Accelerator-driven systems have been proposed for incineration of transuranic elements from spent nuclear fuel. For safe operation of such facilities, a robust method for reactivity monitoring is required. In this thesis, the most important existing reactivity determination methods have been evaluated experimentally in the subcritical YALINA-experiments in Belarus. It is concluded that the existing methods are sufficient for calibration purposes, but not for reactivity monitoring during regular operation of an accelerator-driven system. Conditions for successful utilization of the various methods are presented, based on the experimental experience. / QC 20101115

The Standard Model has been greatly successful in predicting the laws that govern our universe. Yet there are still seemingly missing pieces to the model. Detector development plays a crucial role in advancing our understanding of particle physics and helps answer some of the most pressing questions in the field, such as the nature of dark matter and why a matter-antimatter asymmetry is observed. This thesis has covered the work of developing detectors for two different experiments. The HIBEAM/NNBAR experimental program will be a search after neutron-sterile neutron and neutron-antineutron oscillations housed in the the European Spallation Source (ESS) in Lund, Sweden. The experiment will reach unprecedented sensitivity for free-neutron searches, surpassing the last the oscillation time limit by 3 orders of magnitude. This thesis presents an overview of the experimental goals and the opportunities afforded by the ESS infrastructure. The primary work for this thesis has been the design, simulation and construction of a prototype calorimeter for NNBAR stage of the experiment, which is presented here. The ATLAS experiment is currently undergoing upgrades to meet the requirements of the high-luminosity, high-radiation environment at the HL-LHC. This thesis provides an overview of the LHC and the ATLAS experiment, with special focus on the hadronic Tile calorimeter. TileCal will be upgraded to provide full granularity data at the lowest trigger level of the upgraded ATLAS trigger and data acquisition system. The work presented here focuses on TileCal upgrades to Daughterboard (DB), the interlink board responsible for the management of on- and off-detector data transmission. This work has been primarily focused on the design and fabrication of two printed circuit boards to test the implementation of a commercial, radiation-hardened FPGA in the upgraded DB design. The FPGA will control access to remote control JTAG in the DB Xilinx FPGA interface.

This thesis presents a search for Supersymmetry in final states containing two same-flavor opposite-sign leptons, jets and large missing transverse momentum. The search makes use of 36.1 fb−1 of proton-proton collision data collected at a center-of-mass energy of √s = 13 TeV by the ATLAS detector at the Large Hadron Collider. Two signal scenarios, which both involve the pair-production of squarks or gluinos decaying into final states with two leptons and the lightest supersymmetric particle, are targeted by the analysis. The first scenario considers decay chains with a leptonically decaying Z boson and is characterized by a peak in the dilepton invariant mass distribution. In the second scenario, decays through intermediate sleptons or an off-shell Z boson are considered. Such processes lead to a kinematic endpoint in the dilepton invariant mass distribution. The main Standard Model backgrounds include the pair-production of top quarks and direct production of Z bosons. These backgrounds are estimated with two data-driven methods. The observed data is found to be consistent with the Standard Model expectation and the results are interpreted in simplified Supersymmetry models for gluino and squark pair-production. Sensitivity is provided for gluino and squark masses up to 1.85 TeV and 1.3 TeV respectively. / I denna avhandling presenteras en analys som letar efter supersymmetriska partiklar producerade i proton-proton-kollisioner vid en kollisionsenergi på √s = 13 TeV. Analysen använder sig av data insamlad under 2015 och 2016 av ATLAS-experimentet vid CERNs Large Hadron Collider. Den totala analyserade datamängden motsvarar 36,1 fb−1. Kollisioner som resulterar i par av elektroner eller myoner med motsatt laddning, jets och en stor obalans i rörelsemängd i det transversella planet väljs ut för analys. Målet är att finna tecken på en produktion av skvarkar eller gluiner som sönderfaller till två leptoner och en oladdad supersymmetrisk partikel som lämnar detektorn utan att lämna någon signal. Inom supersymmetriska modeller kan sådana slutliga tillstånd uppkomma genom sönderfallskedjor med Z-bosoner som sönderfaller leptoniskt, eller genom sönderfallskedjor med sleptoner. Flera processer som förutspås av Standardmodellen kan efterlikna den eftersökta signalen och utgör bakgrunder i analysen. De viktigaste bakgrunderna består av Z-bosoner och par av toppkvarkar som produceras direkt i proton-proton-kollisionerna. Dessa bakgrunder uppskattas genom att använda data, medan andra mindre bakgrunder uppskattas genom att använda simuleringar. Ingen signifikant signal utöver den uppskattade backgrunden uppmäts i analysen. Istället tolkas resultaten med hjälp av simuleringar av förenklade supersymmetriska modeller. På så sätt kan exkluderingsgränser med 95% konfidensnivå beräknas för gluino- och skvark-massorna. Massor över 1,85 TeV utesluts för gluiner och massor över 1,3 TeV utesluts för skvarkar. / <p>QC 20180109</p>

