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.

The European XFEL is an X-ray free electron laser research facility that generates ultrashort, high intensity flashes. Three SASE undulator systems are made of undulator segments and intersection components. Permanent magnets that form the segments, may potentially suffer demagnetization due to the stray radiation that comes from the interaction between electrons and the beam pipe. A gamma spectrometer (GR1-A, developed by Kromek) is planned to be placed at the entrance of one of the undulator segments of SASE1. Monte Carlo simulations, using Geant4, have been performed to study gamma radiation flux at possible measurement areas. The results show that in some cells the expected flux is larger than the maximum throughput, while for two segments there are areas which satisfy the limitations of the detector. An improvement of the geometry of the Geant4 code has also been done to make simulations more in line with the real systems. A comparison between dose results from the new and the former code shows that components placed at the intersections have a significant impact on dose distributions, especially quadrupole magnets.

For a long time voltage spikes has been seen in measurement data from accelerator magnets during current ramps. These has been believed to be caused by movements, but has never before been studied in depth. The purpose of this thesis is therefore to prove, or disprove, that these events are caused by movements and to analyse what kind of displacements that actually occur. Measurement data from coil voltage, magnetic pick-up coils and current during transients has been acquired and analysed for the Nb3Sn-dipole magnets FRESCA2 and 11T models—named MBHSP107 and MBHSP109. The measurement data is compared to movement simulations that was done with the ROXIE-program, which is used to calculate mutual inductance change for a number of different movement types. The study strongly suggests that the transients are caused by movements, and also indicates that the maximal length of a single slip-stick motion can be up to around 10 micrometers, mostly in the direction of the magnet’s internal forces. The study has proven that transients in measurement data occur due to coil movements, and that these can be quantified—a discovery that can possibly affect future construction and design of accelerator magnets.

The Super Proton Synchrotron (SPS) injection system plays a fundamental role to preserve the quality of injected high-brightness beams for the LHC physics program and to maintain the maximum storable intensity. The present set-up is the result of years of upgrades and patches of a system that was not conceived for such intensities and beam qualities. In this study, we propose the design of a completely new injection system based on multi-level numerical optimisation of the different constraints, including realistic hardware assumptions. We present the different algorithms and procedures applied in the optimisation process, and we also outline how this generic optimisation framework can be adapted to other situations for optimal accelerator system design.

In this thesis the linearity of the ATLAS track-counting luminosity measurement is studied using two different sets Monte Carlo simulated crossings of proton-proton bunches. A primary high-momentum, or hard, interaction must be chosen for the Monte Carlo simulation. The first of the two sets is simulated using Z→µµ as primary hard scatter in the bunch crossings while the second set is simulated with a single neutrino particle gun as the primary hard scatter. The luminosity can be determined by track counting from the relationship between the number of reconstructed charged particle tracks and the number of proton-proton interactions per bunch crossing in the ATLAS detector. The relationship between the two is theoretically linear but is affected by non-linear effects from the presence of fake tracks and the reduced tracking efficiency at large µ.  The linearity is studied and compared for eight different sets of track selection criteria called working points. Four of the working points were used during Run 2 of the Large Hadron Collider and four are introduced for Run 3.  It is found that the use of the physical hard scatter, Z→µµ, in the Monte Carlo generation results in the appearance of tracks at all interaction rates, to a degree that does not agree with experiment. The use of the single neutrino particle gun for the simulation of hard scatter interactions is found to be more suitable for the track counting studies. Two of the working points introduced for Run 3, called TightModHighPtStrictLumi and TightModFullEtaHighPtStrictLumi, are found to outperform the rest of the working points. / I denna uppsats studeras linjäriteten av en luminositet-mätningsmetod kallad track-counting som används vid ATLAS-detektorn. Linjäriteten studeras för två olika uppsättningar av simulerade proton-protonkollisioner. Kollisionerna produceras med hjälp av Monte Carlo-simuleringar. Den första uppsättningen simuleras användandes Z→µµ som mest högenergetisk interaktion i alla event medan den andra uppsättningen istället simuleras användandes en högenergetisk neutrinopartikel i alla event. Med hjälp av track-counting bestäms luminositeten genom förhållandet mellan antalet rekonstruerade laddade partikelspår och antalet proton-protoninteraktioner per "bunch crossing" i ATLAS-detektorn. I teorin är relationen mellan de två linjär, men track-counting metoden påverkas av icke-linjära effekter såsom falskt rekonstruerade partikelspår och minskad effektivitet vid stora µ-värden. Linjäriteten studeras och jämförs för åtta olika uppsättningar av kriterier som appliceras på partikelspåren. Linjäriteten jämförs for åtta olika uppsättningar av spårkriterier som kallas "Working points". Fyra Working points har tidigare använts under den andra körningen av "the Large Hadron Collider" medan fyra Working points är introducerade inför den tredje körningen.   Användningen av uppsättningen kollisioner som simuleras med Z→µµ som mest högenergetisk interaktion resulterar i spår vid alla µ-värden till en grad som inte överensstämmer med förväntningar. Användningen av neutrinopartikeln som mest högenergetsik interaktion vid simulering av event visar sig vara mer lämplig för studier som berör track-counting. Två av de Working points som introducerades inför den tredje körningen av "The Large Hadron Collider" visar sig prestera bättre än de andra. Dessa Working points har namnen TightModHighPtStrictLumi och TightModFullEtaHighPtStrictLumi.

