D. Loukas

The Forward Ring Imaging Cherenkov detector of the DELPHI experiment at LEP provides hadron identification at polar angles15° < θ < 35° and 145° < θ < 165°. Two radiator media, a layer of liquid C6F14 and a volume of gaseous C4F10, in combination provide coverage of momenta up to 40 GeV/c. A single array of photosensitive Time Projection Chambers registers the impact points of ultraviolet photons from both radiators. The design of the detector and of its readout system is described. First results obtained with a partly installed detector are reported.

A short explanation is given of the Barrel Ring Imaging CHerenkov (BRICH) detector and its performance. We discuss in brief some of the requirements to run this detector. Special attention is paid to the functioning of the Cherenkov photon detector — a photosensitive gas-filled drift chamber where the photoelectrons drift to a MWPC of special construction. We illustrate the BRICH performance with some preliminary results.

The ring imaging Cherenkov detector system in the DELPHI experiment at the Large Electron-Positron storage ring at CERN, is designed to do particle identification over most of the solid angle in the momentum range from ∼2 GeVc to ∼40 solGeVc. Two radiator media are used to cover the momentum range; (i) a 1 cm layer of liquid C6F14, and (ii) a volume filled with gaseous C5F12 or C4F10. Photosensitive time projection chambers record the conversion points of the ultraviolet photons produced in both radiator systems. The total active area is ∼30 m2 in the barrel region and ∼8 m2 in the two endcaps. The design of the detector systems is described in this paper. We will also report performance figures and compare them to simulation studies.

A ring imaging Cherenkov (RICH) detector system has been built and is now in full operation within the DELPHI experiment. Large data samples of Z/sup 0/ decays are being collected with good resolution on the observed Cherenkov angles. Several studies of Z/sup 0/ decays using the RICH have already been performed on limited samples. Disturbance of the detector operation caused by shrinkage of polymeric construction materials and by migration of radiator substance is reported. These effects have been counteracted and do not endanger the quality of the data.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Abstract The Miniaturized Detector for Application in Space (MIDAS) device is developed in response to the requirement of the European Space Agency for a device whose size, power consumption, and radiation data output would increase the level of space‐flight crew autonomy regarding operational decisions related to radiation hazards. It is designed as a wristwatch‐dimension cube detector for measuring track direction and energy deposition in silicon pixels, as well as energy depositions by neutrons in a plastic scintillator, which is the core of the cube. Miniaturization was achieved by using fully depleted silicon pixel detectors with the signal processing electronics residing on pixel. The device concept, simulated performance, and first measurements are presented. Simulation results indicate that it is possible to discriminate all significant ions with the aid of appropriate variables constructed using the data provided by the device. 252 Cf energy spectra were reconstructed successfully using measurements obtained with the first device prototype.

The DELPHI experiment has already collected 2.5 million Z0 decays with the ring imaging Cherenkov detector (RICH) operational. This detector, covering most of the solid angle, is designed to perform πK separation from 0.8 to 20 GeV/c and K/p separation from 0.8 to 35 GeV/c. After a brief detector description we discuss the actual operating conditions, the data monitoring and the signal treatment. The collected data from Z0 decays and the detector response to signals from the calibration system are used to evaluate the performance of the RICH system.

The gating system of the MWPCs of the DELPHI Barrel RICH is essentially a means to prevent positive ions originating from avalanches in the chambers to escape into the Barrel RICH drift tubes. These ions would otherwise seriously affect the imaging quality of the Barrel RICH. We describe the gating grid, the gating pulser and results of tests at pressures of 1 and 1.3 bar in a magnetic field of 1.2 T and without. In the ungated (“closed”) mode, transfer of electrons and ions are 8% and 0% respectively; a further reduction of electron transfer is limited by power dissipation of the pulsing circuit. The occupation time of the readout electronics after the gating pulse is less than 1 μs. The test results are compared with those of electrostatic simulations. A triggering scheme is proposed.

