Spectral indices and flatness scaling exponents corresponding to solar wind plasma measurements before, during and after a coronal mass ejection (CME) detected by NASA's Wind spacecraft on September 2014 have been obtained. The Politano-Pouquet (PP) law for isotropic and incompressible magnetohydrodynamic (MHD) turbulence has been validated over a series of selected time intervals. The performed analysis showed that turbulence was well established within most of such intervals and several mean energy transfer rates were computed. Furthermore, the results detailed in this essay suggest possible correlations between the aforementioned energy transfer rates and the spectral indices and flatness scaling exponents, and also between enhanced intermittencies and large values of the mean energy transfer rates.

Ultraviolet (UV) light has been used for disinfection purposes for over 100 years. Irradiation by UV light is a method to disinfect surfaces in order to prevent microbiological growth. At Tetra Pak this is of great importance as they are manufacturer of filling machines. Those filling machines must ensure a certain level of sterility on all packages produced. The irradiation process can be simulated using Geant4 which is a software package that tracks particles through matter. The simulation model used today does not consider the absorption of photons inside of medium-pressure UV lamps. By understanding the absorption that takes place in the lamp, one can quantify how changes in the design would impact the emitter output. In this master's thesis, the aim is to develop a model that can describe the interaction of photons with a medium-pressure UV lamp. An absorption model was suggested and developed with the assumption of local thermodynamical equilibrium and existing Hg radiative data. A simulation including the collision process in Geant4 was used. In this collision process the non-radiative transition probabilities were assumed to be the same as that of the radiative, this was done in order to demonstrate how it can be done. It resulted in collisions populating other states allowing more transitions to be present in the final output spectrum. The collision process and a method for computing the Einstein's emission coefficient with the software package General Relativistic Atomic Structure Package is proposed as future work. / I över 100 år har ultraviolet (UV) ljus använts till desinficering. UV bestrålning är en metod för att desinficera ytor med målet att förhindra mikrobiologisk tillväxt. För Tetra Pak som är ledande inom tillverkning av fyllmaskiner är det extra viktigt. Förpackningarna inuti fyllningsmaskinerna måste garantera en viss nivå av sterilitet för alla förpackningar. Dagens simuleringar av medeltrycks UV lampa utförs i Geant4 som är ett mjukvarupaket som möjliggör följandet av partiklar genom olika medium. Detta görs utan att ta hänsyn till absorptionen av fotoner. Genom att förstå absorptionen som sker i lampans gas kan man kvantifiera hur förändringar i design skulle påverka emittorns utgående effekt. I detta examensarbete är målet att utveckla en modell som kan beskriva hur fotoner växelverkar med gasen i en medeltrycks UV lampa. En modell utvecklas och föreslås med antagandet att lokalt termodynamisk jämvikt råder och att enbart Hg strålnings data används. En simulering med en kollisionsprocess i Geant4 inkluderades. I denna kollisionsprocess antas den icke-optiska övergångssannolikheten vara densamma som för de optiska övergångarna. Detta inkluderades för att demonstrera hur en sådan process kan gå till. Detta resulterade i att kollisionerna populerade andra tillstånd vilket gjorde att dessa övergångar visade sig i utgående spektrum. Kollisionsprocessen och en metod för att beräkna Einsteins emissions koefficient med mjukvarupaketet General Relativistic Atomic Structure Package föreslås även som framtida arbete.

In this thesis, we investigate the interaction between electromagnetic, gravitational, and plasma related perturbations on homogeneous and hypersurface orthogonal Locally Rotationally Symmetric (LRS) class II spacetimes. By using these spacetimes, which allow for the inclusion of a non-zero magnetic field, as backgrounds in a perturbative approach, we are able to see interactions between the electromagnetic and gravitational variables already to first order in the perturbations. This is in contrast to earlier works using isotropic Friedmann-Lemaı̂tre-Robertson-Walker (FLRW) backgrounds, where one is usually faced with going to second order in the perturbations. To get the equations governing our perturbations, we use a 1+1+2 covariant approach and gather relations from the Ricci and Bianchi identities, Maxwell’s equations, particle conservation, and energy-momentum conservation for the individual plasma components. After linearising these equations around a LRS background, performing a harmonic decomposition, and using the Magnetohydrodynamic (MHD) approximation for a cold plasma, we then arrive at a closed system for the first order perturbations. This system, consisting of ordinary differential equations in time and a set of constraints, is then reduced to two separate subsectors, containing seven and nine variables respectively. These variables include quantities related to the Weyl tensor, the vorticity, and the electromagnetic fields, as well as perturbations in the plasma velocity and energy density. Through numerical calculations, we use the equations for these variables to show that perturbations in the magnetic field can be sourced by perturbations in both the plasma velocity and the gravitational variables. We also observe beat-like interference patterns for large values of the Alfvén velocity. These results can be of interest when considering the large scale cosmic magnetic fields, as their origin still seems to elude us. However, since we neglect thermal pressures and dissipative fluxes, it should be noted that our results are mainly applicable in the limit of low temperature and in cases where the thermal pressure is smaller than the pressure due to the electromagnetic fields.

