Dissertations / Theses on the topic 'Cavity beam position monitors'

The FONT beam-based, intra-train feedback system has been designed to provide beam position stabilisation in single-pass accelerators. A FONT feedback system utilising position information from three high-resolution cavity beam position monitors (BPMs) has been commissioned at the interaction point (IP) of the Accelerator Test Facility 2 (ATF2) at KEK, Japan. The ultimate goal of the feedback in the IP region is to stabilise the low-emittance electron beam to the nanometre level. The operation, optimisation and resolution performance of this IP system forms the subject of this thesis. The IP feedback system makes use of beam position measurements from the BPMs to drive an upstream kicker and provide a local correction. The BPMs have a fast decay time of ~25 ns to allow bunches within the beam train to be resolved. The operation of the IP BPMs, the noise floor, and position sensitivity to phase are discussed in detail. Attempts are made to diagnose an unwanted ~60 MHz oscillation in the cavity signals, which is bunch charge-dependent and thus likely beam generated. The BPM resolution estimate was notably improved from 50 nm to 20 nm using waveform integration in analysis of the BPM signals. A multi-parameter fit was used to address inaccurate calibrations and charge-dependencies to achieve more consistent resolution performance and produce a best-ever resolution estimate for the BPMs of 17.5 ± 0.4 nm. A novel mode of IP beam position stabilisation using two BPMs as input to the feedback has been successfully demonstrated. The beam position was stabilised to 57 ± 4 nm, as measured at an independent BPM. Feedback performance was improved to this level by sampling the waveform to optimise bunch-to-bunch correlation. Analysis suggests correction capability could be enhanced by firmware waveform integration to achieve a measurable beam stabilisation of ~40 nm in the future.

The FONT beam-based, intra-train feedback system has been designed to provide beam stability at single-pass accelerators, such as at the interaction point (IP) of the International Linear Collider. Two FONT feedback systems have been commissioned at the Accelerator Test Facility (ATF) at KEK, Japan, and the operation, optimisation and performance of these systems is the subject of this thesis. For each system, the accelerator is operated with two-bunch trains with a bunch separation of around 200 ns, allowing the first bunch to be measured and the second bunch to be subsequently corrected. The first system consists of a coupled-loop system in which two stripline beam position monitors (BPMs) are used to characterise the incoming beam position and angle, and two kickers are used to stabilise the beam. A BPM resolution of about 300 nm has been measured. On operating the feedback system, a factor ~ 3 reduction in position jitter has been demonstrated at the feedback BPMs and the successful propagation of this correction to a witness BPM located 30 m downstream has been confirmed. The second system makes use of a beam position measurement at the ATF IP that is used to drive a kicker to provide a local correction. The measurement is performed using a high-resolution cavity BPM with a fast decay time of around 20 ns designed to allow multiple bunches to be resolved. The linearity of the cavity BPM system and the noise floor of the electronics are discussed in detail. The performance of the BPM system under standard ATF operation and with the beam waist at the BPM is described. A BPM resolution of about 50 nm has been measured. This IP feedback system has been used to stabilise the beam position to the 75 nm level.

Beam position monitors are required in all accelerators for the measurement and optimization of the beam parameters. Cavity beam position monitors (CBPM) offer the possibility of measurement of beam centroid positions at the nanometer scale. These devices can be and typically are used at electron accelerator facilities, both existing light sources and test facilities proposed for future linear colliders, such as the International Linear Collider (ILC) and Compact Linear Collider (CLIC). The requirements for the CLIC main linac are to measure the beam position using approximately 5000 beam position monitors (BPM) with 50 nm resolution, at every 50 ns. The high resolution, enormous scale of the system and the small bunch separation of 0.5 ns present many challenges and demand innovative approaches for the design and operation of the CBPM system. A cylindrical cavity BPM system has been designed in collaboration with the Diamond Light Source, in the C-Band frequency region. The design ideas, which will be beneficial to CLIC BPM and other designs, such as the deliberate separation of modes coupled to the x and y position measurements and the cavity operation without mechanical tuning are tested in the design. The major resonance modes of the cavity are simulated using Eigenmode simulation. The coupling and isolation characteristics are simulated using S-parameter simulations, while the beam coupling is studied through time domain simulations. Four cavities were fabricated according to the design discussed in this this. Their coupling and isolation were tested through S-parameter measurements. The dipole modes are separated by more than 5 MHz in frequency. The values of the quality factors were measured using the impedance method. The field orientation of the dipole and quadrupole modes were measured using the bead-pull perturbation technique and found to be rotated by 12° and 30 from x-axis respectively. The initial beam studies were carried out at the Diamond Light Source and at the ATF2 beam line, and are presented in this thesis. The techniques for position determination of temporally closely spaced bunches are studied. A method was developed to remove the errors in the position determination, due to the overlap of the signals from the previous bunches, by subtracting the decayed phasors from the previous bunch. The method is applied to the signals from the CBPM system on the ATF2 beam line, in the two and three bunch mode operation. The overestimation in position determination of the second bunch is reduced from more than 67% to less than 2%. Position resolution of better than 3 um is demonstrated for the second bunch. The observed phase difference between the consecutive bunches is studied for different bunch spacing. The performance of the code is verified against simulated data.