In this report, the effects of adding 11B4C as interlayers into Fe/Si multilayers is studied. Fe/Si multilayers are commonly used for neutron polarization at large research facilities, and improving the polarizing properties would improve their efficiency. To study this, DC magnetron sputtering was used to make different sets of samples varying interlayer thicknesses, period thicknesses, number of periods, layer thickness ratios and also testing it with steel instead of iron in the multilayers. The samples were then studied using a series of characterization techniques to study how different growth parameters affected the sample’s properties. X-ray diffraction(XRD) and selected area electron diffraction (ED) were used for studying the crystal structure of the samples. X-ray reflectometry (XRR) was used to for fitting layer thicknesses and interface widths, and also to compare reflectivities. Elastic recoil detection analysis (ERDA) was used to study the compositions changes of the samples. Vibrating sample magnetometry (VSM) gave information about how the magnetization changed between samples. Transmission electron microscopy (TEM) visualized the structure of the samples. Finally, polarized neutron reflectometry (PNR) was done at Institute Laue Langevin (ILL), revealing the actual polarization of the samples. The results of the measurements concluded that for a sample with 40 periods, a period thickness of approximately 16 Å and a thickness ratio of around 0.5 for iron and silicon, using 1 Å thick 11B4C interlayers improved the polarization between the Bragg peaks by 60 %, and at the angle of the spin up peak by 130 %. The results also indicate improved polarization for samples with more or thicker periods. Using low carbon steel instead of iron showed poor results for thin layers, however showed promise for thicker layers due to good reflectivity results, but further testing is required.

With the construction of the European Spallation Source (ESS) steadily approaching the operational phase, an environmental monitoring program will soon be implemented with the purpose of monitoring emissions. With regard to radiation safety, it is highly important to monitor alpha emitting radionuclides in aerosol form. Thus, an experimental investigation of direct alpha spectroscopy methods was conducted in order to evaluate the current experimental setup at Medical Radiation Physics in Malmö. Direct alpha spectroscopy measurements of aerosols collected on filters collected during combustion of earth soil samples were performed. Additionally, the natural alpha background in aerosols was intended to be assessed from filter samples collected at Hyltemossa Research Station in northern Scania (Sweden). Furthermore, simulations of direct alpha spectroscopy measurements are conducted in order to anticipate a measured spectra during normal operation but also in the case of an emergency at the ESS, simulations used calculated data by the ESS together with a dispersion model in order to track emissions to ground level concentrations. Direct alpha spectroscopy for environmental samples, was able to detect the presence of 210Po with a low approximate activity level of 2.8 mBq per filter. The well-defined peaks resulted from the use of a multi stage impactor when sampling, which lead to a high surface deposition of the particles. The simulations illustrate this further by showing the effect of surface deposition and how it highly affects the quality of the attained spectrum for both the normal operation and the emergency scenario. Simulated spectrum for normal operation suggest the possible detection of 148Gd without any treatment of the filters. For the emergency scenario the activity level of 148Gd is much lower than from other radionuclides. Thus the simulated spectra instead show the possible need of chemical separation of the wanted radionuclide. / Den Europeiska spallationskällans (ESS) konstruktion fortgår precis vid utkanten av Lund och den börjar närma sig driftsfasen. I takt med det här kommer ett program för att säkerställa miljö, säkerhet och hälsa att startas, ett av målen kommer vara att övervaka utsläpp och säkerställa nivåer i förhållande till regelbestämda värden. Därav görs en experimentell undersökning av metoder för direkt alfaspektroskopi, som mål att utvärdera den nuvarande experimentuppställningen vid Medicinsk Strålningsfysik i Malmö. Mätningar av filter görs med direkt alfaspektroskopi, både filter med naturlig alfabakgrund och filter med innehåll uppsamlat under förbränningstest av jordprover. Filterinsamlingen av naturlig bakgrund görs vid Hyltemossa forskningsstation i nordöstra Skåne. Utöver den experimentella studien, simulering av förväntade spektrum vid mätning av uppsamlade filter görs, både vid normal drift för ESS och vid ett hypotetiskt olyckscenario där radioaktiva partiklar släpps ut. ESS egna beräkningar för utsläpp används som grund till de undersökta scenarierna. De resulterande mätningarna av jordprover gav goda resultat som styrker användandet av direkt alfaspektroskopi vid identifiering av miljöprover, närvaro av 210Po identifieras och uppskattas med beräkning till en låg aktivitetsnivå på 2.8 mBq per uppmätt filter. Grunden till den väldefinierade energitoppen för 210Po antas komma ifrån användandet av en kaskadimpaktor, vilket resulterade i en hög ytdeposition av partiklar vid insamling. Resulterande spektrum från simuleringarna för både normal operation och hypotetiskt olycksscenario fortsätter att illustrera den enormt positiva effekten av ytdeposition vid insamling. Slutsatsen från det simulerade spektrumet vid normal drift av ESS är att 148Gd kommer vara möjligt att upptäcka med den använda metoden för direkt alfaspektroskopi. För det simulerade olycksscenariot vid ESS är andelen utsläppt 148Gd i förhållande till andra radionuklider mycket lägre, vilket leder till en låg signal i spektrumet. Slutsatsen är därav att kemisk separation antagligen kommer behövas för att mäta nivåerna av 148Gd.

