Institutskolloquium des IPP 2021

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Realistic simulations of electromagnetic turbulence are of crucial importance to understand and predict behavior of burning plasmas before they become experimentally available. Burning plasmas are complex systems with multiple spatial and temporal scales. Electromagnetic turbulence is ubiquitous in such plasmas. It is the basic component of the ``scenery'' involving the fast-particle dynamics, the global Magneto-Hydrodynamical and Alfvenic activity, zonal flows, and transport. The saturation of the electromagnetic turbulence is a consequence of a complex interplay between these components. A single numerical first-principle framework, based on the global gyrokinetic electromagnetic formulation and including self-consistently all parts of the problem, is needed. An approach to this task based on the gyrokinetic particle-in-cell codes will be addressed in the presentation. Electromagnetic simulations are known to be very challenging for the gyrokinetic particle-in-cell codes because of the numerical stability issues related to the cancellation problem [1]. Such simulations are also very time consuming since the fast electron dynamics has to be resolved. We address the numerical stability problem using the pullback mitigation technique [2,3] for the cancellation problem. Very long simulation times normally required when the electron dynamics is resolved are substantially accelerated deploying GPUs. In our talk, we will discuss the challenges and describe results of the global gyrokinetic modelling in the electromagnetic regime. [1] Physics of Plasmas, 24(8):081206, 2017 [2] Physics of Plasmas, 21(9):092110, 2014 [3] Computer Physics Communications, 238:194–202, 2019 [mehr]

Realistic simulations of electromagnetic turbulence are of crucial importance to understand and predict behavior of burning plasmas before they become experimentally available. Burning plasmas are complex systems with multiple spatial and temporal scales. Electromagnetic turbulence is ubiquitous in such plasmas. It is the basic component of the ``scenery'' involving the fast-particle dynamics, the global Magneto-Hydrodynamical and Alfvenic activity, zonal flows, and transport. The saturation of the electromagnetic turbulence is a consequence of a complex interplay between these components. A single numerical first-principle framework, based on the global gyrokinetic electromagnetic formulation and including self-consistently all parts of the problem, is needed. An approach to this task based on the gyrokinetic particle-in-cell codes will be addressed in the presentation. Electromagnetic simulations are known to be very challenging for the gyrokinetic particle-in-cell codes because of the numerical stability issues related to the cancellation problem [1]. Such simulations are also very time consuming since the fast electron dynamics has to be resolved. We address the numerical stability problem using the pullback mitigation technique [2,3] for the cancellation problem. Very long simulation times normally required when the electron dynamics is resolved are substantially accelerated deploying GPUs. In our talk, we will discuss the challenges and describe results of the global gyrokinetic modelling in the electromagnetic regime. [1] Physics of Plasmas, 24(8):081206, 2017 [2] Physics of Plasmas, 21(9):092110, 2014 [3] Computer Physics Communications, 238:194–202, 2019 [mehr]

What psychological factors drive the popularity of conspiracy theories, that explain significant events and circumstances as secret plots by malevolent groups? What are the psychological consequences of adopting these theories? In this talk, I will review research that attempts to answer these questions. First, I will outline research which suggests that belief in conspiracy theories is driven by psychological needs that can be characterised as epistemic (e.g., needing to reduce uncertainty), existential (e.g., needing to feel autonomous and in control) and social (e.g., needing to maintain a high level of self-esteem). I will then talk about some of the consequences of conspiracy theories for individuals' wellbeing and for society. [mehr]

The Standard Model of particle physics was completed by discovery of the Higgs boson in 2012. This model beautifully explains most of the experimental facts but does contradict with some important exceptions. One of the major issues of particle physics is lack of dark matter candidates in its present form, and therefore, lots of possible extensions beyond the Standard Model have been proposed, including super string theory. Such extensions naturally predict new particles which may very weakly interact with the ordinary particles in the Standard Model. Some of them can be dark matter candidates. Since an ordinary photon may couple with such hypothetical particles, new photon technology, in particular above 30 GHz, is a key to address such particles in unexplored parameter regions. In this colloquium, general introduction of this research field of particle physics will be presented, followed by two specific projects related to gyrotrons, originally developed for plasma heating and nuclear fusion. First, we will discuss precision measurement of atomic levels of positronium, a bound state of electron and position, by using gyrotrons. Secondly, direct search for new massive gauge bosons, often referred to as dark photons, with gyrotrons of frequency higher than 30 GHz, will be proposed. The latter project is under the preliminary consideration with Karlsruhe Institute for Technology to use their R&D gyrotron. In these applications for particle physics, a crucial engineering aspect is the ultimate frequency stability of gyrotrons with for example phase-lock loop and injection locking techniques. The impact of these new techniques to the fundamental physics will be described. Furthermore, ultimate limitation of classical electrodynamics for photon detection will be introduced with its remedy with superconducting quantum sensors, which is a hot topic in the particle physics community with a link to quantum computing technology. [mehr]

