This thesis presents the measurement of the differential cross section of the top-antitop pair production in proton-proton collisions at center-of-mass energy of 8 TeV at the ATLAS experiment. The measurement is performed for top-antitop events in the single lepton decay channel in the boosted topol- ogy. The measured differential cross section is expressed as a function of the top quark transverse momentum at particle level and at parton level. The mea- sured distributions are compatible with the theoretical predictions of the Standard Model. The experimental techniques used in this measurement are discussed with emphasis on the jet reconstruction and on the identification of jets originating from b-quark fragmentation. The jet reconstruction is influenced by simultane- ous proton-proton collisions (pileup), and the mitigation of these pileup effects is studied. A novel pileup subtraction technique for jets is proposed using an ex- tension of the methods currently being employed by the LHC experiments. The new method has a good performance in removing the pileup contributions at the level of jet constituents. 1

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.

This project has investigated the muon background of the SHiP experiment to determine whether it can boost the experiment sensitivity to visible Dark Photon decay. Using Fermi-Weizsäcker-Williams approximation to muon scattering we found the probability of muons generating massive photons, using Bremsstrahlung and direct lepton pair production as an estimation of the frequency of muon EM-interactions. In this work we only considered muons with momenta above 10 GeV/c. The number of visible Dark Photon decays was calculated for a range of the coupling constant and photon mass. The resulting range that promised visible decay has already been excluded by previous experiments, but the method could be used to further investigate enhanced production of Dark Photons from muons and electrons, and possibly also production of Axion-like particles. The work could also be used to estimate sensitivities of other experiments using muons.

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.

Den snabbt växande utvecklingen av AI-baserade applikationer och den stora mängden data dessa applikationer behandlar ställer ökade krav på prestanda och optimering av datorsystemen. För att tillfredsställa de växande datorbehoven används hårdvaruacceleratorer som förbättrar databehandlingshastigheten genom att avlasta den befintliga utrustningen genom att hjälpa till med uppgifter och komplexa beräkningar. De befintliga lösningarna som används i dagsläget är kostsamma och MT-FoU på Umeå Universitetssjukhus efterfrågar därför en alternativ lösning i form av att kombinera mindre integrerande acceleratorer på ett större PCIe-kort. I detta examensarbete designas och implementeras en AI-accelerator bestående av fyra Google Coral Dual Edge TPU M.2 på ett 16x PCIe-kort. Arbetet genomfördes på MT-FoU och målet med examensarbetet var att undersöka om den tilltänkta konstruktionen kan förbättra prestandan hos AI-baserade system och fungera som ett billigare alternativ i verksamheten. Schemaritning och PCB-design utfördes i KiCad och information om gränssnitt och komponenter hämtades främst från tillverkares hemsidor och datablad. Kretsen består i huvudsak av fyra stycken M.2 E key kontaktdon, en 16port/16lane packetswitch och en 16x PCIe-anslutning. Switchen delar upp banorna från PCIe porten så att Edge TPU’erna kan anslutas parallellt i M.2 kontakterna. Edge TPU’erna använder pipelineparallellism för att fördela arbetsuppgifter på varje TPU så att större, mer komplexa program kan exekveras. Vid monteringen av kretskortet uppstod problem med fastlödningen av vissa komponenter. För att undvika att dessa problem uppstår och möjliggöra avlägsnandet av dessa felkällor bör montering istället beställas av fabrik där lödrobot finns tillgängligt. På grund av att tiden för kursen tog slut hann en sådan beställning inte göras och evaluering av den framtagna designen var därför inte möjlig att genomföra. Den design som togs fram var dock betydligt billigare än de existerande lösningarna och med pipelineparallellism förväntas designen kunna utföra komplexa beräkningar och därmed förbättra prestandan i befintliga system. / The rapidly growing development of AI-based applications and the large amount of data these applications process place increased demands on the performance and optimization of conventional computer systems. To satisfy these growing computing requirements, hardware accelerators are used to improve the data processing speed by offloading the existing equipment by executing models and complex calculations. The existing solutions currently used are costly and MT-R&D at Umeå University Hospital is therefore requesting an alternative solution by combining smaller integrating accelerators on a larger PCIe card. In this thesis, an AI accelerator using four Google Coral Dual Edge TPU M.2 on a 16x PCIe card is designed and implemented. The work was carried out at MT-R&D and the goal of the thesis was to investigate whether the intended design can improve the performance of AI-based systems and serve as a cheaper alternative in the institution. Schematic and PCB were designed in KiCad and information on interfaces and components was obtained from manufacturers' websites and data sheets. The circuit’s main components are four M.2 E key connectors, a 16port/16lane packet switch and a 16x PCIe connection. The switch divides the lanes from the PCIe port so that the Edge TPUs can be connected in parallel in the M.2 connectors. The Edge TPUs use pipeline parallelism to distribute models across each TPU so that larger, more complex programs can be executed. When assembling the circuit board, problems arose with the soldering of certain components. In order to avoid these sources of error, assembly should instead be ordered from a factory where a soldering robot is available. Due to the fact that the time for the course ran out, such an order could not be placed and evaluation of the design was therefore not possible to carry out. However, the design that was produced was significantly cheaper than the existing solutions and by using pipeline parallelism, the design is expected to be able to perform complex calculations and thus improve the performance of existing systems.