In a plasma environment particles and plasma waves have complex interactions and can affect each other significantly. The velocity distribution functions (VDFs) can effectively be used to try and understand these interactions. This study uses VDFs to investigate heavy ion temperatures in the Venusian plasma environment. A Maxwellian fitting methodology previously used to obtain proton plasma parameters is used to obtain plasma parameters for heavy ions instead. Ion and magnetic-field data are gathered from the ion mass analyser IMA and the magnetometer MAG which were on board the European spacecraft Venus Express. The temperature anisotropies are analysed to see if they may affect the observed plasma waves around Venus. Spatial maps of the obtained plasma parameters are presented, and the average values are shown. The temperature ratio T⊥/T∥ is calculated to look for anisotropies. Case studies were made to investigate how well the methodology worked with heavy ion data. The methodology is shown to work well in the magnetotail, where heavy ions are expected, and less well in the magnetosheath and solar wind, where heavy ions were not expected. No statistically significant anisotropies were found for the heavy ions in the Venusian plasma environment.

Solar Orbiter is a mission launched in 2020 that will take images closer than ever of the Sun. It has ten instruments on board, including The Spectrometer/Telescope for Imaging X-rays (STIX) and The Extreme Ultraviolet Imager (EUI). STIX is a hard X-ray imaging spectrometer which observes bremsstrahlung from the non-thermal accelerated electrons in the footpoints of solar flares and from thermal hot plasma in flare loops. EUI consists of three telescopes, including a Full Sun Imager which is a one-mirror telescope that observes the solar corona and chromosphere in extreme ultraviolet (EUV) wavelengths 174Å and 304Å, respectively.   The purpose of the project was to determine the alignment between STIX and EUI to better understand and improve the pointing of STIX. It is important to know the accuracy of the pointing before using the instruments for science. The alignment was studied by looking at the flare location of the two instruments for about 30 flares. The flare location was approximated to be the brightest pixel in the image. The aspect solution of STIX was applied and this was also compared to the flare seen by EUI. For some of the flares, also imaging data from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) was used to get a more detailed comparison. One flare was studied in more detail, using thermal and non-thermal emission seen by STIX, EUV emission seen by EUI 174Å and AIA 171Å as well as UV emission seen by AIA 1600Å. For four flares, the flare location was determined from the visible ribbons and loops instead of the brightest pixel. The methods of finding the flare location by brightest pixel and by looking at flare features were compared.   The average difference between the EUI and STIX flare location was within 12 arcseconds with a standard deviation between 18 and 42 arcseconds for the brightest pixel method. This difference has two main contributions: the accuracy of the STIX aspect solutions and the accuracy of identifying the common source features in EUV and X-rays. To increase the accuracy of finding common sources, four flares with well defined ribbons and loops were analyzed in detail. For these events, the accuracy of the STIX aspect system was determined to be better than 10.5 arcseconds. This is still significantly higher than the design requirements of being better than 4 arcsecs. Detailed analysis clearly showed that the method of determining the flare location by brightest pixel was not accurate enough to evaluate the STIX pointing. Further studies need to be done to improve the aspect solution.

The work presented in this thesis involves experimental and theoretical studies related to plasma properties in high power impulse magnetron sputtering (HiPIMS), and more specifically plasma transport. HiPIMS is an ionized PVD method based on conventional direct current magnetron sputtering (dcMS). In dcMS very little of the sputtered material is ionized since the plasma power density is not high enough. This is not the case for HiPIMS, where a substantial part is ionized, and thus presents many new opportunities for thin film growth. Understanding the dynamics of the charged species in the HiPIMS discharge is therefore of essential value when producing high-quality thin film coatings. In the first part of the work a new type of anomalous electron transport was found. Investigations of the transport resulted in the discovery that this phenomenon could quantitatively be described as being related and mediated by highly nonlinear waves, likely due to the modified two-stream instability (MTSI), resulting in electric field oscillations in the MHz-range (the so-called lower hybrid frequency). Measurements in the plasma confirmed these oscillations as well as trends predicted by the theory of these types of waves. The degree of anomalous transport in the plasma could also be determined by measuring the current density ratio between the azimuthal current density (of which the Hall current density is one contribution) and the discharge current density, Jφ / JD. The results provided important insights into understanding the mechanism behind the anomalous transport. It was furthermore found that the current ratio Jφ / JD is inversely proportional to the transverse resistivity, eta_perpendicular , which governs how well momentum is transferred from the electrons to the ions in the plasma. By looking at the forces involved in the charged particle transport it was expected that the azimuthally rotating electrons would exert a volume force on the ions tangentially outwards from the circular race track region. The effect of having an anomalous transport would therefore be a large fraction of highly energetic ions being transported sideways and lost to the walls. In a series of experiments, deposition rates as well as incoming ion energy distributions were measured directly at the side of the magnetron. It was found that a substantial fraction of sputtered material is transported radially away from the cathode and lost to the walls in HiPIMS as well as dcMS, but more so for HiPIMS giving one possible explanation to why the deposition rate for substrates placed in front of the target is lower for HiPIMS compared to dcMS. Furthermore, the recorded, incoming ion energy distributions confirmed theoretical estimations on this type of transport regarding energy and direction.

