We have used Cassini measurements of electron density from Saturn's magnetosphere to search for a plasma tail behind the moon Titan. Such a plasma tail would consist of plasma that manage to escape Titan's gravitational pull and leave Titan's ionosphere to contribute to the plasma distribution in the Saturn system. The Cassini spacecraft was in orbit around Saturn for 13 years and performed 127 close flybys of Titan as well as many passes through Titan's orbit within the planets plasma-filled magnetosphere. We have used measurements of electron density from the Langmuir probe instrument, built by the Swedish Institute of Space Physics in Uppsala to search for such a tail. The data was analyzed in terms of looking at the spatial distribution of plasma around Titan and Saturn by examining the plasma density in Titan’s orbit in comparison to the rest of system, as well as comparisons of plasma density in front of Titan and behind Titan. The analysis provided no evidence of an extended plasma tail or torus.

It is demonstrated that control software updates for the magnetic confinement fusion experiment EXTRAP T2R can enable novel studies of plasma physics. Specifically, it is shown that the boundary radial magnetic field in T2R can be maintained at finite levels by feedback. System identification methods to measure in situ magnetohydrodynamic stability are developed and applied with encouraging results. Subsequently, results from closed-loop identification are used for retooling the T2R regulator. The track of research here pursued could possibly be relevant for future thermonuclear fusion reactors. / QC 20100518

The reversed-field pinch (RFP) is a magnetic confinement fusion (MCF) device. It exhibits a variety of unstable modes that can be explained by magnetohydrodynamic (MHD) theory. A particular unstable mode that is treated in this work is the resistive wall mode (RWM), which occurs when the shell of the device has finite conductivity. Application of control engineering tools appears to be important for the operation of the RFP. A model-based control approach is pursued to stabilize the RWM. The approach consists of experimental modeling of RWM using a class of system identification techniques. The obtained model is then used as a basis for Mode Predictive Control (MPC) design. The MPC employs the model to build predictions of the system and find a control input that optimizes the predicted behavior of the system. It is shown that the formulation of the MPC allows the user to incorporate several physics relevant phenomena aside from RWMs. The results are encouraging for MPC to be a useful tool for future MCF operation. / <p>QC 20150605</p>

Ground-based and in-situ observations of the aurora demonstrate an extreme richness in fine structure, with spatial scales down to tens of metres and time variations occurring on a fraction of a second. To further our understanding of the aurora, it is esssential to understand the mechanisms responsible for the small-scale structuring, since this is an intrinsic property of the auroral plasma. Still many questions about dynamics and structuring of aurora on small scales remain unanswered. In this thesis the low-light optical instrument ASK (Auroral Structure and Kinetics) is used to image small-scale structures in the aurora at very high spatial and temporal resolution. ASK is a multi-spectral instrument, imaging the aurora in three selected emission lines simultaneously. This provides information on the energy of the precipitating electrons. The SIF (Spectrographic Imaging Facility) instrument has been used in conjunction with ASK, to give a more complete picture of the spectral characteristics of the aurora, and to determine the contamination of the emission lines by other emissions. Data from ASK and SIF is used to study the relation between the morphology and dynamics of small-scale structures in the aurora and the energy of the precipitating electrons. By comparing electron density profiles provided by EISCAT (European Incoherent SCATter) measurements with modeling results, information on characteristic energy and energy flux of the precipitating electrons can be obtained. One of the ASK channels is imaging a metastable O+ emission, which has a lifetime of 5 s. By tracing the afterglow in this channel optically a direct measure of the E × B drift and thus of the local ionospheric electric fields is provided. / QC 20101109