2011/2012
Il laser ad elettroni liberi (FEL) è una sorgente luminosa di quarta generazione che ha specifiche più stringenti rispetto alle sorgenti luminose di terza generazione, tra le quali ricordiamo i sincrotroni. La cosiddetta emittanza e la traiettoria del fascio determinano la qualità del fascio, e devono soddisfare severi requisiti nei FEL. Per esempio, nella sala ondulatori, la posizione del fascio deve essere misurata con risoluzione micrometrica. Il controllo della posizione del fascio può essere effettuato utilizzando i “Cavity Beam Position Monitor” (Cavity BPM). Questa tesi descrive l’attività di ricerca eseguita sui Cavity BPM. Precisamente, la progettazione, la simulazione elettromagnetica e l'ottimizzazione di un Cavity BPM sono state effettuate. Successivamente, 25 Cavity BPM sono stati fabbricati e installati nella sala ondulatori del progetto FERMI@Elettra. I segnali sono stati acquisiti e processati con un nuovo tipo di elettronica, e una serie di misure sono state effettuate. Il secondo dispositivo studiato in questo dottorato è l'acceleratore lineare di particelle. Tradizionali strutture acceleranti, dotate di un accoppiatore a singolo ingresso causano la degradazione delle proprietà fascio elettronico, a causa dell’ asimmetria del campo elettromagnetico. Un nuovo tipo di accoppiatore, con cortocircuito mobile, viene proposto, nel quale il campo elettrico è stato simmetrizzato. La progettazione, simulazione elettromagnetica e ottimizzazione del dispositivo sono state effettuate, e un prototipo della struttura accelerante è stato prodotto e sintonizzato. Il campo elettrico è stato misurato con il metodo bead-pull. Infine, in questa tesi sono descritti i deflettori RF ad alta energia, che sono degli strumenti di diagnostica in grado di misurare le proprietà fascio elettronico, in particolare la lunghezza del banco di elettroni e lo spazio longitudinale di fase.
The Free Electron Laser (FEL) is a fourth generation light source that has more stringent specifications with respect to the third generation light sources, such as synchrotrons. The so-called emittance and the beam trajectory determine the beam quality, and must satisfy stringent requirements in FELs. For example, in the undulator hall, the beam position must be measured with the micrometer resolution. The control in the beam position can be achieved using a cavity beam position monitor (Cavity BPM). This thesis describes the research performed on the cavity BPM. Precisely, the electromagnetic design, the simulation and the optimization of a cavity BPM have been carried out. Subsequently, 25 cavity BPMs have been manufactured and installed in the undulator hall of the FERMI@Elettra project. A new RF front-end has been set up, and a series of measurements have been performed. The second device studied in this PhD is the travelling wave linear accelerator. Traditional accelerating structures endowed with a single feed coupler cause degradation of the electron beam properties, due to the electromagnetic field asymmetry. A new type of single feed structure with movable short circuit is proposed, where the electric field has been symmetryzed. The electromagnetic design, simulation and optimization of the device have been carried out, and a prototype of the accelerating structure has been produced and tuned. The electric field has been measured with the bead-pull method. Finally, in this thesis are described the High Energy RF Deflector (HERFD), which are a fundamental diagnostic tool to measure the electron beam properties, in particular the bunch length and the longitudinal phase space.
XXV Ciclo
1984

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 no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/34327
TESIS