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.

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.

Contemporary art spaces are typically structured in accordance with a visual paradigm. However, sound has the capacity to leak into other spaces and does not conform to visual logics. Still, sounding artworks are frequently presented in these spaces. Thus, the aim of this thesis is to examine the effects of leaking sounding works within art spaces with an emphasis on the sensory experience of sound, and to further the understanding of how this can be operationalised curatorially. The research is focused on these questions: How is sound operating to produce experiential effects in the respective exhibition situations? What are the transformative potentials of sounding works in art spaces? What are the curatorial implications of these effects? The study investigates two cases, the exhibitions Mother Courage and Her Children (2022) and Undamming Rivers (2022) that both provide examples of the interactions of sounding works in contemporary art spaces. The material is gathered through observation and analysed using the theory of performativity. The analysis defines a set of terms that describe different experiences of sounding works in the art spaces. Furthermore, these effects are shown to operate transformatively on the art event as aspects of a contemporaneous production and reception of the art. The concluding discussion elaborates on the curatorial implications of these terms in the curation of sounding works to show how sonic leakage facilitates definition of space, movement through space, and a layering of experience.

Significant discrepancies had been identified by many research groups world wide between calculated and measured neutron doses from the ⁷Li(p,n) accelerator based neutron source, and therefore precise characterization of the source was needed. In this work neutron spectra from the ⁷Li(p,n) source were measured with a ³He ion chamber in the incident proton energy range from 1.95 to 2.3 MeV. The ³He detector is hypersensitive to slow neutrons, so a time-of-flight based slow neutron rejection acquisition system was built and tested. The system is based on an electrostatic proton chopper and an acquisition system working on coincidence mode. The response function of the ³He was extended down to 30 keV neutron energy and the collected neutron spectra were unfolded using two methods: van Cittert iterative algorithm with Jansson constraint, and a regularized constrained inversion. Theoretical neutron spectra emitted by the ⁷Li(p,n) source were calculated and compared with experimental unfolded spectra, as well as with results of the Monte Carlo simulations of the lithium target assembly and the walls of the experimental area. Using fluence to kerma conversion coefficients, the neutron dose was calculated and compared with results obtained from an independent experiment using the microdosimetric technique with a tissue equivalent proportional counter. Total neutron yield of the ⁷Li(p,n) reaction was measured using induced activity of ⁷Be. Results showed a negative energy offset of the incident proton beam between 50 and 58 keV with respect to the generating voltmeter indication of the accelerator terminal. Shapes of the measured neutron spectra showed significant moderation originating from neutron scattering on the lithium target assembly and walls of the experimental area. When accounting for this offset, neutron yields showed an agreement with calculated values within 22% for 1.95 MeV and within approximately 7% for higher proton energies. / Thesis / Doctor of Philosophy (PhD)

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