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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Coordinate conversion for the Hough transform

Eriksson, Edvin January 2021 (has links)
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.
32

Laser Metrology for assembly of ATLAS ITk-Strips

Arvin, Jonathan, Berg Wallin, Johannes, Eskner, Hugo, Lindman Jardfelt, Olof January 2023 (has links)
The ATLAS detector at CERN's Large Hadron Collider has been instrumental in scientific discoveries,including the Higgs particle. As part of the High Luminosity (HL) upgrade, the current Inner Detector (ID) isbeing replaced by the new IInner Tracker (ITk), and Uppsala University is collaborating with industrypartner NOTE to produce around 700 modules for the ITk. The production process involves gluing hybridsto sensors using a glue robot, which currently lacks a complete metrology system needed to verify thegeometry of produced items. This project aims to integrate a Micro Epsilon ILD1900 laser sensor with theglue robot to enable accurate measurements in the z-axis. In order to reach this goal, a few differenttasks had to be completed. These included creating a measurement API to enable the utilisation of thelaser sensor, recommending modifications to the glue robot syringe and camera holder in order to holdthe laser sensor, performing validation tests of the laser sensor's measuring capability, developing a lasersensor mount for a mock-up glue robot used during the validation process and developing a holder for aUSB/RS422 converter necessary for communication with the laser sensor. As a result of the project, themeasurement API was successfully created and utilised, appropriate modifications to the syringe holderwere made, validation tests were conducted though deemed insufficient due to limitations of the setup,and, finally, the laser sensor mount for the mock-up glue robot and the USB/RS422 holder weresuccessfully designed and produced.
33

Generation of attosecond X-ray pulses in free-electron lasers using electron energy modulation and undulator tapering

Boholm Kylesten, Karl-Fredrik January 2023 (has links)
Free-electron lasers (FELs) are among the world's most intense artificial artificial sources of coherent light and are tunable to various wavelengths, including the X-ray spectrum. X-ray FELs (XFELs) are extremely useful for diffraction experiments to study molecules, materials, and quantum systems. A FEL consists of an electron accelerator and a structure of magnets called an undulator. The undulator has a periodic magnetic field, and when an electron beam passes through the undulator, the Lorentz force forces the electrons to oscillate and emit what is known asspontaneous undulator radiation. Initially, the undulator radiation is spontaneously emitted and incoherent. However, aAs the electrons interact with this initial spontaneous undulator radiation, they change their relative positions and form micro-bunches of electrons. These microbunches are shorter than the undulator radiation wavelength. Hence, the waves emitted by the electrons from the same microbunch arethey become in phase, meaning the radiation is now coherent with the radiation field, and the state of coherence develops. This process is known as self-amplified spontaneous emission (SASE). Due to the coherence, tThe radiation intensity grows exponentially along the undulator, forming several peaks in the radiation pulse known as SASE spikes. One technique for obtaining ultra-short laser pulses is to isolate single SASE spikes by controlling where, along the electron beam, the SASE spikes can grow. This growth limitation is archieved by modulating the electron energies, thus only allowing electrons at specific positions along the electron beam to radiate. In addition, to keep positive interference between undulator radiation from electrons with different energies, the energy modulation must be compensated with a gradient of the magnetic field amplitude of the undulator, so-called tapering. There are plans to implement this technique at one of the beamlines at the European X-ray FEL (EuXFEL) to generate attosecond X-ray pulses and study quantum systems. One goal of the design process is to choose design parameters for the electron beam's modulation amplitude and the undulator's tapering coefficient. These design parameters shall be chosen so that the XFEL will have as short pulse duration as possible while at the same time not getting too low peak power. This thesis aims to study the effect of electron energy modulation and undulator tapering on the SASE and how the modulation amplitude and the tapering coefficient affect the XFEL's peak power and pulse duration. A model was developed to simulate SASE with a modulated electron beam in a tapered undulator. With this model, a parameter scan gave the average peak power and pulse duration as functions of the modulation amplitude and the tapering coefficient. The parameter scan showed that the peak power and the pulse duration decrease as the modulation amplitude and the tapering coefficient increase. Therefore, a trade-off exists between high peak power and short pulse duration. It was possible to exclude sets of the parameters that gave too low peak power or long pulse duration. This study also found an optimum range for the tapering coefficient where the peak power had a local maximum without a significant increase in pulse duration. The physics behind this optimal tapering coefficient is also discussed in connection to the electrons' energy modulation.
34

