Increasing oil prices and concerns about global warming have reinforced the interest in biofuels for domestic and district heating, most commonly through combustion of solid biomass like wood logs, hog fuel and pellets. Combustion at non-optimal conditions can, however, lead to substantial emissions of noxious compounds like unburned hydrocarbons, carbon monoxide, and nitrogen oxides as well as the generation of soot. Depending on the rate of combustion more or less air is needed per unit time to completely oxidize the fuel; deficiency of air leading to emissions of unburned matter and too much of excess air to slow combustion kinetics and emissions of mainly carbon monoxide. The rate of combustion is influenced by parameters like fuel quality – moisture and ash content etc. – and in what phase the combustion takes place (in the gas phase through combustion of evaporated substances or on the surface of char coal particles), none of which is constant over time. The key to boiler operation, both from an environmental as well as a power to fuel economy point of view, is thus the careful adjustment of the air supply throughout the combustion process. So far, no control schemes have been applied to small-scale combustors, though, mainly due to the lack of cheap and simple means to measure basic flue gas parameters like oxygen, total hydrocarbon, and carbon monoxide concentrations. This thesis reports about investigations on and characterization of silicon carbide (SiC) based Metal Insulator Semiconductor (MIS) field effect gas sensors regarding their utility in emissions monitoring and combustion control applications as well as the final development of a sensor based control system for wood fired domestic heating systems. From the main sensitivity profiles of such sensor devices, with platinum (Pt) and iridium (Ir) as the catalytic metal contacts (providing the gas sensing ability), towards some typical flue gas constituents as well as ammonia (NH3), a system comprising four individual sensors operated at different temperatures was developed, which through the application of Partial Least Squares (PLS) regression, showed good performance regarding simultaneous monitoring of propene (a model hydrocarbon) and ammonia concentrations in synthetic flue gases of varying content. The sensitivity to CO was, however, negligible. The sensor system also performed well regarding ammonia slip monitoring when tested in real flue gases in a 5.6 MW boiler running SNCR (Selective Non-Catalytic reduction of nitrogen oxides with ammonia). When applied to a 200 kW wood pellet fuelled boiler a similar sensor system was, however, not able to follow the flue gas hydrocarbon concentration in all encountered situations. A PCA (Principal Components Analysis) based scheme for the manipulation of sensor and flue gas temperature data, enabling monitoring of the state of combustion (deficiency or too much of excess air), was however possible to develop. The discrepancy between laboratory and field test results was suspected and later on shown to depend on the larger variation in CO and oxygen concentrations in the flue gases as compared to the laboratory tests. Detailed studies of the CO response characteristics for Pt gate MISiC sensors revealed a highly non-linear sensitivity towards CO, a large response only encountered at high CO/O2 ratios or low temperatures. The response exhibits a sharp switch between a small and a large value when crossing a certain CO/O2 ratio at constant operating temperature, correlated to the transition from an oxygen dominated to an almost fully CO covered Pt surface, originating from the difference in adsorption kinetics between CO and O2. Indications were also given pointing towards an increased sensitivity to background hydrogen as being the mediator of at least part of the CO response. Some general characteristics regarding the response mechanism of field effect sensors with differently structured metal contacts were also indicated. The CO response mechanism of Pt metal MISiC sensors could also be utilized in developing a combustion control system based on two sensors and a thermocouple, which when tested in a 40 kW wood fired boiler exhibited a good performance for fuels with extremely low to normal moisture content, substantially decreasing emissions of unburned matter.

<p>The world’s largest particle accelerator, Large Hadron Collider, located at CERN outside Geneva performed its first proton-proton collisions in November 2009. One of the four main experiments is LHCb, studying rare decays of hadrons containing the beauty quark. An essential part of the particle identification in LHCb is made by the two Ring Imaging Cherenkov detectors. These detectors use pixel Hybrid Photon Detectors for detection and imaging of Cherenkov rings. This paper reports on measurements carried out on the Hybrid Photon Detectors, including a discussion of the results. In particular, ageing effect and image stability are studied. A fraction of the photon detectors show a degradation in performance within these fields.</p> / <p>Världens största partikelaccelerator, LHC, belägen vid CERN utanför Genève utförde sina första proton-proton kollisioner i November 2009. Ett av de fyra huvudexperimenten är LHCb, som studerar sällsynta sönderfall av hadroner innehållande <em>b</em> kvarken. En viktig del av partikelidentifikationen i LHCb görs av de två RICH detektorerna. Dessa använder hybrida fotondetektorer för detektering och avbildning av Cherenkov ringar. Denna rapport handlar om mätningar utförda på dessa hybrida fotondetektorer, med en diskussion av resultaten. I synnerhet studeras åldringseffekter och bildstabilitet. En andel av fotondetektorerna visar en degradering i prestanda inom dessa områden.</p>

