Neste trabalho apresentamos o projeto do microtron principal do IFUSP. Inicialmente são apresentados os fundamentos teóricos relativos à estabilidade do feixe em um microtron, bem como discussões sobre a ótica do feixe. No trabalho são feitas basicamente 3 tipos de simulações distintas: simulação da dinâmica longitudinal e transversal da etapa síncrona, simulação da dinâmica transversal das linhas de transferência (inserção e extração) e a simulação relativa à otimização do projeto dos eletroímãs principais. As simulações longitudinais mostraram que é possível reduzir a energia de entrada do microtron principal de 4,9 para 2,5 MeV, o que permitira a eliminação do primeiro estágio síncrono (microtron booster). A energia final do microtron principal passa a ser 38 MeV. Foram realizados os projetos de duas linhas de inserção no principal para essas as duas energias (2,5 e 4,9 MeV) e foi feita uma análise comparativa desses dois projetos. O projeto da linha de extração também foi analisado levando em consideração duas energias de extração (5,8 e 38 MeV) para se mostrar a viabilidade dessa etapa. / In this work we present the design of the IFUSP main microtron. Initially, the theoretical foundations for the beam stability in the microton are presented as well as the beam optics is discussed. Three different kinds of simulations were done: Longitudinal and transversal beam dynamics in the synchronous part of the machine, transversal beam dynamics concerning the transfer lines and simulations related to the design of the main magnets. The longitudinal simulations sugested that it is possible to reduce the initial energy of the main microtron from 4.9 to 2.5 MeV, this would permit the elimination of the first synchronous stage (booster microtron). The final energy of the main microtron will be 38 MeV. The design of two insertion lines in the main microtron for the two different energies (2.5 and 4.9 MeV) was done and a comparative analysis between these two designes is presented. The design of the extraction line also takes into account two different extraction energies (5.8 and 38 MeV) in order to show de viability of this part.

Neste trabalho apresentamos o projeto, construção e testes de eletroímãs dipolares usados na linha de transporte do feixe do Microtron do IFUSP. Inicialmente são feitos estudos da contribuição do campo de borda dos eletroímãs na curvatura total do feixe e posteriormente esses valores foram usados para a definição de parâmetros de projeto. Foram construídos e caracterizados dois dipolos (30 e 45o) e ainda um eletroímã seletor (+/- 90o) com simetria azimutal. Os resultados obtidos nos testes realizados com os dipolos mostraram um desempenho adequado à operação do acelerador. Também é descrito um método para a simulação da trajetória de elétrons na presença de um campo magnético. / In this work we present the design, construction and testing of dipole magnets used on the beam line of IFUSP-Microtron. Initially we studied the fringe field of the magnets on the total beam bending, these values had been used for the definition of design parameters. It has been constructed two dipoles (30 and 45o) as well as a switch magnet (+/- 90o) with azimuthal symmetry. The tests results of the dipoles had shown an adequate performance to the accelerators operation. A method for the simulation of the electron path in the presence of a magnetic field is also described.

This thesis discusses the design, construction and testing of a highefficiency, 100 MHz, 1 kW, Class-E solid state power amplifier. The design was performed with the aid of computer simulations using electronic design software (ADS). The amplifier was constructed around Ampleon's BLF188XR LDMOS transistor in a single ended design. The results for 100 MHz operation show a power added efficiency of 82% at 1200 W pulsed power output. For operation at 102 MHz results show a power added efficiency of 86% at 1050 W pulsed power output. Measurements of the drain- and gate voltage waveforms provide validation of Class-E operation.

