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S. Lazanu

Publications and source records attributed to S. Lazanu.

10 recordsLinked to original sources
arXiv2006

The role of primary point defects in the degradation of silicon detectors due to hadron and lepton irradiation

The principal obstacle to long-time operation of silicon detectors at the highest energies in the next generation of experiments arises from bulk displacement damage which causes significant degradation of their macroscopic properties. The analysis of the behaviour of silicon detectors after irradiation conduces to a good or reasonable agreement between theoretical calculations and experimental data for the time evolution of the leakage current and effective carrier concentration after lepton and gamma irradiation and large discrepancies after hadron irradiation and this in conditions where a reasonable agreement is obtained between experimental and calculated concentrations of complex defects. In this contribution, we argue that the main discrepancies could be solved naturally considering as primary defects the self-interstitials, classical vacancies and the new predicted fourfold coordinated silicon pseudo-vacancy defects. This new defect is supposed to be introduced uniformly in the bulk during irradiation, has deep energy level(s) in the gap and it is stable in time. Considering the mechanisms of production of defects and their kinetics, it was possible to determine indirectly the characteristics of the SiFFCD defect: energy level in the band gap and cross section for minority carrier capture. In the frame of the model, the effects of primary defects on the degradation of silicon detectors are important in conditions of continuous long time irradiation and /or high fluences.

physics.ins-det↗
arXiv2005

Silicon detectors for the next generation of high energy physics experiments: expected degradation

There exists an enormous interest for the study of very high energy domain in particle physics, both theoretically and experimentally, in the aim to construct a general theory of the fundamental constituents of matter and of their interactions. Until now, semiconductor detectors have widely been used in modern high energy physics experiments. They are elements of the high resolution vertex and tracking system, as well as of calorimeters. The main motivation of this work is to discuss how to prepare some possible detectors - only silicon option being considered, for the new era of HEP challenges because the bulk displacement damage in the detector, consequence of irradiation, produces effects at the device level that limit their long time utilisation, increasing the leakage current and the depletion voltage, eventually up to breakdown, and thus affecting the lifetime of detector systems. In this paper, physical phenomena that conduce to the degradation of the detector are discussed and effects are analysed at the device level (leakage current and effective carrier concentration) in the radiation environments expected in the next generation of hadron colliders after LHC, at the next lepton and gamma-gamma colliders, as well as in astroparticle experiments, in conditions of long time continuum irradiations, for different technological options. The predicted results permit a better decision to obtain devices with harder parameters to radiation.

physics.ins-det↗
arXiv2004

Some possible explanations of the discrepancies in the results of modelling the leakage current of detectors after hadron irradiation

In this contribution we argue that the main discrepancies between model calculations and experimental data for leakage current after hadron irradiation could be explained considering the contributions of primary defects in silicon: vacancy, interstitial and Si_FFCD defect. The source of discrepancies between data and previous modelling was tentatively attributed to the Si_FFCD defect. Vacancies and interstitials have a major contribution to the current short time after irradiation. If these hypotheses are correct, thus, in conditions of continuous long time irradiation, as e.g. LHC and its upgrades in energy and luminosity, S-LHC and V-LHC respectively, these contributions will represent a major problem.

hep-ph↗
arXiv2002

Long-term damage induced by hadrons in silicon detectors for uses at the LHC-accelerator and in space missions

In the present paper, the phenomenological model developed by the authors in previous papers has been used to evaluate the degradation induced by hadron irradiation at the future accelerator facilities or by cosmic protons in high resistivity silicon detectors. The damage has been analysed at the microscopic (defects production and their evolution toward equilibrium) and at the macroscopic level (changes in the leakage current of the p-n junction). The rates of production of primary defects, as well as their evolution toward equilibrium have been evaluated considering explicitly the type of the projectile particle and its energy. Vacancy-interstitial annihilation, interstitial migration to sink, complex (VP, VO, CiOi, CiCs) and divacancy formation are taken into account for different initial silicon material. The influence of these defects on the leakage detector current has been calculated in the frame of the Schokley-Read-Hall model.

hep-ph↗
arXiv2002

Microscopic modelling of defects production and their annealing after irradiation in silicon for HEP particle detectors

In this contribution, the production of defects in radiation fields and their evolution toward equilibrium in silicon for detector uses has been modelled. In the quantitative model developed, the generation rate of primary defects is calculated starting from the projectile - silicon interaction and from recoil energy redistribution in the lattice. Vacancy-interstitial annihilation, interstitial migration to sinks, divacancy and vacancy-impurity complex (VP, VO, V2O, CiOi and CiCs) formation are considered. The results of the model support the experimental available data. The correlation between the initial material parameters, temperature, irradiation and annealing history is established. The model predictions could be a useful clue in obtaining harder materials for detectors at the new generation of accelerators or for space missions.

hep-ph↗
arXiv2000

Expected behaviour of different semiconductor materials in hadron fields

The utilisation of semiconductor materials as detectors and devices operating in high radiation environments, at the future particle colliders, in space applications or in medicine and industry, necessitates to obtain radiation harder materials. A systematic theoretical study has been performed, investigating the interaction of charged hadrons with semiconductor materials and the mechanisms of defect creation by irradiation. The mechanisms of the primary interaction of the hadron with the nucleus of the semiconductor lattice have been explicitly modelled and the Lindhard theory of the partition between ionisation and displacements has been considered. The behaviour of silicon, diamond, and some AIIIBV compounds, as GaAs, GaP, InP, InAs, InSb has been investigated. The nuclear energy loss, and the concentration of primary defects induced in the material bulk by the unit hadron fluence have been calculated. The peculiarities of the proton and pion interactions as well as the specific properties of the semiconductor material have been put in evidence.

physics.ins-det↗
arXiv1999

Analytical approximations of the Lindhard equations describing radiation effects

Starting from the general Lindhard theory describing the partition of particles energy in materials between ionisation and displacements, analytical approximate solutions have been derived, for media containing one and more atomic species, for particles identical and different to the medium ones. Particular cases, and the limits of these equations at very high energies are discussed.

hep-ph↗
arXiv1999

Comparative Energy Dependence of Proton and Pion Degradation in Diamond

A comparative theoretical study of the damages produced by protons and pions, in the energy range 50 MeV - 50 GeV, in diamond, is presented. The concentration of primary defects (CPD) induced by hadron irradiation is used to describe material degradation. The CPD has very different behaviours for protons and pions: the proton degradation is important at low energies and is higher than the pion one in the whole energy range investigated, with the exception of the Delta33 resonance region, where a large maximum of the degradation exists for pions. In comparison with silicon, the most investigated and the most studied material for detectors, diamond theoretically proves to be one order of magnitude more resistant, both to proton and pion irradiation.

hep-ph↗
arXiv1999

Diamond degradation in hadron fields

The energy dependence of the concentration of primary displacements induced by protons and pions in diamond has been calculated in the energy range 50 MeV - 50 GeV, in the frame of the Lindhard theory. The concentrations of primary displacements induced by protons and pions have completely different energy dependencies: the proton degradation is very important at low energies, and is higher than the pion one in the whole energy range investigated, with the exception of the delta33 resonance region. Diamond has been found, theoretically, to be one order of magnitude more resistant to proton and pion irradiation in respect to silicon.

hep-ph↗