Today, bibliometrics is a standard instrument in research evaluation besides peer review. The instrument is used for assessing single researchers, research groups, institutions, countries etc. The presentation will focus on several aspects of the use of bibliometrics in research evaluation. After some basic information on bibliometrics in the first part (e.g., the difference between citizen and professional bibliometrics), the presentation will explain in more detail one of the most important type of indicators: field-normalized citation impact indicators. In the second part of the presentation, it will be shown how field-normalized citation impact indicators can be used to assess research of single researchers, institutions, and countries. In the final part, two web-based tools will be presented that can be used to assess (1) the distribution of institutional performance worldwide (see www.excellencemapping.net) and (2) the success of institutional collaboration activities worldwide (see www.excellence-networks.net). [mehr]

The interdisciplinary field of plasma material interactions encompasses all physical processes that lead to the exchange of particles, momentum and energy between plasmas and condensed matter bodies. Modelling of the interface between the plasma and the fusion reactor wall is a highly challenging task as the problem involves various aspects of disparate physics disciplines. On one side of ‘the border’, complicated plasma effects are dictated by classical electromagnetism. Near the interface, intense plasma-material interactions are governed by quantum mechanics. On the other side, the metallic melt (produced by incident heat loads) evolves according to the fluid mechanics laws. In addition to solid or liquid material boundaries surrounding plasmas, there are also dust particles, a by-product of plasma-surface interaction, whose remobilization from surfaces and collisions with the vessel are described by contact mechanics and impact mechanics. In this talk, we discuss some of the microscopic processes occurring on the plasma-material boundaries and modelling approaches for predictive studies of metallic plasma-facing component damage under energetic transient events, including the relevant issue of dust transport and in-vessel accumulation. [mehr]

Clearly, the laws of physics hold and are exploited in living organisms. Speaking as a physicist, most biological characteristics stem from the laws of classical physics that students learn in their first year. However, crucial characteristics in organisms are governed by quantum physics. The latter characteristics are those in which biological processes involve the jumps of electrons from one state to another. The quantum behavior of electrons covers all chemical transformations, for example it arises in optical transitions induced through light absorption by biomolecules.The mechanism by which night-migratory songbirds sense the direction of the Earth's magnetic field appears to possibly rely on the quantum spin dynamics of light-induced radical pairs in cryptochrome proteins located in the retina [1-4]. Cryptochrome binds internally the flavin cofactor (FAD), which governs it signaling through light-induced electron transfer involving a chain of four tryptophan residues, TrpA, TrpB, TrpC, TrpD. In this presentation I will review the latest experimental findings [3] that demonstrate that the photochemistry of cryptochrome 4 (CRY4) from the night-migratory European robin (Erithacus rubecula) is magnetically sensitive in vitro, and more so than CRY4 from two non-migratory bird species, chicken (Gallus gallus) and pigeon (Columba livia). Site-specific mutations of ErCRY4 reveal the roles of four successive flavin–tryptophan radical pairs in generating magnetic field effects and in stabilizing potential signaling states in a way that could enable sensing and signaling functions to be independently optimized in night-migratory birds. The experimental findings will be closely linked to the state-of-the-art computational investigations accomplished by my group in the recent years which help underpin the nature of the electron transfers and explain its unique features in the case of ErCRY4. REFERENCES[1] H. Mouritsen, Nature 558, 50 (2018). [2] D.R. Kattnig, J.K. Sowa, I.A. Solov'yov, and P.J. Hore, New J. Phys. 18 063007 (2016)[3] Xu, J., Jarocha, L.E., Zollitsch, T. et al. Nature 594, 535–540 (2021)[4] E. Sjulstok and I.A. Solov’yov, J. Phys. Chem. Lett 11, 3866 (2020) [mehr]

The National Institute for Fusion Science (NIFS) in Japan started an international joint project for building a stellarator device in China together with a Chinese university in Chengdu city. The device name is CFQS (Chinese First Quasi-axisymmetric Stellarator) which has an advanced stellarator configuration of the quasi-axisymmetry. The device size is R = 1 m, which is appropriate for the university experiment. However, the magnetic field strength is B = 1 T for the ECH plasma production and the NBI plasma heating, for which we can plan plasma confinement experiments with the medium level of beta. The talk will describe the history of this program with reports of the present status of the device construction. The strategy and the important physics targets of the program will be also explained. [mehr]

