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| 3. |
- Bombarda, F., et al.
(författare)
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Runaway electron beam control
- 2019
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 1361-6587 .- 0741-3335. ; 61:1
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Tidskriftsartikel (refereegranskat)
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| 11. |
- Joffrin, E., et al.
(författare)
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Overview of the JET preparation for deuterium-tritium operation with the ITER like-wall
- 2019
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 59:11
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Forskningsöversikt (refereegranskat)abstract
- For the past several years, the JET scientific programme (Pamela et al 2007 Fusion Eng. Des. 82 590) has been engaged in a multi-campaign effort, including experiments in D, H and T, leading up to 2020 and the first experiments with 50%/50% D-T mixtures since 1997 and the first ever D-T plasmas with the ITER mix of plasma-facing component materials. For this purpose, a concerted physics and technology programme was launched with a view to prepare the D-T campaign (DTE2). This paper addresses the key elements developed by the JET programme directly contributing to the D-T preparation. This intense preparation includes the review of the physics basis for the D-T operational scenarios, including the fusion power predictions through first principle and integrated modelling, and the impact of isotopes in the operation and physics of D-T plasmas (thermal and particle transport, high confinement mode (H-mode) access, Be and W erosion, fuel recovery, etc). This effort also requires improving several aspects of plasma operation for DTE2, such as real time control schemes, heat load control, disruption avoidance and a mitigation system (including the installation of a new shattered pellet injector), novel ion cyclotron resonance heating schemes (such as the three-ions scheme), new diagnostics (neutron camera and spectrometer, active Alfven eigenmode antennas, neutral gauges, radiation hard imaging systems...) and the calibration of the JET neutron diagnostics at 14 MeV for accurate fusion power measurement. The active preparation of JET for the 2020 D-T campaign provides an incomparable source of information and a basis for the future D-T operation of ITER, and it is also foreseen that a large number of key physics issues will be addressed in support of burning plasmas.
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| 22. |
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- 2018
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 58:9
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Tidskriftsartikel (refereegranskat)
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| 23. |
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- 2018
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 58:1
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Forskningsöversikt (refereegranskat)
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| 24. |
- Andersson, Pehr, et al.
(författare)
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Working memory and virtual endoscopy simulation
- 2004
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Ingår i: Proceedings of the twenty-sixth annual conference of the cognitive science society. - Mahwah : Lawrence Erlbaum Associates. - 9780805854640 ; , s. 1519-1519
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Konferensbidrag (refereegranskat)
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| 25. |
- Citrin, J., et al.
(författare)
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Tractable flux-driven temperature, density, and rotation profile evolution with the quasilinear gyrokinetic transport model QuaLiKiz
- 2017
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 1361-6587 .- 0741-3335. ; 59:12
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Tidskriftsartikel (refereegranskat)abstract
- Quasilinear turbulent transport models are a successful tool for prediction of core tokamak plasma profiles in many regimes. Their success hinges on the reproduction of local nonlinear gyrokinetic fluxes. We focus on significant progress in the quasilinear gyrokinetic transport model QuaLiKiz (Bourdelle et al 2016 Plasma Phys. Control. Fusion 58 014036), which employs an approximated solution of the mode structures to significantly speed up computation time compared to full linear gyrokinetic solvers. Optimisation of the dispersion relation solution algorithm within integrated modelling applications leads to flux calculations x 10(6-7) faster than local nonlinear simulations. This allows tractable simulation of flux-driven dynamic profile evolution including all transport channels: ion and electron heat, main particles, impurities, and momentum. Furthermore, QuaLiKiz now includes the impact of rotation and temperature anisotropy induced poloidal asymmetry on heavy impurity transport, important for W-transport applications. Application within the JETTO integrated modelling code results in 1 s of JET plasma simulation within 10 h using 10 CPUs. Simultaneous predictions of core density, temperature, and toroidal rotation profiles for both JET hybrid and baseline experiments are
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| 26. |
- Eriksson, Frida, 1986, et al.
(författare)
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Impact of fast ions on density peaking in JET : fluid and gyrokinetic modeling
- 2019
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Ingår i: Plasma Physics and Controlled Fusion. - : Institute of Physics Publishing (IOPP). - 0741-3335 .- 1361-6587. ; 61:7
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Tidskriftsartikel (refereegranskat)abstract
- The effect of fast ions on turbulent particle transport, driven by ion temperature gradient (ITG)/trapped electron mode turbulence, is studied. Two neutral beam injection (NBI) heated JET discharges in different regimes are analyzed at the radial position rho(t) = 0.6, one of them an L-mode and the other one an H-mode discharge. Results obtained from the computationally efficient fluid model EDWM and the gyro-fluid model TGLF are compared to linear and nonlinear gyrokinetic GENE simulations as well as the experimentally obtained density peaking. In these models, the fast ions are treated as a dynamic species with a Maxwellian background distribution. The dependence of the zero particle flux density gradient (peaking factor) on fast ion density, temperature and corresponding gradients, is investigated. The simulations show that the inclusion of a fast ion species has a stabilizing influence on the ITG mode and reduces the peaking of the main ion and electron density profiles in the absence of sources. The models mostly reproduce the experimentally obtained density peaking for the L-mode discharge whereas the H-mode density peaking is significantly underpredicted, indicating the importance of the NBI particle source for the H-mode density profile.
