Particle accelerators are a leading tool for frontier science. Pushing that frontier further demands more machines with higher performance, and more of a very expensive technology: superconducting radio-frequency (SRF) acceleration. From a materials perspective this means reducing residual surface resistance or raising the operating temperature (currently ~2 K) of SRF cavities. Both are pursued by materials modification: nitrogen doping/infusion in the first instance and coating with Nb3Sn in the second. Materials characterization is key to achieving understanding and directing RandD. However, very little has been done. This present work aims to fill the knowledge gap and to provide needed, validated tools to the accelerator science community. In this connection, SIMS, XPS and EBSD have proven especially valuable and represent the majority of discussion in this dissertation. / Doctor of Philosophy / Particle accelerators are a powerful tool that helps us expand our knowledge of science and how the universe works. Pushing that knowledge further requires us to use more and more powerful particle accelerators. Particle accelerators are based on a very expensive technology: superconducting radio-frequency (SRF) cavities. These cavities are hollow tubes made from niobium and shaped in such a way as to cause electromagnetic waves to form. These waves are what are used to accelerate particles. The energy input and loss of energy as heat are massive resulting in millions of dollars a year in electric bills at particle accelerator facilities. In order to build bigger and more powerful particle accelerates they most be more efficient or they become prohibitively expensive. In this dissertation I look at several next generation materials used in building particle accelerators. In particular I describe and go into detail about how to characterize these materials. In other words, how we determine the materials properties and how those properties affect the performance.

Neste trabalho é apresentado um estudo do espalhamento elástico e de reações nucleares dos sistemas exóticos leves 6He+9Be e 7Be+9Be. A colisão 6He+9Be foi medida nas energias de Elab = 16,2 MeV e 21,3 MeV utilizando o sistema RIBRAS (Radioactive Ion Beams in Brasil) do Instituto de Física da Universidade de São Paulo. Foram medidas distribuições angulares do espalhamento elástico, inelástico e a distribuição de partículas alfa produzidas na colisão 6He+9Be. As distribuições angulares elásticas foram analisadas por cálculos de Modelo Óptico, Canais Acoplados (CC) e Canais Acoplados com Discretização do Contínuo (CDCC). A secção de choque total de reação foi obtida da análise do espalhamento elástico. As distribuições de partículas alfa medidas foram comparadas com os resultados dos cálculos de CDCC para a quebra do projétil 6He e de CC para a quebra do alvo de 9Be e a secção de choque integrada em ângulo foi obtida. Analisamos dados do espalhamento quasielástico 7Be+9Be em Elab = 23,7 MeV que foram obtidos no laboratório CRC de Louvain-la-Neuve, na Bélgica. A distribuição angular quasielástica foi analisada primeiramente utilizando o formalismo de Modelo Óptico, o que forneceu o potencial de interação para este sistema e um fator de normalização para os dados experimentais que não foi obtido no experimento. A contribuição da excitação inelástica do núcleo 7Be na secção de choque quasielástica e a influência dos estados do contínuo no canal elástico foram investigadas por meio de cálculos de Canais Acoplados e de CDCC, respectivamente. A secção de choque total de reação 7Be+9Be foi obtida e comparada com 6He+9Be e outros sistemas da literatura. / A study of the elastic scattering and nuclear reactions in light exotic systems 6He+9Be and 7Be+9Be is presented. The 6He+9Be collision was measured at the energies Elab = 16.2 MeV and 21.3 MeV, using the RIBRAS system (Radioactive Ion Beams in Brasil) of the Institute of Physics of the University of São Paulo. Angular distributions of the elastic and inelastic scattering and the alpha-particles production in the 6He+9Be collision were measured. The elastic scattering angular distributions were analyzed by Optical Model, Coupled Channels (CC) and Continuum- Discretization Coupled-Channels (CDCC) calculations. The total reaction cross section was obtained from the elastic scattering analysis. The alpha-particle angular distributions were compared with the results of the CDCC calculations for the breakup of the 6He projectile and CC for the breakup of the 9Be target and the angle-integrated cross section have been obtained. The data for the 7Be+9Be quasielastic scattering has been measured at Elab = 23.7 MeV at CRC Radioactive Beam Facility at Louvain-la-Neuve, Belgium. The quasielastic angular distribution was analyzed firstly using the optical model formalism, which provided the potential for the 7Be+9Be interaction and a normalization factor for the experimental data that was not obtained in the experiment. The contribution of the inelastic excitation of the 7Be nucleus to quasielastic cross sections and the influence of the states of the continuum in the elastic scattering were investigated by Coupled Channels and CDCC calculations. The total reaction cross section 7Be+9Be has been obtained and compared with the 6He+9Be system and other systems of the literature.