Characterization of Multi Plate Field Mill for Lunar Deployment

Forssén, Clayton January 2018 (has links)
During the Apollo 10 and 17 missions NASA astronauts reported that they saw streamers emanating from the surface of the moon. They concluded that the streamers were produced by light scattering from dust particles. The particles are believed to be transported by an ambient electric field. This theorized electric field has never been measured directly, although the electric potential on the surface and above it has. The exact behavior and origin of the electric field is unknown, but has been approximated to be between 1 and 12 V/m. To measure this electrical field a new type of instrument, called Multi Plate Field Mills (MPFM) has been developed. This type of instrument is capable of measuring both the amplitude and directionality of the electrical field. Three of these instruments will be mounted on a 1U CubeSat to be lunched with the PTS mission to the moon scheduled to Q4 2019. In this work the MPFM were characterized. The precision of the instrument for electrical fields applied along the z, y and x axis was found to be 0.6, 1.3, 1.4 (V/m)/(Hz)^(1/2) respectively for measurements in air and 0.14, 0.6, 0.6 (V/m)/(Hz)^(1/2) for measurements in vacuum. This sensitivity outperforms the current state of the art Field Mills and, in addition to that, it provides an assessment of the directionality of the electrical field. / Umeå Lunar Venture
35

Characterization of γ-rays at MAST

Blom, Erik January 2019 (has links)
The γ-ray characterizing possibility of the neutron collimated flux monitor (in short, Neutron Camera) at the Mega Ampere Spherical Tokamak (MAST) is explored. Typically used to monitor neutron emission, the Neutron Camera has excellent neutron/γ-ray discrimination properties and thus presents the opportunity to measure spatially and temporally resolved γ-ray emission - a possibility of an additional fusion diagnostics method with already existing equipment. An Online Data Analysis (ODA) code was used to analyze the data on γ-rays from several plasma discharges with similar plasma parameters. A high statistics temporal distribution of the γ-ray emission and a lower statistics spatial distribution were analyzed. However, the low energy resolution and range for the Neutron Camera γ-ray measurements revealed few conclusive results on the origin of the higher energy γ-rays. Detection systems with higher energy resolution and range are suggested for an extensive analysis of γ-ray emission at MAST Upgrade.
36

Laser Beam Pathway Design and Evaluation for Dielectric Laser Acceleration

Rasouli, Karwan January 2019 (has links)
After nearly 100 years of particle acceleration, particle accelerator experiments continue providing results within the field of high energy physics. Particle acceleration is used worldwide in practical applications such as radiation therapy and materials science research. Unfortunately, these accelerators are large and expensive. Dielectric Laser Acceleration (DLA) is a promising technique for accelerating particles with high acceleration gradients, without requiring large-scale accelerators. DLA utilizes the electric field of a high energy laser to accelerate electrons in the proximity of a nanostructured dielectric surface.The aim of this project was limited to laser beam routing and imaging techniques for a DLA experiment. The goal was to design the laser beam pathway between the laser and the dielectric sample, and testing a proposed imaging system for aiming the laser. This goal was achieved in a test setup using a low-energy laser. In the main setup including a femtosecond laser, the result indicated lack of focus. For a full experimental setup, a correction of this focus is essential and the beam path would need to be combined with a Scanning Electron Microscope (SEM) as an electron source.
37

Toward a Novel Gas Cell for X-Ray Spectroscopy : Finite Element Flow Simulation and Raman Characterization

