195859757
Radiation hard strip detectors on oxygenated silicon
Recent results of the RD48 (ROSE) collaboration suggest the usage of oxygen enriched silicon for sensors operated in the harsh radiation environment of future high luminosity experiments. To investigate if the anticipated beneficial properties are still present after full processing of the wafers, strip detectors for the innermost ring of the ATLAS forward region have been fabricated on oxygen enriched silicon by CiS, Germany. These sensors, together with sensors on standard and thin substrates, have been exposed to 3/spl middot/10/sup 14/ 24 GeV/c protons/cm/sup 2/ at the CERN PS. We are presenting here the comparison between the sensors based on the CV measurements and the investigation of the charge collection efficiency obtained with a /sup 90/Sr source and the analogue readout chip SCT128A.
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.
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.
73653251
Imaging performance of a DEPFET pixel Bioscope system in Tritium autoradiography
Abstract A Bioscope system based on a 64 × 64 -matrix of DEPFET pixels has been developed for real-time digital autoradiography in biomedical applications. It provides very good energy and spatial resolution at the same time. The DEPFET pixel cells consist of p -channel JFETs integrated into the high-ohmic n -silicon substrate. This leads to a very low noise performance at room temperature. Two dedicated ASIC chips have been developed for steering and readout of the pixel matrix. The measured system noise of ( 69 ± 4 ) e - at 35 ∘ C is mostly due to sensor leakage current and can be largely reduced by cooling or a faster readout. The spatial resolution is examined by measurements with a laser as well as with a dedicated test chart and is determined to be ( 6.7 ± 0.7 ) μ m for 6 keV-X-rays and 4.3 ± 0.8 μ m for 22 keV-X-rays. The measurements are compared to simulation results with different reconstruction algorithms. Due to the thin entrance window at the detector backside and the low noise performance, a detection of low-energy β -emitters such as 3H is possible. Measurements with 3H-labeled biological samples were taken. The ability of the DEPFET pixel Bioscope to separate different radiolabels in the same sample is demonstrated by a measurement with 3H and 14C.
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.
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.
125139430
Measurement of the Reactions $\bar{P} P \to \bar{\Lambda} \Lambda$, $\bar{p} p \to \bar{\Lambda} \Sigma^0$ and $\bar{P} P \to \bar{\Lambda}$ (Missing Mass) at 6-{GeV}
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.
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.
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.