In this review paper, we present radiation effects on silica-based optical fibers. We first describe the mechanisms inducing microscopic and macroscopic changes under irradiation: radiation-induced ...attenuation, radiation-induced emission and compaction. We then discuss the influence of various parameters related to the optical fiber, to the harsh environments and to the fiber-based applications on the amplitudes and kinetics of these changes. Then, we focus on advances obtained over the last years. We summarize the main results regarding the fiber vulnerability and hardening to radiative constraints associated with several facilities such as Megajoule class lasers, ITER, LHC, nuclear power plants or with space applications. Based on the experience gained during these projects, we suggest some of the challenges that will have to be overcome in the near future to allow a deeper integration of fibers and fiber-based sensors in radiative environments.
Résumé: La consultation « famille » est un objet protéiforme qui sera appréhendé depuis ses éléments de surface, objectivables, jusqu’à ses éléments internes, subjectifs. Examiner, réfléchir, penser ...à la qualité de ce qui se passe dans le contexte particulier des relations singulières entre le patient et le psychologue, dans cette relation éphémère permettra d’utiliser des notions telles que l’empathie et le Moi auxiliaire de l’analyste au service du Moi du patient. Cet objectif est-il modélisable ? Quelles articulations peut-on y trouver avec le groupe des enfants de parents malades ? Quelle en est la pertinence et quelles en sont les limites ? Peut-on comprendre la consultation famille dans le registre de la clinique du deuil ? Des vignettes cliniques permettront d’aborder la complexité de ce singulier objet.
Abstract: Family therapy is a complex practice to grasp, from its external, demonstrable aspects to its internal, subjective elements. The challenge is to examine, carefully consider and focus on the nature of what transpires in the special context of the unique, although short-lived, relationship between the patient and the psychologist, using concepts such as empathy and the analyst’s auxiliary ego for the benefit of the patient’s ego. Is it possible to create a model from this goal? Can we find links between the goal and the children of terminally ill parents? What is the relevance, and what are the limitations? Can we comprehend family therapy in the context of the clinical aspects of grief and bereavement? Selected clinical cases will enable us to understand the complexity of this subject.
Several Pinned Photodiode (PPD) CMOS Image Sensors (CIS) are designed, manufactured, characterized and exposed biased to ionizing radiation up to 10 kGy(SiO 2 ). In addition to the usually reported ...dark current increase and quantum efficiency drop at short wavelengths, several original radiation effects are shown: an increase of the pinning voltage, a decrease of the buried photodiode full well capacity, a large change in charge transfer efficiency, the creation of a large number of Total Ionizing Dose (TID) induced Dark Current Random Telegraph Signal (DC-RTS) centers active in the photodiode (even when the Transfer Gate (TG) is accumulated) and the complete depletion of the Pre-Metal Dielectric (PMD) interface at the highest TID leading to a large dark current and the loss of control of the TG on the dark current. The proposed mechanisms at the origin of these degradations are discussed. It is also demonstrated that biasing (i.e., operating) the PPD CIS during irradiation does not enhance the degradations compared to sensors grounded during irradiation.
We report an experimental investigation on the effects of Ce-codoping in determining the radiation response of germanosilicate and phosphosilicate Optical Fibers (OFs) in the UV-Visible domain and up ...to doses of 1 MGy(SiO 2 ). We show that the addition of Ce strongly impacts the Radiation Induced Attenuation (RIA) of both types of fibers. In the first case the radiation induced losses increase, whereas in the second one decrease. By combining the online RIA measurements with the Electron Paramagnetic Resonance (EPR) ones, we are able to infer the basic microscopic mechanisms taking place under irradiation, which involve the cerium codopant and some of the known Ge-related or P-related defects. More precisely, we found that part of the Ce atoms are incorporated in the glass matrix as Ce 3+ ions by the production process and act as electron donor centers under irradiation. Consequently, the concentrations of radiation induced hole centers of Ge and P are drastically reduced. The reported results give an insight into possible ways of exploiting Ce codoping to control the radiation sensitivity of the OFs. Moreover, the OFs doped with cerium and phosphorous show a strongly reduced saturation effect at high radiation doses that make them a potential candidate for RIA-based dosimetry applications in a wide range of radiation doses.
We present an approach coupling a limited experimental number of tests with numerical simulations regarding the design of radiation-hardened (RH) rare earth (RE)-doped fiber amplifiers. Radiation ...tests are done on RE-doped fiber samples in order to measure and assess the values of the principal input parameters requested by the simulation tool based on particle swarm optimization (PSO) approach. The proposed simulation procedure is validated by comparing the calculation results with the measured degradations of two amplifiers made with standard and RH RE-doped optical fibers, respectively. After validation, the numerical code is used to theoretically investigate the influence of some amplifier design parameters on its sensitivity to radiations. Simulations show that the RE-doped fiber length used in the amplifier needs to be adjusted to optimize the amplifier performance over the whole space mission profile rather than to obtain the maximal amplification efficiency before its integration in the harsh environment. By combining this coupled approach with the newly-developed RH RE-doped fibers, fiber-based amplifiers nearly insensitive to space environment may be designed in the future.
The total ionizing dose (TID) is a well-known reliability issue for integrated circuits (ICs). It consists in changes of MOSFETs dc characteristics following the irradiation of devices in a given ...radiative environment, such as space environment. TID effects have been investigated from an experimental and theoretical standpoint, and the compact modeling of TID effects has been included into BULK transistor compact models using PSP formalism in the case of uniform and nonuniform energetic distributions of interface traps. However, TID effects are still not included in fully depleted SOI (FDSOI) standard models. In this paper, TID effects modeling is proposed and included in Leti-UTSOI compact model for FDSOI MOSFETs. This model takes both uniform and nonuniform energetic distributions of both gate oxide/silicon and silicon/buried oxide (BOX) interface traps into account, as well as the contribution of oxide/BOX-trapped charges. Validation of the model has been done through TCAD simulations, and we used this model to extract TID parameters from the experimental data.
We investigate the response of Ge-doped, P-doped, pure-silica, or Fluorine-doped fibers to extreme environments combining doses up to MGy(SiO 2) level of 10 keV X-rays and temperatures between 25 ° C ...and 300 ° C. First, we evaluate their potential to serve either as parts of radiation tolerant optical or optoelectronic systems or at the opposite, for the most sensitive ones, as punctual or distributed dosimeters. Second, we improve our knowledge on combined ionizing radiations and temperature (R&T) effects on radiation-induced attenuation (RIA) by measuring the RIA spectra in the ultraviolet and visible domains varying the R&T conditions. Our results reveal the complex response of the tested fibers in such mixed environments. Increasing the temperature of irradiation increases or decreases the RIA values measured at 25 ° C or sometimes has no impact at all. Furthermore, R&T effects are time dependent giving an impact of the temperature on RIA that evolves with the time of irradiation. The two observed transient and stationary regimes of temperature influence will make it very difficult to evaluate sensor vulnerability or the efficiency of hardening approaches without extensive test campaigns.
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