Institutskolloquium des IPP 2024
Wissenschaftliches Kolloquium des IPP in Garching und Greifswald mit Videoübertragung
In tokamaks, the three hydrogen isotopes have a different impact on physical processes in high temperature plasmas. They play a crucial role in everything related to the main ion mass itself and particularly the electron to ion mass ratio: collisions, gyro-radii, fast-ion slowing down, edge stability and more. The implications for how the main ion mass influences the plasma are discussed: from L- to H-mode, in the core and at the edge, from hydrogen and deuterium to deuterium-tritium and pure tritium plasmas. The most significant impact on confinement is often by indirect mechanisms, like the fast-ion content or the core-edge coupling. When taking these into account, observations can be explained which were previously not understood.
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The present-day expansion rate of the Universe, or Hubble constant (H0), is a fundamental parameter of cosmology. H0 sets the age of the Universe, its critical density, and sets the absolute scale for a wide array of cosmological observables that probe the laws of physics on extremely large scales and across time. However, the last decade has brought about an increasing disagreement between the values of H0 measured directly in today's Universe and the values of H0 determined indirectly from observations of the very early Universe. This 5-6 sigma disagreement has come to be known by the term "Hubble constant tension" and has become one of the most pressing issues to resolve in observational cosmology, with potential implications ranging from measurement systematics to altering the particle physics sector or even general relativity. Following a brief summary of the current situation in the "tension", I will first describe the observational setup that achieves the most accurate direct H0 measurement using an extragalactic distance ladder in which pulsating stars anchor type-Ia supernovae to geometrically measured distances. In turn, I will present the key developments that have more than halved the uncertainty on H0 over the last 8 years. Further major improvements towards a direct 1% measurement of H0 are coming within reach thanks to state-of-the-art observational facilities, such as the James Webb Space Telescope, the ELT, and future data releases of the ESA Gaia mission. With further improved systematics and accuracy, the distance ladder will put precision cosmology to the test, with potentially far-reaching consequences.
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The term chemical energy storage is used to describe the production of value-added chemicals from renewable electricity (RE) and abundant molecules (CO2, N2, etc.), aimed towards replacing fossil fuels as energy carriers. This approach requires improvement of the efficiency of existing technologies and development of new technologies that are compatible with properties of RE, such as intermittency. Plasma processes have the potential to enable unique reaction pathways that are not accessible through other conversion technologies, while simultaneously offering key advantages with regards to RE utilisation. To explore the role of low temperature plasmas in the energy transition as an emerging technology through experimental research, the plasma for gas conversion (P4G) group has been established at IPP in 2017. Initially, the emphasis of the research has been directed towards the conversion of CO2 into CO, resulting in technological developments that allowed for the achievement of competitive efficiencies when compared with electrolysis, demonstrating distinct advantages with regard to intermittent operation. More recently, the same methodology has been applied to other molecules, specifically microwave-plasma driven pyrolysis of methane (CH4) and dry reforming of methane (CO2+ CH4) towards hydrogen and syngas (CO+ H2) production. Furthermore, investigation of synthesis/decomposition of ammonia (NH3) for hydrogen storage is enabled by recently developed dielectric barrier discharges as plasma-catalyst hybrid reactors.
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