The power quality of modern society relies on the electrical properties of the dielectric insulators used in the power industry. Much research work has been conducted with an aim to understand and predict the insulating behaviour of such materials under different kinds of atmospheric conditions, but still there are many unsolved problems. In particular, there is a lack of knowledge concerning the electrohydrodynamic and electrophysical processes at the insulator surface and the surrounding medium. No detailed knowledge exists at present of the processes governing the development of electrical discharges along the surface of insulators. With an aim to enhance the knowledge in this field in general and on the electrical performance of outdoor insulators in particular a detailed study of the positive streamer discharges in air and along dielectric surfaces was conducted. The study was also extended to gain more knowledge on the water drop initiated electrical discharges in air and the attachment of natural lightning flashes to a Franklin conductor. In the first phase, the study was focused on positive streamer discharges propagating in air. The spatial distribution of the charge of a branched streamer discharge was obtained and the charge contained in a single streamer branch was quantified. In the second phase measurements and simulations of streamer discharges propagating along insulating surfaces were conducted with an aim to understand how the insulating surfaces interact with streamer discharges. In addition to quantifying the parameters of streamer discharges propagating along insulating surfaces, the results of these studies made it possible to separate and quantify the effects of the dielectric constant and the surface properties on the streamer discharges. In the third phase a comprehensive computer algorithm was developed to simulate 3-dimensional propagation of positive streamer discharges in air and along dielectric surfaces taking into account the branching effect. The conditions necessary for the initiation of streamer discharges were applied to obtain the minimum strength of the background electric field required to initiate electrical discharges in the presence of water drops. In particular the study provided an explanation of how lightning flashes are initiated in thunderclouds in background electric fields as low as 200 kV/m. Finally, the study was extended to understand the performance of lightning conductors paying special attention to the influence of conductor radius and the streamer inception criterion.

The optical properties of electrochromic materials can be changed by application of an electrical voltage. The conventional electrochromic device consists of several thin films of electrochromic materials and layers for electron- and ion conduction. The ion conductor in devices intended for applications using visible light is often a polymer electrolyte that is used to laminate two half-cells together. The miniaturization of satellites has led to reduced mass and volume available for systems to handle temperature variations onboard. The satellite will be submitted to large variations in the radiating environment in an earth bound orbit. An electrochromic device could provide adaptable radiation exchange due to its variable infrared optical properties. The polymer electrolyte is not a desirable component in the space environment, but it can be replaced by an inorganic thin film so that an all-thin-film (ATF) device is obtained. This thesis investigates the optical properties of amorphous and crystalline WO3, as well as the performance of ATF devices with sputtered ZrO2 as the ion conductor. The infrared reflectance for Li-intercalated WO3 has been measured in the wavelength range 2-50 mm. The near infrared absorption for low intercalation levels showed good agreement with large polaron theory. The infrared reflectance increased with higher intercalation levels and exhibited a free-electron behaviour. The infrared reflectance of a laminated device with polymer electrolyte was measured, and the calculated emittance varied between 0.56 and 0.65. The ATF device consisted of thin films of WO3, ZrO2 and NiVxOyHz, as well as evaporated Al top contacts. The substrates were commercial ITO on glass. The emittance for different device designs was calculated from reflectance measurements, and could be varied between 0.33 and 0.59. This makes them strong contenders to other contemporary emittance modulating devices.

In this thesis permanent magnet direct drive generator for power conversion from water currents is studied. Water currents as a power source involves a number of constrains as well as possibilities, especially when direct drive and permanent magnets are considered. The high power fluxes and low current velocities of a water current, in combination with its natural variations, will affect the way the generator is operated and, flowingly, the appearance of the generator. The work in this thesis can, thus, be categorized into two general topics, generator technology and optimization. Under the first topic, fundamental generator technology is used to increase the efficiency of a water current generator. Under the latter topic, water current generators are optimized to a specific environment. The conclusion drawn from this work is that it is possible to design very low speed direct drive generators with good electromagnetic properties and wide efficiency peak.