Stångberg Valgeborg, Fredrik January 2019 (has links)
The new millennium has seen revolutionary advances in photonsource technology. As the newly constructed synchrotron facilityMAX IV in Lund, Sweden, pushes brilliance toward what isphysically possible, low-yield spectroscopic techniques, such asresonant inelastic X-ray scattering (RIXS), open new doors inmolecular and condensed matter research. The VERITAS beamline atMAX IV is designed for high-resolution vibrational RIXS on gases.X-rays interact with flowing molecules inside a window-cappedcell, but the radiation intensity is expected to be large enoughto damage the windows, and cause build-up of photochemicalproducts, which lowers transmission. To address these issues, anovel gas cell design is presented, wherein the distance betweensample gas and window is increased by using a flowing heliumbuffer. The main challenge is maintaining a steep sample gasconcentration gradient within the cell, and to that end, gas flowswere simulated on various geometries by using the finite elementmethod to solve the Navier-Stokes equations. Results were used toconstruct a prototype, and confocal Raman microscopy was used forconcentration characterization. Preliminary measurements revealeda uniform sample gas distribution, and the technique proved to beinefficient for wide scanning of parameter values. This suggeststhat a supplementary experiment is required to find roughestimates of good parameter values, which can then be followed upwith new Raman measurements for fine-tuning of the properparameter space. Real-time visualization of the sample gas flow,using a visible gas under an optical microscope, is one candidatefor this supplementary experiment.
38

Application of GEANT4 toolkit for simulations of high gradient phenomena

Persson, Daniel January 2018 (has links)
To study electron emissions and dark currents in the accelerating structures in particle colliders, a test facility with a spectrometer has been constructed at CERN. This spectrometer has been simulated in the C++ toolkit GEANT4 and in this project the simulation has been improved to handle new realistic input data of the emitted electrons. The goal was to find relations between where the electrons are emitted inside the accelerating structure and the energy or position of the particles measured by the spectrometer. The result was that there is a linear relation between the initial position of the electrons and the width in the positions of the particles measured by the spectrometer. It also appears to be a relations between energy the emitted electrons get in the accelerating structure, which is related to the position, and the energy they deposit in the spectrometer. Further studies where the simulations are compared with real measurement data are required to determine whether these relations are true or not, find better reliability in the relations and get a better understanding of the phenomena.
39

Thermo-mechanical analysis of cryo-cooled electrode system in COMSOL

Olofsson, Joel January 2018 (has links)
In the planned linear accelerator called Compact Linear Collider, CLIC, electrons and positrons will be accelerated to velocities near the speed of light. A limiting factor in accelerating structures are vacuum breakdowns, which are electrical discharges from a surface as a result of a large electric field being applied. In the preparatory studies for the CLIC, Uppsala University in collaboration with The European Organization for Nuclear Research, CERN, is building a DC Spark system to analyze vacuum breakdowns. This system containing large planar electrodes will be cooled down all the way down to around 4 K in order to limit the rate of wich vacuum breakdowns happen. When cooling a system like this, which consists of different components made of different materials there is the question of how the system will be affected. The objective of this project is to investigate how the cooling will affect the stability in terms of stresses and to analyze the cool down time of the system. Another goal is to make a material recommendation for a few parts based on the results. This will be done by simulating the cooling in COMSOL Multiphysics, which is a program that uses finite element analysis to solve complex problems where different branches of physics interact. The conclusion is that the system will most likely be stable as it is and there is no need to redesign it. The choice of recommended material is alumina with the reason being it should cause the least stress and the smallest gap between the electrodes when the cooling is done. There was no big difference in the cool down time between the materials. Further studies and simulations on the system is also recommended since there are many factors not taken into consideration in this study.
40

Dark Matter signals at the Large Hadron Collider with Deep Learning

Andersson, Max, Glöckner, Edward, Löfkvist, Carl January 2023 (has links)
While holding a firm position in popular culture and science fiction, Dark Matter (DM) is nonetheless a highly relevant topic at the forefront of modern particle physics. We study the applicability of characterizing DM particle candidates SUSY neutralino and sneutrino using Deep Learning (DL) methods. We focus on the monojet and mono-Z signatures and the emergence of missing transverse energy as the result of the undetectable DM candidates. Based on kinematic distributions of outgoing particles as input, a DM candidate classifier is built for each signature, along with a DM mass regressor. The DM candidate classifier obtained near perfect accuracy of 0.995 for the monojet, and 0.978 for mono-Z signature. The monojet and mono-Z mass regressors achieved a Mean Absolute Percentage Error (MAPE) of 17.9 % and 8.5 % respectively. Furthermore, we discuss both the shortcomings and simplification that our choice of model implied, as well as an interpretation of the results. Finally, we debate the prospects of DL in the discovery of new physics and it's use in experiments.

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