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As one of the most promising continuous wave (CW) injectors for high brightness electron beams, ELBE superconducting radio-frequency (SRF) gun has been developed and optimized. This gun can provide beams with good quality for the ELBE user facility. One important aspect is to measure the transverse emittance accurately and efficiently. This thesis contributes to the progress in this field and focuses on measuring and optimizing the transverse emittance for ELBE SRF gun. The slit-scan, quadrupole scan, and an advanced thermal emittance measurement method, called single shot cathode transverse momentum imaging, have been studied and applied at this SRF gun. A fast slit-scan emittance measurement system consisting of a continuously moving slit and a yttrium aluminium garnet (YAG) screen has been developed. During the beamlet image processing, the machine learning (ML) algorithms have been integrated in order to improve the signal-to-noise ratio effectively. This is the first time to successfully apply the ML in such diagnostic methods. The measurement speed is improved about ten times and accuracy is also better than before. The errors of slit-scan emittance measurement, arising from slit position, beamlet intensity, center position and root mean square (RMS) width uncertainties, have been analyzed. The quadrupole scan emittance measurement method has been studied too. The influence of the space charge effect on quadrupole scan results has been revealed. The error of the quadrupole scan measurement has also been analyzed. To compensate the transverse emittance due to space charge effect, a superconducting (SC) solenoid is placed as close as possible to the exit of the SRF cavity. Another important part in this thesis is the investigation and optimization of the SC solenoid. The spherical aberration of the SC solenoid has been analyzed. In order to decrease it, a new yoke geometry of SC solenoid for the next generation SRF gun has been designed. The multipole transverse field modes of the solenoid caused by an axis tilt have bean analyzed by means of simulations and experimental investigations using a formalism fitting method. The influences of the multipole modes, especially the quadrupole and sextupole fields on transverse emittance have been calculated. A pair of a normal quadrupole and a skew quadrupole, called correctors, have been adopted to compensate the influence of the quadrupole field on the emittance. The cathode intrinsic emittance can contribute a non-negligible part to the transverse emittance. So in this thesis the cathode intrinsic emitttance is measured too. The single shot transverse momentum imaging method has been used to measure the cathode intrinsic emittance. A further advantage is that this method allows to determine the transverse momentum locally at different positions on the cathode.

The MYRRHA ("Multi-purpose hYbrid Research Reactor for High-tech Applications") project aims to be the first demonstrator of an accelerator-driven system. It is part of research and development on the transmutation of highly radiotoxic wastes produced in existing reactors. Controlling the subcritical reactor requires coupling with a very high reliability an accelerator which deliver a proton beam at 600 MeV energy and 4mA intensity. In order to validate the accelerator requirements, a first phase called MINERVA ("MYRRHA Isotopes productioN coupling the linEar acceleRator to the Versatile proton target fAcility") is currently under construction at SCK CEN in Belgium. This project will also allow the scientific community to use the accelerated proton beam at energy of 100 MeV. The work carried out in this thesis falls within this context. Detailed design studies of the high energy beam transport lines positioned downstream of the LINAC are presented. These transfer lines, with a total length of around 120m, deliver the beam at nominal energy of 100 MeV and intensity of 4mA on three sites: an installation receiving a fraction of the proton beam dedicated to the physics, a full power beam dump device and a line dedicated to the qualification of the machine foreshadowing the future position of the LINAC and connected to the MYRRHA reactor. The design of these lines takes into account all the constraints set by the project. As part of this work, the studies focused on a beam position monitor. To this end, an analytical simulation tool was designed. It takes into account all the important parameters: the geometry of the BPM and the characteristics of the beam. We were able to compare this analytical tool with our experimental results carried out at the IPHI installations at CEA Saclay and at GANIL/SPIRAL2 in Caen. This allowed us to propose an optimized design of such BPM for the high energy lines of the MINERVA project., Le projet MYRRHA (« Multi-purpose hYbrid Research Reactor for High-tech Applications ») a pour objectif d’être le premier démonstrateur de réacteur piloté par un accélérateur. Il s’inscrit dans le cadre des recherches et des développements sur la transmutation des déchets hautement radiotoxiques produits dans les réacteurs actuels. Le pilotage du réacteur sous-critique nécessite le couplage avec un accélérateur de très haute fiabilité délivrant un faisceau de protons à l’énergie 600 MeV et d’intensité 4 mA. Afin de valider les exigences de l’accélérateur, une première phase nommée MINERVA (« MYRRHA Isotopes productioN coupling the linEar acceleRator to the Versatile proton target fAcility ») est à présent en cours de construction au SCK CEN en Belgique. Ce projet permettra également de proposer à la communauté scientifique d’utiliser le faisceau de protons accélérés à l’énergie de 100 MeV. Les travaux effectués dans cette thèse s’inscrivent dans ce contexte. Les études détaillées de la conception des lignes de haute énergie positionnées en aval du LINAC sont présentées. Ces lignes de transfert, d’une longueur totale de l’ordre de 120 m, permettent de délivrer le faisceau d’énergie nominale de 100 MeV et d’intensité 4 mA sur trois sites : une installation recevant une fraction du faisceau de protons dédiée à la physique, un dispositif d’arrêt du faisceau de pleine puissance et une ligne dédiée à la qualification de la machine préfigurant la position future du LINAC et connectée au réacteur de MYRRHA. La conception de ces lignes a intégré l’ensemble des contraintes fixées par le projet. Dans le cadre de ce travail, les études ont porté sur un diagnostic de la mesure de position du faisceau. Pour cela, un outil de simulation analytique a été conçu. Il prend en compte tous les paramètres importants : la géométrie du système et les caractéristiques du faisceau. Nous avons pu confronter cet outil analytique avec les résultats de nos mesures effectuées auprès des installations IPHI au CEA Saclay et sur le LINAC de SPIRAL2 au GANIL à Caen. Cela nous a permis alors de proposer une conception optimisée d’un tel diagnostic pour les lignes de haute énergie du projet MINERVA.