Neste trabalho é apresentado um estudo do espalhamento elástico e de reações nucleares dos sistemas exóticos leves 6He+9Be e 7Be+9Be. A colisão 6He+9Be foi medida nas energias de Elab = 16,2 MeV e 21,3 MeV utilizando o sistema RIBRAS (Radioactive Ion Beams in Brasil) do Instituto de Física da Universidade de São Paulo. Foram medidas distribuições angulares do espalhamento elástico, inelástico e a distribuição de partículas alfa produzidas na colisão 6He+9Be. As distribuições angulares elásticas foram analisadas por cálculos de Modelo Óptico, Canais Acoplados (CC) e Canais Acoplados com Discretização do Contínuo (CDCC). A secção de choque total de reação foi obtida da análise do espalhamento elástico. As distribuições de partículas alfa medidas foram comparadas com os resultados dos cálculos de CDCC para a quebra do projétil 6He e de CC para a quebra do alvo de 9Be e a secção de choque integrada em ângulo foi obtida. Analisamos dados do espalhamento quasielástico 7Be+9Be em Elab = 23,7 MeV que foram obtidos no laboratório CRC de Louvain-la-Neuve, na Bélgica. A distribuição angular quasielástica foi analisada primeiramente utilizando o formalismo de Modelo Óptico, o que forneceu o potencial de interação para este sistema e um fator de normalização para os dados experimentais que não foi obtido no experimento. A contribuição da excitação inelástica do núcleo 7Be na secção de choque quasielástica e a influência dos estados do contínuo no canal elástico foram investigadas por meio de cálculos de Canais Acoplados e de CDCC, respectivamente. A secção de choque total de reação 7Be+9Be foi obtida e comparada com 6He+9Be e outros sistemas da literatura. / A study of the elastic scattering and nuclear reactions in light exotic systems 6He+9Be and 7Be+9Be is presented. The 6He+9Be collision was measured at the energies Elab = 16.2 MeV and 21.3 MeV, using the RIBRAS system (Radioactive Ion Beams in Brasil) of the Institute of Physics of the University of São Paulo. Angular distributions of the elastic and inelastic scattering and the alpha-particles production in the 6He+9Be collision were measured. The elastic scattering angular distributions were analyzed by Optical Model, Coupled Channels (CC) and Continuum- Discretization Coupled-Channels (CDCC) calculations. The total reaction cross section was obtained from the elastic scattering analysis. The alpha-particle angular distributions were compared with the results of the CDCC calculations for the breakup of the 6He projectile and CC for the breakup of the 9Be target and the angle-integrated cross section have been obtained. The data for the 7Be+9Be quasielastic scattering has been measured at Elab = 23.7 MeV at CRC Radioactive Beam Facility at Louvain-la-Neuve, Belgium. The quasielastic angular distribution was analyzed firstly using the optical model formalism, which provided the potential for the 7Be+9Be interaction and a normalization factor for the experimental data that was not obtained in the experiment. The contribution of the inelastic excitation of the 7Be nucleus to quasielastic cross sections and the influence of the states of the continuum in the elastic scattering were investigated by Coupled Channels and CDCC calculations. The total reaction cross section 7Be+9Be has been obtained and compared with the 6He+9Be system and other systems of the literature.

