X-ray sensors are essential to many applications which are not limited to diagnostics and imaging technologies. Such sensors are extensively used in industry, medicine, research and space technology for applications such as safety, security, quality control, imaging and treatment. Depending on the effect of the radiation on the matter employed in the sensor, different types of X-ray sensors are fabricated. However, available techniques of X-ray detection have been under development due to specific shortcomings such as finite life time, low sensitivity, and post-processing requirements. This thesis is focused on design, fabrication and characterization of novel radiation sensors based on bio/nanomaterials. Bacteriorhodopsin (BR), a proton pump protein in the cell membrane of Halobacterium Salinarum, has been used to fabricate a sensor to measure dose and dose rate of X-ray beam in the kilovoltage and megavoltage energy range. The mass attenuation coefficients, effective atomic numbers and electron densities of BR and its comprising amino acids have been calculated for 1 keV-100 GeV photons to better understand the interaction of BR with X-ray photons. A theoretical formulation for calculating the change in the conductivity of nanoparticles under radiation is also provided. In particular, the dependence of radiation induced conductivity to irradiated particle size is given. In addition to that, an X-ray sensor based on thin film of bismuth sulfide has been fabricated using laser micromachining and chemical deposition techniques. This sensor has been characterized under a diagnostic X-ray machine with kilovoltage energy beam.

La mesure des niveaux de rayonnement est une exigence essentielle dans le LHC et ses lignes d'injection afin de quantifier les effets des radiations sur l'électronique et de fournir une connaissance détaillée du champ de rayonnement. Le système de surveillance des rayonnements pour l'électronique au CERN, le "RadMon '', a été installé dans les zones critiques où l'équipement est ou sera placé. Les problèmes rencontrés au cours des dernières années d'utilisation du Radmon, et la nécessité d'améliorer la précision et la résolution des mesures a conduit au lancement d'une nouvelle conception du moniteur.Ce travail décrit l'architecture du nouveau RadMon (V6), sa fiabilité dans les environnements radiatifs et de la stratégie adoptée pour choisir et qualifier les capteurs utilisés pour surveiller le champ de rayonnement mixte des accélérateurs du LHC. Les directives du CERN ont été adoptées pour qualifier les composants RadMon sous rayonnement afin de développer une nouvelle architecture à la fois plus tolérante au rayonnement et plus polyvalente que celui de la version précédente. Dans ce contexte, les défis que les tests de rayonnement imposent pour mesurer les Single Event Upsets (SEUs) sur un composant complexe à signaux mixtes tels que le convertisseur analogique-numérique, ont conduit au développement d'une technique de test innovant, qui sera décrit dans cette thèse.L'environnement radiatif complexe du LHC impose un processus de qualification particulier qui sera décrit et discuté dans ce travail pour les RadFets (capteur dose ionisante) et les mémoires SRAM (capteur de fluence High Energy Hadrons).L'utilisation du RadFet dans un champ mixte de rayonnement a été étudié et analysé au moyen de sources de 60Co et de faisceaux de protons de différentes énergies.Les RadFets ont été ré-étalonné en étudiant le débit de dose, les sources de particules, la température, la guérison thermique en fonction de l'épaisseur d'oxyde. En outre, grâce à la nouvelle architecture de la RadMon, de nouvelles configurations de polarisation ont été testées pour améliorer la résolution.Deux types de mémoires SRAM avec des nœuds technologiques de 400 et 90 nm ont été testés et calibrés en suivant une méthode de qualification stricte qui comprend des tests protons,dans la plage de 30 à 400 MeV et neutrons, depuis les énergies thermiques jusqu'à des énergies intermédiaires (~ 14 MeV). La mémoire 90 nm améliore la précision et la résolution de la mesure de la fluence hadronique. En outre, l'utilisation simultanée des deux types de mémoires améliore la précision de la détection des neutrons thermiques par rapport à la version précédente, grâce à d'une procédure qui sera détaillée dans ce travail.Les efforts en vue de l'amélioration de la résolution des mesures de TID pour le nouveau RadMon conduisent à la recherche et à l'étude d'un nouveau type de dosimètre : le dosimètre a Grille Flottante (FGDOS). Le capteur intégrant une électronique complexe, une qualification complète sous rayonnement était nécessaire. Des tests en champ mixte, des tests au 60Co et des tests au protons ont été réalisés afin d'évaluer les performances et les problèmes potentiels du capteur. Dans ce contexte, un modèle analytique du capteur a été conçu pour démontrer que la structure à Grille Flottante pouvait être utilisée comme instrument de mesure du ‘charge yield' à température ambiante et sous des champs électriques faibles.La caractérisation de la tolérance au rayonnement du matériel, le processus de qualification et les étalonnages des capteurs ont considérablement amélioré la fiabilité globale et la qualité des mesures sur la nouvelle version du RadMon. Ces améliorations font du RadMon un instrument de référence pour la surveillance des rayonnements des champs mixtes complexes, tels que ceux rencontrés dans le LHC et sa chaîne d'injecteurs, mais aussi pour d'autres centres de recherche en physique des particules, comme JLAB aux États-Unis, J-PARC au Japon. / The measurement of the radiation levels is an essential requirement in the LHC and its injection lines in order to quantify radiation effects on electronics and provide a detailed knowledge of the radiation field. The radiation monitoring system for the electronics at CERN, the “RadMon'', was installed in critical areas where equipment is or will be placed. Issues experienced in the