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| 27. |
- Eriksson, Frida, 1986, et al.
(författare)
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Interpretative and predictive modelling of Joint European Torus collisionality scans
- 2019
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Ingår i: Plasma Physics and Controlled Fusion. - : Institute of Physics Publishing (IOPP). - 0741-3335 .- 1361-6587. ; 61:11
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Tidskriftsartikel (refereegranskat)abstract
- Transport modelling of Joint European Torus (JET) dimensionless collisionality scaling experiments in various operational scenarios is presented. Interpretative simulations at a fixed radial position are combined with predictive JETTO simulations of temperatures and densities, using the TGLF transport model. The model includes electromagnetic effects and collisions as well as (E)over-right-arrow x (b)over-right-arrow shear in Miller geometry. Focus is on particle transport and the role of the neutral beam injection (NBI) particle source for the density peaking. The experimental 3-point collisionality scans include L-mode, and H-mode (D and H and higher beta D plasma) plasmas in a total of 12 discharges. Experimental results presented in (Tala et al 2017 44th EPS Conf.) indicate that for the H-mode scans, the NBI particle source plays an important role for the density peaking, whereas for the L-mode scan, the influence of the particle source is small. In general, both the interpretative and predictive transport simulations support the experimental conclusions on the role of the NBI particle source for the 12 JET discharges.
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| 29. |
- Gerdin, Linda, et al.
(författare)
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The Swedish Crohn Trial: A Prematurely Terminated Randomized Controlled Trial of Thiopurines or Open Surgery for Primary Treatment of Ileocaecal Crohns Disease
- 2016
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Ingår i: Journal of Crohn's & Colitis. - : OXFORD UNIV PRESS. - 1873-9946 .- 1876-4479. ; 10:1, s. 50-54
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Tidskriftsartikel (refereegranskat)abstract
- Background and aims: The importance of efficient and safe treatment of Crohns disease is highlighted by its chronicity. Both medical and surgical treatments have shown good results in the symptomatic control of limited ileocaecal Crohns disease. The aim of this study was to compare medical treatment with surgical treatment of ileocaecal Crohns disease. Methods: Thirty-six patients from seven hospitals with primary ileocaecal Crohns disease were randomized to either medical or surgical treatment. The medical treatment was induction of remission with budesonide and thereafter maintenance treatment with azathioprine. The surgical treatment was open ileocaecal resection. Crohns disease activity index over time, expressed as area under the curve at 1, 3 and 5 years, was the primary endpoint. Subjective health measured with the 36-item Short Form Survey Instrument (SF36) and a visual analogue scale (VAS) were secondary endpoints. Results: There were no differences between the treatment groups in Crohns disease activity index over time. General health, measured as SF36 score, was higher in patients receiving surgical treatment than in those receiving medical treatment at 1 year, but there was no corresponding difference in VAS. Due to the slow inclusion rate and changes in clinical practice, the study was t = erminated prematurely. Conclusion: The study ended up being underpowered and should be interpreted with caution, but there was no clinically significant difference between the two treatment arms. Further studies are needed to address this important clinical question.
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| 32. |
- Johnson, Ericka, 1973-, et al.
(författare)
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Evaluating instruction of medical students with a haptic surgical simulator : The importance of coordinating students' perspectives
- 2004
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Ingår i: Journal on Information Technology in Healthcare. - 1479-649X. ; 2:3, s. 155-163
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To examine the practices surrounding the use of a surgical simulator in training medical students. Design: Non-randomised observational study. Setting: Teaching hospital in Sweden. Methods: Two separate studies were performed using a haptically enabled (i.e. providing tactile feedback) surgical simulator. In the first study a total of 46 students and two instructors were observed as the students trained their speed and accuracy in locating spheres in a simulated abdomen, shoulder and knee. Through qualitative analysis of video of the instructors' teaching, methods for reconstituting medical practice in the simulations were observed. In the second, quantitative, study, a subgroup of 30 students performed two tests on the simulator, the first relying solely on the on-screen instructions available with the simulator and the second after receiving individual instruction from a practising surgeon. The difference between these two scores was analysed and students were asked to evaluate their experience of the simulator and training session. Results: The first study demonstrated what methods the instructors used to help students relate the computer screen image to human anatomy, and to make the training with the simulator clinically relevant and authentic. The instructors did this by actively aligning and coordinating the students' perspectives, and by reconstituting patient bodies into the simulation. In the second study the students' test results were significantly improved after receiving instruction from the surgeon. Conclusion: The results from these two studies demonstrate the important role that instructors play in simulator training. They also suggest practices to consider when designing a programme for simulator training.