No description available.

Innerhalb der handschriftlichen Überlieferung, die aus dem Mittelalter auf uns gekommen ist, gehören Palimpseste zu den Zeugnissen, die schon immer in besonderer Weise das Interesse auf sich gezogen und Phantasien beflügelt haben.

This thesis attempts to develop a conversion algorithm between local coordinates in constituent detector modules and global coordinates encompassing the whole detector structure in a generic detector. The thesis is a part of preparatory work for studying the Hough Transform as a means of track reconstruction in the level-1 hardware trigger in the upgraded trigger and data acquisition (TDAQ) system in the phase 2 upgrade of the ATLAS detector at CERN. The upgrades being made are to withstand much more extreme conditions that come with the high-Luminosity Large Hadron Collider (HL-LHC). Two algorithms have been made and then implemented in Python scripts to test their feasibility and to compare them against each-other. The Rotation algorithm uses several rotations to correctly place the local coordinates in the global system. The second, the Shear algorithm, simplifies the process into two shears and one rotation, using the small angle approximation. Both algorithms need to be extended to work with more parts of the detector to be considered complete. Despite having lower maximum precision the second algorithm is considered the most promising attempt, since it is much less sensitive to the truncation error that results from working in an integer environment, which is a requirement for use in FPGAs. / I denna uppsats görs ett försök att skapa en omvandlingsalgoritm mellan lokala koordinater i konstituerande detektormoduler och globala koordinater i hela detektorstrukturen för en generisk detektor. Uppsatsen är en del i förberedande arbete för att undersöka hur Houghtransformen kan användas för spårrekonstruktion i den hårdvarubaserade level-1 triggern i det uppgraderade trigger- och datainsamlingssystemet (TDAQ) i fas två-uppgraderingen av ATLAS detektorn vid CERN. Uppgraderingarna som görs är för att kunna utstå de mycket mer extrema förhållanden som medförs av högluminositetsuppgraderingen av Large Hadron Collider (HL-LHC). Två algoritmer har skapats och implementerats i Pythonskript för att testa genomförbarhet och för att jämföra med varandra. Rotationsalgoritmen använder ett antal rotationer för att korrekt placera ut de lokala koordinaterna i det globala systemet. Den andra, Skjuvalgortimen, förenklar processen till två skjuvningar och en rotation med hjälp av liten vinkel-approximationen. Båda algoritmerna behöver utökas för att fungera för fler delar av detektorn för att anses kompletta. Trots lägre maximal precision bedöms den andra algoritmen vara det mest lovande försöket, eftersom den är mycket mindre känslig för trunkeringsfelet som kommer av att arbeta i en heltalsmiljö, som är ett krav för FPGA-implementationen.

Notre recherche en didactique des sciences, explore la potentialité des objets scientifiques contemporains à devenir des objets de patrimoine à travers un cas d'étude : l'accélérateur de particules Cockcroft-Walton (CW). Nous faisons l'hypothèse que la valorisation des objets scientifiques contemporains, étape importante du processus de patrimonialisation, est spécifique et nécessite une expertise particulière. Notre travail a été réalisé grâce au dispositif CIFRE, nous permettant de travailler aux côtés du musée des Confluences à Lyon, qui expose un accélérateur de particules CW dans Sociétés : le théâtre des hommes. L'Institut de Physique Nucléaire de Lyon (IPNL) possède également un appareil de ce type, qui est aujourd'hui au cœur d'un projet de valorisation. Notre analyse s'appuie sur une étude du contexte, historique, épistémologique et social, de « naissance » du premier accélérateur CW et d'une étude scientifique de l'objet. Nous avons également mené deux enquêtes, la première visant à retracer la trajectoire de l'accélérateur CW à Lyon, la seconde à retrouver l'ensemble des accélérateurs CW dans le monde. En nous appuyant sur différents travaux qui ont souligné les étapes du processus de patrimonialisation, nous avons caractérisé les spécificités du patrimoine