El objetivo principal de esta tesis consiste en desarrollar un metodo para medir los terminos resonantes del Hamiltoniano de un acelerador mediante la transfomada de Fourier de la posicion del haz vuelta tras vuelta. Dos aspectos fundamentales de este metodo de medida son: el efecto de la decoherencia del haz en el espectro de Fourier y la variacion longitudinal de estos terminos resonantes. Ambos se estudian analiticamente y mediante simulaciones numericas. Con el fin de probar la validez de esta tecnica se realizaron experimentos en dos aceleradores de hadrones: el SPS del CERN y el RHIC del BNL. Por ultimo se estudia como utilizar dipolos AC para que esta tecnica no sea destructiva
The aim of this thesis is to develop a beam based method to measure the Hamiltonian terms of an accelerator by precise Fast Fourier Transform (FFT) of turn-by-turn beam position data. The effect of beam decoherence on the turn-by-turn Fourier spectrum and the longitudinal variation of the resonance terms are studied analytically and via computer simulations. Experiments to validate the proposed technique are performed at the CERN SPS and at the RHIC of BNL. Finally, the improvement of replacing the single kicks by an AC dipole is analytically described

Higher order modes (HOM) are electromagnetic resonant fields. They can be excited by an electron beam entering an accelerating cavity, and constitute a component of the wakefield. This wakefield has the potential to dilute the beam quality and, in the worst case, result in a beam-break-up instability. It is therefore important to ensure that these fields are well suppressed by extracting energy through special couplers. In addition, the effect of the transverse wakefield can be reduced by aligning the beam on the cavity axis. This is due to their strength depending on the transverse offset of the excitation beam. For suitably small offsets the dominant components of the transverse wakefield are dipole modes, with a linear dependence on the transverse offset of the excitation bunch. This fact enables the transverse beam position inside the cavity to be determined by measuring the dipole modes extracted from the couplers, similar to a cavity beam position monitor (BPM), but requires no additional vacuum instrumentation.At the FLASH facility in DESY, 1.3 GHz (known as TESLA) and 3.9 GHz (third harmonic) cavities are installed. Wakefields in 3.9 GHz cavities are significantly larger than in the 1.3 GHz cavities. It is therefore important to mitigate the adverse effects of HOMs to the beam by aligning the beam on the electric axis of the cavities. This alignment requires an accurate beam position diagnostics inside the 3.9 GHz cavities. It is this aspect that is focused on in this thesis. Although the principle of beam diagnostics with HOM has been demonstrated on 1.3 GHz cavities, the realization in 3.9 GHz cavities is considerably more challenging. This is due to the dense HOM spectrum and the relatively strong coupling of most HOMs amongst the four cavities in the third harmonic cryo-module. A comprehensive series of simulations and HOM spectra measurements have been performed in order to study the modal band structure of the 3.9 GHz cavities. The dependencies of various dipole modes on the offset of the excitation beam were subsequently studied using a spectrum analyzer. Various data analysis methods were used: modal identification, direct linear regression, singular value decomposition and k-means clustering. These studies lead to three modal options promising for beam position diagnostics, upon which a set of test electronics has been built. The experiments with these electronics suggest a resolution of 50 micron accuracy in predicting local beam position in the cavity and a global resolution of 20 micron over the complete module. This constitutes the first demonstration of HOM-based beam diagnostics in a third harmonic 3.9 GHz superconducting cavity module. These studies have finalized the design of the online HOM-BPM for 3.9 GHz cavities at FLASH.