Thin film devices for windows, mirrors, space applications and other purposes, have become an essential part of modern technology. A great advantage with a thin film device is the small amount of material used and the compact volume of the device. Dynamic control of thin film device properties is usually obtained by the application of a potential with a resulting charge transport. To understand this charge transport, thus become of great importance to improve, develop, and invent new thin film devices. Charge transport in transition metal oxide thin films and electrochromic devices have been studied in this thesis using dielectric and electrochemical methods. The dielectric methods used are impedance spectroscopy, the isothermal transient ionic current technique and current-voltage measurements. The electrochemical methods include the galvanostatic intermittent titration technique and electrochemical impedance spectroscopy. Ion intercalation parameters have been obtained for sputtered and ALD ZrO2 and sputtered TiO2, and the ion conduction processes have been analysed. The dielectric permittivity of as-deposited as well as intercalated thin films of ZrO2 and TiO2 have been studied and electron conduction mechanisms in as-deposited films deduced. From the impedance spectroscopy it is found that the dielectric response changes drastically upon ion intercalation. The complex dielectric response suggests different relaxation processes being important at different levels of intercalation and an explanation built on defect induced dipoles is proposed. Moreover, ion transport in electrochromic devices has been studied. The transient ionic current has been analysed to extract transport parameters both in single layers and whole devices and a deeper understanding of the ionic motion has been achieved.

Ericsson in Linkoping houses one of the largest test laboratories within thewhole Ericsson Company. Mainly, the laboratories contain equipment forGSM, WCDMA and LTE. To test these systems, a quite large number ofRadio Base Stations are needed. The RBS's are housed in a proportionatelysmall area. Instead of sending signals through the air, cables are used totransfer the RF signals. In this way the equipment communicating witheach other are well speci ed. However this may not be the case if leakageoccur.This thesis work is about developing a system for monitoring the radioenvironment and detect leakages in the test site. There is a need to de newhat a leakage really is and measurements needs to be performed in order toaccomplish this. This report describes how the work has proceeded towardsthe nal implemented solution.

Quantum optics offers a huge variety of exciting phenomena. Many of them are still in their infancy and especially when it comes to implementing devices using these effects for more than a proof of principle demonstration still many things have to be investigated and understood. In this thesis I discuss the role of correlations in some areas of quantum optics and in some cases compare it to classical optics. Four papers form the core of the thesis. In the first paper, I propose a new measure for entanglement. This measure is based on correlations between two states. I show, how this measure relates to another measure, the concurrence. It turns out that the measure is a bijective map of the concurrence for a pure state of two qubits. I motivate why the new measure is useful if one wants to implement it experimentally. I discuss its behaviour for the case of two qubits and show its properties when dealing with pure and with mixed states. The second paper extends the result of the first one to the case where one has higher-dimensional states than qubits. In the third paper I look at phase super-resolution. I show that it can be interpreted as a purely classical effect and I analyse what is needed and what is not needed to achieve it. Specifically, I show that quantum correlations in terms of entanglement is not needed to demonstrate phase super-resolution. By doing so I propose how one could achieve arbitrarily high phase super-resolution. Finally, the last paper looks at the efficiency of quantum lithography and quantum imaging. It shows, that some basic assumptions in the original proposals of quantum lithography seems unfounded and that, as a consequence, the efficiency is poor. I give formulæ for the explicit scaling behaviour when changing the number of photons in a mode or when changing the number of pixels. The effect of the results on the future of quantum lithography is discussed as well. / Kvantoptiken erbjuder ett stort antal spännande fenomen. Många av dem är fortfarande i sin linda och särskilt när man vill tillämpa kvantoptiska effekter snarare än att bara visa att principen fungerar så finns det många saker och ting som måste förstås och undersökas bättre. I denna avhandling ska jag diskutera vilken roll korrelationer spelar i några områden inom kvantoptik och i några fall ska jag jämföra dem med klassisk optik. Fyra vetenskapliga artiklar bildar kärnan i avhandlingen. I det första pappret föreslår jag ett nytt sammanflätningsmått. Detta mått har sin ursprung i korrelationer mellan två tillstånd. Jag visar hur måttet förhåller sig till ett annat mått, den så kallade "concurrence". Det visar sig att måttet är en bijektiv avbildning av concurrence för rena tillstånd av två qubitar. Jag motiverar varför det nya måttet är användbart när man vill implementera det experimentellt. Jag diskuterar hur måttet beter sig för två qubitar och visar dess egenskaper för rena och blandade tillstånd. Det andra pappret utvidgar första papprets resultat till situationer där man har tillstånd med högre dimension än qubitar. I det tredje pappret undersöker jag superfasupplösning. Jag visar att man kan tolka detta som en rent klassisk effekt och jag undersöker vad man behöver och vad man inte behöver för att uppnå superfasupplösning. Jag visar särskilt att kvantkorrelationer genom sammanflätning inte behövs för att visa superfasupplösning. Därigenom ger jag förslag om hur man kan uppnå godtyckligt hög superfasupplösning. Slutligen tittar jag i sista pappret på effektiviteten av kvantlitografi och kvantavbildning. Pappret visar att några grundläggande antaganden i originalförslaget till kvantlitografi verkar vara illa underbyggda och att därigenom kvantlitografins effektivitet reduceras kraftigt. Jag ger ekvationer för det exakta skalningsbeteendet när man ändrar antalet fotoner i en mod eller när man ändrar antalet pixlar. Jag diskuterar också implikationerna som det medför för kvantlitografins framtid. / QC 20110524