In this paper a search routine in MATLAB was developed in order to find and analyze oblique whistler waves in the data from the ESA and NASA spacecraft Solar Orbiter. Oblique whistler waves are a type of plasma wave which propagate at an angle with respect to the background magnetic field. They are efficient at scattering electrons in the solar wind but their role in interplanetary coronal mass ejections (ICMEs) is yet unknown. Magnetic field data from 1-31st of June 2022, as well as the 24th and 27-28th of January 2022 was examined. The search routine found six whistler waves in June and 12 for the dates in January. Among these, all found whistler waves were found in the sheath region of the ICMEs, and all had a plasma beta > 1. However due to instrumental artefacts the values of θk were found to be smaller than detected by the search routine, indicating less obliqueness than first expected. Some of the whistler waves seemed to have an obliqueness that changed with time and the bandwidth of the waves varied among the identified.

In this thesis, theoretical studies are conducted to see whether plasma will detach from the magnetic field lines of the VASIMR thruster, and if so, at which location detachment takes place. A magnetic field similar to the field of the VASIMR VF-24 engine [1] is used and ions of different speed and massare sent from various radial positions in the exhaust. Calculation with different values of the anomalous resistivity parameter ωτ is conducted and the sensitivity to this parameter is studied. The validity of the method is studied by comparing results to previous work by Carl Wesslén [2]. From the results it is concluded that using heavy ions sent at high speeds will achieve detachment and high thrust efficiency, even when assuming relatively high values of ωτ. Ejecting ions at a slower pace or using lighter ions will make the engine less efficient, requiring low ωτ which is difficult to achieve. For some combinations of mass and speed, detachment is not possible at all. Ions with heavy mass are recommended to use as propellant for this type of thruster.

Understanding of material migration and its impact on the formation of co-deposited mixed material layers on plasma-facing components is essential for the development of fusion reactors. This thesis focuses on this topic. It is based on experiments performed at JET and TEXTOR tokamaks. The major objectives were to determine: (i) fuel and impurity removal from plasma-facing components by ICWC in different gas mixtures, (ii) fuel and impurity transport connected to ICWC operation, (iii) plasma impact on diagnostic mirrors. All these issues are in line with the ITER needs: mitigation of co-deposition and fuel inventory, and the performance of first mirrors in long-term operation. The novelty in research is demonstrated by several elements. In wall conditioning studies, tracer techniques based on injection of rare isotopes (N-15, O-18) were used to determine conclusively the impact of respective gases. Also, a new approach to ICWC was developed by combining global gas balance studies based on mass spectrometry and the use of multiple surface probes exposed to discharges and then studied ex-situ with accelerator-based techniques. Impact of plasma on diagnostic mirrors was determined after exposure to the entire first experimental campaign in JET-ILW. / <p>QC 20141103</p>

The BIOMASS mission from the European Space Agency (ESA) is designed to measurebiomass and carbon content in Earth’s forests. To account for phase changes caused byionospheric variations, a map-drift autofocus algorithm is developed, which utilises a phasescreen of the ionosphere to eliminate phase errors in the signal. In this development, a filteris employed to integrate and remove noise from the second-order derivative of the ionosphericphase screen. This thesis aims to analyse methods to implement this filter andcompare their efficiency. Two filters are constructed using two methods, a Least Mean Square (LMS) filter and aWiener filter. Further emphasis is placed on the Wiener filter, and the most optimal way tocalculate it is explored in detail. The aim is to produce a filter that can integrate, lower theimpact of noise as much as possible and be computationally efficient. An implementationwas made in Python using simulated data of an ionosphere. The conclusion is that the Wiener filter can yield improved results if a precise estimation ofthe autocorrelation function of the ionospheric phase screen can be determined, and thatlinear regression models might be a method to do so. There is also consideration taken tothe noise of the data, it is compensated for by utilising multiple data sources. Additionally,to enhance computational efficiency, a comparison of different solving methods for the linearsystem of equations that is the filter where made, showing a LU-decomposition method tobe efficient.