This Master's thesis investigates a method to measure atomic nuclei with record precision using muonic atom X-ray spectroscopy. In particular, 6Li is measured experimentally. The method used is independent from the previous most precise measurement of the 6Li nuclear charge radius which uses electron scattering. Measuring low-Z elements using muonic X-ray transitions requires excellent detectors which have so far been mostly optimised for higher energies. This project investigates methods to reach precision requirements for low-Z elements which can yield insight into nuclear structure models, and uses a Silicon Drift Detector (SDD) which is here characterised in detail and found to allow for significantly improved results over previous attempts. So far, the SDD and developed calibration scheme demonstrates a 3.7 eV precision compared to the target 0.5 eV. It appears to be limited by detector resolution, which also makes curve fitting difficult for complex line structures. A new method for generating calibration lines, X-ray fluorescence, is tested and shows good promise for future use. The planned use of a Metallic Magnetic Microcalorimeter will potentially improve results significantly, having a much-improved resolution over SDD's. Preliminary experimental results find ΔEµLi-6, 2p-1s = 18780.6 ± 15.7 eV, which is a factor of 4 improvement over the previous best measurement of this transition and the world's most precise measurement to date. While the uncertainty is larger than seen in designated calibration runs, it demonstrates the ability to perform high-precision muonic atom spectroscopy. With new detector technologies, this thesis finds no immediate obstacles to the target 0.5 eV precision.

Gauge theories is one of the most pervasive and important subject of modern theoretical physics, and there are still many things about them we do not understand. In particular dealing with strongly coupled theories where normal perturbative techniques do not apply is a fundamental open problem. In this thesis, we study a particular class of toy-models that have supersymmetry, which makes them much easier to deal with. We employ the mathematical technique of localization, which for supersymmetric theories lets us evaluate certain path integrals exactly and for any value of the coupling. This is used to study the 5d N=1 theories placed on toric Sasaki-Einstein manifolds and compute their partition functions, finding that they factorize into a product of contributions from each closed Reeb orbit of the manifold. This computation leads us to define two new hierarchies of special functions associated to these manifolds, and we study their properties. Finally, we use the 5d N=1 theories to construct new 4d N=2 theories on a large class of curved backgrounds. These theories have some interesting features, such as supporting both instantons and anti-instantons, and having a position-dependent complexified coupling constant.

<p>Frisch grid ionization chambers are commonly used experimental tools for charged particle spectroscopy. In the ideal Frisch grid chamber the anode pulse height is independent of where inside the sensitive volume the charge has been created. This ideal cannot be realized because of imperfect shielding of the anode by the grid. The effect of the imperfect shielding is generally referred to as grid inefficiency. For accurate energy determination the anode pulse height needs to be corrected for this.</p><p>At present two opposing explanation for grid inefficiency exist. The first explanation suggests that there is a reduction of the anode pulse height. This is said to arise from positive ions inducing charge on the anode as the electrons are collected. The second explanation suggests that there is a too large anode signal. The addition to the anode signal is said to arise from the drift of electrons.</p><p>In this thesis the concept of grid inefficiency is investigated by means of wave form digitization. The use of digital signal processing makes it possible to maintain information on the drift of electrons. This information is lost in charged particle spectroscopy experiments using electronic signal processing networks.</p><p>A series of experiments is described in this thesis. The first experiment was performed to find good measuring conditions for the following experiments. For this purpose the drift velocity of electrons was measured in two chamber filling gases, P-10 and CF4. The measured drift velocities are presented for the two gases. Finally, P-10 was chosen as filling gas for the following experiments.</p><p>In the second experiment the grid inefficiency was measured for two different types of shielding electrodes. The method of determining the grid inefficiency is based on the analysis of the shape of digitized charge signals. The measured values are shown to be in good agreement with calculated values.</p><p>In the final experiment the effects of grid inefficiency on alpha particle spectroscopy is investigated. It is shown how the correction for grid inefficiency by the two existing models yield equivalent results for energy determination. An attempt to separate the two models is also presented indicating that there is in fact a reduction of the anode pulse height because of grid inefficiency. The thesis is concluded with a theoretical discussion of the anode pulse shape. There grid inefficiency is explained by the drift of electrons. It is shown in this section how explaining grid inefficiency by the drift of electrons should yield the same result as explaining it by the effect of positive ions.</p>

