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.Comment: 10 pages, 5 figures, latex2e, submitted to Nucl. Instr. Meth. in Phys. Res.

Annealing of radiation induced defects in silicon in a simplified phenomenological model

The concentration of primary radiation induced defects has been previously estimated considering both the explicit mechanisms of the primary interaction between the incoming particle and the nuclei of the semiconductor lattice, and the recoil energy partition between ionisation and displacements, in the frame of the Lindhard theory. The primary displacement defects are vacancies and interstitials, that are essentially unstable in silicon. They interact via migration, recombination, annihilation or produce other defects. In the present work, the time evolution of the concentration of defects induced by pions in medium and high resistivity silicon for detectors is modelled, after irradiation. In some approximations, the differential equations representing the time evolution processes could be decoupled. The theoretical equations so obtained are solved analytically in some particular cases, with one free parameter, for a wide range of particle fluences and/or for a wide energy range of the incident particles, for different temperatures; the corresponding stationary solutions are also presented.Comment: 14 pages, 5 figures, accepted to Nuclear Instruments and Methods in Physics Research B second version, major revisio

Theoretical calculations of the primary defects induced by pions and protons in SiC

In the present work, the bulk degradation of SiC in hadron (pion and proton) fields, in the energy range between 100 MeV and 10 GeV, is characterised theoretically by means of the concentration of primary defects per unit fluence. The results are compared to the similar ones corresponding to diamond, silicon and GaAs.Comment: 9 pages, 2 figures, in press to Nuclear Instruments and Methods in Physics Research A v2 - modified title, and major revision

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.Comment: 7 pages, 3 figure

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.Comment: 7 pages, 5 figure

Modelling spatial distribution of defects and estimation of electrical degradation of silicon detectors in radiation fields at high luminosity

The irradiation represents a useful tool for determining the characteristics of defects in semiconductors as well as a method to evaluate their degradation, fact with important technological consequences. In this contribution, starting from available data on the degradation of silicon detector characteristics in radiation fields, these effects are explained in the frame of a model that supposes also the production of the SiFFCD defect due to irradiation. The displacement threshold energies - different for different crystallographic axes, considered as parameters of the model, are established and the results obtained could contribute to clarify these controversial aspects. Predictions of the degradation of electrical parameters (leakage current, effective carrier concentration and effective trapping probabilities for electrons and holes) of DOFZ silicon detectors in the hadron background of the LHC accelerator, supposing operation at -10 grdC are done. The non uniformity of the rate of production of primary defects and of complexes, as a function of depth, for incident particles with low kinetic energy was obtained by simulations in some particular and very simplifying assumptions, suggesting the possible important contribution of the low energy component of the background spectra to detector degradation.Comment: prepared for the 6-th Int. Conf. on Radiation Effects on Semiconductor Materials Detectors and Devices, Florence, Italy, Oct. 10-13, 2006, work in the frame of CERN RD 50 Collaboratio