scientifique contemporain, et recherché les traces laissées par ces caractéristiques dans la mise en exposition de l'objet. Nos résultats mettent en évidence le manque d'informations permettant l'interprétation et l'appropriation de l'accélérateur CW par un public, et nous invitent à interroger le contenu représentationnel de l'objet, véhiculé à travers d'autres contextes d'utilisation, formel ou fictionnel / Our thesis in science education explore the potentiality of contemporary scientific objects to become objects of heritage through a study case: the Cockcroft-Walton particle accelerator (CW). We call it “patrimonialisation” (the making of heritage) according to Information and Communication Sciences. We assume that the value of contemporary scientific objects, an important stage of the patrimonialisation, is specific and requires a particular expertise. Our work was realized thanks to a french financing facility, allowing us to work with Le musée des Confluences in Lyon (France), which exposes a particle accelerator CW in Societies: the human theater. The Institute of Lyon Nuclear physics (IPNL) also possesses a device of this type, who is the focus of a recognition project. sing a multidisciplinary approach, our analysis begin with a study of historical, epistemological, social and scientific context, of the first one CW. We also led two inquiries, the first one to redraw the accelerator CW trajectory in Lyon, the second to find all the accelerators CW in the world. Several studies have indeed highlighted the stages of the patrimonialisation. Relying on these studies we characterized the specificities of the contemporary scientific heritage, and looked for tracks left by these characteristics in the exhibition text (museography). Our results demonstrate the lack of information allowing the interpretation (lecture) and the appropriation of the accelerator CW by a public, and invite us to question the representational contents of the object, conveyed through other contexts of use, formal or fictional

Der Betrieb eines Freien Elektronen Lasers (FEL), bei dem die spontan emittierte Undulatorstrahlung ueber Wechselwirkung mit dem Elektronenstrahl selbst verstaerkt wird, setzt eine praezise Ausrichtung des Elektronenstrahls mit dem Photonenstrahl voraus. Um den Ueberlapp von Elektronen-und Photonenstrahl zu gewaehrleisten, wurde ein neuartiger Typ von Wellenleiter-Strahllagemonitor entwickelt, der in eine Vakuumkammer des Undulators des FELs der TESLA Test Facility (TTF) integriert ist. Vier um das Strahlrohr verteilte Wellenleiter koppeln ueber schmale Schlitze einen Bruchteil jenes elektromagnetischen Feldes aus, welches den Strahl begleitet. Die induzierten Signale haengen von der transversalen Strahlposition und der Strahlintensitaet ab. Mit vier Schlitz-Wellenleiter Paaren laesst sich ein lineares Signal ableiten, anhand dessen die Position des Elektronenstrahls bestimmt werden kann. Die induzierten Signale werden mittels eines stegbelasteten Wellenleiters in die erste Stufe eines bei 12 GHz arbeitenden Empfaengers zugefuehrt. Die vorliegende Arbeit beschreibt Design, Tests und Implementierung dieses neuartigen Typs von Strahllagemonitor. / The operation of a free electron laser working in the Self Amplified Spontaneous Emission mode (SASE FEL) requires the electron trajectory to be aligned with very high precision in overlap with the photon beam. In order to ensure this overlap, one module of the SASE FEL undulator at the TESLA Test Facility (TTF) is equipped with a new type of waveguide beam position monitor (BPM). Four waveguides are arranged symmetrically around the beam pipe, each channel couples through a small slot to the electromagnetic beam field. The induced signal depends on the beam intensity and on the transverse beam position in terms of beam--to--slot distance. With four slot--waveguide combinations a linear position sensitive signal can be achieved, which is independent of the beam intensity. The signals transduced by the slots are transferred by ridged waveguides through an impedance matching stage into a narrowband receiver tuned to 12 GHz. The present thesis describes design, tests, and implementation of this new type of BPM.

