High electrical fields are needed inside the accelerating cavities of particle accelerators in order to accelerate the particles to higher energies in shorter distances. But high electrical fields will lead to electrical breakdowns. The electrical breakdowns are events in which the insulating proprieties of a typically electrically insulating medium are weakened due to the presence of high electrical fields. One of the best insulating mediums is the ultra high vacuum because there are no molecules that will ionize and that will conduct the electricity. But even in vacuum, there will be electrical breakdowns. They are called vacuum arc breakdowns. The conducting medium in this case is given by the ions and the electrons emitted from the metal surface of the electrodes that create the high electrical fields.  It has been observed that applying repeatedly high electrical fields on the surface of the electrodes reduces the number of breakdowns. This process is called conditioning. One explanation is that the large electric fields create dislocations near the surface of the metal that reduce the probability of having new vacuum arc breakdowns. These dislocations should also increase the electrical resistivity of the metal near its surface. To test if new dislocations are formed during conditioning, precise measurements of the surface resistivity are needed. These measurements will be made with radio pulses in the GHz range. In this range of frequencies, the electromagnetic fields penetrate only a few microns inside the surface of the metal and it will be possible to measure only the resistivity of the metal near its surface. The surface resistivity data is encoded in the quality factor (Q-factor) of a resonant cavity. This parameter describes how fast the energy is dissipated inside the cavity. A larger surface resistivity leads to a larger dissipation of energy in the walls of the cavity and to a lower Q-factor. It is advantageous to perform the measurements in cryogenic conditions because the increase in resistivity due to the formation of dislocations is much more pronounced at very low temperatures. The measurements are planned for the discharge system available in FREIA laboratory, that consists of two electrodes, separated by a small gap (60 µm), and placed inside a cryostat cooled with liquid helium. In this thesis, I describe the algorithms used to extract the Q-factor from experimental data and the results of some experiments done using the electrodes and test cavities. Small changes in resistivity (less than 0.6%), induced by temperature changes, were measured. The final chapter explores the results of the 3D EM simulations, where the electrode system in the cryogenic setup in FREIA laboratory is modified to act as a resonant cavity.

Att få en fördjupad bild av energiförlusten när joner med olika initialenergier interagerar med diverse material kan lägga grunden till viktig forskning inom till exempel materialvetenskap och strålbehandling. Det här projektet gick ut på att utföra flygtidsmätningar för att bestämma energiförlust för accelererade jod och vanadinjoner med energier mellan 4 och 44 MeV vid passage genom tunna fristående filmer av aluminium och titan. För att framställa tunna filmer sputtras material på en saltbelagd glasskiva som därefter sänks ner i vatten så saltet löses upp och filmen kan fiskas upp på en hållare. I en accelerator bombarderas folierna med joner och flygtiden mäts i en flygtidsdetektor. Skillnaden mellan de flygtider som mätts med och utan en folie kan sedan kalibreras om till energiförlust. Vid analys av filmernas tjocklek visade sig, framförallt för titanfilmerna, föroreningar och ojämnheter bidra till felkällor och påverka resultatet. Resultatet följer tidigare forskning väl vilket ger metoden merit men med vissa avvikelser som antas bero på felanpassad mätdata.

<p>Presentation held over Zoom.</p>

The thermodynamics inside the helium liquefier in the FREIA laboratory still contains many unknowns. The purpose of this project is to develop a theoretical model and implement it in MATLAB, with the help of the CoolProp library. This theoretical model of the FREIA liquefaction cycle aims at finding the unknown parameters not specified in the manual of the manufacturer, starting from the principle of enthalpy conservation. Inspiration was taken from the classical liquefaction cycles of Linde-Hampson, Claude and Collins. We developed a linear mathematical model for cycle components such as turboexpanders and heat exchangers, and a non-linear model for the liquefaction in the phase separator. Liquefaction yields of 10% and 6% were obtained in our model simulations, with and without liquid nitrogen pre-cooling respectively - similar to those in the FREIA liqueuefier within one percentage point. The sensors placed in FREIA showed similar pressure and temperature values, even though not every point could be verified due to the lack of sensors. We observed an increase of more than 50% in yield after adjustments of the heat exchanger design in the model, especially the first one. This constitutes a guideline for possible future improvements of the liquefier. / Termodynamiken bakom heliumförvätskaren i FREIA-laboratoriet innehåller fortfarande många okända aspekter. Detta kandidatarbete syftar till att utveckla en teoretisk modell och implementera den i MATLAB med hjälp av biblioteket CoolProp. Denna modell av FREIA:s förvätskningscykel syftar till att hitta de okända parametrar som inte specificerats av tillverkaren, och baserar sig på principen om entalpins bevarande. Inspiration togs från de klassiska förvätskningscyklerna Linde-Hampson, Claude och Collins. Vi utvecklade en linjär matematisk modell för cykelkomponenter såsom expansionsturbiner och värmeväxlare, och en icke-linjär modell för själva förvätskningen i fasseparatorn. En förvätskningsverkningsgrad på 10% och 6% uppnåddes i våra modellsimuleringar, med respektive utan förkylning med flytande kväve - liknande verkningsgraderna i FREIA- förvätskaren inom en procentenhet. Sensorerna placerade i FREIA visade på liknande tryck och temperaturer, även om bristen på sensorer gjorde att vi inte kunde bekräfta varje punkt. Vi observerade en ökning på mer än 50% i verkningsgrad efter att ha justerat värmeväxlardesignen något, speciellt för den första. Detta kan utgöra riktlinjer för var man framöver kan förbättra den faktiska förvätskaren. / <p>Subject reader/Ämnesgranskare: Roger Ruber</p>