We confirm the stationary character of the spontaneous Hawking radiation in an analogue black hole. Furthermore, we follow the time evolution of the Hawking radiation, and compare and contrast it with the predictions for real black holes. We observe the ramp up of the Hawking radiation, similar to a real black hole. The end of the spontaneous Hawking radiation is marked by the formation of an inner horizon. The Maryland group predicted that particles emanating from the inner horizon can cause stimulated Hawking radiation. We find that these stimulated Hawking pairs are directly observable. [mehr]

With the successful demonstration of its 20T, full-scale toroidal field model coil in September 2021, Commonwealth Fusion Systems (CFS) is now entering the SPARC Era. Over the next four years, CFS and its partners will build, commission and operate the SPARC net-energy tokamak. SPARC shares much of the ITER physics basis and will be capable of achieving burning plasma conditions in a parameter regime similar to ITER’s at relevant plasma timescales, such as the current relaxation and energy confinement time. In parallel, CFS will demonstrate the fusion technology advances required for the first generation of the ARC commercial fusion power plant, which is due to be commissioned in the early 2030’s.This is motivated by the market requirements of the global clean energy transition, and in particular the requirements for fusion to take its place as an industrial energy concern capable of combating climate change. CFS as a company and fusion as a technology are well positioned to reach these goals. CFS has raised over $2b in private funding to date and built a global network of over 40 partner institutions. CFS' roadmap is highly aligned with the strategic goals identified by the US fusion community and National Academy of Sciences, and is involved in multiple public-private partnerships, including many supported in part by competitive DOE awards. In addition, the experience of building, commissioning, and operating a DT-capable superconducting tokamak in the reactor-relevant regime is expected to provide significant opportunities for US contribution to international fusion programs. In this talk, CFS’ CEO, Bob Mumgaard, will present an overview of the new public-private fusion landscape, CFS’ current status and position in that landscape, and the open problems and challenges on the path to commercial fusion energy. [mehr]

In contrast to ITER a DEMO Reactor needs large blanket segments (5 per sector) with a thickness of > 1m, which have to be removed through a vertical upper port. Due to the fact that these blanket segments may not be drained (liquid LiPb) or in case of solid Pb as neutron multiplier cannot be drained each has a weight of 160 to 180 tones. In comparison to ITER the contamination potential is significantly larger when considering radioactive dust and Tritium. This is true for the inside of the tokamak and thus for the volume connected to the open port (Cask). However, also in contrast to ITER the activation of the blankets and thus the after heat as well as the amount of Tritium inside the components are also significantly higher. Therefore, the outgassing of Tritium during transport to the Hot Cell (Active Maintenance Facility – AMF) is much higher than in ITER. The sealing of the contamination control door (CCD) by rubber seals is not sufficient to guarantee no diffusion of Tritium to the external environment of the transport cask. Therefore, we need not only a cask-based handling system but we need a secondary containment structure which prevents contamination to spread throughout the tokamak building. In September 2020 a small team (3 to 4 persons including myself) were asked to look into this problem because no good solution has been found to this date. Due to manpower problems the work was performed on and off and in total in less than one year. In this presentation the considerations and the design solutions for a RH system for blanket segments will be presented. [mehr]

W7-X performed three experimental campaigns, the last one (OP1.2b) featuring among others high density, high power, low Z_eff detached plasmas kept stable over tens of seconds. Meanwhile several tens of diagnostic systems are in operation at W7-X, quite a number of them used for spectroscopic observation of the plasma edge. Due to the inherent 3D topology of the magnetic islands plasma observation in only one poloidal plane insufficient. This results, in combination with the limited port access for plasma observation, in complex setups of diagnostic hardware and analysis tools. Selected diagnostic methods based on passive and active spectroscopy will be presented together with their implementation at W7-X and with the information they provide about important parameters determining the W7-X island divertor plasma behaviour. Moreover, some of the spectroscopic signals were used in the last campaign as input for feedback-controlled gas injection. Results of the precise control and stabilisation of the detached plasma state over the longest high-power detached discharge in W7-X, to date, will be presented. [mehr]

