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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Tools for Comparing ICON EUV Data with Different Ground Based and Space-based Proxies

Das, Satyaki 19 June 2019 (has links)
The ionosphere is the part of Earth's upper atmosphere, from about 60 km to 1,000 km altitude and contains ionized particles and plasma. In this region at about 150 kilometers above the surface of the earth starts the F region and it extends up to 500 kilometers. The Ionosphere is filled with tenuous gases and is a mixture of neutral and charged particles. These winds do not follow any flow pattern and changes with season, the day's heating and cooling, and incoming bursts of radiation from the sun. In order to study the behavior of these ions and understand this complicated region, NASA has developed the ICON mission. The satellite consists of four major instruments which are IVM, EUV, FUV and MIGHTI. This work is concentrated on the EUV instrument which measures the ionized oxygen densities in the F region of the Ionosphere. Different atmospheric model including the IRI and TIEGCM, along with data obtained from ground-based observations and the ICON FUV instrument will be compared to the ionized oxygen profile, NmF2, HmF2 and various other parameters that are obtained from the EUV. The tool developed for ICON EUV instrument is tested using SSULI data and it agrees with the IRI and TIEGCM model. / Master of Science / The ionosphere is the part of Earth's upper atmosphere, from about 60 km to 1,000 km altitude and contains ionized particles and plasma. In this region at about 150 kilometers above the surface of the earth starts the F region and it extends up to 500 kilometers. The Ionosphere is filled with tenuous gases and is a mixture of neutral and charged particles. In order to study the behavior of these ions and understand this complicated region, NASA has developed the ICON mission. This work is concentrated on retrieving the data from EUV (Extreme Ultra Violet) instrument and compares the data with previously obtained data to check how consistent it is.
2

The Sun's Influence on the vertical structure of the ionospheres of Venus and Mars

Girazian, Zachary 13 February 2016 (has links)
The ionospheres of Venus and Mars are important components of the planet-space boundary that play a major role in atmospheric escape processes. Characterization of these regions reveals the physical processes that control them and provides a foundation for more detailed studies of chemistry, dynamics, and energetics. At both planets the ionospheres contain two layers: the main layer, which is formed by photoionization from extreme ultraviolet radiation (EUV, λ<120 nm), and the lower layer, which is formed by photoionization from soft X-rays (SXRs, λ<10 nm) and subsequent electron impact ionization. In this dissertation I investigate how the solar EUV and SXR irradiance controls these layers at Venus and Mars. First, I develop an empirical model of the ultraviolet (UV, λ<190 nm) solar spectrum as a function of F10.7, which is a commonly used proxy of the UV irradiance. I derive power-law relationships between F10.7 and the ionizing irradiance for five neutral species and show that the relationships are nonlinear. These relationships can be used to estimate the EUV irradiance when no solar spectrum measurements are available. Second, I show that the peak electron densities in the ionospheres of Venus and Mars are proportional to the square-root of the ionizing irradiance, which is in contrast to previous studies that have used F10.7 as their representation of the UV irradiance. This finding ameliorates a discrepancy between theory and observations and is in agreement with the prediction that dissociative recombination is the main ion loss mechanism near the ionospheric peaks at Venus and Mars. Third, using a numerical model and electron density profiles from Venus Express, I examine the behavior of the peak altitude, peak density, and morphology of the lower layer at Venus. I show that the peak altitudes and densities in the lower and main layers vary similarly with solar zenith angle (SZA). This implies that neutral and electron thermal gradients at these altitudes vary little with SZA. I also show that, compared to the main layer, the lower layer morphology and peak density varies more over the solar cycle due to the hardening of the solar spectrum.
3

Offline study of next generation EUV pellicle materials and performances : From experimental design to material characterization