The advantages of contemporary particle injectors are high bunch charges and good beam quality in the case of normal conducting RF guns and increased repetition rates in the one of DC injectors. The technological edge of the concept of superconducting radio frequency injectors is to combine the strengths of both these sides. As many future accelerator concepts, such as energy recovery linacs, high power free electron lasers and certain collider designs, demand particle sources with high bunch charges and high repetition rates combined, applying the superconductivity of the accelerator modules to the injector itself is the next logical step. However, emittance compensation — the cornerstone for high beam quality — in case of a superconducting injector is much more challenging than in the normal conducting one. The use of simple electromagnets generating a solenoid field around the gun’s resonator interferes with its superconducting state. Hence, it requires novel and sophisticated techniques to maintain the high energy gain inside the gun cavity, while at the same time alleviating the detrimental fast transverse emittance growth of the bunch. In the case of the ELBE accelerator at the Helmholtz-Zentrum Dresden-Rossendorf, a superconducting electron accelerator provides beam for several independent beamlines in continuous wave mode. The applications include IR to THz free electron lasers, neutron and positron generation, to Thompson backscattering with an inhouse TW laser, and hence, call for a flexible CW injector. Therefore, the development of a 3.5 cell superconducting electron gun was initiated in 1997. The focus of this thesis lies on three approaches of transverse emittance compensation for this photoinjector: RF focusing, the installation of a superconducting solenoid close to the cavity’s exit, and the introduction of a transverse electrical mode of the RF field in the resonator. All three methods are described in theory, examined by numerical simulation, and experimentally reviewed in the particular case of the ELBE SRF Gun II at HZDR and a copy of its niobium resonator at Thomas Jefferson National Laboratory, Newport News, VA, USA.

Wakefields and the corresponding frequency-domain phenomenon beam coupling impedance have been well studied for a number of years as a source of beam instabilities within particle accelerators. With the development of the Large Hadron Collider (LHC) and the large beam currents stored in the LHC during fills for physics production, wakefield driven instabilities and strong beam induced heating have become a limiting factors in luminosity production due to both instantaneous luminousity and the available time for collisions.In this thesis is presented an in depth study of the beam coupling impedance of two important (from an impedance and operational point of view) devices in the LHC; the collimation system and the injection kicker magnets (MKIs). These systems have both been sources of concern for the beam impedance of the LHC, the collimators due to their large transverse impedance and the MKIs due to the strong heating observed during the increased of beam current during operation in 2011 and 2012. The source of the heating for the MKIs is studied in depth, found to be power lost by the beam to wakefields in the MKIs. Simulations and measurements are used to characterise the impedance and localise the areas responsible for the high impedance, here the beam screen and ferrite yoke of the magnet; improvements are proposed to better screen the ferrite yoke and verified. A new RF damping system using ferrite for the collimation system is studied and compared to the existing RF damping system, focusing on the heating of the damping system. Highlights include a new method for measuring the quadrupolar and constant transverse impedances of an asymmetric structure using a coaxial wire technique is proposed and verified using computational simulations, and a study of the heat loss in a ferrite damped cavity, focusing on the location of the power loss for cavities being damped to varying degrees.

As part of the Large Hadron Collider high luminosity upgrade it is proposed to include crab cavities and large aperture niobium tin final focussing magnets in the lattice in order to enhance the luminosity. In this thesis the dynamics of a proposed cavity design were considered in terms of their impact upon the dynamic aperture of the machine. Taylor maps for the cavity were created and used to perform this analysis with a full assessment of their validity. A set of symplectic thin cavity models were also developed and cross checked with the Taylor maps. Finally, dynamic aperture studies were performed using these models in order to determine which components of the crab cavity dynamics are important when considering the long term stability of the beam in the LHC upgrade. It is shown that crab cavities exhibit little impact on the LHC beam stability. For the final focussing magnets a preliminary study was conducted into the importance of including their fringe fields in a model of the LHC upgrade. A technical study was carried out into developing a symplectic model which was compatible with the current magnet models use for dynamic aperture studies. A preliminary dynamic aperture study was performed with the inclusion of fringe fields for the final focussing magnets from which the fringe fields are shown to have a negative impact on the long term beam stability.

abstract: X-ray free electron lasers (XFELs) provide several orders of magnitude brighter x-rays than 3rd generation sources. However, the electron beamlines and undulator magnets required are on the scale of kilometers, costing billions of dollars with only a half dozen or so currently operating worldwide. One way to overcome these limitations is to prebunch the electron beam on the scale of the x-ray wavelength. In this paper one such scheme is discussed, which uses a nanopatterned grating called a dynamical beam stop. This uses diffraction from crystal planes of the etched portion of a grating to impart a transverse modulation which becomes a temporal modulation via an emittance exchange (EEX). To expand upon this topic, dynamical electron diffraction intensities for a 200 nm thick Si(001) unpatterned membrane are simulated via the multislice method and compared to experiment for various crystallographic orientations at MeV energies. From this as well as an analysis of the experimental inelastic plasmon diffuse scattering, it is determined that the optimal transverse modulation would be formed from a bright field image of the beam stop, with the nanopattern being etched all the way through the membrane. A model quantifying the quality of the modulation - the bunching factor - as a function of contrast and duty factor is formulated and the optimal modulation is determined analytically. A prototype beam stop is then imaged in a transmission electron microscope (TEM) at 200 KeV, with the measured bunching factor of 0.5 agreeing with the model and approaching a saturated XFEL. Using the angular spectrum method, it is determined that the spatial coherence of the MeV energy electron beam is insufficient for significant self-imaging to occur for gratings with pitches of hundreds of nanometers. Finally, the first-order EEX input requirements for the electron beam are examined in the transverse dimension as are newly proposed longitudinal requirements to compensate for lingering correlations between the initial and final longitudinal phase spaces. / Dissertation/Thesis / Doctoral Dissertation Physics 2020

