Gianandrea Quadri

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.

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.

New model for assessing dose, dose rate, and temperature sensitivity of radiation-induced absorption in glasses

A new theoretical approach is proposed to explain the dose, dose rate and temperature sensitivity of the radiation-induced absorption (RIA) in glasses. In this paper, a βth-order dispersive kinetic model is used to simulate the growth of the density of color centers in irradiated glasses. This model yields an explanation for the power-law dependence on dose and dose rate usually observed for the RIA in optical fibers. It also leads to an Arrhenius-like relationship between the RIA and the glass temperature during irradiation. With a very limited number of adjustable parameters, the model succeeds in explaining, with a good agreement, the RIA growth of two different optical fiber references over wide ranges of dose, dose rate and temperature.

Evaluation of Static and Dynamic Performance of Silicon-Based Bipolar Phototransistors Under Radiation

Total dose and displacement damage irradiations were performed on two references of silicon-based bipolar phototransistors. The evolution of photocurrent and dynamic performances (rise and fall time) were analyzed. The main results are presented in this paper.

Bipolar Phototransistors Reliability Assessment for Space Applications

Life test, total dose and proton irradiations were performed on silicon-based bipolar phototransistors. A high radiation sensitivity was observed together with abnormal fluctuations of phototransistors collector current during life test. In an attempt to solve this problem, a failure analysis was conducted. Mobile charges located in the photobase passivation layer were found to be at the origin of these fluctuations and are probably also related to the high radiation sensitivity of these devices. Based on the obtained results a new device selection method for space application is proposed.

Optomechanical microswitch behavior in a space radiation environment

The effect of total ionizing dose on a commercial optomechanical microswitch has been studied in this paper. One microswitch was irradiated using a Co/sup 60//spl gamma/-ray radiation source at a dose rate of 330 rad/h to total dose up to 22.5 krad (Si). Little effect was observed in this device which is consistent with the technological design that does not contain insulators.

Implementation of a “Design of Experiments” Methodology for the Prediction of Phototransistor Degradation in a Space Environment

A Design Of Experiments (DOE) methodology was suggested to define an optimized irradiation test plan. In this paper, the proposed test plan was used to model the degradation of the main performances (photo and dark current) of silicon based phototransistors arrays with respect to the Total Ionizing Dose (TID) and to the Displacement Damage Dose (DDD), over a wide range of space-kind environments. The expected performance degradation after an 18-year Low Earth Orbit (LEO) mission was calculated using this model. End-Of-Life (EOL) prediction results were compared to experimental ones obtained on devices irradiated with a proton beam degrader that simulates the 18 year LEO environment. The excellent agreement found between theoretical and experimental data makes this methodology particularly valuable for the space qualification of such devices.

Hardening Principles and Characterization of an Optocoupler Including a Vertical Cavity Surface Emitting Laser

This paper reports the hardening principles and the first characterization of an optocoupler structure that uses a Vertical Cavity Surface Emitting Laser (VCSEL) as a light emitter. Current Transfer Ratio (CTR) measurements carried out before and after proton irradiations show that this architecture improves the radiation hardness by a factor of 10 or more above the present state-of-the-art hardened optocouplers.

Total Dose Effects: A New Approach to Assess the Impact of Radiation on Device Reliability

In this paper, a new Radiation Hardness Assurance methodology applicable to cumulative effects is proposed to assess the impact of radiation on device reliability. This approach, that relies on the stochastic interpolation of experimental data, is based on the notion of Wiener process. An example of application of this methodology is presented and a comparison with a more conventional Radiation Hardness Assurance is discussed.

An original DoE-based tool for silicon photodetectors EoL estimation in space environments

Abstract In our previous works we have demonstrated that Design of Experiments (DoE) is an innovative methodology defining optimized irradiation test plan and particularly valuable for the space qualification of silicon photodetectors. In particular, it provided us with the degradation model of photocurrent, darkness current, and spectral responsivity of silicon based phototransistors arrays with respect to the Total Ionizing Dose (TID) and to the Displacement Damage Dose (DDD), over a wide range of space-mission profiles. In this paper, we will summarize at first main results obtained thanks to the DoE methodology. Then we present how we can easily obtain, by exploiting DoE collected data, End-of-Life predictions of such devices with a reduced number of experiments, with a small batch of devices, and in relatively short time.