75 research outputs found
Ion beam intensity and phase space measurement techniques for ion sources
No full textIon sources produce beams used in accelerators and other applications. Both development and use of ion sources need beam diagnostics to probe the plasma processes and beam formation for optimization purposes and to produce beam parameters needed for transport tuning. These diagnostics include beam intensity measurements usually carried out with Faraday cups or inductive pickups, magnetic separation, profile measurements with scintillation screens and wires, and phase space measurements with different types of emittance scanners.peerReviewe
Development and use of computational tools for modelling negative hydrogen ion source extraction systems
No full textunknown accessibilityei tietoa saavutettavuudest
Ionilähdelaitteiston kehitys säteilytystestausta varten
No full textunknown accessibilityei tietoa saavutettavuudest
Deviation of H− beam extraction simulation model
No full textNegative hydrogen ion source extraction system development is dependent on accurate and fast simulation methods for modelling the behaviour of ion and electron beams. Traditionally this type of work has been done using ray-tracing extraction codes, such as IBSimu. The plasma extraction model in IBSimu has been observed to under-estimate the charge density near the plasma sheath, leading to incorrect prediction of the current at which the system produces the optimum emittance. It is suspected that this deviation results from the approximations made by the model, neglecting the magnetic field and collisional effects near the sheath region. Results and comparisons to simulations are presented for three ion sources, for which two show similar variation and one is more accurately modelled. Conclusions with the currently available data can not be made and therefore further experimental and simulation campaigns to study the effect are suggested.peerReviewe
Agenda Setting in a Sociological Perspective
No full textIn this paper the author attempts to put forth a new theoretical explanation of how the phenomenon known as “agenda setting” functions. The paper begins with a summary of current knowledge about this phenomenon, including the two theoretical explanations given to date: the psychological explanation and the explanation based on trust in the information media
Photoelectron emission induced by low temperature hydrogen plasmas
No full textExperimental results of low temperature hydrogen plasma induced photoelectron emission measurements comparing two different plasma heating methods are summarized. By exposing the samples to the vacuum ultraviolet radiation of a filament-driven multi-cusp arc discharge ion source and a 2.45 GHz microwave-driven ion source, it has been measured that the total photoelectron emission from various metal surfaces is on the order of 1 A per kW of plasma heating power, which can be increased by a factor of 2–3.5 with a thin layer of alkali metal. The possible effects of the photoelectrons on the plasma sheath structure are studied with a 1D collisionless model extended to include the contribution of photoelectron emission from the surface.peerReviewe
Twilight and its readership - an analysis of the phenomenon of Twilight (Twilight Saga author S. Meyer)
No full textVe své diplomové práci jsem se zaměřila na analýzu čtenářů Twilight ságy. Sága svým charakterem spadá do populární kultury.Empirická část práce je založena na metodách obsahové analýzy a polostrukturovaných rozhovorů. Obsahová analýza byla provedena na internetovém portálu ságy Twilight. Dále jsem zrealizovala polostrukturované rozhovory s dvanácti ženami, které se zaměřovaly na čtení ságy Twilight. Twilight sága má velkou základnu fanoušků, která se skládá z relativně mladých lidí, zejména dívek. Twilight saga dosáhla popularity v souvislosti s žánrovým zařazením do romantické literatury a romány pro dospělé.Katedra sociologieObhájenoI have focused on an analysis of readers of Twilight saga in my diploma work. According to its characteristics this saga is numbered among pop culture.
Empiric part of this work is founded on methods of content analysis and semi-structured interviews. Content analysis was made on Internet portal of Twilight saga. I realized semi-structures interviews with twelve women reading Twilight.
Twilight saga has large fan base relatively which consists of low age-class girls especially. Twilight saga has reached the popularity by the correspondence of genre convention of romantic literature and novels for adults
Low-threshold facilities as a tool for integration of youths at risk
No full textBachelor's thesis concentrates on low threshold facilties as a means of integration of youth at risk to society. The author defines the terms youth and youth at risk, concentrates on integration of youth to society and defines roma youth as a specific group inside our society with specific needs.She describes the history of these facilities in Czech republic, similiar institutions from abroad and their experience, the definition and principles of institutions that are low threshold and the legislative basis in the system of social services. In the practical part of this thesis, the author describes similarities and differences between opinions on the functionality of low threshold facilites among their workers and clients. She concentrates on two concrete clubs where she realizes a case study. The main differences are shown by ethnic divergences of the target group of clubs. In one of the clubs there are only Roma. One of the differences were favorite activities of clients in the club. For Roma's youth, it was mainly dancing, playing instruments, as well as tutoring. For the majority youth then spending time on computer. Likewise, the main reason why Roma youth visited club, was for tutoring.For the representative of the majority population, it was boring. Workers differed in opinion on the main objectives..
Spectroscopic method to study low charge state ion and cold electron population in ECRIS plasma
No full textThe results of optical emission spectroscopy experiments probing the cold electron population of a 14 GHz Electron Cyclotron Resonance Ion Source (ECRIS) are reported. The study has been conducted with a high resolution spectrometer and data acquisition setup developed specifically for the diagnostics of weak emission line characteristic to ECRIS plasmas. The optical emission lines of low charge state ions and neutral atoms of neon have been measured and analyzed with the line-ratio method. The aforementioned electron population temperature of the cold electron population (Te < 100 eV) is determined for Maxwell-Boltzmann and Druyvesteyn energy distributions to demonstrate the applicability of the method. The temperature was found to change significantly when the extraction voltage of the ion source is turned on/off. In the case of the Maxwellian distribution, the temperature of the cold electron population is 20 ± 10 eV when the extraction voltage is off and 40 ± 10 eV when it is on. The optical emission measurements revealed that the extraction voltage also affects both neutral and ion densities. Based on the rate coefficient analysis with the aforementioned temperatures, switching the extraction voltage off decreases the rate coefficient of neutral to 1+ ionization to 42% and 1+ to 2+ ionization to 24% of the original. This suggests that switching the extraction voltage on favors ionization to charge states ≥2+ and, thus, the charge state distributions of ECRIS plasmas are probably different with the extraction voltage on/off. It is therefore concluded that diagnostics results of ECRIS plasmas obtained without the extraction voltage are not depicting the plasma conditions in normal ECRIS operation.peerReviewe
Status of new 18 GHz ECRIS HIISI
No full textA new 18 GHz ECR ion source HIISI is under commissioning at the Accelerator Laboratory at the University of Jyväskylä (JYFL). The main purpose of HIISI is to produce high-energy beam cocktails, e.g. Xe44+, for radiation effects testing of electronics with the K130 cyclotron. The initial commissioning results in 18+14 GHz operation with oxygen, argon and xenon are reported. The beam currents are compared to those produced by reference ion sources (JYFL 14 GHz ECRIS, GTS and SuSI). At the moment (October 2017) 560 µA of O6+ and 310 µA of Ar13+, for example, have been reached with HIISI at 2.3 kW total power.peerReviewe
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