The work for this thesis is in line with the field of Instrumentation for Particle Accelerators, so called Beam Diagnostics. It is presented the development of a series of electro-mechanical devices called Inductive Pick-Ups (IPU) for Beam Position Monitoring (BPM). A full set of 17 BPM units (16 + 1 spare), named BPS units, were built and installed into the Test Beam Line (TBL), an electron beam decelerator, of the 3rd CLIC Test Facility (CTF3) at CERN ¿European Organization for the Nuclear Research¿. The CTF3, built at CERN by an international collaboration, was meant to demonstrate the technical feasibility of the key concepts for CLIC ¿Compact Linear Collider¿ as a future linear collider based on the novel two-beam acceleration scheme, and in order to achieve the next energy frontier for a lepton collider in theMulti-TeV scale. Modern particle accelerators and in particular future colliders like CLIC requires an extreme alignment and stabilization of the beam in order to enhance its quality, which rely heavily on a beam based alignment techniques. Here the BPMs, like the BPS-IPU, play an important role providing the beam position with precision and high resolution, besides a beam current measurement in the case of the BPS, along the beam lines. The BPS project carried out at IFIC was mainly developed in two phases: prototyping and series production and test for the TBL. In the first project phase two fully functional BPS prototypes were constructed, focusing in this thesis work on the electronic design of the BPS on-board PCBs (Printed Circuit Boards) which are based on transformers for the current sensing and beam position measurement. Furthermore, it is described the monitor mechanical design with emphasis on all the parts directly involved in its electromagnetic functioning, as a result of the coupling of the EM fields generated by the beam with those parts. For that, it was studied its operational parameters, according the TBL specifications, and it was also simulated a new circuital model reproducing the BPS monitor frequency response for its operational bandwidth (1kHz-100MHz). These prototypes were initially tested in the laboratories of the BI-PI section¿Beam Instrumentation - Position and Intensity¿ at CERN. In the second project phase the BPS monitor series, which were built based on the experience acquired during the prototyping phase, the work was focused on the realization of the characterization tests to measure the main operational parameters of each series monitor, for which it was designed and constructed two test benches with different purposes and frequency regions. The first one is designed to work in the low frequency region, between 1kHz-100MHz, in the time scale of the electron beam pulse with a repetition period of 1s and an approximate duration of 140ns. This kind of test setups called Wire Test-bench are commonly used in the accelerators instrumentation field in order to determine the characteristic parameters of a BPM (or pick-up) like its linearity and precision in the position measurement, and also its frequency response (bandwidth). This is done by emulating a low current intensity beam with a stretched wire carrying a current signals which can be precisely positioned with respect the device under test. This test bench was specifically made for the BPS monitor and conceived to perform the measurement data acquisition in an automated way, managing the measurement equipment and the wire positioning motors controller from a PC workstation. Each one of the BPS monitors series were characterized by using this system at the IFIC labs, and the test results and analysis are presented in this work. On the other hand, the high frequency tests, above the X band in the microwave spectrum and at the time scale of the micro-bunch pulses with a bunching period of 83ps (12GHz) inside a long 140ns pulse, were performed in order to measure the longitudinal impedance of the BPS monitor. This must be low enough in order to minimize the perturbations on the beam produced at crossing the monitor, which affects to its stability during the propagation along the line. For that, it was built the high frequency test bench as a coaxial waveguide structure of 24mm diameter matched at 50¿ and with a bandwidth from 18MHz to 30GHz, which was previously simulated, and having room in the middle to place the BPS as the device under test. This high frequency test bench is able to reproduce the TEM (Transversal Electro-Magnetic) propagative modes corresponding to an ultra-relativistic electron beam of 12GHz bunching