In this thesis, results from Mutual Neutralization experiment carried out atthe DESIREE facility, involving merged interacting ion beams, of oppositelycharged C60 ions are presented. This reaction may be of importance for explain-ing reliable estimates of the ionization balance in astrophysical environments,which defines the chemistry in molecular gas clouds. To interpret the resultsfrom the experiment, and for estimating the reaction cross section as a functionof collision energy, the Landau-Zener model is employed, with the electronicexcited states of neutral C60 calculated using Time-Dependent Density Func-tional Theory. The importance of applying an interacting potential that takesinto account mutual polarization effects and the finite sizes of the collisionpartners, in the Landau-Zener model is highlighted. We find that the total MNcross section is similar for different coupling elements. A good agreement isobserved between the Landau-Zener model and the experiment, and the modelis applied to calculate the total Mutual Neutralization cross section as a functionof center-of-mass collision energy, for a range of (0.0 - 4.98) eV excitationenergy. We find the cross section is almost an order of magnitude larger thanwhat has been reported for H+ + H− collisions and comparable with modelresults for C+60 + e− → C60 reactions. Thus, it suggests that Mutual Neutraliza-tion processes indeed may be important for the charge balance in interstellarmolecular clouds where electrons are not the main carriers of negative charges.©Raka Paul, Stockholm 2023Distributor: Department of Physics, Stockholm University

In the ongoing climate crisis, transitioning to renewable energy sources is essential to manage the increasing energy demand. One such renewable energy source is the weather-dependent energy source, wind power. Many wind farms are located in Cold Climate (CC) regions, known for their vast potential for wind power production. The weather conditions of the CC regions favor ice events, such as iceformation and accumulation on the wind turbine blades. This negatively impacts power production by changing the aerodynamic behavior and introducing an imbalance between the turbine blades. Hence, predicting ice events in advance is compelling to transition wind power into a more reliable energy source. This thesis presents a new method for predicting ice formation on wind turbine blades. It aims to improve the existing short-term wind power forecasting models by utilizing supervised Ma-chine Learning (ML). Three ML models were trained, evaluated, and compared. The three ML models examined were XGBoost (XGB) Regression, Random Forest (RF) Regression, and Support Vector Regression (SVR). The best-performing model was used for classifying ice formation. Two wind farms (wind farm A and B) of different sizes and complexities were examined. The supervised ML models were trained by merging Supervisory Control And Data Acquisition (SCADA) data holding the power output of each wind turbine of each wind farm with local Numerical Weather Prediction (NWP) data holding atmospheric parameters of the wind farm sites. For wind farm A, it was found that the XGB Regression model was the best-performing ML model with an R2 value of 69.64% when evaluated on data ranging from August to November (non-ice data). When evaluated on data including ice events, the performance decreased, giving an R2 value of 59.56%. The best-performing model for wind farm B gave an R2 value of 38.69%, when evaluated on winter data and was not good enough to perform ice classification. The predicted values from the best-performing ML model of wind farm A were used for classifying the ice formation by estimating the percentage difference between a reference power curve and the predicted values. The predicted values falling outside the 10th percentile of the reference power curve were classified as production losses caused byice formation. Using the predicted values for the winter period, we found that ice formation could be accurately performed, where 89.33% of the predicted production losses caused by ice formation values were found during periods in which ice was detected. From the findings, we can conclude that the investigated method of improving wind power forecasting and predicting production losses caused by ice formation on wind turbine blades shows potential. By improving the model to handle day-ahead forecasts better, the method could potentially be used to predict ice formation and accumulation on the wind turbine blades, using daily NWP data as input.

This thesis summarises the experimental results on molecular spectroscopy of gas phase molecules using synchrotron radiation in the UV- VUV and soft-X rays regions. The results of applying Photon Induced Fluorescence Spectroscopy (PIFS) to D2, H2S, H2O and pyrimidine are presented and discussed. Both inner and outer shell excitations of free molecules lead to different relaxation processes. However, a common result is that when the molecule breaks and the resulting neutral fragments are left in an excited state, they might fluoresce in the UV- Vis range. PIFS technique has two main advantages, it permits to detect neutral fragments and to identify the fluorescing species. From this fact, we can infer dissociation channels and trace back the electronic processes that led to the fluorescence. For these molecules we have analysed and interpreted both dispersed and undispersed fluorescence. What motivates our work is the lack of fluorescence studies and in a more general sense, to contribute to the knowledge of important molecules for life such as water and pyrimidine. / QC 20101125

I takt med den nya utvecklingen av fotonräknande datortomografi med möjligheter till lägre stråldoser kommer även krav på bättre metoder för brusreducering och bildrekonstruktion. För att lösa detta problem föreslås appliceringen av ett neuralt nätverk för att filtrera bort brus och rekonstruera bilderna. Detta kan göras både före och efter övergången från sinogramdomänen till bilddomänen. Denna rapport undersöker tillämpningen av ett sådant neuralt nätverk i sinogramdomänen med fokus på hur hyperparametrarna ska bestämmas för att uppnå optimala resultat. Datamängden som tränades på bestod av basmaterialsuppdelade sinogram i form av datorsimulerade Shepp-Logan-fantomer. Hyperparametrarna som undersöktes var batchstorlek, epoker, förlustfunktion och antal faltningslager.

