Showing papers by "Claude Leroy published in 2001"

Radiation hard silicon detectors—developments by the RD48 (ROSE) collaboration

Abstract: The RD48 (ROSE) collaboration has succeeded to develop radiation hard silicon detectors, capable to withstand the harsh hadron fluences in the tracking areas of LHC experiments. In order to reach this objective, a defect engineering technique was employed resulting in the development of Oxygen enriched FZ silicon (DOFZ), ensuring the necessary O-enrichment of about 2×1017 O/cm3 in the normal detector processing. Systematic investigations have been carried out on various standard and oxygenated silicon diodes with neutron, proton and pion irradiation up to a fluence of 5×1014 cm−2 (1 MeV neutron equivalent). Major focus is on the changes of the effective doping concentration (depletion voltage). Other aspects (reverse current, charge collection) are covered too and the appreciable benefits obtained with DOFZ silicon in radiation tolerance for charged hadrons are outlined. The results are reliably described by the “Hamburg model”: its application to LHC experimental conditions is shown, demonstrating the superiority of the defect engineered silicon. Microscopic aspects of damage effects are also discussed, including differences due to charged and neutral hadron irradiation.

Physics in ATLAS at a possible upgraded LHC

Abstract: The impact on the physics capabilities of the ATLAS detector of possible LHC upgrades is discussed. A doubling of the LHC energy or an increase in the luminosity by a factor of ten are considered. Both upgrades significantly enhance the physics capabilities of ATLAS. In general, the energy upgrade is more powerful since the pile-up of minimum bias events at higher luminosity impacts the physics performance of ATLAS in some areas.

Study of the characteristics of silicon MESA radiation detectors

Abstract: The MESA process for building silicon diodes is described. I – V and C – V features of MESA detectors are given. Results of pulse-height spectra measurements with α particles incident on the front and back sides of a MESA diode establish the energy resolution of these detectors, show the evolution of their response as a function of applied bias voltage, and bring information about the influence of MESA structure on charge collection. The characteristics of MESA detectors as a function of fluence are investigated in view of their possible use in high particle fluence environment. Charge collection data obtained from the measurements of the current-pulse response induced by β and α particles are presented as a function of applied bias voltage and particle fluence. Some electrical characteristics of detector material, namely the effective impurity or dopant concentrations ( N eff ), the electron ( μ e ) and hole ( μ h ) mobilities, are studied as a function of fluence using a charge transport model. A comparison is made with the features of standard planar (SP) silicon detectors.

The operation of large-mass room-temperature superheated droplet detectors

Abstract: Large-volume room-temperature superheated droplet detectors are being constructed for measuring very weakly interacting radiation fields, such as those produced by cold dark matter particles (CDM particles, or weakly interacting massive particles: WIMPS). Large mass droplet detectors are modular, their sensitivity is strongly operation temperature and pressure dependent. Their operation necessitates therefore measurements and control functions which are unique to this particular detection medium. We present the detectors developed for the PICASSO project: fabrication, signal production and analysis, acoustic noise identification and rejection. Other types of applications of such detectors are also being investigated.

Low-energy protons scanning of intentionally partially damaged silicon MESA radiation detectors

Abstract: The main aim of this work was to measure the spectroscopic response of intentionally damaged MESA silicon detectors. A uniformly damaged region was created using protons delivered by the University of Montreal, Montreal, QC, Canada, 6-MV tandem accelerator at different energies and fluences. Only the back half of the detectors was damaged. The vacancy density created in the damaged region was built at a level of 7/spl times/10/sup 15/ vacancies/cm/sup 3/. The detectors were scanned over their whole volume with protons of well-defined ranges. The response characteristics were studied using protons backscattered from a thin gold foil at nine different primary proton beam energies. The highest energy was selected for allowing the protons to reach the ohmic side (n/sup +/-side). This reach confirms that the detectors thickness is 300 /spl mu/m, accordingly to the wafer thickness. The scanning of the detectors from the undamaged frontside was performed with three different proton energies of ranges within the undamaged region. Two proton energies were selected for probing the transient region extending between the damaged and undamaged regions of the detectors. Three energies of protons were chosen to probe the damaged region of the diodes. The same set of energies was selected for the study of the detectors spectroscopic features while illuminating the detectors' backside. The measured spectroscopic responses of the irradiated detectors were compared to the response of the undamaged detector. For frontside illumination, the total charge collection efficiency (TCCE) was determined close to 100% and 50% for protons stopped in the undamaged and damaged region, respectively. In the case of backside illumination, the TCCE was significantly smaller for protons of low energy, about 15-30% at a depth of 100 /spl mu/m, and increases up to 80%-85% for the highest proton energy stopped in the detector. The results show that the silicon detectors can be partly and strongly deteriorated by megaelectronvolt protons of fluences of 10/sup 11/ p/cm/sup 2/.