37405387
Power supply system for the ATLAS muon spectrometer: design specifications and test
In this paper, the problem of the low-voltage (LV) and high-voltage (HV) power supply distribution of the monitored drift tubes (MDT) detector is addressed. Due to the high number of channels (1168 for low voltage and twice for high voltage) involved and to the dimension of the apparatus, these power supply systems are very complicated. Both systems are made of three different parts: a power generator, a system controller, and an active distributor. The first two parts will be localized in the cavern close to the experimental area, so they are subjected to standard environmental conditions. The third part (the active distributor) will be placed in the experimental area on the platforms just outside the detector, where the environmental conditions are more severe, due to the presence of magnetic field (about 0.08 T) and radiations. In the paper, we present the design specifications and tests for the power supply systems.
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.
120324718
Integration, commissioning and installation of monitored drift tube chambers for the ATLAS barrel muon spectrometer
The ATLAS experiment at the Large Hadron Collider (LHC) at CERN is currently being assembled to be ready to take data in 2007. Its muon spectrometer is designed to achieve a momentum resolution better than 10% at 1 TeV. In the barrel part, a toroidal air-core magnet is instrumented with three layers of Monitored Drift Tube (MDT) chambers for precision tracking. The Max-Planck-Institut fur Physik and the Ludwig-Maximilians-University in Munich have built 88 MDT chambers for the outermost barrel layer. We report on our experience with the tests of the MDT chambers, their integration with the Resistive Plate trigger chambers and the installation of the muon stations in the experiment. First results of their commissioning in the ATLAS detector will be presented.
126243744
Measurement of the reaction π−p→π+π−n on a transversely polarized target at 17.2 GeV
Preliminary results from a high statistics measurement (1 M events) of the reaction π−p→π+π−n on strong polarization effects which must be attributed to amplitudes corresponding to ’’A1’’ exchange.
122359864
Large-scale production of Monitored Drift Tube chambers for the ATLAS muon spectrometer
Abstract Precision drift tube chambers with a sense wire positioning accuracy of better than 20 μm are under construction for the ATLAS muon spectrometer. 70% of the 88 large chambers for the outermost layer of the central part of the spectrometer have been assembled. Measurements during chamber construction of the positions of the sense wires and of the sensors for the optical alignment monitoring system demonstrate that the requirements for the mechanical precision of the chambers are fulfilled.
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.
110599112
Sensor design for the ATLAS-pixel detector
Abstract The inner detector of the ATLAS experiment will contain three layers of pixel detectors. The first prototype of the sensor part will be an n + n-device in order to allow partial depleted operation after bulk inversion and a guard-ring scheme keeping the entire detector surface close to the electronic chip on ground potential. Further, a bias structure is introduced providing testability of the sensors before mounting them to the electronics. The design of the single pixel cell is the result of a detailed device simulation study.
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.
5682028
Computation of D-brane instanton induced superpotential couplings: Majorana masses from string theory
We perform a detailed conformal field theory analysis of D2-brane instanton effects in four-dimensional type IIA string vacua with intersecting D6-branes. In particular, we explicitly compute instanton induced fermion two-point couplings which play the role of perturbatively forbidden Majorana mass terms for right-handed neutrinos or MSSM {mu} terms. These results can readily be extended to higher-dimensional operators. In concrete realizations of such nonperturbative effects, the Euclidean D2-brane has to wrap a rigid, supersymmetric cycle with strong constraints on the zero-mode structure. Their implications for type IIA compactifications on the T{sup 6}/(Z{sub 2}xZ{sub 2}) orientifold with discrete torsion are analyzed. We also construct a local supersymmetric GUT-like model allowing for a class of Euclidean D2-branes whose fermionic zero modes meet all the constraints for generating Majorana masses in the phenomenologically allowed regime. Together with perturbatively realized Dirac masses, these nonperturbative couplings give rise to the seesaw mechanism.
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.
110657741
Novel silicon n-in-p pixel sensors for the future ATLAS upgrades
Abstract In view of the LHC upgrade phases towards HL-LHC the ATLAS experiment plans to upgrade the inner detector with an all silicon system. The n-in-p silicon technology is a promising candidate for the pixel upgrade thanks to its radiation hardness and cost effectiveness that allow for enlarging the area instrumented with pixel detectors. We present the characterization and performance of novel n-in-p planar pixel sensors produced by CiS (Germany) connected by bump bonding to the ATLAS readout chip FE-I3. These results are obtained before and after irradiation up to a fluence of 10 16 1-MeV n eq cm − 2 , and prove the operability of this kind of sensors in the harsh radiation environment foreseen for the pixel system at HL-LHC. We also present an overview of the new pixel production, which is on-going at CiS for sensors compatible with the new ATLAS readout chip FE-I4.