The Eu-XFEL, a 3.4 km long free electron laser situated in Hamburg, Germany was commissioned in 2017, and has since been at the forefront of cutting edge technologies. The short laser-like X-ray pulses produced within the facility can be used to film ultrafast phenomena such as the formation or breakup of chemical bonds, research the composition and structure of complex biomolecules on the atomic scale, and can even be used to study matter under extreme conditions. Since its commissioning, a concern has been raised regarding the demagnetization of the permanent magnets present in the undulator system as a result of stray radiation. To monitor this, Gafchromic EBT-3 films along with other dosimetric tools have been installed at various points along the beamline to monitor radiation induced damages and predict the lifetime of the undulator system. This work focuses on optimizing the calibration of Gafchromic EBT-3 films for accurate estimations of the unwanted dose absorbed in the magnetic material, and was achieved by increasing the amount of calibration measurements and segmenting the measurements, in turn performing the calibration in parts. The results show that calibrating the EBT-3 films according to the proposed method can accurately estimate unknown doses up to 52 Gy.

The European X-Ray Free-Electron Laser facility (XFEL) provides ultra-short x-ray pulsesof high peak brilliance that are used in research to analyse atomic or molecular structures.The facility accelerates electrons and moves them through an undulator system consistingof several undulator cells containing permanent magnet poles supplying an alternatingmagnetic field, which causes the electrons to emit x-ray pulses. A concern is raised overthe deterioration of the permanent magnets due to radiation damage originating from strayradiation in the undulator system. The stray radiation is believed to be released by the highenergy electrons interacting with the beam pipe wall. In this study particle simulations aremade using the Monte Carlo particle transport code FLUKA to compare to previous sim-ulations and measurements performed at XFEL. A beam line model was made in FLUKA,simulating electron beams interacting with the vacuum pipe at several points. The sim-ulated energy deposition distribution along the undulator segment surface was fitted tomeasurement data of the dose over the magnets in different undulator cells at XFEL. Thisway the probability of the stray radiation originating from different electron beam interac-tion points could be studied. For the undulator cells that were studied the radiation wasfound to originate from interactions mainly in the gap between undulator segments. Forcell 4 and 12 it was found that radiation also originates from electron interactions with thebeam pipe inside the undulator segments. It was concluded that improvements can bemade in the simulation technique by simulating electron beam interactions at more posi-tions along the vacuum pipe’s longitudinal axis and around its lateral cross section. Furtherresearch is needed to find the impact of the alternating magnetic field over the undulatorsegments as well as to find which particles contribute to the radiation damage at XFEL. Asthe undulator cells had different relative contributions to the damaging dose from differentelectron beam interaction points it could be of interest to use the same method for fittingsimulated dose distributions to measurements of other undulator cells at XFEL.

The Super Proton Synchrotron (SPS) injection system plays a fundamental role to preserve the quality of injected high-brightness beams for the Large Hadron Collider (LHC) physics program and to maintain the maximum storable intensity. The present system is the result of years of upgrades and patches of a system not conceived for such intensities and beam qualities. In this study, we first investigate the effect of emittance growth due to amplitude-dependent tune shifts for erroneously injected beams. As a next step, we propose the design of a completely new injection system for the SPS using multi-level numerical optimisation, including realistic hardware assumptions. Methods and pseudo-algorithms of how this hierarchical optimisation framework can be adapted to other situations for optimal accelerator system design are shown. In addition, we explore the benefits of a numerical optimisation framework for the current SPS injection kicker timing system to minimise residual injection oscillations for maximised delivered beam intensity. We also demonstrate how a simple neural network based upon recorded data can approximate the injection system as a surrogate model, allowing for further studies of different optimisation algorithms even without beam time.