One quarter of the Forward Ring Imaging Cherenkov (Forward RICH) detector has been installed and operated in the DELPHI experiment. The detector covers the forward-backward regions (15 degrees < theta <35 degrees ). Two radiator systems are used for particle identification in the momentum range up to 40 GeV/c, i.e., a liquid perfluorohexane and perfluorobutane gas. UV-photons with wavelengths from approximately 170 nm to approximately 200 nm (7.3-6.2 eV) are detected with high efficiency. The total active area of the photon detector is approximately 8 m/sup 2/.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The front-end readout electronics chain of the forward ring imaging Cherenkov (FRICH) detector used at the Delphi experiment of the Large Electron Positron (LEP) collider is presented. The system incorporates a wideband low-noise preamplifier, mounted in the proximity of the multiwire proportional chamber, an amplifying-discriminating-multiplexing FASTBUS unit for further signal amplification, discrimination, and channel reduction, and a LEP time digitizer FASTBUS unit for time digitization. The detector and its electronics are discussed, with particular emphasis on the novel characteristics and capabilities of the system.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The DELPHI detector installed in the LEP (Large Electron-Positron Collider) is equipped with RICH (ring imaging Cherenkov) counters. The barrel part incorporates a liquid (C/sub 6/F/sub 14/) and a gaseous (C/sub 5/F/sub 12/) radiator, providing particle identification up to 20 GeV/c. The Cherenkov photons of both radiators are detected by TPC (time projection chamber)-like photon detectors. The drift gas (75% CH/sub 4/+25% C/sub 2/H/sub 6/) is doped with TMAE (tetrakis-dimethylamine-ethylene) by which the ultraviolet Cherenkov photons are converted into single free photoelectrons. These are drifted towards multiwire proportional chambers at the end of the drift tubes, and the space coordinates of the conversion point are determined. One half of the barrel RICH is now equipped with drift tubes and has provided results from the liquid radiator since spring 1990. The gas radiator has been tested with C/sub 2/F/sub 6/ as a preliminary filling since August 1990. The data obtained demonstrate the good particle identification potential. For the liquid radiator, the number of detected photons per ring in hadron jets is N=8, whereas for muon pairs (single tracks) N=10 has been obtained. For the gas radiator, 2.1 photons per track were observed, which demonstrates good functioning of the focussing mirrors.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The Barrel Ring Imaging Cherenkov detector of the DELPHI experiment at LEP provides particle identification by the detection of the radiation emitted in UV transparent perfluorocarbons. We will present the principles of the operation of the detector together with a discussion of the automatized control of all the relevant physical parameters. The observed performances of the detector are very close to their design values.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The Forward Ring Imaging Cherenkov detector covers both end-cap regions of the DELPHI experiment at LEP in the polar angle 15/spl deg/>

Radiation doses received by astronauts outside the geomagnetic field are a main risk factor for human space exploration. The Miniaturized Detector for Application in Space (MIDAS) device is a highly miniaturized radiation detector (mass <50 g, volume < 5 × 5 × 1 cm3) which is under development using fully depleted monolithic active pixel sensors and a plastic scintillator readout by a Silicon Photomultiplier. Its purpose is to measure dose and dose equivalent from both charged particles and fast neutrons. The device simulated response to galactic cosmic rays spectra has been treated with artificial intelligence techniques i.e. multi-classification for particle identification and regression for the determination of the kinetic energy of protons. Results indicate that particle identification and kinetic energy determination with the aid of these methods could be a viable approach.

The general purpose particle detector DELPHI at the Large Electron Positron collider at CERN was built to give the complete information of each event. DELPHI uses ring imaging Cherenkov counters to provide hadron identification in most of the momentum range below 45 GeV/c and over almost the full solid angle. Charged particles traversing gaseous and liquid fluorocarbon radiators create photons used for Cherenkov angle reconstruction. Some of the design features of the detector will be presented, with emphasis on the experience which was gained in the operation of these large systems. The hadron identification power of the ring imaging Cherenkov detector closely meets the main design values. Data processing and performance of the detector will be discussed using dimuon events collected during 1994. Pion rejection factors for kaon tagging will be shown.

The ring imaging Cherenkov detector in the DELPHI Experiment at LEP allows hadron identification over a momentum range up to about 40 Gev/c over a near to 4π solid angle. Photons emitted by charged particles traversing gas and liquid radiators which are filled with UV-transparent perfluorocarbons, are used for Cherenkov angle reconstruction. Stable operation ensures that the detector is an efficient and powerful instrument. Monitoring of the detector parameters is of utmost importance to achieve good data quality and adequate data processing. The hadron identifying power of the ring imaging Cherenkov detector closely meets the main design values. Computerized control and monitoring features of the different subsystems will be presented. The interplay between detector parameters and the particle separating capacity of the detector will be discussed.

A prevailing imaging method with X rays in interventional medicine is connected to the field of angiography. Calculations are presented of absorbed doses based on spectral energy distributions of the backscattered X ray field recorded with a portable X ray system. Measurements were performed in two positions carefully selected in the intervention room. The two selected positions, namely the eye/thyroid level and the abdominal/gonads level, are critical for the personnel who have to stand next to the patient during intervention. The aim of the work is to provide measured values for doses absorbed by the personnel performing cine examination or intervention in catheterisation laboratories.