The study presented in this thesis was motivated by the large uncertainty on the concentration of atmospheric electrical discharges to the global nitrogen budget. This uncertainty is partly due to the fact that information concerning the NOx production efficiency of electrical discharges having current signatures similar to those of lightning flashes is not available in the literature. Another reason for this uncertainty is the fact that energy is used as a figure of merit in evaluating NOx production from lightning flashes even though insufficient knowledge is available concerning the energy dissipation in lightning flashes. The third reason for this uncertainty is the lack of knowledge concerning the contribution of discharge processes other than return strokes to the NOx production in the atmosphere. Lightning is not the only process in the atmosphere that causes ionisation and dissociation of atmospheric air. Cosmic rays continuously bombard the Earth with high energetic particles and radiation causing ionization and dissociation of air leading to the production of NOx in the atmosphere. The work carried out in this thesis is an attempt to improve the current knowledge on the way in which these processes contribute to the global NOx production. Experiments have been conducted in this thesis to estimate the NOx production efficiency of streamer discharges, laser-induced plasma, laboratory sparks having current signatures similar to those of lightning flashes, alpha particle impact in air and finally with the lightning flash itself. The results obtained from laboratory electrical discharges show the following: (a) The NOx production efficiency, in terms of energy, of positive streamer discharges is more or less similar to those of hot discharges. (b) The NOx production efficiency of an electrical discharge depends not only on the energy but also on the peak and the shape of the current waveform. (c) The current signature is a better figure of merit in evaluating the NOx yield of electrical discharges. As a part of this thesis work a direct measurement of NOx generated by lightning flashes was conducted and the results show that slow discharge processes such as continuing currents could be the main source of NOx in lightning flashes. Concerning NOx production by other ionisation processes such as alpha particle impacts in the atmosphere, the data gathered in this thesis show that each ionising event in air leads to the creation of one NOx molecule. In terms of energy the NOx production efficiency of alpha particles is similar to that of electrical discharges. The theoretical studies conducted within this thesis indicate that M-components contribute more than the return strokes to the NOx production. The calculations also show that the contribution to the global NOx budget by return stroke is not as high as that assumed in the current literature.

<p>In several x-ray related areas there is a need for high-precision elements for x-ray generation and focusing. An elegant way of realizing x-ray related elements with high precision and low surface roughness is by the use of microfabrication; a combination of semiconductor processing techniques and miniaturization. Photolithographic patterning of silicon followed by deposition, etching, bonding and replication is used for batchwise fabrication of small well-defined structures. This thesis describes microfabrication of a miniature x-ray source and a refractive x-ray lens. A miniature x-ray source with diamond electrodes has been tested for x-ray fluorescence. Another version of the source has been vacuum encapsulated and run at atmospheric pressure. One-dimensionally focusing saw-tooth refractive x-ray lenses in silicon, epoxy, and diamond have been fabricated and tested in a synchrotron set-up. Sub-micron focal lines and gains of up to 40 were achieved. The conclusion of the thesis is that the use of microfabrication for construction of x-ray related components can not only improve the performance of existing components, but also open up for entirely new application areas.</p>

