110815032
Development of thin pixel sensors and a novel interconnection technology for the SLHC
Abstract We present an R&D activity aiming to develop a new detector concept in the framework of the ATLAS pixel detector upgrade in view of the Super-LHC. The new devices combine 75–150 μm thick pixels sensors with a vertical integration technology. A new production of thin pixel sensors on n- and p-type material is under way at the MPI Semiconductor Laboratory. These devices will be connected to the ATLAS read-out electronics with the new Solid–Liquid InterDiffusion technique as an alternative to the bump-bonding process. We also plan for the signals to be extracted from the back of the electronics wafer through Inter-Chip-Vias. The compatibility of the Solid–Liquid InterDiffusion process with the silicon sensor functionality has already been demonstrated by measurements on two wafers hosting diodes with an active thickness of 50 μm.
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.
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.
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.
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.
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.
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.
120013685
A position sensitive target counter for photons above 50 MeV
Abstract We describe the construction and performance of a position sensitive sandwich counter consisting of 27 strip-shaped elements which form a cylinder around a liquid hydrogen target. The lead-scintillator strips are equipped with photomultipliers at both ends; the position of the shower is determined from the time difference of the two photomultiplier signals. Over the sensitive range of the strips (122 cm) the spatial resolution is better than 4.5 cm (fwhm) for electron energies above 250 MeV. The thickness of the counter is 4 radiation lengths of lead, which yields an efficiency above 94% for photon energies above 150 MeV. This detector surrounded a liquid hydrogen target and was used in an experiment with a magnetic spectrometer to detect fast forward particles. From the analysis of this experiment we deduce the probability of detecting a given number of photons in the channel K − p → Λ (forward) π 0 . The results are found to be in agreement with Monte Carlo predictions.
118584194
Construction and Test of MDT Chambers for the ATLAS Muon Spectrometer
Abstract 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 monitoring system to correct deformations. The full-scale prototype of a large MDT chamber has been constructed with methods suitable for large-scale production. X-ray measurements at CERN showed a positioning accuracy of the sense wires in the chamber of better than the required 20 μm (rms). The performance of the chamber was studied in a muon beam at CERN. Chamber production for ATLAS now has started.
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.
117476620
On closed-string twist-field correlators and their open-string descendants
In a recent paper we have proposed the possibility that the lightest massive string states could be identified with open strings living at intersections of D-branes forming small angles. In this note, we reconsider the relevant twist-field correlation functions and perform the analysis of the sub-dominant physical poles in the various channels. Our derivation is new in that it is based on the algebraic procedure for the construction of open string models starting from their closed-string `parents' rather than on the stress-tensor method. We also indicate possible generalizations and diverse applications of our approach.