Fourier filtering is a powerful technique to improve the contrast when imaging through turbid media. However, the trade-off between contrast and spatial resolution is a long-standing issue that limits the Fourier filtering technique to low spatial resolution requirements. This report circumvents this trade-off by combining several high contrast but low spatial resolution images into one high spatial resolution, high contrast image using a phase retrieval algorithm. The high contrast, low resolution images were obtained in two methods; rotating an asymmetric Fourier filter and translating a symmetric pinhole filter across the Fourier domain. The former approach, when combined with the phase retrieval algorithm, successfully constructed a high spatial resolution, high contrast image through an optical density of OD = 13.7. The problem with this technique is its temporal sluggishness as several images need to be captured and then processed to form one high resolution image making it difficult to use for fast moving object e.g. Combustion sprays. Here, I propose a new technique called Phase Retrieval Algorithm for Multiple Exposures (PhRAME) which is an instantaneous method to capture all the required images for the phase retrieval algorithm by utilising an ultra-fast imaging technique called Frequency Recognition Algorithm for Multiple Exposures (FRAME). FRAME captures several images in one exposure allowing different spatial frequencies to be captured with the same high contrast in each image. These images are then combined via the phase retrieval algorithm into one high contrast, high spatial resolution image. While this report doesn't demonstrate the working of PhRAME, it demonstrates an intermediately step, that FRAME and the phase retrieval algorithm work in tandem.

The initial goal of the project as given to us was a fully automatic control system for the beam align-ment of an ion microprobe in order to improve efficiency building on previous automation efforts.We have worked in python to develop code for reading two 4-channel picoammeters connected toadjustable rods along the beam line and translating those electrical readings into a calculated beamposition with no visual input. We then use this to recommend current adjustments to the steeringdipole electromagnets. Development was started on a standalone GUI to ease this process for newbeam compositions but was not feature complete in time.

ESS neutrino Super Beam (ESSnuSB) is a project that aim to create ahigh energy beam of neutrinos and anti-neutrinos to study thephenomenon neutrino oscillation and learn more about symmetryviolations in quantum mechanics. To create the neutrino beam, negativeHydrogen ions must be transported from the ESS linear accelerator at2.5 GeV, to a proton accumulation ring. This is done through a transferline, that shall direct the ion beam while preserve the beam as much aspossible. In thisproject, there was an attempt at finding a design for this transferline. Preferably, the line consists of a long main line of FODO cellsand two matching sections at each end. A simulation of the beam wasdone that gives the progression beta and dispersion functions,statistical measurements of the particle distribution, through a partof the transfer line. A design for the main line was found. For tuningthe quadrupole magnets, an iterative method using the system's responsematrix was used. However, it could not match more than four parametersat the time, while six was required for complete matching. Because ofthis, it is not able to match thedispersion.

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.

Particle accelerators are indispensable tools for probing matter at the smallest scales and the improvements of such tools depend on the progress and understanding of accelerator physics. The Compact Linear Collider (CLIC) is a proposed, linear electron–­positron collider on the TeV-scale, based at CERN. In such a large accelerator complex, diagnostics and alignment of the beam are crucial in order to maintain beam quality and luminosity. In this thesis we have utilized the nonlinear fields from the octupole component of the radio-frequency fields in the CLIC accelerating structures for beam-based diagnostics. We have investigated methods where the nonlinear position shifts of the beam are used to measure the strength of the octupole component and can also be used for alignment. Furthermore, from the changes in transverse beam profile, due to the nonlinear octupole field, we determine the full transverse beam matrix, which characterizes the transverse distribution of the beam. In circular accelerators, nonlinear fields result in nonlinear beam dynamics, which often becomes the limiting factor for long-term stability. In theoretical studies and simulations we investigate optimum configurations for octupole magnets that compensate amplitude-dependent tune-shifts but avoid driving fourth-order resonances and setups of sextupole magnets to control individual resonance driving terms in an optimal way.

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.