of the tree-level gauge couplings, the metrics for the moduli and matter fields. The non-vanishing fluxes correspond in the T -dual type IIA description to intersecting D6-branes. This allows us to determine the moduli dependence of the tree-level matter field metrics in the effective action of intersecting D6-brane models. In addition we derive the physical Yukawa couplings with their correct normalization.