In the colloquium lecture I will explain how leaders such as Singapore’s Lee Kuan Yew and Peru’s Alberto Fujimori pioneered less violent, more covert, and more effective methods of monopolizing power. They cultivated an image of competence, concealed censorship, and used democratic institutions to undermine democracy, all while increasing international engagement for financial and reputational benefits. We will discuss why most of today’s authoritarians are spin dictators—and how they differ from the remaining “fear dictators” such as Kim Jong-un and Bashar al-Assad, as well as from masters of high-tech repression like Xi Jinping.I will attempt to explain some of the great political puzzles of our time—from how dictators can survive in an age of growing modernity to the disturbing convergence and mutual sympathy between dictators and populists like Donald Trump. [mehr]

SCK•CEN is at the forefront of Heavy Liquid Metal (HLM) nuclear technology worldwide with the development of the MYRRHA accelerator driven system (ADS). MYRRHA is serving since the FP5 EURATOM framework as the backbone of the P&T strategy of the European Commission based on the "4 building Blocks at Engineering level" and fostering the R&D activities in EU related to the ADS and the associated HLM technology developments. At the same time MYRRHA is conceived as a flexible fast-spectrum pool-type research irradiation facility cooled by Lead Bismuth Eutectic (LBE), and was identified by SNETP (www.snetp.eu) as the European Technology Pilot Plant for the Lead-cooled Fast Reactor. MYRRHA is proposed to the international community of nuclear energy and nuclear physics as a pan-European large research infrastructure to serve as a multipurpose fast spectrum irradiation facility for various fields of research such as; transmutation of High Level Waste (HLW), material and fuel research for Gen.IV reactors, material for fusion energy, innovative radioisotopes development and production and for fundamental physics. As such MYRRHA is since 2010 on the high priority list of the ESFRI roadmap (http://www.esfri.eu/roadmap-2016). Since 1998 SCK•CEN is developing the MYRRHA project as an accelerator driven system based on the lead-bismuth eutectic as a coolant of the reactor and a material for its spallation target. The nominal design power of the MYRRHA reactor is 100 MWth. It is driven in sub-critical mode (keff = 0.95) by a high power proton accelerator based on LINAC technology delivering a proton beam in Continuous Wave (CW) mode of 600 MeV proton energy and 4 mA intensity. The choice of LINAC technology is dictated by the unprecedented reliability level required by the ADS application. In the MYRRHA requirements the proton beam delivery should be guaranteed with a number of beam trips lasting more than 3 seconds limited to maximum 10 for a period of 3 months corresponding to the operating cycle of the MYRRHA facility. Since 2015, SCK•CEN and Belgium government decided to implement the MYRRHA facility in three phases to minimize the technical risks associated to the needed accelerator reliability. On September 7, 2018 the Belgian federal government decided to build this large research infrastructure. In this lecture we will present the status of the MYRRHA project as a whole and in particular stressing the role of Accelerator Driven Systems in closing efficiently the nuclear fuel cycle and burning the Minor Actinides for reducing the radiotoxicity burden in the high level storage. [mehr]

There is tremendous public concern about an upcoming energy crisis in Europe and specifically in Germany. I will first assess the actual situation of Germany using, as basis, the “energy triangle” – security of supply, affordability, and sustainability. The options for future clean energy forms are rather limited. It is obvious that renewable energies will play an important role in the future supply mix. This is the reason why their intrinsic properties and limitations have to be presented and discussed in detail – under what circumstances are renewable energies sustainable, what are their limitations (e.g. of biomass), what are the technical consequences of the intermittent nature of wind and photo-voltaic power, what is the national potential of renewable energies of Germany, what are the electricity import options within Europe, is a storage system devoted exclusively to electricity meaningful, what is the possible role of hydrogen and how much electricity and energy can Germany produce by itself. The political plans for the German supply in 2030 and the role of methane for the transition period of the “Energiewende” will be discussed. At the end, if there is still time, I will try to confront the local energy problems with a more global perspective. [mehr]

Random quantum vacuum fluctuations exist everywhere leading to the Casimir interaction between macroscopic bodies. The Casimir effect can dominate the interaction between microstructures at small separations, and hence a device that can leverage the Casimir force is in demand. In this talk, I will present the first Casimir diode and Casimir transistor system. For the Casimir diode system, we realize the first experimental demonstration of quantum vacuum mediated non-reciprocal energy transfer between two micromechanical oscillations. For the Casimir transistor system, we observe the three-body Casimir effects experimentally for the first time and demonstrate switching and amplifying quantum-fluctuation-mediated energy transfer in a three-terminal Casimir system. These two works represent an important development in optomechanics with virtual photons and will have potential applications in sensing and information processing. [mehr]

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