Supernovae (SNe) are explosions following the death of massive stars. Core-collapse supernovae (CCSNe) occur when the heavy iron core of these stars collapse in on themselves. The resulting remnant of the core of a CCSN is a compact object: either a black hole or a neutron star. During the collapse and following explosion, massive amounts of energy and material are expelled. The compact objects emit high-energy radiation. With X-ray astronomy, we can observe it and study the processes behind these events. In this thesis, we determine a limit on the X-ray luminosity of SN 2002ap, and constrain the parameters for the magnetic field of the central object, potentially a neutron star. We model the absorption of the radiation by the material in the surrounding area, the so-called SN ejecta, as well as the absorption by the interstellar medium (ISM). We construct the model using the spectral fitting program XSPEC. Assumptions about the abundance of X-ray absorbing elements in the ejecta and ISM are based on earlier models and the explosion energy is taken from previous estimations. The mass of the ejecta is assumed to be 2.5-5 solar masses and the distance 9.34 Mpc. We compare the absorption model to the data taken by the Chandra telescope in 2018. From this comparison, we determine the maximum luminosity to be L < 2*10^40 erg/s and constrain the magnetic field to a minimum of B > 3*10^13 G.

The purpose of this thesis is to implement three numerical methods for solving and examining the time-dependent Schrödinger equation (TDSE) of the analytically solved quantum harmonic oscillator (QHO) and the, to our knowledge, analytically unsolved double well potential (DW), and to compare the numerical solutions. These methods are the Crank-Nicolson method and two split operator methods of different orders. For the QHO, the exact solution is used to determine the errors of the methods, while other methods for examining the DW had to be used (due to the lack of exact solutions). The solutions converged for the QHO, and depending the desired accuracy, either the Crank-Nicolson method or the modified split operator method were the most effective choices with regards to the global error and computation time. Applied on the DW potential, the numerical methods succeeded in displaying expected behaviours, such as locally behaving like a QHO under specific conditions, and displaying the quantum tunneling effect. For very small time-steps and fine spacial discretizations, the solutions did not deviate much from each other, indicating on convergence toward a correct solution.

För att minska skada från strålning er det viktigt att kunna modellera hur strålning påverkar biologisk vävnad. I kvantiteten kallad lineala energin är det nödvändigt att använda ett bra värde på längden av den genomsnittliga vägen för strålning genom en kropp, även känd som medelkordan. För att studera hur strålning interagerar i små volymer används jonkammare. I en jonkammare finns det en anod som mäter hur laddade partiklar interagerar i kammaren. Anodens storlek borde påverka medelkordan, men hit-tills finns ingen modell som beskriver detta på ett tillfredsställande sätt. Istället antas att anoden är försumbar.  Man kan även ställa sig frågan om en matematisk modell är tillräckligt bra, eller om man behöver ta hänsyn till effekterna från interaktioner och spridning mellan foto-ner och elektroner. Genom att använda Monte Carlo-simuleringar undersökte vi ämnet djupare. Från simuleringarna ses det att den matematiska modellen som ignorerar Comptonspridning och anodstorlek inte är bra nog. Den uppskattar däremot medelkordan för raka strålar genom en volym med liten anod väl.

In this report we study theoretical models for calculating mass spectra of exotic hadrons and carry out numerical predictions for selected states. A brief introduction to the Standard Model and other key concepts are presented in order to contextualize and aid the reader. Four mass models are described and classified, applicable to different multiquark systems. Then, predictions for mass spectra of six non-strange dibaryon candidates are performed, using a simple mass formula with parameters fixed from experimentally determined baryon masses. Finally, results are discussed in relation to other existing work on the subject.

The aim of the report is to numerically construct solutions to two analytically solvable non-linear differential equations: the Korteweg–De Vries equation and the Boussinesq equation. To accomplish this, a range of numerical methods where implemented, including Galerkin methods. To asses the accuracy of the solutions, analytic solutions were derived for reference. Characteristic of both equations is that they support a certain type of wave-solutions called "soliton solutions", which admit an intuitive physical interpretation as solitary traveling waves. Theses solutions are the ones simulated. The solitons are also qualitatively studied in the report.

XL-Calibur is a balloon-borne hard X-ray polarimetry mission with goals to analyze celestial objects too small and distant to be imaged. A crucial part of XL-Calibur is the anti-coincidence shield which through active collimation reduces unwanted hits when gathering data. The active collimation is done with a scintillator in combination with photo-multiplier tubes (PMTs). The PMTs are sensitive to external factors such as magnetic fields and varying temperatures. This report seeks to test and characterize the effects of these on the PMTs. The temperature tests are conducted by measuring the output while temperature-cycling in a light-tight vacuum thermal chamber. The magnetic-field tests are conducted in a light-tight box while applying magnetic fields of varying strength. This report finds a negative correlation between the PMT gain and temperature. As the PMTs are expected to be below room temperature during the fight, this effect is actually beneficial to their gain. This report also finds that magnetic fields can greatly impact the gain of the PMTs, which has led to the design decision of wrapping the PMTs in layers of magnetic shielding for the flight.