Licheri, Susanna January 2019 (has links)
Lithography is the most crucial step in the semiconductor microfabrication workflow. Continuous features size shrinking co-occurs with the reduction of the exposure wavelength: a move from 193 nm light to extreme ultra-violet (EUV) at 13.5 nm is performed. The change poses a vast number of challenges that have been overcome in the past years. Among the others, the protection of the reticle front side from defects is crucial. Shielding can be achieved by means of EUV pellicles: large area (~150 cm2), freestanding, ultra-thin (~50 nm) membranes that prevent particles from landing on the reticle surface. Defects fall on the pellicle membrane, which is out-of-focus with respect to the reticle. During operation, the pellicle has to endure mechanical movements (&gt;100 m/s2) and withstand the EUV scanner environment. With increasing source power (resulting in temperatures &gt;500 ºC) structural and chemical integrity must be guaranteed. With multiple semiconductor manufacturers introducing EUV in HVM, an urgent need for a mass volume production-ready pellicle solution is present.In this thesis project, new generation pellicle materials are exposed to EUV light and gas atmosphere at BESSY II synchrotron beamline. The purpose is to investigate the performances of the new membrane samples in terms of the HVM production specifications. Two sets of 10x10 mm2 samples Type (A – B) with different core thickness are tested. Samples are characterized by using the following techniques: EUV transmittance and reflectance measurements, RBS, XPS, and FTIR. After exposure, all the samples undergo degradation. The main root causes are the atmosphere environment and the temperature. On the other hand, EUV light itself plays a marginal role in the process. The material etching mechanism must be further investigated through additional pellicle tests. This is a necessary step to make towards the high-volume manufacturing standards required for mass production. / Litografi är det mest avgörande steget i arbets flödet för halvledar mikrotillverkning. Kontinuerliga funktioner storlek krympande co-sker med minskning av exponeringen våglängd: en över gången från 193 nm ljus till extrem ultraviolett (EUV) vid 13.5 nm utförs. Förändringen innebär ett stort antal utmaningar som har övervunnits under de senaste åren. Bland de andra, är skyddet av rikt medel fram sidan från defekter avgörande. Avskärmning kan åstadkommas med hjälp av EUV-pellicles: stort område (~ 150 cm2), fristående, ultratunna (~ 50 nm) membran som hindrar partiklar från att landa på rikt medlet ytan. Defekter faller på denna tunna membranet, som är out-of-fokus med avseende på rikt medlet. Under drift har denna tunna att uthärda mekaniska rörelser (&gt; 100 m/s2) och motstå EUV skanner miljö. Med ökande käll effekt (vilket resulterar i temperaturer &gt; 500 º C) måste strukturell och kemisk integritet garanteras. Med flera halvledar tillverkare införa EUV i HVM, ett brådskande behov av en massa volym produktions klara denna tunna lösning är närvarande.I detta arbete, exponeras nya generationens denna tunna material för EUV ljus-och gasatmosfär på BESSY II Synchrotron beamline. Syftet är att undersöka prestandan hos de nya membranproverna i form av HVM-produktionsspecifikationer. Två uppsättningar av 10x10 mm2 prover typ (A – B) med olika kärna tjocklek testas. Proverna kännetecknas av att använda följande tekniker: EUV-transmission och reflektansmätningar, RBS, XPS och FTIR. Efter exponering genomgår alla prover nedbrytning. De viktigaste bakomliggande orsakerna är atmosfären miljö och temperaturen. Å andra sidan spelar EUV-ljuset självt en marginell roll i processen. Materialetsnings mekanismen måste undersökas ytterligare genom ytterligare denna tunna-tester. Detta är ett nödvändigt steg för att göra mot de höga volymer tillverknings standarder som krävs för Mass produktion.
4

Proxies to describe ionospheric variability and heating rates of the upper atmosphere: current progress

Unglaub, C., Jacobi, Christoph, Schmidtke, G., Nikutowski, B., Brunner, R. 09 October 2017 (has links)
An updated version of the EUV-TEC proxy, describing the total primary ionisation of the upper atmosphere, is calculated from satellite-borne EUV measurements. Regional number densities of the background model atmosphere consisting of four major constituents are taken from the NRLMSISE-00 climatology. Furthermore, a first estimate of a global thermospheric heating rate is calculated from the absorbed energy. For the calculations the Lambert-Beer law is used to describe the decrease of the radiation along their way through the atmosphere. The EUV-TEC proxy is compared against the global mean total electron content (TEC), obtained from vertical TEC maps derived from GPS data. Strong correlations between these indices are found on different time scales. Results show that the EUV-TEC proxy describes the ionospheric variability better than the conventional solar index F10.7, especially at short time scales of days to weeks.
5

Determination of Solar EUV Intensity and Ion Flux from Langmuir Probe Current Characteristics