last years of Radmon operation, the obsolescence of a few fundamental components of the electronic board and the necessity to improve both the accuracy and the resolution of measurements led to the launch of a new design of the monitor.This work describes the architecture of the new RadMon (V6), its reliability in radiation environments and the strategy adopted to choose and qualify the sensors, used for monitoring the mixed radiation field of the LHC accelerators. The CERN guidelines were adopted to qualify the RadMon components under radiation in order to develop a new architecture both more tolerant to radiation and more versatile than that of the previous version. In this context, the challenges that radiation tests impose for measuring Single Event Effects (SEUs) on a complex mixed-signal component such as the Analog to Digital converter, led to the development of an innovative test technique, which will be described in this thesis.The reliability of the RadMon measurements strongly depends on the calibration of its sensors. The complex radiation environment of the LHC imposes a peculiar qualification process which will be described and discussed in this work for the RadFets (Total Ionizing Dose sensor) and the SRAM memories (High Energy Hadrons fluence sensor).The use of the RadFet in a mixed field radiation environment has been studied and analyzed by means of 60Co sources as well as proton beams at different energies.The RadFets have been re-calibrated by studying the dose rate, particle sources, temperature, annealing and fading effects as a function of the oxide thickness. Furthermore, thanks to the new architecture of the RadMon, new biasing configurations have been tested to improve the resolution.Two types of SRAM memories with technology nodes of 400 and 90nm have been tested and calibrated by following a strict qualification methodology which includes tests with protons in the range 30-400 MeV, and with neutrons from thermal energies up to intermediate energies (~14 MeV). The 90nm memory improves the accuracy and resolution of the hadron fluence measurement. Moreover, the simultaneous use of both types of memories permits an improvement on the accuracy of the thermal neutron detection with respect to the previous version, as a result of a procedure which will be detailed in this work.The efforts towards the improvement of the TID measurements resolution for the new RadMon lead to the research and study of a new type of dosimeter sensor: the Floating Gate dosimeter (FGDOS). The sensor embeds complex circuitry, thus a full radiation qualification was necessary. Mixed field radiation tests, 60Co and protons tests have been carried out in order to evaluate the performance and the possible issues of the sensor. In this context, an analytical model of the sensor was developed to prove that the floating gate structure can be used as charge yield measurement instrument at room temperature and at low electric fields.The radiation tolerance characterization of the hardware, the qualification and calibration process of the sensors have significantly improved the overall reliability and quality of the measurements of the new RadMon. These improvements turned it into a reference instrument for radiation monitoring of complex mixed fields, such as the one encountered in the LHC, its injectors chain, and other particle physics research centers, such as JLAB in US, J-PARC in Japan.

abstract: Chalcogenide glass (ChG) materials have gained wide attention because of their applications in conductive bridge random access memory (CBRAM), phase change memories (PC-RAM), optical rewritable disks (CD-RW and DVD-RW), microelectromechanical systems (MEMS), microfluidics, and optical communications. One of the significant properties of ChG materials is the change in the resistivity of the material when a metal such as Ag or Cu is added to it by diffusion. This study demonstrates the potential radiation-sensing capabilities of two metal/chalcogenide glass device configurations. Lateral and vertical device configurations sense the radiation-induced migration of Ag+ ions in germanium selenide glasses via changes in electrical resistance between electrodes on the ChG. Before irradiation, these devices exhibit a high-resistance `OFF-state' (in the order of 10E12) but following irradiation, with either 60-Co gamma-rays or UV light, their resistance drops to a low-resistance `ON-state' (around 10E3). Lateral devices have exhibited cyclical recovery with room temperature annealing of the Ag doped ChG, which suggests potential uses in reusable radiation sensor applications. The feasibility of producing inexpensive flexible radiation sensors has been demonstrated by studying the effects of mechanical strain and temperature stress on sensors formed on flexible polymer substrate. The mechanisms of radiation-induced Ag/Ag+ transport and reactions in ChG have been modeled using a finite element device simulator, ATLAS. The essential reactions captured by the simulator are radiation-induced carrier generation, combined with reduction/oxidation for Ag species in the chalcogenide film. Metal-doped ChGs are solid electrolytes that have both ionic and electronic conductivity. The ChG based Programmable Metallization Cell (PMC) is a technology platform that offers electric field dependent resistance switching mechanisms by formation and dissolution of nano sized conductive filaments in a ChG solid electrolyte between oxidizable and inert electrodes. This study identifies silver anode agglomeration in PMC devices following large radiation dose exposure and considers device failure mechanisms via electrical and material characterization. The results demonstrate that by changing device structural parameters, silver agglomeration in PMC devices can be suppressed and reliable resistance switching may be maintained for extremely high doses ranging from 4 Mrad(GeSe) to more than 10 Mrad (ChG). / Dissertation/Thesis / Ph.D. Electrical Engineering 2013