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When relativistic electrons are used to irradiate tissues, such as during FLASH pre-clinical irradiations, the electron beam energy is one of the critical parameters that determine the dose distribution. Moreover, during such irradiations, linear accelerators (linacs) usually operate with significant beam loading, where a small change in the accelerator output current can lead to beam energy reduction. Optimisation of the tuning of the accelerator’s radio frequency system is often required. We describe here a robust, easy-to-use device for non-interceptive monitoring of potential variations in the electron beam energy during every linac macro-pulse of an irradiation run. Our approach monitors the accelerated electron fringe beam using two unbiased aluminium annular charge collection plates, positioned in the beam path and with apertures (5 cm in diameter) for the central beam. These plates are complemented by two thin annular screening plates to eliminate crosstalk and equalise the capacitances of the charge collection plates. The ratio of the charge picked up on the downstream collection plate to the sum of charges picked up on the both plates is sensitive to the beam energy and to changes in the energy spectrum shape. The energy sensitivity range is optimised to the investigated beam by the choice of thickness of the first plate. We present simulation and measurement data using electrons generated by a nominal 6 MeV energy linac as well as information on the design, the practical implementation and the use of this monitor.

En l'actualitat vivim en un entorn amb tendència a la connectivitat entre tot el que ens envolta. Això comporta l'ús massiu de dispositius electrònics de radiofreqüència, que necessiten de nous mètodes de fabricació i materials per poder reduir l'impacte mediambiental que suposarà aquest escenari. En aquest context, el present Treball de Final de Grau té l'objectiu principal d'estudiar la possibilitat d'us del paper com a substrat per a la fabricació de circuits de microones. Per poder realitzar aquest estudi, en primer lloc es descriu l'actualitat en la investigació de tecnologies desenvolupades sobre aquest substrat. El posterior repàs en els paràmetres utilitzats al llarg de la memòria té la finalitat de començar la lectura de l'estudi redactat amb un millor coneixement de les magnituds i conceptes involucrats. La metodologia es basa en el càlcul inicial de les diferents variables de cada un dels dispositius tractats . Aquests resultats son contrastats amb l'assistent de simulació, i posteriorment es confecciona el disseny del circuit. Amb la simulació electromagnètica, la qual és la mesura de major precisió atès son aplicades les equacions de Maxwell en el circuit; es realitza un exercici de discussió sobre el resultat obtingut, de manera que s'estudia la viabilitat del circuit en el seu disseny en substrat de paper. La memòria conclou amb una reflexió general sobre diferents aspectes del treball realitzat, així com diferents línies de treball futur. Nowadays we live in an environment with a tendency to connect between everything that surrounds us. This entails the massive use of radio frequency electronic devices, which need new manufacturing methods and materials for reducing the environmental impact due to this reality. In this context, the present Final Degree Project has the main objective of studying the possibility of using paper as a substrate in the microwave circuits. First of all, the study explains the current situation in the research of technologies developed on the described substrate. Secondly, it's necessary a review of the parameters used throughout the memory has the purpose of beginning the reading of the study written with a better knowledge of the magnitudes and concepts involved. The methodology is based on the initial calculation of the different variables of each one of the treated devices. These results are contrasted with the simulation assistant and also with the circuit schema. The simulation concludes with electromagnetic test, which is the measure of greater precision, due to be applied the Maxwell equations in the circuit. Then, with all results obtained, it starts the study of viability. The report concludes with a general reflection on different aspects of the work done, as well as different lines of future work. En la actualidad vivimos en un entorno con tendencia a la conectividad entre todo lo que nos rodea. Esto conlleva el uso masivo de dispositivos electrónicos de radiofrecuencia, que necesitan de nuevos métodos de fabricación y materiales para poder reducir el impacto medioambiental que supondrá este escenario. En este contexto, el presente Trabajo de Fin de Grado tiene el objetivo principal de estudiar la posibilidad de uso del papel como sustrato para la fabricación de circuitos de microondas. Para poder realizar este estudio, en primer lugar se describe la actualidad en la investigación de tecnologías desarrolladas sobre este sustrato. El posterior repaso en los parámetros utilizados a lo largo de la memoria tiene el fin de comenzar la lectura del estudio redactado con un mejor conocimiento de las magnitudes y conceptos involucrados. La metodología se basa en el cálculo inicial de las diferentes variables de cada uno de los dispositivos tratados. Estos resultados son contrastados con el asistente de simulación, y posteriormente se confecciona el diseño del circuito. Con la simulación electromagnética, la cual es la medida de mayor precisión dado son aplicadas las ecuaciones de Maxwell en el circuito; se realiza un ejercicio de discusión sobre el resultado obtenido, por lo que se estudia la viabilidad del circuito en su diseño en sustrato de papel. La memoria concluye con una reflexión general sobre diferentes aspectos del trabajo realizado, así como diferentes líneas de trabajo futuro.

session: Antenna and Propagation; International audience; The design of antennas on cellulosic flexible materials such as paper can be very challenging because of the limited thickness and the high losses in the Radio Frequency (RF) domain. In this paper, a novel patch antenna with an origami structure is proposed to address the null radiation efficiency obtained with the conventional paper-based structure. As the electromagnetic waves mostly travel in the air, ideal conditions such as no loss and a low dielectric constant allow for the asymptotic value of directivity of microstrip antennas to be reached with a 63 % experimental radiation efficiency. This flexible antenna can be used for RF energy harvesting or sensing applications due to the sensitivity of paper on atmospheric conditions.

This paper presents a wireless, self-powered, affinity-based biosensor based on the integration of paper-based microfluidics with our previously reported method for self-assembling radio-frequency (RF) antennas. At the core of the proposed approach is a silver-enhancement technique that grows portions of a RF antenna in regions where target antigens hybridize with target specific affinity probes. The hybridization regions are defined by a network of nitrocellulose based microfluidic channels which implement a self-powered approach to sample the reagent and control its flow and mixing. The integration substrate for the biosensor has been constructed using polyethylene and the patterning of the antenna on the substrate has been achieved using a low-cost ink-jet printing technique. The substrate has been integrated with passive radio-frequency identification (RFID) tags to demonstrate that the resulting sensor-tag can be used for continuous monitoring in a food supply-chain where direct measurement of analytes is typically considered to be impractical. We validate the proof-of-concept operation of the proposed sensor-tag using IgG as a model analyte and using a 915 MHz Ultra-high-frequency (UHF) RFID tagging technology.

In this paper, we report highly conductive, highly flexible, light weight and low cost printed graphene for wireless wearable communications applications. As a proof of concept, printed graphene enabled transmission lines and antennas on paper substrates were designed, fabricated and characterized. To explore its potentials in wearable communications applications, mechanically flexible transmission lines and antennas under various bended cases were experimentally studied. The measurement results demonstrate that the printed graphene can be used for RF signal transmitting, radiating and receiving, which represents some of the essential functionalities of RF signal processing in wireless wearable communications systems. Furthermore, the printed graphene can be processed at low temperature so that it is compatible with heat-sensitive flexible materials like papers and textiles. This work brings a step closer to the prospect to implement graphene enabled low cost and environmentally friendly wireless wearable communications systems in the near future.