The Gesellschaft für Schwerionenforschung (GSI) facility in Darmstadt, Germany, will be upgraded to accommodate a new generation of physics experiments. The future accelerator facility will be called FAIR and one of the experimentsat the site will be PANDA, which aims at performing hadron physics investigations by colliding anti-protons with protons. The licentiate thesis consistsof three sections related to PANDA. The first contains energy resolutionstudies of PbWO4 crystals, the second light yield uniformity studies of PbWO4 crystals and the third reconstruction of the lambda-bar-polarisation in the PANDA experiment. Two measurements of the energy resolution were performed at MAX-Lab in Lund, Sweden, with an array of 3x3 PbWO4 crystals using a tagged photon beam with energies between 19 and 56 MeV. For the April measurement, the crystals were cooled down to -15 degrees C and for the September measurement down to -25 degrees C. The measured relative energy resolution, <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Csigma" />/E, is decreasing from approximately 12% at 20 MeV to 7% at 55 MeV. In the standard energy resolution expression <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Csigma" />/E = a/<img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Csqrt%5B%5D%7BE%7D" /> <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Coplus" /> b/E <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Coplus" /> c, the three parameters a, b and c seem to be strongly correlated and thus difficult to determine independently over this relative small energy range. The value of a was therefore fixed to that one would expect from Poisson statistics of the light collection yield (50 phe/MeV) and the results from fits were <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Csigma" />/E=0.45%/<img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Csqrt%5B%5D%7BE_%7BGeV%7D%7D" /> <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Coplus" />0.18%/EGeV <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Coplus" />8.63% and <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Csigma" />/E = 0.45%/<img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Csqrt%5B%5D%7BE_%7BGeV%7D%7D" /><img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Coplus" />0.21%/EGeV <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Coplus" />6.12% for the April and September measurements, respectively. The data from the September measurement was also combined with previous data from MAMI for higher energies, ranging from approximately 64 to 715 MeV. The global fit over the whole range of energies gave an energy resolution expression of <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Csigma" />/E = 1.6%/<img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Csqrt%5B%5D%7BE_%7BGeV%7D%7D" /> <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Coplus" />0.095%/EGeV <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Coplus" />2.1%. Light yield uniformity studies of five PbWO4 crystals, three tapered and two non-tapered ones, have also been performed. The tapered crystals delivered a light output which increased with increasing distance from the Photo Multiplier Tube (PM tube). Black tape was put on different sides of one tapered crystals, far from the PM tube to try to get a more constant uniformity prole. It was seen that the light output profile depends on the position of the tape. Generally, the steep increase in light output at large distances from the PM tube could be damped. The third part of the thesis concerns the reconstruction of the lambdabar polarisation in the reaction <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?pbar+p%20%5Crightarrow%20lambdabar%20+%20lambda" />. Events were generated using a modied generator from the PS185 experiment at LEAR. With a 100% polarisation perpendicular to the scattering plane, a polarisation of (99±1.8)% was reconstructed. Slight non-zero polarisations along the axis determined by the outgoing hyperon as well as the axis in the scattering plane, were also reconstructed. These were (4.1±2.1)% and (2.6±2.0)% respectively. From this investigation it was shown that the detector efficiency was not homogeneous and that slow pions are difficult to reconstruct.

No description available.

Frisch grid ionization chambers are commonly used experimental tools for charged particle spectroscopy. In the ideal Frisch grid chamber the anode pulse height is independent of where inside the sensitive volume the charge has been created. This ideal cannot be realized because of imperfect shielding of the anode by the grid. The effect of the imperfect shielding is generally referred to as grid inefficiency. For accurate energy determination the anode pulse height needs to be corrected for this. At present two opposing explanation for grid inefficiency exist. The first explanation suggests that there is a reduction of the anode pulse height. This is said to arise from positive ions inducing charge on the anode as the electrons are collected. The second explanation suggests that there is a too large anode signal. The addition to the anode signal is said to arise from the drift of electrons. In this thesis the concept of grid inefficiency is investigated by means of wave form digitization. The use of digital signal processing makes it possible to maintain information on the drift of electrons. This information is lost in charged particle spectroscopy experiments using electronic signal processing networks. A series of experiments is described in this thesis. The first experiment was performed to find good measuring conditions for the following experiments. For this purpose the drift velocity of electrons was measured in two chamber filling gases, P-10 and CF4. The measured drift velocities are presented for the two gases. Finally, P-10 was chosen as filling gas for the following experiments. In the second experiment the grid inefficiency was measured for two different types of shielding electrodes. The method of determining the grid inefficiency is based on the analysis of the shape of digitized charge signals. The measured values are shown to be in good agreement with calculated values. In the final experiment the effects of grid inefficiency on alpha particle spectroscopy is investigated. It is shown how the correction for grid inefficiency by the two existing models yield equivalent results for energy determination. An attempt to separate the two models is also presented indicating that there is in fact a reduction of the anode pulse height because of grid inefficiency. The thesis is concluded with a theoretical discussion of the anode pulse shape. There grid inefficiency is explained by the drift of electrons. It is shown in this section how explaining grid inefficiency by the drift of electrons should yield the same result as explaining it by the effect of positive ions.

In this thesis a characterization of air showers induced by magnetic monopoles is presented. Monopoles are predicted to exist and be accelerated to relativistic velocities. High energy monopoles traversing earth’s atmosphere continuously deposit energy, inducing an air shower. These air showers have been described based on simulations run in CORSIKA. It was found that monopole air showers are continuous; they plateau after the shower maximum, and have a large electromagnetic component. As such,they can easily be distinguished from normal cosmic rays and most other air shower sources. Very high energy photons and muons could induce similar showers but do not produce identical signals in track-following detectors such as IceCube.