Holmberg, Madeleine January 2010 (has links)
<p>This report presents a model to determine the solar Extreme UltraViolet (EUV) intensity and the ion flux in the vicinity of Saturn, by using measurements from the Langmuir probe, a plasma investigation instrument, of the Cassini satellite. The model is based on in situ measurements and does therefore provide an improved estimation of the wanted parameters compared to previously used calculations based only on the EUV flux measured near Earth. The solar EUV and ion flux were determined by analysing and processing the current measurements from the Cassini Langmuir probe in several steps. Initially the time intervals where the measured current were expected to be due only to the photoelectron current was extracted. The photoelectron current is the part of the measured probe current that is only due to electrons ejected from the probe by photons coming from the Sun. The measurements showed a periodic behaviour which was concluded to be due to the attitude of the satellite. This interfering effect was corrected for and the data was then plotted against an EUV index, estimated from a traditionally used proxy of the EUV flux near Earth; the F10.7 solar radio flux index. In agreement with the theory of the photoelectric effect a linear relationship between the EUV flux and the photoelectron current <em>m<sub>ph</sub></em> was expected. A least square linear fit to the extracted photoelectron current data provided the relation, for the Langmuir probe on Cassini, in the form of the equation <em>m<sub>ph</sub></em>=0.1842<em>EUV</em>+0.2405, where <em>m<sub>ph</sub></em> is the photoelectron current in nA and <em>EUV</em> is the EUV index in W/Hzm^2. The derived equation is the result of the study, showing how to estimate the solar EUV flux using the Langmuir probe current measurements. This result was used to derive the other wanted parameter, the ion flux. The derivation was done by calculating the photoelectron current <em>m<sub>ph</sub> </em>at all time and subtracting the result from the total current. The retrieved difference gives the magnitude of the ion current for every measurement.</p>
6

Compact Liquid-Jet X-Ray Sources

Hemberg, Oscar January 2004 (has links)
This thesis describes the development, characterization andoptimization of compact, high-brightness, liquid-jet-targetx-ray sources. Two different source types have been developedfor different wavelength regions and applications. A laser-plasma source for generating soft x-ray andextreme-ultraviolet radiation has been further developed forsoft x-ray microscopy and extreme-ultraviolet lithography. Thiswork focused on improved target stability, increased conversionefficiency and decreased debris production. For x-raymicroscopy applications using carbon-containingliquid-jetdroplet targets, the droplet stability has beeninvestigated and a method for source stabilization introduced.This source has also been optimized in terms of flux per debriswith respect to target material and size. Forextreme-ultraviolet lithography applications, aliquid-xenon-jet-target laser-plasma source system has beengreatly improved, especially in terms of stability andconversion efficiency. This source has also been characterizedin terms of, e.g., source size, angular distribution, andrepetition-rate capability. For extremeultraviolet lithography,the possible use of tin as a target material has also beenstudied and conversion efficiency and debris measurementsperformed. A new anode concept for electron-impact hard x-ray sourcesbased on high-speed liquidmetal jets has been introduced.Initial calculations show that this new target concept couldpotentially allow more than a hundred-fold increase in sourcebrightness compared to existing state-of-the-art technology. Alow-power, proof-of-principle, experiment has been performed,verifying the basic source concept. Scaling tohigh-poweroperation is discussed and appears plausible. A main obstaclefor high-power operation, the generation of a microscopichigh-speed jet in vacuum, is investigated usingdynamic-similarity experiments and shown to be feasible.Finally, initial medium-power experiments, approaching currentstate-of-the-art sources in terms of brightness, have beenperformed.
7

Determination of Solar EUV Intensity and Ion Flux from Langmuir Probe Current Characteristics