<p>The topic of this thesis concerns the LHC, the next large particle accelerator at CERN which will start operating in 2007. Being based on superconductivity, the LHC needs to operate at very low temperatures, which makes great demands on the cryogenic system of the accelerator. To cope with the heat loads induced by the particle beam, a beam screen cooled with forced flow of supercritical helium is used.</p><p>There is an interest in upgrading the energy and luminosity of the LHC in the future and this would require a higher heat load to be extracted by the beam screen cooling system. The objective of this thesis is to quantify different ways to upgrade this system by mainly studying the effects of different pressure and temperatures levels as well as a different cooling medium, neon.</p><p>For this a numerical program which simulates one-dimensional pipe flow was constructed. The frictional forces were accounted for by the empirical concept of friction factor. For the fluid properties, software using empirically made correlations was used. To validate the numerical program, a comparison with previous experimental work was done. The agreement with experimental data was good for certain flow configurations, worse for others. From this it was concluded that further comparisons with experimental data must be made in order to tell the accuracy of the mathematical model and the correlations for fluid properties used.</p><p>When using supercritical helium, thermo-hydraulic instabilities may arise in the cooling loop. It was of special interest to see how well a numerical program could simulate and predict this phenomenon. It was found that the numerical program did not function for such unstable conditions; in fact it was much more sensitive than what reality is.</p><p>For the beam screen cooling system we conclude that to cope with the increased heat loads of future upgrades, an increase in pressure level is needed regardless if the coolant remains helium, or is changed to neon. Increasing the pressure level also makes that the problems with thermo-hydraulic instabilities can be avoided. Of the two coolants, helium gave the best heat extraction capacity. Unlike neon, it is also possible to keep the present temperature level when using helium.</p>

No description available.

The topic of this thesis concerns the LHC, the next large particle accelerator at CERN which will start operating in 2007. Being based on superconductivity, the LHC needs to operate at very low temperatures, which makes great demands on the cryogenic system of the accelerator. To cope with the heat loads induced by the particle beam, a beam screen cooled with forced flow of supercritical helium is used. There is an interest in upgrading the energy and luminosity of the LHC in the future and this would require a higher heat load to be extracted by the beam screen cooling system. The objective of this thesis is to quantify different ways to upgrade this system by mainly studying the effects of different pressure and temperatures levels as well as a different cooling medium, neon. For this a numerical program which simulates one-dimensional pipe flow was constructed. The frictional forces were accounted for by the empirical concept of friction factor. For the fluid properties, software using empirically made correlations was used. To validate the numerical program, a comparison with previous experimental work was done. The agreement with experimental data was good for certain flow configurations, worse for others. From this it was concluded that further comparisons with experimental data must be made in order to tell the accuracy of the mathematical model and the correlations for fluid properties used. When using supercritical helium, thermo-hydraulic instabilities may arise in the cooling loop. It was of special interest to see how well a numerical program could simulate and predict this phenomenon. It was found that the numerical program did not function for such unstable conditions; in fact it was much more sensitive than what reality is. For the beam screen cooling system we conclude that to cope with the increased heat loads of future upgrades, an increase in pressure level is needed regardless if the coolant remains helium, or is changed to neon. Increasing the pressure level also makes that the problems with thermo-hydraulic instabilities can be avoided. Of the two coolants, helium gave the best heat extraction capacity. Unlike neon, it is also possible to keep the present temperature level when using helium.

