F. Hauler

A transition radiation detector for AMS

Abstract For cosmic particle spectroscopy on the International Space Station the AMS experiment will be equipped with a Transition Radiation Detector to improve proton background supression up to 300 GeV. The TRD has 20 layers of fleece radiator with Xe/CO2 proportional-mode straw-tube chambers. They are supported in a conically shaped octagon structure made of CFC-Al-honeycomb. For low power consumption VA analog multiplexers are used as front-end readout. A 20 layer prototype has achieved proton rejections above 100 at 90% electron efficiency for beam energies up to 250 GeV. The detector is under construction at RWTH Aachen, the gas system will be built at MIT, slow-control and DAQ at TH Karlsruhe.

Optimization of electric field distribution by free carrier injection in silicon detectors operated at low temperatures

We present a study of the modeling of the electric field distribution, which is controlled by injection and trapping of nonequilibrium carriers, in Si detectors irradiated by high neutron fluences. An analytical calculation of the electric field distribution in detectors irradiated by neutrons up to fluences of 1 /spl middot/ 10/sup 14/ to 5 /spl middot/ 10/sup 15/ cm/sup -2/ shows the possibility of reducing the full depletion voltage at low temperatures via hole injection. For this calculation, we use the detector operating parameters and equivalent neutron fluences expected for Large Hadron Collider experiments. The results of the calculation are in good qualitative agreement with published experimental data, lending strong support for the model and for an earlier proposal of electric field manipulation by free carrier injection.

An algorithm for calculating the Lorentz angle in silicon detectors

Future experiments will use silicon sensors in the harsh radiation environment of the LHC (Large Hadron Collider) and high magnetic elds. The drift direction of the charge carriers is aected by the Lorentz force due to the high magnetic eld. Also the resulting radiation damage changes the properties of the drift. In this paper measurements of the Lorentz angle of electrons and holes before and after irradiation are reviewed and compared with a simple algorithm to compute the Lorentz angle.

Cryogenic operation of silicon detectors

This paper reports on measurements at cryogenic temperatures of a silicon microstrip detector irradiated with 24 GeV protons to a #uence of 3.5]1014 p/cm2 and of a p}n junction diode detector irradiated to a similar #uence. At temperatures below 130 K a recovery of charge collection e

Beam-monitors for TESLA based on diamond-strip-detectors

ciency and resolution is observed. Under reverse bias conditions this recovery degrades in time towards some saturated value. The recovery is interpreted qualitatively as

Silicon detectors irradiated ''in situ'' at cryogenic temperatures

For TeV energy superconducting linear accelerator (TESLA), it is foreseen to measure the beam profile with so-called wire scanners. A thin carbon fiber is moved through the beam and the number of scattered secondary particles is measured in correlation to the position of the wire. From this, a beam profile can be calculated as an average over many bunches of the beam. With strip detectors made from diamond, the beam profile can be measured online for single bunches. With two perpendicular arrays of strips on the front and the back side of the detector, the beam profile can also be measured in the X and Y direction. If fast electronics are used and the bunches are not too short, even a longitudinal profile in the Z direction can be obtained. We successfully tested a diamond detector in a heavy ion beam with bunches of up to 3/spl middot/10/sup 10/ O/sup 6+/ ions and in a beam of 10/sup 10/ electrons in bunches with a length of 300 /spl mu/m, as planned for TESLA. The fluence of 10/sup 15/ e/sup -//cm/sup 2/ or more by one of the bunches foreseen for TESLA corresponds to the irradiation a vertex detector receives during ten years of large hadron collider. The results of our measurements will be presented and discussed.

Recent progress in low-temperature silicon detectors

Though several studies have proved the radiation tolerance of silicon detectors at cryogenic temperatures, following room temperature irradiation, no previous investigation has studied the behaviour of detectors irradiated ‘‘in situ’’ at low temperatures. In this work, effects of irradiation of 450 GeV protons at 83 K will be presented, showing that after a dose of 1.2 � 10 15 pc m � 2 a charge collection efficiency (CCE) of 55% is reached at 200 V before the annealing. The same results were found at the end of the irradiation, after the sample has spent more then one year at room temperature. This shows that the CCE recovery by low temperature operation is not affected by the temperature of irradiation and by the reverse annealing. r 2002 Elsevier Science B.V. All rights reserved.

Cryogenic semiconductor high-intensity radiation monitors

The CERN RD39 Collaboration studies the possibility to extend the detector lifetime in a hostile radiation environment by operating them at low temperatures. The outstanding illustration is the Lazarus effect, which showed a broad operational temperature range around 130 K for neutron irradiated silicon detectors.

Measurements with a CMOS pixel sensor in magnetic fields

Abstract This paper describes a novel technique to monitor high-intensity particle beams by means of a semiconductor detector. It consists of cooling a semiconductor detector down to cryogenic temperature to suppress the thermally generated leakage current and to precisely measure the integrated ionization signal. It will be shown that such a device provides very good linearity and a dynamic range wider than is possible with existing techniques. Moreover, thanks to the Lazarus effect, extreme radiation hardness can be achieved providing in turn absolute intensity measurements against precise calibration of the device at low beam flux.

The Lorentz angle in silicon detectors

Abstract CMOS technique, which is the standard process used by most of the semiconductor factories worldwide, allows the production of both cheap and highly integrated sensors. The prototypes MIMOSA 1 -I and MIMOSA-II were designed by the IReS–LEPSI collaboration in order to investigate the potential of this new technique for charged particle tracking (Design and Testing of Monolithic Active Pixel Sensors for Charged Particle Tracking, LEPSI, IN2P3, Strasbourg, France). For this purpose it is necessary to study the effects of magnetic fields as they appear in high-energy physics on these sensors.