Holmberg, Madeleine January 2010 (has links)
This report presents a model to determine the solar Extreme UltraViolet (EUV) intensity and the ion flux in the vicinity of Saturn, by using measurements from the Langmuir probe, a plasma investigation instrument, of the Cassini satellite. The model is based on in situ measurements and does therefore provide an improved estimation of the wanted parameters compared to previously used calculations based only on the EUV flux measured near Earth. The solar EUV and ion flux were determined by analysing and processing the current measurements from the Cassini Langmuir probe in several steps. Initially the time intervals where the measured current were expected to be due only to the photoelectron current was extracted. The photoelectron current is the part of the measured probe current that is only due to electrons ejected from the probe by photons coming from the Sun. The measurements showed a periodic behaviour which was concluded to be due to the attitude of the satellite. This interfering effect was corrected for and the data was then plotted against an EUV index, estimated from a traditionally used proxy of the EUV flux near Earth; the F10.7 solar radio flux index. In agreement with the theory of the photoelectric effect a linear relationship between the EUV flux and the photoelectron current mph was expected. A least square linear fit to the extracted photoelectron current data provided the relation, for the Langmuir probe on Cassini, in the form of the equation mph=0.1842EUV+0.2405, where mph is the photoelectron current in nA and EUV is the EUV index in W/Hzm^2. The derived equation is the result of the study, showing how to estimate the solar EUV flux using the Langmuir probe current measurements. This result was used to derive the other wanted parameter, the ion flux. The derivation was done by calculating the photoelectron current mph at all time and subtracting the result from the total current. The retrieved difference gives the magnitude of the ion current for every measurement.
8

Compact Liquid-Jet X-Ray Sources

Hemberg, Oscar January 2004 (has links)
<p>This thesis describes the development, characterization andoptimization of compact, high-brightness, liquid-jet-targetx-ray sources. Two different source types have been developedfor different wavelength regions and applications.</p><p>A laser-plasma source for generating soft x-ray andextreme-ultraviolet radiation has been further developed forsoft x-ray microscopy and extreme-ultraviolet lithography. Thiswork focused on improved target stability, increased conversionefficiency and decreased debris production. For x-raymicroscopy applications using carbon-containingliquid-jetdroplet targets, the droplet stability has beeninvestigated and a method for source stabilization introduced.This source has also been optimized in terms of flux per debriswith respect to target material and size. Forextreme-ultraviolet lithography applications, aliquid-xenon-jet-target laser-plasma source system has beengreatly improved, especially in terms of stability andconversion efficiency. This source has also been characterizedin terms of, e.g., source size, angular distribution, andrepetition-rate capability. For extremeultraviolet lithography,the possible use of tin as a target material has also beenstudied and conversion efficiency and debris measurementsperformed.</p><p>A new anode concept for electron-impact hard x-ray sourcesbased on high-speed liquidmetal jets has been introduced.Initial calculations show that this new target concept couldpotentially allow more than a hundred-fold increase in sourcebrightness compared to existing state-of-the-art technology. Alow-power, proof-of-principle, experiment has been performed,verifying the basic source concept. Scaling tohigh-poweroperation is discussed and appears plausible. A main obstaclefor high-power operation, the generation of a microscopichigh-speed jet in vacuum, is investigated usingdynamic-similarity experiments and shown to be feasible.Finally, initial medium-power experiments, approaching currentstate-of-the-art sources in terms of brightness, have beenperformed.</p>
9

Solar activity and ionospheric response as seen from combined SolACES and SDO-EVE solar EUV spectra

Jacobi, Christoph, Nikutowski, B., Hein, J., Unglaub, C., Erhardt, Ch., Brunner, R., Schmidtke, G. 10 October 2017 (has links)
Ionospheric response to solar EUV variability during late 2012 through mid 2013 is shown by the EUV-TEC proxy based on combined SolACES and SDO/EVE solar spectra. The results are compared with global TEC analyses. We found that EUV-TEC describes TEC variability better than the conventional F107 index, especially during periods of strong solar flare activity.
10

Extending F10.7's Time Resolution to Capture Solar Flare Phenomena

Acebal, Ariel O. 01 December 2008 (has links)
Solar ultraviolet (UV) radiation ionizes the neutral components in the atmosphere, which is partly responsible for the formation of the ionosphere, and contributes to heating of the atmosphere. Solar flares change the solar spectrum at times by several orders of magnitude. These changes modify the Earth's upper atmosphere, causing problems to communication systems and space operations, such as increased satellite drag. Unfortunately, solar UV measurements are limited since they can only be observed with space-based sensors. In order to work around this limitation, the solar radio emissions at a wavelength of 10.7 cm have been used as a proxy for the solar UV radiation. These measurements, known as the F10.7 index, are a snapshot of the solar activity at the time they are taken and do not capture the changes that occur throughout the day, such as flares. In order to capture this daily variation, we used 1-second cadence solar radio data and compared it to solar UV measurements taken once per orbit by the TIMED satellite. We found significant correlations between some radio frequencies and different UV wavelengths during quiet times. These correlations changed in terms of radio frequency and UV wavelength during solar flares.

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