108645383
The ATLAS Silicon Pixel Sensors
Abstract Prototype sensors for the ATLAS silicon pixel detector have been developed. The design of the sensors is guided by the need to operate them in the severe LHC radiation environment at up to several hundred volts while maintaining a good signal-to-noise ratio, small cell size, and minimal multiple scattering. The ability to be operated under full bias for electrical characterization prior to attachment of the readout integrated circuit electronics is also desired.
195868697
Irradiation tests of double-sided silicon strip detectors with a special guard ring structure
The results of the first irradiation tests of newly designed silicon microstrip detectors performed with 21 MeV protons at the Max-Planck-Institut in Heidelberg are presented. The detectors were developed and produced by the semiconductor laboratory of the Max-Planck-Institut in Munich. Novel guard ring structures allow operation of the detectors at voltages exceeding 300 V.
120274396
Timing properties of an avalanche diode for single photon counting
A new concept for a silicon single photon counter has been developed at the Semiconductor Laboratory of the Max-Planck-Institute for Physics. The concept combines the principles of a drift diode and an avalanche diode. The electron which is generated by an incoming photon has to drift to the small avalanche region and avalanche breakdown will take place. The detector is operated in Geiger mode. In order to provide high efficiency and good timing properties, the electrons have to be focussed properly with short time jitter. Therefore, drift and timing properties have been investigated using simulations.
34283775
Tracking and level-1 triggering in the forward region of the ATLAS muon spectrometer at sLHC
In the endcap region of the ATLAS Muon Spectrometer (η  >  1) precision tracking and Level-1 triggering are performed by different types of chambers. Monitored Drift Tube chambers (MDT) and Cathode Strip Chambers (CSC) are used for precision tracking, while Thin Gap Chambers (TGC) form the Level-1 muon trigger, selecting muons with high transverse momentum (pT). When by 2018 the LHC peak luminosity of 1034 cm−2s−1 will be increased by a factor of ~ 2 and by another factor of ~ 2–2.5 in about a decade from now (``SLHC''), an improvement of both systems, precision tracking and Level-1 triggering, will become mandatory in order to cope with the high rate of uncorrelated background hits (``cavern background'') and to stay below the maximum trigger rate for the muon system, which is in the range of 10–20 % of the 100 kHz rate, allowed for ATLAS. For the Level-1 trigger of the ATLAS Muon Spectrometer this means a stronger suppression of sub-threshold muons in the high-pT trigger as well as a better rejection of tracks not coming from the primary interaction point. Both requirements, however, can only be fulfilled if spatial resolution and angular pointing accuracy of the trigger chambers, in particular of those in the Inner Station of the endcap, are improved by a large factor. This calls for a complete replacement of the currrently used TGC chambers by a new type of trigger chambers with better performance. In parallel, the precision tracking chambers must be replaced by chambers with higher rate capability to be able to cope with the intense cavern background. In this article we present concepts to decisively improve the Level-1 trigger with newly developed trigger chambers, being characterized by excellent spatial resolution, good time resolution and sufficiently short latency. We also present new types of precision chambers, designed to maintain excellent tracking efficiency and spatial resolution in the presence of high levels of uncorrelated background hits, as generated by γ and neutron conversions.
121460348
Irradiation tests of double-sided silicon strip detectors optimized for the ATLAS-inner-detector-region
Abstract Silicon detectors, which will be used as tracking detectors in LHC-experiments, face special requirements; one major challenge is the long term operation of the detectors in very intense radiation fields. This paper describes a design for double-sided strip detectors, which takes these requirements into account. Irradiation tests have been carried out using 24 GeV protons. The change of detector characteristics in particular guardring-behaviour, punchthrough biasing and interstrip isolation has been studied.