frequency, so that the Scattering parameters can be measured to obtain the longitudinal impedance of the BPS in the frequency range of interest. Finally, it is also presented the results of the beam test made in the TBL line, with beam currents from 3.5A to 13A (max. available at the moment of the test). In order to determine the minimum resolution attainable by a BPS monitor in the measurement of the beam position, being the device figure of merit, with a resolution goal of 5¿m at maximum beam current of 28A according to the TBL specifications. / García Garrigós, JJ. (2013). Development of the Beam Position Monitors for the Diagnostics of the Test Beam Line in the CTF3 at CERN [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/34327

[EN] The Compact Linear Collider (CLIC) is an electron-positron collider conceived for the study of High-Energy Physics in the TeV center of mass energy region, is based on a two-beam operation principle: instead of using active elements (klystrons), the necessary RF power to accelerate the Main Beam (MB) is obtained from the deceleration of a high-current, moderate energy Drive Beam (DB) in the so-called Power Extraction and Transfer Structures (PETS). These structures emit an RF signal of about 130 MW power at 12 GHz. As this frequency is above the cut-o ff frequency of the fundamental mode for the specified beam pipe dimensions (7.6 GHz), the inference propagates from the PETS to the neighboring devices, including the Beam Position Monitors (BPM). According to the CLIC Conceptual Design Report (CDR), an ef ficient beam position monitoring system for the CLIC DB decelerator needs to meet the following requirements: - It should be as simple and economic as possible, as 41580 units are required, amounting to 75% of all CLIC BPMs. - The signal processing scheme should not be a ffected by the PETS interference. This rules out processing the signals at the beam bunching frequency (12 GHz). - The resulting position signal should detect changes in the beam position whose duration is 10 ns or longer. - The required spatial resolution is 2 um for a 23 mm diameter vacuum pipe. - Wide dynamic range: the electronic acquisition system must be able to process signals with extreme levels, induced by either very high (100 A) or very low (3 A) current beams. This PhD thesis describes the electromagnetic and mechanical design of the first prototype BPM developed for the CLIC Drive Beam and its characterization tests in laboratory and with beam. The first two chapters introduce the CLIC project and review the state-of-the-art beam position monitoring techniques. Chapter 3 presents the design of the BPM. The stripline technology has been selected, as it is the only one among the most commonly used BPM techniques to present a suitable frequency response to filter out the RF interference caused by the PETS. Choosing an appropriate length for the electrodes, it is possible to tune one the periodic notches in the stripline frequency response to 12 GHz. The influence of di erent electromagnetic and geometrical aspects is also studied, such as beam coupling impedance or the ratio between longitudinal and transverse dimensions. The design of the electronic acquisition system is presented in Chapter 4, considering the project requirements in terms of resolution (2 u m), accuracy (20 um) and time resolution (10 ns). Due to the high amount of units required, the number of electronics components has been minimized. As the designed signal processing scheme is based on charge integration, it can be adapted to di erent stripline pick-ups by simply modifying the attenuator settings according to the required output signal levels. The laboratory characterization tests of the prototype stripline BPM, in the low and the high frequency ranges, performed with a thin wire and a coaxial waveguide, respectively, are described in Chapter 5. The measurement results are compared with the theoretical estimation and the electromagnetic field simulations. In addition, the high-frequency test reveals that the first prototype stripline BPM does not provide su cient suppression of the 12 GHz PETS RF interference. An additional study proposed several modifications and guidelines for a second prototype stripline BPM. Finally, Chapter 6 presents the beam tests of the prototype stripline BPM at the CLIC Test Facility 3 (CTF3) in the Test Beam Line (TBL), a scaled version of the CLIC Drive Beam decelerator. Two types of tests were performed: linearity/sensivity and resolution. These results are compared to the ones in the