Olivier Gilard

A model for the prediction of EDFA gain in a space radiation environment

Erbium-doped fiber amplifiers (EDFAs) were irradiated with /sup 60/Co /spl gamma/-rays up to a total dose of 3 kGy. Gain measurements and 1310-nm absorption were achieved during the irradiation to characterize the radiation-induced damage on the fiber. A model based on classical equations was developed to perform accurate predictions of the effects of radiation on EDFAs. This model was shown to be consistent with the experiment at various dose rates and temperatures, therefore allowing the extrapolation to a space environment simulation.

Radiation-resistant erbium-doped-nanoparticles optical fiber for space applications

We demonstrate for the first time a radiation-resistant Erbium-Doped Fiber exhibiting performances that can fill the requirements of Erbium-Doped Fiber Amplifiers for space applications. This is based on an Aluminum co-doping atom reduction enabled by Nanoparticules Doping-Process. For this purpose, we developed several fibers containing very different erbium and aluminum concentrations, and tested them in the same optical amplifier configuration. This work allows to bring to the fore a highly radiation resistant Erbium-doped pure silica optical fiber exhibiting a low quenching level. This result is an important step as the EDFA is increasingly recognized as an enabling technology for the extensive use of photonic sub-systems in future satellites.

Analysis of multijunction solar cell degradation in space and irradiation induced recombination centers

We demonstrate how, using electroluminescence, the parameters characterizing the recombination center induced by irradiation in a solar cell can be measured. Because electroluminescence is able to provide information on an individual cell in a multijunction (MJ) cell device, independently of the others, we apply this technique to measure these parameters in InGaP/GaAs/Ge MJ cells. We then calculate the variations of the open-circuit voltage and short-circuit current of such cells versus fluence. The results are compared with experimental data obtained for 1 MeV electron irradiations.

New Approach for the Prediction of CCD Dark Current Distribution in a Space Radiation Environment

Commercial Off-The-Shelf Charge Coupled Devices were irradiated with protons at energies ranging from 17 MeV to 200 MeV. Evolution of the dark current distribution during irradiation is discussed. A general method is presented to predict the increase of both mean dark current and associated non-uniformity after a monoenergetic proton irradiation. The results are found to be in good agreement with the experimental outputs. The model is then used to assess the dark signal degradation of a device exposed to a multienergetic proton beam. Again, the predictions are shown to be consistent with the experimental data. This makes possible the assessment of the dark signal distribution of a device exposed to a real space environment.

Theoretical study of radiation effects on GaAs/AlGaAs and InGaAsP/InP quantum-well lasers

Radiation hardness assurance of light emitters such as laser diodes is a primary concern before using such devices in space. In this article, both gallium arsenide (GaAs) and indium phosphide (InP) based laser diodes are theoretically analyzed from a radiation hardness point of view. It has been found that InP based lasers are less sensitive to radiation than GaAs lasers. We will also demonstrate that threshold carrier density is the key parameter to consider when assessing the radiation sensitivity of laser diodes.

Annealing of Proton-Induced Random Telegraph Signal in CCDs

A silicon CCD imager has been irradiated with 10 MeV protons and measurements focused on random telegraph signal (RTS). A variance detection method is applied for quantifying the number of RTS after irradiation and through isochronal annealing. The observed behavior is analyzed and corresponds to the annealing of phosphorus-vacancies.

Measurements of Random Telegraph Signal in CCDs Irradiated With Protons and Neutrons

CCD imagers have been irradiated with 10 to 100 MeV protons, 45 MeV neutrons and measurements focussed on random telegraph signal (RTS) characterization. The objective is to propose a method for RTS detection and to analyse pixels behaviour with temperature, particle species and energy.

CoRoT Satellite: Analysis of the In-Orbit CCD Dark Current Degradation

This paper presents the analysis of the CoRoT CCDs dark current degradation measured during more than 2.5 years in orbit. Starting from on-ground irradiation results obtained during the space qualification of the detectors, a model is proposed to calculate the in-orbit pixel dark current distribution (including the hot pixels one). The modeling results are found to be in good agreement with the in-flight data. We therefore use this model to extrapolate the evolution of the dark signal distribution beyond 2.5 years. This is of primary interest in the context of a mission duration extension to 6 years proposed for the CoRoT mission.

Theoretical explanation of enhanced low dose rate sensitivity in erbium-doped optical fibers

A new theoretical framework is proposed to explain the dose and dose-rate dependence of radiation-induced absorption in optical fibers. A first-order dispersive kinetics model is used to simulate the growth of the density of color centers during an irradiation. This model succeeds in explaining the enhanced low dose rate sensitivity observed in certain kinds of erbium-doped optical fiber and provides some insight into the physical reasons behind this sensitivity.

Proton and

The dark current random telegraph signal (RTS) behavior has been studied in a five-transistor-per-pixel (5T) pinned photodiode 0.18-μm COTS active pixel sensor (APS). Several devices, irradiated using protons and gamma rays, have been studied in order to assess the ionizing and displacement damage effects. The influence of the proton energy, fluence, ionizing dose and applied bias during irradiation on the number of RTS pixels, the number of discrete levels, maximum transition amplitude, and mean switching time constants is investigated.