Experiments and numerical investigations on trapped electron plasmas and traveling electron bunches are discussed. A Thomson backscattering diagnostics set up was installed in the ELTRAP (Electron TRAP) device, a Penning-Malmberg trap operating at the Department of Physics of the University of Milano since 2001. Here, an infrared (IR) laser pulse collides with nanosecond electron bunches with an energy of 1-20 keV traveling through a longitudinal magnetic field in a dynamical regime where space-charge effects play a significant role. The backscattered radiation is optically filtered and detected by means of a photomultiplier tube. The minimum sensitivity of the backscattering diagnostics has been estimated for the present set-up configuration. Constraints on the number of photons and thus on the information one can obtain with the Thomson backscattering technique are determined by the relatively low density of the electron beam as well as by noise issues. Solutions to increase the signal level and to reduce the noise are briefly discussed. The generation of an electron plasma by stochastic heating was realized in ELTRAP under ultra-high vacuum conditions by means of the application of low power RF (1-20 MHz) drives on one of the azimuthally sectored electrodes of the trap. The relevant experimental results are reviewed. The electron heating mechanism has been studied by means of a two-dimensional (2D) particle-in-cell (PIC) code, starting with a very low electron density, and applying RF drives of various amplitudes in the range 1-15 MHz on different electrodes. The axial kinetic energy of the electrons is in general increasing for all considered cases. Of course, higher temperature increments are obtained by increasing the amplitude of the RF excitation. The simulation results indicate in particular that the heating is initially higher close to the cylindrical wall of the device. These results on the electron heating point in the same direction of the experimental findings, where the plasma formation due to the ionization of the residual gas is found to be localized close to the trap wall. The simulations indicate also major heating effects when the RF drive is applied close to one end of the trap. Similar results are obtained for an electron plasma at higher densities, simulating a situation in which the RF is applied to an already formed plasma. With the aim to extend these RF studies to the microwave range, a bench test analysis has been performed of the transmission efficiency of a microwave injection system up to a few GHz. The test was based on the use of a prototype circular waveguide with the same diameter and length of the ELTRAP electrode stack and of a coupled rectangular waveguide with dimensions suitable for a future installation in the device. Electromagnetic PIC simulations have also been performed of the electron heating effect, again both at very low and relatively high electron densities, applying a microwave drive with a frequency of approximately 3 GHz close to the center and close to one end of the trap. Both the bench test of the injection system and the numerical simulations indicate that the new microwave heating system will allow the extension of the previous RF studies to the GHz range. In particular, the electron cyclotron resonance heating of the electrons will be aimed to increasing the electron temperature, and possibly its density as a consequence of a higher ionization rate of the residual gas. The installation of the new RF system will open up the possibility to study, e.g., the interaction between the confined plasma and traveling electron bunches.