laboratory characterization tests. An upper bound of the resolution is estimated performing a Singular Value Decomposition (SVD) analysis. / [ES] El Colisionador Lineal Compacto (Compact Linear Collider, CLIC), un colisionador de electrones y positrones concebido en el CERN para el estudio de la Física de Altas Energías en la región de los TeV, se basa en un principio de funcionamiento de doble haz: en lugar de emplear elementos activos (klystrons) para proporcionar la potencia RF requerida para acelerar el haz principal (Main Beam, MB), ésta se obtiene de la deceleración de un haz secundario (Drive Beam, DB), de alta corriente y energía moderada, en las llamadas estructuras de extracción y transferencia de potencia (Power Extraction and Transfer Structures, PETS). Estas estructuras emiten una señal interferente RF de más de 130 MW de potencia a 12 GHz, que, por estar localizada en una frecuencia superior a la de corte del modo fundamental en el tubo de vacío del haz (7.6 GHz), se propaga por éste hacia los dispositivos adyacentes, entre los cuales se encuentran los sistemas de monitorización de la posición (Beam Position Monitor, BPM). De acuerdo con el informe conceptual de diseño de CLIC (Conceptual Design Report, CDR) , un sistema eficiente de monitorización de la posición del haz en el decelerador del haz secundario deberá cumplir los siguientes requisitos: - Debe ser lo más sencillo y económico posible, ya que se precisan 41580 unidades: el 75% de todos los BPMs de CLIC. - El procesado de señal en el sistema de adquisición deberá ser inmune a la interferencia generada en las PETS. Esto excluye la solución habitual de procesar las señales del BPM a la frecuencia de pulsado del haz (12 GHz). - La señal de posición resultante del procesado debe ser capaz de detectar cambios en la posición del haz de duración igual o mayor a 10 ns (resolución temporal). - La resolución espacial requerida es de 2 um para un tubo de vacío de 23 mm de diámetro, con una calibración precisa. - Amplio rango dinámico: el sistema electrónico de adquisición del BPM debe poder resistir los altos valores de señal provocados por los casos de desviación extrema del haz nominal (se contempla una desviación máxima de la mitad del radio del tubo), así como detectar las señales inducidas por las configuraciones de haz con menor carga de todas las previstas, cuyos niveles serán muy débiles. / [CA] El Col·lisionador Lineal Compacte (Compact Linear Collider, CLIC), un col·lisionador d'electrons i positrons concebut per l'estudi de la Física d'Altes Energies a la regió dels TeV (energía del centre de massa), es basa en un principi de funcionament de doble feix:en lloc de fer servir elements actius (klystrons) per proporcionar la potència RF requerida per accelerar el feix principal (Main Beam, MB), aquesta s'obtè de la desacceleració d'un feix secundari (Drive Beam, DB), d'alt corrent i energia moderada, a les anomenades estructures d'extracció i transferència de potència (Power Extraction and Transfer Structures, PETS). Aquestes estructures emeten una senyal interferent RF de més de 130 MW de potència a 12 GHz, que, pel fet d'estar localitzada a una freqüència superior a la de tall del mode fonamental al tub de buit del feix (7.6 GHz), es propaga a través d'aquest fins els dispositius adjacents, entre els quals trobem els sistemes de monitorització de la posició (Beam Position Monitor, BPM). D'acord amb l'informe conceptual de disseny de CLIC (Conceptual Design Report, CDR), un sistema eficient de monitorització de la posició del feix al desaccelerador del feix secundari haurà de complir els següents requisits: ¿ - Ha de ser el més senzill i econòmic possible, ja que es necessiten 41580 unitats: el 75% de tots els BPMs de CLIC. ¿ - El processat de la senyal al sistema d'adquisició haurà de ser inmune a la interferència generada als PETS. Això exclou la solució habitual de processar les senyals del BPM a la freqüència de pulsacions del feix (12 GHz). ¿- La senyal de posició resultant del processat ha de ser capaç de detectar canvis a la posició del feix de durada igual o més gran que 10 ns (resolució temporal). ¿- La resolució espaial necessària és de 2 um per a un tub de buit de 23 mm de diàmetre. ¿- Ampli rang dinàmic: el sistema electrònic d'adquisició del BPM ha de poder processar senyals amb nivells extrems, induïdes per feixos de molt alt (100 A) i molt baix (3 A) corrent. / Benot Morell, A. (2016). Beam position monitoring in the clic drive beam decelerator using stripline technology [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/64067