XMM-Newton is a X-ray telescope launched december 1999, by the European Space Agency, ESA. On board XMM-Newton are two EPIC-MOS X-ray detectors. The detectors are build by Charged Coupled Devices (CCDs), of Metal Oxide Semi-conductor type. The EPIC-MOS cameras have four science operating modes. This project aims to evaluate the calibration for one of these four modes, the timing mode. The evaluation is divided into two parts. The first part is the evaluation of the flux calibration, performed by analysing various observation made in timing mode. The second part is the evaluation of timing properties by performing timing analysis of XMM-Newton observations of the Crab nebula compared to observations made in the radio wavelengths.

Wind power capacity is currently growing fast around the world. At the same time different forms of life cycle analysis are becoming common for measuring the environmental impact of wind energy systems. This thesis identifies several problems with current methods for assessing the environmental impact of wind energy and suggests improvements that will make these assessments more robust. The use of the exergy concept combined with life cycle analysis has been proposed by several researchers over the years. One method that has been described theoretically is life cycle exergy analysis (LCEA). In this thesis, the method of LCEA is evaluated and further developed from earlier theoretical definitions. Both benefits and drawbacks with using exergy based life cycle analysis are found. For some applications the use of exergy can solve many of the issues with current life cycle analysis methods, while other problems still remain. The method of life cycle exergy analysis is used to evaluate the sustainability of an existing wind turbine. The wind turbine assessed appears to be sustainable in the way that it gives back many times more exergy than it uses during the life cycle.

Porphyrins consist of twenty-atom rings containing four nitrogen atoms and can be used as sensor to detect odours and gases. This thesis investigates whether or not porphyrins can be used as functional materials on grid gate devices.  Drops of PVC embedded porphyrins were deposited on the surface of a grid gate which is a Metal Oxide Semiconductor (MOS) capacitor. In order to detect the gas sensing properties of the porphyrins a light addressable method called Scanning Light Pulse Technique (SLPT) has been used. Drops of porphyrins were deposited with a stretched capillary tube (1 mm diameter). The MOS capacitor has been exposed to nitrogen atmosphere as reference environment, while the target gases were carbon monoxide (100 ppm) and ammonia (500 ppm). The result from the eight porphyrins is that one of them [Pt(II) TPP] has a response for both gases, ammonia induces a change in both the work function and surface resistance, while the carbon monoxide induces only a change in the surface resistance.

The world’s largest particle accelerator, Large Hadron Collider, located at CERN outside Geneva performed its first proton-proton collisions in November 2009. One of the four main experiments is LHCb, studying rare decays of hadrons containing the beauty quark. An essential part of the particle identification in LHCb is made by the two Ring Imaging Cherenkov detectors. These detectors use pixel Hybrid Photon Detectors for detection and imaging of Cherenkov rings. This paper reports on measurements carried out on the Hybrid Photon Detectors, including a discussion of the results. In particular, ageing effect and image stability are studied. A fraction of the photon detectors show a degradation in performance within these fields. / Världens största partikelaccelerator, LHC, belägen vid CERN utanför Genève utförde sina första proton-proton kollisioner i November 2009. Ett av de fyra huvudexperimenten är LHCb, som studerar sällsynta sönderfall av hadroner innehållande b kvarken. En viktig del av partikelidentifikationen i LHCb görs av de två RICH detektorerna. Dessa använder hybrida fotondetektorer för detektering och avbildning av Cherenkov ringar. Denna rapport handlar om mätningar utförda på dessa hybrida fotondetektorer, med en diskussion av resultaten. I synnerhet studeras åldringseffekter och bildstabilitet. En andel av fotondetektorerna visar en degradering i prestanda inom dessa områden.

<p>XMM-Newton is a X-ray telescope launched december 1999, by the European Space Agency, ESA. On board XMM-Newton are two EPIC-MOS X-ray detectors. The detectors are build by Charged Coupled Devices (CCDs), of Metal Oxide Semi-conductor type. The EPIC-MOS cameras have four science operating modes. This project aims to evaluate the calibration for one of these four modes, the timing mode.</p><p>The evaluation is divided into two parts. The first part is the evaluation of the flux calibration, performed by analysing various observation made in timing mode. The second part is the evaluation of timing properties by performing timing analysis of XMM-Newton observations of the Crab nebula compared to observations made in the radio wavelengths.</p>