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.
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.
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.
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.
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.
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.
91179768
SLID-ICV Vertical Integration Technology for the ATLAS Pixel Upgrades
Abstract We present the results of the characterization of pixel modules composed of 75 μm thick n-in-p sensors and ATLAS FE-I3 chips, interconnected with the SLID (Solid Liquid Inter-Diffusion) technology. This technique, developed at Fraunhofer-EMFT, is explored as an alternative to the bump-bonding process. These modules have been designed to demonstrate the feasibility of a very compact detector to be employed in the future ATLAS pixel upgrades, making use of vertical integration technologies. This module concept also envisages Inter-Chip-Vias (ICV) to extract the signals from the backside of the chips, thereby achieving a higher fraction of active area with respect to the present pixel module design. In the case of the demonstrator module, ICVs are etched over the original wire bonding pads of the FE-I3 chip. In the modules with ICVs the FE-I3 chips will be thinned down to 50 um. The status of the ICV preparation is presented.
120821170
Breakdown protection and long-term stabilisation for Si-detectors
Abstract Normally, guardrings are used to shield the sensitive part of detectors from surface and edge leakage currents. We propose a structure which in addition provides a gradual drop of the potential from the detector rim towards the bulk potential. Different structures were measured and also simulated with the two-dimensional semiconductor analysis package TOSCA. The possibilities of this package are briefly discussed. The agreement between the measurements and the simulation is very good. Based on these simulations, a layout of a detector protection structure with optimized performance is proposed.
118440611
On stable higher spin states in heterotic string theories
We study properties of 1/2 BPS Higher Spin states in heterotic compactifications with extended supersymmetry. We also analyze non BPS Higher Spin states and give explicit expressions for physical vertex operators of the first two massive levels. We then study on-shell tri-linear couplings of these Higher Spin states and confirm that BPS states with arbitrary spin cannot decay into lower spin states in perturbation theory. Finally, we consider scattering of vector bosons off higher spin BPS states and extract form factors and polarization effects in various limits.
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.
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.