L. Smykov

Energy loss of pions and electrons of 1– in drift chambers operated with Xe,CO2(15%)

Abstract We present measurements of the energy loss of pions and electrons in drift chambers (DC) operated with a Xe,CO 2 (15%) mixture. The measurements are carried out for particle momenta from 1 to 6 GeV /c using prototype DC for the ALICE transition radiation detectors. Microscopic calculations are performed using input parameters calculated with GEANT3. These calculations reproduce well the measured average and most probable values for pions, but a higher Fermi plateau is required in order to reproduce our electron data. The widths of the measured distributions are smaller for data compared to the calculations. The electron/pion identification performance using the energy loss is also presented.

Pulse height measurements and electron attachment in drift chambers operated with Xe, CO2 mixtures

We present pulse height measurements in drift chambers operated with Xe,CO2 gas mixtures. We investigate the attachment of primary electrons on oxygen and SF6 contaminants in the detection gas. The measurements are compared with simulations of properties of drifting electrons. We present two methods to check the gas quality: gas chromatography and 55 Fe pulse height measurements using monitor detectors.

Development of low-mass drift chambers for the HADES spectrometer

Abstract The High Acceptance Di-Electron Spectrometer (HADES) is a detector arrangement combined with a superconducting toroid for lepton pair spectroscopy presently built up at GSI (Darmstadt). HADES is designed to cope with the high-multiplicity environment of heavy ion collisions at 1xa0AGeV and intensities of up to 10 8 beam particles per second and central event rates of 10 5 s −1 . The detector has a geometrical acceptance of almost 50% for e + e − pairs and a mass resolution of 0.8% for ρ and ω mesons. Four low-mass drift chamber systems, two before and two behind the magnet, serve for charged particle track reconstruction. Design aspects of the drift chambers and first results from beam tests are presented.

Position reconstruction in drift chambers operated with Xe, CO2 (15%)

Abstract We present measurements of position and angular resolution of drift chambers operated with a Xe, CO 2 (15%) mixture. The results are compared to Monte Carlo simulations and important systematic effects—in particular the dispersive nature of the absorption of transition radiation and non-linearities—are discussed. The measurements were carried out with prototype drift chambers of the ALICE Transition Radiation Detector, but our findings can be generalized to other drift chambers with similar geometry, where the electron drift is perpendicular to the wire planes.

Space charge in drift chambers operated with the Xe,CO2(15%) mixture

Using prototype modules of the ALICE Transition Radiation Detector (TRD) we investigate space-charge effects and the dependence of the pion rejection performance on the incident angle of the ionizing particle. The average pulse height distributions in the drift chambers operated with the Xe; CO2ð15%Þ mixture provide quantitative information on the gas gain reduction due to space charge accumulating during the drift of the primary ionization. Our results demonstrate that the pion rejection performance of a TRD is better for tracks which are not at normal incidence to the anode wires. We present detailed simulations of detector signals, which reproduce the measurements and lend strong support to our interpretation of the measurements in terms of space-charge effects. r 2004 Elsevier B.V. All rights reserved. PACS: 29.40.Cs

X-ray detectors based on multiwire proportional chambers

The multiwire proportional chamber (MWPC), operating in a direct photon-counting mode, is used as the basis of 1D and 2D X-ray detectors. The 1D detector used in our scanning radiographic systems is serially produced. Its counting rate is about 200 MHz, its spatial resolution 0.6 mm, the number of channels is 640. The 2D detector, designed for diffraction structural researches on synchrotron radiation at the storage ring VEPP-3, is being commissioned now. Its characteristics are: 5 MHz, 1.5 mm, 65536 channels. The second 1D detector (10 MHz, 75 μm, 3300 channels, σ = 150 μm) is made for the same purposes. A third 1D detector with a registration angle of 60° (500 MHz, 0.6 mm, 1900 channels) is under development. All the detectors operate in a frame-by-frame mode and are free (except 2D) of parallax error.

Automatized One-dimensional X-Ray-Detector

One-dimensional gas-filled X-ray detectors with delay line readout have been developed and tested on line with IBM-PC. The pressure of a xenon (90) and CH4 (10) mixture can be set over a range of 1–10 atm. The position resolution for 8 keV photons is about 170 μm. Main properties and possible applications of the detector are presented.

Parallax-free X-ray area detector with high spatial resolution

The new parallax-free X-ray 2D detector (SD-1000) with the pixel array of 1024 × 1024 has been designed and tested. This detector is the basic element of the X-ray diffractometer which is constructed for the investigation of biological macromolecules, viruses, liquid crystals and powders. The first test results are presented.

The development and utilization of multiwire coordinate detectors for an express-analysis of labelled compounds in thin layer chromatography

Abstract Characteristics of multiwire position sensitive chambers for an express-analysis of labelled compounds in thin layer chromatography are described. The analysis is characterized by a relatively high detection sensitivity, good data reproducibility and high spatial resolution.

The HADES tracking system

Abstract The HADES dielectron spectrometer has recently launched its physics program at the heavy ion synchrotron SIS at GSI Darmstadt. The spectroscopy of vector mesons in heavy ion collisions via their dielectron decay channel makes great demands on the HADES tracking system regarding acceptance and spatial resolution. The tracking system is formed out of 24 low-mass, trapezoidal multi-layer drift chambers providing about 30 m 2 of active area. Low multiple scattering in the in total four planes of drift chambers before and after the magnetic field is ensured by using helium-based gas mixtures and aluminum cathode and field wires. First in-beam performance results are contrasted with expectations from simulations. Emphasis is placed on the energy loss information, exploring its relevance regarding track recognition.