| 1. |
- Murari, A., et al.
(författare)
-
A control oriented strategy of disruption prediction to avoid the configuration collapse of tokamak reactors
- 2024
-
Ingår i: Nature Communications. - 2041-1723 .- 2041-1723. ; 15:1
-
Tidskriftsartikel (refereegranskat)abstract
- The objective of thermonuclear fusion consists of producing electricity from the coalescence of light nuclei in high temperature plasmas. The most promising route to fusion envisages the confinement of such plasmas with magnetic fields, whose most studied configuration is the tokamak. Disruptions are catastrophic collapses affecting all tokamak devices and one of the main potential showstoppers on the route to a commercial reactor. In this work we report how, deploying innovative analysis methods on thousands of JET experiments covering the isotopic compositions from hydrogen to full tritium and including the major D-T campaign, the nature of the various forms of collapse is investigated in all phases of the discharges. An original approach to proximity detection has been developed, which allows determining both the probability of and the time interval remaining before an incoming disruption, with adaptive, from scratch, real time compatible techniques. The results indicate that physics based prediction and control tools can be developed, to deploy realistic strategies of disruption avoidance and prevention, meeting the requirements of the next generation of devices.
|
|
| 2. |
- Stroth, U., et al.
(författare)
-
Progress from ASDEX Upgrade experiments in preparing the physics basis of ITER operation and DEMO scenario development
- 2022
-
Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 62:4
-
Tidskriftsartikel (refereegranskat)abstract
- An overview of recent results obtained at the tokamak ASDEX Upgrade (AUG) is given. A work flow for predictive profile modelling of AUG discharges was established which is able to reproduce experimental H-mode plasma profiles based on engineering parameters only. In the plasma center, theoretical predictions on plasma current redistribution by a dynamo effect were confirmed experimentally. For core transport, the stabilizing effect of fast ion distributions on turbulent transport is shown to be important to explain the core isotope effect and improves the description of hollow low-Z impurity profiles. The L-H power threshold of hydrogen plasmas is not affected by small helium admixtures and it increases continuously from the deuterium to the hydrogen level when the hydrogen concentration is raised from 0 to 100%. One focus of recent campaigns was the search for a fusion relevant integrated plasma scenario without large edge localised modes (ELMs). Results from six different ELM-free confinement regimes are compared with respect to reactor relevance: ELM suppression by magnetic perturbation coils could be attributed to toroidally asymmetric turbulent fluctuations in the vicinity of the separatrix. Stable improved confinement mode plasma phases with a detached inner divertor were obtained using a feedback control of the plasma β. The enhanced D α H-mode regime was extended to higher heating power by feedback controlled radiative cooling with argon. The quasi-coherent exhaust regime was developed into an integrated scenario at high heating power and energy confinement, with a detached divertor and without large ELMs. Small ELMs close to the separatrix lead to peeling-ballooning stability and quasi continuous power exhaust. Helium beam density fluctuation measurements confirm that transport close to the separatrix is important to achieve the different ELM-free regimes. Based on separatrix plasma parameters and interchange-drift-Alfvén turbulence, an analytic model was derived that reproduces the experimentally found important operational boundaries of the density limit and between L- and H-mode confinement. Feedback control for the X-point radiator (XPR) position was established as an important element for divertor detachment control. Stable and detached ELM-free phases with H-mode confinement quality were obtained when the XPR was moved 10 cm above the X-point. Investigations of the plasma in the future flexible snow-flake divertor of AUG by means of first SOLPS-ITER simulations with drifts activated predict beneficial detachment properties and the activation of an additional strike point by the drifts.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Andersson, Anders, 1983-, et al.
(författare)
-
Co-simulation architecture with pedestrian, vehicle, and traffic simulators
- 2021
-
Ingår i: Actes (IFSTTAR). - : Driving Simulation Association. ; , s. 181-184
-
Konferensbidrag (refereegranskat)abstract
- Automated and connected traffic systems with cooperative functionality need effective testing. One way to enable such testing is to represent the current traffic environment by co-simulating different simulators using a communication layer between the simulators for cooperative functionality. With this approach, this paper presents a platform with its included simulators (vehicle, pedestrian, and traffic simulators), the used run-time infrastructure (RTI) for co-simulation, and the connection to the Unreal Engine based visual system for the simulators. The architecture was tested with two vehicle simulators (one autonomous bus and a truck), one pedestrian simulator, and one traffic simulator connected using a cloud-based service for the RTI.