Las exigentes tolerancias de alineación en los componentes de los futuros colisionadores lineales de partículas requieren el desarrollo de nuevas técnicas de alineación más precisas que las existentes. Este es el caso del Colisionador Lineal Compacto (Compact Linear Collider, CLIC), cuyos objetivos altamente restrictivos de alineamiento alcanzan los 10 um. Para poder lograr el máximo rendimiento del acelerador, es necesario que el posicionamiento de las estructuras que aceleran las partículas y de los campos que las guían cumplan las tolerancias de alineación para dirigir el haz a lo largo de la trayectoria diseñada. Dicho procedimiento consiste en relacionar la posición de los ejes de referencia de cada componente con respecto a objetos externos, o fiduciales, lo cual resulta muy tedioso y económicamente costoso. Los errores sistemáticos y aleatorios se van acumulando en cada paso del proceso y, en consecuencia, la precisión final de alineamiento es todo un desafío. En este contexto, nace el proyecto PACMAN (Particle Accelerator Components Metrology and Alignment to the Nanometre scale), subvencionado por la Unión Europea en el programa FP7 de financiación para la investigación e innovación. El objetivo principal de PACMAN es investigar, desarrollar e implementar una solución integrada alternativa que incorpore todos los pasos de alineación en una misma ubicación, con el objetivo de mejorar la precisión de alineación de los componentes de los aceleradores, en concreto: las estructuras aceleradoras, los cuadrupolos y los monitores de posición de haz. La viabilidad de las soluciones desarrolladas y la precisión de alineamiento alcanzada deben de demostrarse en un banco de pruebas utilizando componentes de CLIC. La estrategia de PACMAN para alcanzar el objetivo técnico se divide en tres pasos. El primero consiste en la fiducialización de los componentes y sus soportes. El segundo paso es el ensamblaje de los componentes en dos tipos de soporte, uno compuesto por un monitor de posición de haz y un cuadrupolo, y otro con cuatro estructuras aceleradoras, tomando como referencia su centro electromagnético. Finalmente, ambos soportes se transportan al túnel para su alineación final utilizando técnicas de hilos tensados. En esta tesis doctoral, se describe el desarrollo de una nueva técnica no destructiva para localizar los ejes electromagnéticos de estructuras aceleradoras y su validación experimental. Para ello, se ha utilizado una estructura aceleradora de CLIC conocida como TD24. Debido a la complejidad mecánica de la TD24, su difícil acceso y su diámetro medio de iris de 5.5 mm, se desarrolla una nueva técnica denominada en esta tesis como 'el método perturbativo' y se realiza una propuesta experimental de validación. El estudio de viabilidad de este método, cumpliendo con los requisitos impuestos de precisión en la medida de 10 um, ha sido realizado con una campaña extensa de simulaciones de campos electromagnéticos en tres dimensiones utilizando la herramienta de software conocida como HFSS. Los resultados de simulación han permitido el desarrollo de un algoritmo muy completo de medidas y han proporcionado las especificaciones técnicas para el diseño conceptual de un banco de pruebas para la medida de los ejes electromagnéticos de la TD24. El preciso ensamblaje del banco de pruebas y sus correspondientes calibraciones, la incorporación de nuevos tratamientos de las medidas en el algoritmo final y la caracterización de fuentes de error en la medida, favorecieron la localización del centro electromagnético en la TD24 con una precisión menor a 1 um con un error estimado menor que 8.5 um, cumplimiendo con los objetivos de precisión establecidos.
In the next generation of linear particle accelerators, challenging alignment tolerances are required in the positioning of the components focusing, accelerating and detecting the beam over the accelerator length in order to achieve the maximum machine performance. In the case of the Compact Linear Collider (CLIC), accelerating structures, beam position monitors and quadrupole magnets need to be aligned in their support with respect to their reference axes with an accuracy of 10 um. To reach such objective, the PACMAN (Particle Accelerator Components Metrology and Alignment to the Nanometer Scale) project strives for the improvement of the current alignment accuracy by developing new methods and tools, whose feasibility should be validated using the major CLIC components. This Ph.D. thesis concerns the investigation, development and implementation of a new non-destructive intracavity technique, referenced here as 'the perturbative method', to determine the electromagnetic axes of accelerating structures by means of a stretched wire, acting as a reference of alignment. Of particular importance is the experimental validation of the method through the 5.5 mm iris-mean aperture CLIC prototype known as TD24, with complex mechanical features and difficult accessibility, in a dedicated test bench. In the first chapter of this thesis, the alignment techniques in particle accelerators and the novel proposals to be implemented in the future linear colliders are introduced, and a detailed description of the PACMAN project is provided. The feasibility study of the method, carried out with extensive electromagnetic fields simulations, is described in chapter 2, giving as a result, the knowledge of the theoretical accuracy expected in the measurement of the electromagnetic axes and facilitating the development of a measurement algorithm. The conceptual design, manufacturing and calibration of the automated experimental set-up, integrating the solution developed to measure the electromagnetic axes of the TD24, are covered in chapter 3. The future lines of research and developments of the perturbative method are also explored. In chapter 4, the most significant results obtained from an extensive experimental work are presented, analysed and compared with simulations. The proof-of-principle is completed, the measurement algorithm is optimised and the electromagnetic centre is measured in the TD24 with a precision less than 1 um and an estimated error less than 8.5 um. Finally, in chapter 5, the developments undertaken along this research work are summarised, the innovative achievements accomplished within the PACMAN project are listed and its impact is analysed.
En la generació pròxima d'acceleradors de partícules lineals, desafiant toleràncies d'alineament és requerit en el posicionament dels components que enfoquen, accelerant i detectant la biga sobre la longitud d'accelerador per tal d'aconseguir l'actuació de màquina màxima. En el cas del Colisionador Compacte Lineal (CLIC), accelerant estructures, monitors de posició de fes i imants necessiten ser alineats en el seu suport amb respectar a les seves destrals de referència amb una precisió de 10 um. Per assolir tal objectiu, el PACMAN (Metrologia de Components de l'Accelerador de partícules i Alineament al Nanometer Escala) projecte s'esforça per la millora de l'actual precisió d'alineament per mètodes nous en desenvolupament i eines, la viabilitat dels quals hauria de ser validada utilitzant els components de CLIC importants. Aquesta tesi concerneix la investigació, desenvolupament i implementació d'un nou no-destructiu tècnica interna, va referenciar ací mentre 'el mètode de pertorbació' per determinar les destrals electromagnètiques d'accelerar estructures mitjançant un cable estès, actuant com a referència d'alineament. De la importància particular és la validació experimental del mètode a través del 5.5 mm iris-roí obertura prototipus de CLIC sabut com TD24, amb característiques mecàniques complexes i accessibilitat difícil, en un banc de prova dedicat. En el primer capítol d'aquesta tesi, les tècniques d'alineament en acceleradors de partícules i les propostes novelles per ser implementades en el futur colisionador lineal és introduït, i una descripció detallada del projecte PACMAN és proporcionat. L'estudi de viabilitat el mètode de pertorbació, va dur a terme amb simulacres de camps electromagnètics extensos, és descrit dins capitol 2, donant com a resultat, el coneixement de la precisió teòrica esperada en la mida de les destrals electromagnètiques i facilitant el desenvolupament d'un algoritme de mida. El disseny conceptual, fabricació i calibratge del conjunt experimental automatitzat-amunt, integrant la solució desenvolupada per mesurar les destrals electromagnètiques del TD24, és cobert dins capitol 3. Les línies futures de recerca i desenvolupaments del mètode és també va explorar. Dins capitol 4, la majoria de resultats significatius van obtenir d'una faena experimental extensa és presentada, analitzat i comparat amb simulacres. La prova-de-el principi és completat, l'algoritme de mida és optimitzat i el centre electromagnètic és mesurat en el TD24 amb una precisió menys d'1 um i un error calculat menys de 8.5 um. Finalment, dins capitol 5, els desenvolupaments empresos al llarg d'aquesta faena de recerca és resumit, les consecucions innovadores van acomplir dins del projecte PACMAN és llistat i el seu impacte és analitzat.
Galindo Muñoz, N. (2018). Development of direct measurement techniques for the in-situ internal alignment of accelerating structures [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/100488
TESIS