This research project centres on advancing data analysis techniques using the Magnetic Proton Recoil Upgrade Neutron Spectrometer (MPRu) for neutron emission spectroscopy during the deuterium tritium experimental campaign (DTE2) at the Joint European Torus (JET). The study aimed to address three pivotal questions, each with implications for optimizing data accuracy, quality, and utility. The first question focused on determining the optimal short-gate settings for the MPRu. Extensive analysis revealed that conventional metrics, such as the Full Width at Half Maximum (FWHM) and spatial positioning of the proton island, were inadequate for precise short-gate configuration. It was concluded that the existing settings, characterized by a +30 offset from the signal onset, proved to be sufficient. This choice was driven by the necessity to distinguish between escape events, shadow events, and the proton island when plotting signals in a 2-D graph, proving effective across all detector channels. Accurate proton counting hinges on the precise assessment of protons within the escape event region, a task complicated by the interference of background events. This study investigated the point at which the accuracy of the escape event region diminishes by comparing the relative count with simulated data. Results demonstrated that higher-energy signals, positioned farther from the background-concentrated origin, yielded more accurate counts. Additionally, a correction factor based on simulated data is suggested for the unaccounted proton signals. The third question explored was the feasibility of modelling the proton island's location based on proton energy and the characteristics of the phoswhich scintillator detector. While initially promising, the model showed of limited use. The biggest limiting factor was the inconsistencies that originate in the detector themselves. It is not possible to account for the unique characteristics of each single detector, using the methods developed here. This could be changed if the individual characteristics of the detectors are taken into account in a future analysis.

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves [328]-333).

This thesis investigates the performance and improves a double color interferometer setup, absolutely calibrates a line radiation Balmer H-alpha measurement setup, and uses measurements from both setups to estimate the particle confinement time of a plasma. The double colour interferometer at the magnetic confinement plasma device EXTRAP T2R measures the line integrated electron density of the plasma. Electron density is an important parameter in fusion plasma diagnostics but the interferometer at EXTRAP T2R have had several problems. The interferometer setup was changed as follows: A piezo phase shifter was added, the beam expander was adjusted with the help of thermal image plates, and the electronics setup was rewired to remove interferences. The setup for Balmer H-alpha line radiation measurements was calibrated and characterized. The particle confinement time was estimated using Abel inversion to produce radial profiles of electron density, electron temperature and H-alpha irradiance. The interferometer upgrades did not solve all the problems, but the electron density measurements are now reliable up to around 10 – 20 ms. Since the interferometer only has one channel the electron density profile could not be determined reliably. However, the particle confinement time was estimated for two possible electron density profiles and the results agree with previous studies. / Fusionsvetenskap strävar efter att producera en ny, effektiv energikälla. I och med den ökande energikonsumtionen får fusionsvetenskap en allt viktigare roll i samhället. Kärnfusion har stor potential som energikälla, men att utvinna dess energi kommer med lika stora tekniska utmaningar. I det här projektet tacklas en av dessa utmaningar; att mäta elektrontätheten och joniseringshastigheten i ett plasma. Detta utfördes på EXTRAP T2R, ett magnetiskt inneslutningssystem för plasma på Alfvén laboratoriet, Kungliga Tekniska högskolan, Stockholm. Projektet behandlar två olika mätinstrument: En interferometer som mäter elektrontätheten i plasmat och en H-alphaexperimentuppställning som mäter joniseringshastigheten i plasmat. Interferometern har uppgraderats och justerats för att ge mer tillförlitliga mätningar. Den behöver förbättras ytterligare men kan ger nu tillförlitliga täthetsmätningar i början av plasma-skott. H$\alpha$-experimentuppställningen har karakteriserats och kalibrerats. Genom att mäta elektrontätheten och joniseringshastigheten kan partikelinneslutningstiden uppskattas. Partikelinneslutningstiden är den genomsnittliga tiden innan en partikel lämnar plasmat via en av många processer. Denna uppskattning baserades på två möjliga täthetsprofiler i plasmat eftersom en fullständig mätning skulle kräva flera interferometrar. Trots detta så stämmer uppskattningen väl överens med tidigare studier.

Thesis--University of Michigan, 1971.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1994. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 233-244).

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