<p>Tungsten trioxide is a material with a variety of application areas. For example, the material is used within thin film technologies as electrochromic material in smart windows, as electrochemically functional material in thermal control applications or as active layer in gas sensing application. Metal-oxide semiconductor gas sensors are of significant interest to detect toxic and hazardous gases. The use of small and cheep sensors is preferable since a large number of sensors easily can be placed at different sites to monitor the concentration of different species without involving huge investments.</p><p>In this work, WO₃ nanoparticle films were produced using an advanced gas deposition unit for gas sensing applications. The structure of the WO₃ nanoparticle films was determined using X-ray diffraction, neutron scattering, X-ray photoelectron spectroscopy, elastic recoil detection analysis and electron microscopy. The as deposited films consist of sub-stoichiometric WO₃ and exhibit a large degree of porosity, which together with the small particle size of about 5 nm results in a large surface area and therefore excellent prospects for gas sensor applications. </p><p>Investigations on the optical properties and temperature dependence of the resistance indicate hopping conduction in the WO₃ films. The bandgaps for tetragonal and monoclinic WO₃ were found to be direct, which is in accordance with band structure calculations.</p><p>Sensor properties were investigated using resistance measurements upon test gas exposures. The experiments were performed at fixed operating temperatures as well as on temperature modulated sensors. The films of WO₃ showed excellent sensitivity to H₂S gas and selectivity to other gases. The responses of temperature modulated sensors were further analyzed using mathematical transformations and pattern recognition methods whereby different gases could be distinguished.</p><p>We also present a sensing technique using conduction noise as a tool for detection of alcohol vapor. The relative change of the noise, due to the inserted alcohol, can be as large as two orders of magnitude. </p>

<p>The study presented in this thesis was motivated by the large uncertainty on the concentration of atmospheric electrical discharges to the global nitrogen budget. This uncertainty is partly due to the fact that information concerning the <i>NO</i><i>x</i> production efficiency of electrical discharges having current signatures similar to those of lightning flashes is not available in the literature. Another reason for this uncertainty is the fact that energy is used as a figure of merit in evaluating <i>NO</i><i>x</i> production from lightning flashes even though insufficient knowledge is available concerning the energy dissipation in lightning flashes. The third reason for this uncertainty is the lack of knowledge concerning the contribution of discharge processes other than return strokes to the <i>NO</i><i>x</i> production in the atmosphere. Lightning is not the only process in the atmosphere that causes ionisation and dissociation of atmospheric air. Cosmic rays continuously bombard the Earth with high energetic particles and radiation causing ionization and dissociation of air leading to the production of <i>NO</i><i>x</i> in the atmosphere. The work carried out in this thesis is an attempt to improve the current knowledge on the way in which these processes contribute to the global <i>NO</i><i>x</i> production. Experiments have been conducted in this thesis to estimate the <i>NO</i><i>x</i> production efficiency of streamer discharges, laser-induced plasma, laboratory sparks having current signatures similar to those of lightning flashes, alpha particle impact in air and finally with the lightning flash itself. The results obtained from laboratory electrical discharges show the following: (a) The <i>NO</i><i>x</i> production efficiency, in terms of energy, of positive streamer discharges is more or less similar to those of hot discharges. (b) The <i>NO</i><i>x</i> production efficiency of an electrical discharge depends not only on the energy but also on the peak and the shape of the current waveform. (c) The current signature is a better figure of merit in evaluating the <i>NO</i><i>x</i> yield of electrical discharges. As a part of this thesis work a direct measurement of <i>NO</i><i>x</i> generated by lightning flashes was conducted and the results show that slow discharge processes such as continuing currents could be the main source of <i>NO</i><i>x</i> in lightning flashes. Concerning <i>NO</i><i>x</i> production by other ionisation processes such as alpha particle impacts in the atmosphere, the data gathered in this thesis show that each ionising event in air leads to the creation of one <i>NO</i><i>x</i> molecule. In terms of energy the <i>NO</i><i>x</i> production efficiency of alpha particles is similar to that of electrical discharges. The theoretical studies conducted within this thesis indicate that M-components contribute more than the return strokes to the <i>NO</i><i>x</i> production. The calculations also show that the contribution to the global <i>NO</i><i>x</i> budget by return stroke is not as high as that assumed in the current literature.</p>