The High Luminosity upgrade of the Large Hadron Collider (HL-LHC), necessitates that the ATLAS experiment replace their current Inner Detector (ID) system. The new Inner Tracker (ITk) will be an all silicon detector, utilising both pixel and strip sensors, with the aim of performing as well, or better than the current system - but in a much more challenging environment. The ITk Strip detector will consist of 17888 modules, ∼ 700 of which will be produced in the Scandinavian ITk Cluster - a collaboration of Copenhagen, Lund, Oslo and Uppsala university and our industrial partner NOTE. This work encompasses the journey from individual components through industrial scale module assembly and on to performance evaluation studies at the DESY II testbeam facility. Optimisation studies were performed of the correlated multi-variable calibration necessary for a glue robot to precisely and reliably dispense the two component epoxy used in the bonding of front-end electronics to the silicon sensor. Procedures and tools were developed for integrating this process into an industrial workflow, and to account for future fundamental changes, such as a switch in the epoxy utilised. To demonstrate sufficient tracking performance of ITk strip modules, even at end-of-life, testbeam campaigns of pre-irradiated modules are conducted. These campaign serve as vi-tal feasibility studies for the ITk as a whole. Reconstruction of end-cap type modules have been historically tricky, due to their complex geometry. This work presents the full integration of semi-automated end-cap type module reconstruction in the Corryvreckan testbeam analysis framework. This represent a major improvement in turnover time from raw data to final result, making the previously impossible concept of live reconstruction during testbeam campaigns within reach.

We have built a spectrometer to investigate the Near-Infrared (NIR) range of this radiation, which is used for bunch diagnostics at the European X-ray Free-Electron Laser. This could give information on the development of microbunching, periodic features in the longitudinal charge profile of the bunches which have a negative impact on the operation of the facility. In general it offers an ability to investigate the influences of the laser heater, the compression, and other factors that affect the structure of the bunches. The CDR is generated 1934 m after the injector, at full acceleration. The spectrometer is based around the KALYPSO detector system, able to read out from a 256 pixel linear array detector at MHz frequencies, making it possible to obtain single bunch readings during current user operation of the facility, at 1.1 MHz. KALYPSO has an InGaAs sensor, sensitive in the range 0.9 – 1.7 μm. A 40 mm N-SF11 equilateral prism is used for dispersion. First measurements have been taken, and CDR has been detected. The spectrometer needs further calibration and resolution was lacking, but it can offer insight in to relative changes, and bunch-to and can be used as for fingerprinting the beam. A reduction in signal in the sensitive range and a skew towards longer wavelengths was seen when going from uncompressed to compressed beam. When varying the power of the laser heater the behavior varied from run to run, with changing machine settings. In some cases the CDR was attenuated, while FEL intensity initially increased, until the induced energy spread from the laser heater was large enough to inhibit the FEL process. Another, less expected, behaviour was also observed, where the initially low CDR intensity at first increased, while FEL intensity stayed the same, before it then followed the same pattern as in the first case.