19809846
Development of Fast High-Resolution Muon Drift-Tube Detectors for High Counting Rates
Abstract Pressurized drift-tube chambers are efficient detectors for high-precision tracking over large areas. The Monitored Drift-Tube (MDT) chambers of the muon spectrometer of the ATLAS detector at the Large Hadron Collider (LHC) reach a spatial resolution of 35 μ m and almost 100% tracking efficiency with 6 layers of 30 mm diameter drift tubes operated with an Ar:CO 2 (93:7) gas mixture at 3 bar and a gas gain of 20 000. The ATLAS MDT chambers are designed to cope with background counting rates due to neutrons and γ rays of up to about 300 kHz per tube which will be exceeded for LHC luminosities larger than the design value of 10 34  cm −1  s −1 . Decreasing the drift-tube diameter to 15 mm while keeping the other parameters, including the gas gain, unchanged reduces the maximum drift time from about 700 to 200 ns and the drift-tube occupancy by a factor of 7. New drift-tube chambers for the endcap regions of the ATLAS muon spectrometer have been designed. A prototype chamber consisting of 12 times 8 layers of 15 mm diameter drift tubes of 1 m length has been constructed with a sense wire positioning accuracy of 20 μ m . The 15 mm diameter drift-tubes have been tested with cosmic rays in the Gamma Irradiation Facility at CERN at γ counting rates of up to 1.85 MHz.
122734759
Measurement and Optimization of the Emittance of a 300-ns 250-A 3.4-MeV Electron Beam
Author(s): Allison, R.W.; Beal, J.W.; Everett, W.L.; Guggemos, J.R.; Lamb, W.A.S.; Richter, R.M.; Sherwood, W.A.; Spoerlein, R.L.; Tanabe, J.; Wright, R.E.; Zajec, E.
110325204
Upgrade of the Readout Electronics of the ATLAS MDT Detector for SLHC
Simulation predicts a high level of ionizing radiation in the ATLAS experimental hall during LHC operation. This radiation will act as a source of background signals to the four subsystems of the ATLAS muon detector. We present the performance of the Monitored Drift Tube detector (MDT) under these background conditions and discuss the consequences for the much higher background rates at SLHC with respect to tracking efficiency, resolution and readout bandwidth. For rates beyond the expected LHC levels, we discuss options to improve the performance of detector and electronics.
120584442
Modelling of the space-to-drift-time relationship of the ATLAS monitored drift-tube chambers in the presence of magnetic fields
Abstract The ATLAS muon spectrometer uses tracking chambers consisting of up to 5 m long drift tubes filled with Ar : CO 2 ( 93 : 7 ) at 3 bar. The chambers are run in a average toroidal magnetic field of 0.4 T created by 8 air core coils. They provide a track-point accuracy of 40 μ m if the space-to-drift-time relationship r ( t ) is known with 20 μ m accuracy. The magnetic field B influences the electron drift inside the tubes: the maximum drift time t max = 700 ns increases by ≈ 70 ns / T 2 B 2 . B varies by up to ± 0.4 T along the tubes of the chambers mounted near the magnet coils which translates into a variation of t max of up to 45 ns. The dependence of r ( t ) on B must be taken into account. Test-beam measurements show that the electron drift in case of B ≠ 0 can be modelled with the required accuracy by a Langevin equation with a friction term which is slightly non-linear in the drift velocity.
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.
92988840
Resolution and efficiency of the ATLAS muon drift-tube chambers at high background rates
Abstract The resolution and efficiency of a precision drift-tube chamber for the ATLAS muon spectrometer with final read-out electronics was tested at the Gamma Irradiation Facility at CERN in a 100 GeV muon beam at photon irradiation rates of up to 990 Hz / cm 2 , which corresponds to twice the highest background rate expected in ATLAS. A silicon strip detector telescope served as external reference in the beam. The pulse-height measurement of the read-out electronics was used to perform time-slewing corrections, which lead to an improvement of the average drift-tube resolution from 104 to 82 μ m without irradiation, and from 128 to 108 μ m at the maximum expected rate. The measured drift-tube efficiency agrees with the expectation from the dead time of the read-out electronics up to the maximum expected rate.