International audience; In order to match the beam exiting the RFQ to the superconducting cavities and to minimize the longitudinal beam extension, three rebunchers will be installed in the Medium Energy Beam Transport (MEBT) of SARAF-LINAC phase II. CEA is in charge of the design and fabrication of the copper-plated stainless steel, 3-gap rebunchers. Beam dynamic simulation leads to the global MEBT design. The rebuncher was successfully conditioned to the RF power of 4.4 kW required for CW operation, with sufficient power margin. A solid state power amplifier of 10 kW developed by SNRC is used during the RF test. The rebuncher shows a good performance in terms of the dissipated power, peak temperatures and vacuum level.

Machine learning entails a broad range of techniques that have been widely used in Science and Engineering since decades. High-energy physics has also profited from the power of these tools for advanced analysis of colliders data. It is only up until recently that Machine Learning has started to be applied successfully in the domain of Accelerator Physics, which is testified by intense efforts deployed in this domain by several laboratories worldwide. This is also the case of CERN, where recently focused efforts have been devoted to the application of Machine Learning techniques to beam dynamics studies at the Large Hadron Collider (LHC). This implies a wide spectrum of applications from beam measurements and machine performance optimisation to analysis of numerical data from tracking simulations of non-linear beam dynamics. In this paper, the LHC-related applications that are currently pursued are presented and discussed in detail, paying also attention to future developments., peer-reviewed

Nuclear emulsions are a formidable tool for detecting charged particles with sub-micrometric spatial resolution, a feature which is essential in quantum interferometry experiments with antimatter. In this context, we have tested the sensitivity of such a detector, devoid of the usual protective layer, with very low energy positrons, that is in the range 0.2-17 keV. The results show that emulsions are sensitive to positrons with energy below 1 keV. Their detection efficiency increases as a function of the energy and it tends to saturate over ∼15 keV. This demonstrates the feasibility of using this type of detector in low energy regime and defines the limits of use for future gravitational studies with antimatter.

The Gamma Beam System (GBS) is a high brightness LINAC to be installed in Magurele (Bucharest) at the new ELI-NP (Extreme Light Infrastructure — Nuclear Physics) laboratory. The accelerated electrons, with energies ranging from 280 to 720 MeV, will collide with a high power laser to produce tunable high energy photons (0.2–20 MeV ) with high intensity ( 1 0 13 photons/s), high brilliance and spectral purity ( 0 . 1 % BW), through the Compton backscattering process. This light source will be open to users for nuclear photonics and nuclear physics advanced experiments. Tested high level applications will play an important role in commissioning and operation. In this paper we report the progress and status of the development of dedicated high level applications. We also present the results of the test on the FERMI LINAC of the electron trajectory control method based on Dispersion Free Steering.

A system for online measurement of the transverse beam emittance was developed. It is named $^{4}$PrOB$\varepsilon$aM (4-Profiler Online Beam Emittance Measurement) and was conceived to measure the emittance in a fast and efficient way using the multiple beam profiler method. The core of the system is constituted by four consecutive UniBEaM profilers, which are based on silica fibers passing across the beam. The $^{4}$PrOB$\varepsilon$aM system was deployed for characterization studies of the 18~MeV proton beam produced by the IBA Cyclone 18 MeV cyclotron at Bern University Hospital (Inselspital). The machine serves daily radioisotope production and multi-disciplinary research, which is carried out with a specifically conceived Beam Transport Line (BTL). The transverse RMS beam emittance of the cyclotron was measured as a function of several machine parameters, such as the magnetic field, RF peak voltage, and azimuthal angle of the stripper. The beam emittance was also measured using the method based on the quadrupole strength variation. The results obtained with both techniques were compared and a good agreement was found. In order to characterize the longitudinal dynamics, the proton energy distribution was measured. For this purpose, a method was developed based on aluminum absorbers of different thicknesses, a UniBEaM detector, and a Faraday cup. The results were an input for a simulation of the BTL developed in the MAD-X software. This tool allows machine parameters to be tuned online and the beam characteristics to be optimized for specific applications., published in Journal of Instrumentation

The ITER project requires additional heating provided by two neutral beam injectors using 40 A negative deuterium ions accelerated at 1 MV. As the beam requirements have never been experimentally met, a test facility is under construction at Consorzio RFX, which hosts two experiments: SPIDER, full-size 100 kV ion source prototype, and MITICA, 1 MeV full-size ITER injector prototype. Since diagnostics in ITER injectors will be mainly limited to thermocouples, due to neutron and gamma radiation and to limited access, it is crucial to thoroughly investigate and characterize in more accessible experiments the key parameters of source plasma and beam, using several complementary diagnostics assisted by modelling. In SPIDER and MITICA the ion source parameters will be measured by optical emission spectroscopy, electrostatic probes, cavity ring down spectroscopy for H^− density and laser absorption spectroscopy for cesium density. Measurements over multiple lines-of-sight will provide the spatial distribution of the parameters over the source extension. The beam profile uniformity and its divergence are studied with beam emission spectroscopy, complemented by visible tomography and neutron imaging, which are novel techniques, while an instrumented calorimeter based on custom unidirectional carbon fiber composite tiles observed by infrared cameras will measure the beam footprint on short pulses with the highest spatial resolution. All heated components will be monitored with thermocouples: as these will likely be the only measurements available in ITER injectors, their capabilities will be investigated by comparison with other techniques. SPIDER and MITICA diagnostics are described in the present paper with a focus on their rationale, key solutions and most original and effective implementations.