|
|
| 7. |
- Brehmer, Daniel, 1973-
(författare)
-
Support for mathematics teachers’ change : Examining catalysts for teacher learning and role of the teacher in professional development programmes
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- When the perception changes regarding what mathematics students should be able to manage, this is typically addressed through a new national curriculum. To establish and implement this new curriculum in practice, teachers must be given the opportunity to change according to it. For such change, they need support in interpreting and implementing the new curriculum. Typically, there are two common ways to support teacher change: (1) developing and launching curriculum materials that correspond to the national curriculum; and (2) implementing professional development programmes (PDPs) that correspond to the new national curriculum. This thesis includes both aspects and aims to contribute to research on support for mathematics teachers’ change. This aim is operationalized by: (1) studying mathematics textbooks in which tasks and plausible teaching intentions are analysed; (2) studying teacher agency in collegial discussions in relation to the design of a PDP; and (3) mapping and describing catalysts for teacher learning from PDPs in research literature. These studies resulted in five papers, which are included in this thesis. The main results of the papers cover: the distribution of types of tasks in Swedish mathematics textbooks; the type of learning approach advocated in these textbooks; how different types of texts in PDPs relate to teacher agency in collegial discussions; and an identification and description of catalysts for teacher learning from PDPs for mathematics teachers. In the kappa1 of this thesis, these results are merged and discussed in relation to different models of teacher change. The focus in the kappa is on examining catalysts for teacher learning from such initiatives and the role of the teacher in PDPs. This examination suggests elaborations on parts of a conceptual framework for effective PDPs (Desimone, 2009). More precisely, the elaborations concern core critical features for effective PDPs, presented in this framework: Content Focus, Active Learning, Collective Participation, Duration, and Coherence. The main contributions of this thesis concern: a tool for analysing tasks in textbooks with respect to problem-solving tasks; an organizing frame for mapping learning catalysts from articles describing PDPs; a description of catalysts for teacher learning from PDPs as specifications of core critical features for effective PDPs; and the role of the teacher in PDPs as a catalyst for learning. Implications and suggestions for future research are discussed.___________________________1The Swedish term kappa will be used in this thesis in the absence of an equivalent English term for the introductory chapters of an aggregation dissertation
|
|
| 8. |
- Reimerdes, H., et al.
(författare)
-
Overview of the TCV tokamak experimental programme
- 2022
-
Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 62:4
-
Tidskriftsartikel (refereegranskat)abstract
- The tokamak a configuration variable (TCV) continues to leverage its unique shaping capabilities, flexible heating systems and modern control system to address critical issues in preparation for ITER and a fusion power plant. For the 2019-20 campaign its configurational flexibility has been enhanced with the installation of removable divertor gas baffles, its diagnostic capabilities with an extensive set of upgrades and its heating systems with new dual frequency gyrotrons. The gas baffles reduce coupling between the divertor and the main chamber and allow for detailed investigations on the role of fuelling in general and, together with upgraded boundary diagnostics, test divertor and edge models in particular. The increased heating capabilities broaden the operational regime to include T (e)/T (i) similar to 1 and have stimulated refocussing studies from L-mode to H-mode across a range of research topics. ITER baseline parameters were reached in type-I ELMy H-modes and alternative regimes with 'small' (or no) ELMs explored. Most prominently, negative triangularity was investigated in detail and confirmed as an attractive scenario with H-mode level core confinement but an L-mode edge. Emphasis was also placed on control, where an increased number of observers, actuators and control solutions became available and are now integrated into a generic control framework as will be needed in future devices. The quantity and quality of results of the 2019-20 TCV campaign are a testament to its successful integration within the European research effort alongside a vibrant domestic programme and international collaborations.
|
|
| 9. |
- Thomas, Rimon, et al.
(författare)
-
Analysis of radioactivity in commercially available products aiming to improve health and wellness
- 2023
-
Ingår i: Radiation Protection Dosimetry. - 0144-8420 .- 1742-3406. ; 199:13, s. 1392-1400
-
Tidskriftsartikel (refereegranskat)abstract
- There are products available on the online market that claim to contain unique ‘energies’ that can improve health and wellness by eliminating toxins and pains and energising food and drinking water. We investigated these products by alpha and gamma spectrometry, and the analysis showed that they contained a few to hundreds of kilobecquerels per kilogram of naturally occurring radionuclides from the 232Th and 238U series. The committed effective dose for an adult drinking water that had been in contact with these products just once was estimated to 12 nSv. Considering a worst-case scenario for the workers inhaling the radioactive substance, 1 d of work would result in an effective dose of 0.39 mSv. The product descriptions do not mention the radionuclide content, and concerns are raised for the consumers and workers exposed to these products with no knowledge of the radioactive content.
|
|