Beam Position Monitors (BPM) are the most frequent non-intercepting diagnostics used at nearly all Linacs, cyclotrons and synchrotrons. Their main purpose is to measure the position of the center of mass of the beam. There are many types of BPMs, which have different design, developed by taking into accounts the beam characteristics and the level of accuracy and resolution wanted. One of the most recent types, which is now used world-wide, is the Cavity Beam Position Monitor (cBPM). The latter became popular mainly because they can achieve the highest measurement resolution of all types of BPMs (up to tens of nanometers) even for low charge beams. Moreover, they can also be used to give information on the beam charge. The trade-off is that the mechanical design is complex and that high frequency read-out electronics is typically needed, which could increase the overall cost of the system. This dissertation is focused mainly on Cavity Beam Position Monitors and their application on novel electron LINACS. The research performed is particularly focused on the resolution of such devices and it also takes into consideration the read-out electronics, that for many aspects is the most critical part of the system. The techniques used to measure the resolution are explained, as well as all the experiments performed both in laboratory and in presence of beams.

The INFN project named EuPRAXIA@SPARC_LAB is a proposal to upgrade the SPARC_LAB test facility (in Frascati, Italy) to a soft X-ray user facility based on plasma acceleration and high-gradient X-band accelerating structures. Furthermore, the European project CompactLight aims to design a compact FEL for users in the hard X-ray range. Its main pillars are a new concept high-brightness photoinjector, high-gradient X-band accelerating sections, and innovative short-period undulators. The control of the charge and the trajectory at a few pC and few um is mandatory in this machine, especially in the plasma interaction region. Great importance has the beam trajectory at the entrance of every RF module, particularly the part of the machine in the X-band and inside the plasma accelerator. Conventional stripline BPM (Beam position monitor), similar to those already in use at SPARC_LAB, can be considered for such a task. They can offer a good signal to noise ratio down to a few pC charge and a resolution in the order of several tens of $mu$m. However, this kind of device can be used only at the beginning of the accelerator, where the beam pipe is 40 mm. However, starting from X band structures, the pipe size decreases. Since one of the most crucial parameters is the device's length, it will be convenient for such a system that length to be as short as possible. As a possible solution, a cavity beam position monitor (cBPM) is proposed. A prototype cavity BPM in the C-band frequency range has been designed. This thesis presents the strategy and the process to specify the parameters that are decisive for achieving the required specifications. The simulations were performed to study RF properties and the electromagnetic response of the device. The developed RF design fits the EuPRAXIA project requirements. Other design ideas, such as a single cavity BPM, where both dipole mode and reference signals are received from one cavity, are also discussed. The resonance modes of the cavity are simulated using eigenmode solvers. By the simulations performed in frequency-domain, the coupling and isolation characteristics are obtained. The beam coupling is studied through time-domain simulations. The possible manufacturing errors were studied by simulation reconstruction. Finally, the performance of the whole system for 5.1 GHz is discussed, and theoretical resolution is approximated.