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| 33. |
- Klamberg, Mark, et al.
(författare)
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FRA-lagen medför massiv kartläggning av oskyldiga
- 2008. - 12
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Annan publikation (populärvet., debatt m.m.)abstract
- Mark Klamberg Doktorand juridik, Stockholms universitet, Mikael Nilsson Doktorand datalogi, Kungliga Tekniska högskolan, Anna Petersson Doktorand matematik, Uppsala universitet, Peter Seipel Professor emeritus rättsinformatik, Stockholms universitet, Janne Flyghed Professor kriminologi, Stockholms universitet, Cecilia Magnusson Sjöberg Professor i rättsinformatik, Stockholms universitet, Jussi Karlgren Docent språkteknologi, Swedish Institute of Computer Science, Markus Bylund Doktor i data- och systemvetenskap inriktning personlig integritet, Swedish Institute of Computer Science, Karl Palmås Civilingenjör och doktor i sociologi, Handelshögskolan vid Göteborgs universitet, Christopher Kullenberg Doktorand vetenskapsteori, Göteborgs universitet, Pär Ström Civilingenjör och författare, integritetsombudsman på tankesmedjan Den nya välfärden, Daniel Thorburn Professor i statistik, Stockholms universitet, Johan Westerholm Kapten, reservofficerare underrättelsetjänst, rådgivare Greycat
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| 34. |
- Krasilnikov, A., et al.
(författare)
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Evidence of 9 Be + p nuclear reactions during 2ω CH and hydrogen minority ICRH in JET-ILW hydrogen and deuterium plasmas
- 2018
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 58:2
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Tidskriftsartikel (refereegranskat)abstract
- The intensity of 9Be + p nuclear fusion reactions was experimentally studied during second harmonic (2ω CH) ion-cyclotron resonance heating (ICRH) and further analyzed during fundamental hydrogen minority ICRH of JET-ILW hydrogen and deuterium plasmas. In relatively low-density plasmas with a high ICRH power, a population of fast H+ ions was created and measured by neutral particle analyzers. Primary and secondary nuclear reaction products, due to 9Be + p interaction, were observed with fast ion loss detectors, γ-ray spectrometers and neutron flux monitors and spectrometers. The possibility of using 9Be(p, d)2α and 9Be(p, α)6Li nuclear reactions to create a population of fast alpha particles and study their behaviour in non-active stage of ITER operation is discussed in the paper.
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| 35. |
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| 37. |
- Murari, A., et al.
(författare)
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A control oriented strategy of disruption prediction to avoid the configuration collapse of tokamak reactors
- 2024
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Ingår i: Nature Communications. - 2041-1723 .- 2041-1723. ; 15:1
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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.
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| 38. |
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| 39. |
- Ström, Pär
(författare)
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Human factors in image guided surgical simulator training : components, visual-spatial and haptic aspects
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- New image-guided surgical techniques such as arthroscopy and laparoscopy are difficult to learn and master. To handle these techniques, there seems to be a need for higher-level abilities such as visual-spatial abilities. Difficulties in human-system interaction could be studied with a human factors perspective in a similar way as already has been done in high-reliability organizations (HROs) such as aviation. The main goal of human factors is to improve human interaction with systems to: improve performance, reduce errors and increase user satisfaction. Health care in general and surgery in particular share high-risk activities with the HROs but unfortunately lack a sufficiently high level of safety. Training in a virtual reality (VR) simulator could help the surgeon to overcome new demands and difficulties through training. There is a relative lack of haptic feedback in image guided surgery compared to open surgery. More precise, more consistent and much safer procedures could be performed if haptic feedback (force feedback and/or tactile feedback) would be integrated into image guided surgery. A major difficulty is also to extract 3-dimensional (3-D) information from 2dimensional (2-D) images on the monitor. A strive to implement these simulators into a surgical curriculum for a standardized, objective and validated surgical skills training and assessment cannot be done without investigating these human factors aspects further. The general aim of this study was to investigate the influence of three important but scarcely studied aspects of human factors in image guided surgery: components in a simulator training context, visual-spatial ability and haptic feedback. In Paper I, medical students (novices) participated in a study with self-controlled design to analyze the effect of training in a simulator with anatomical graphics and haptic feedback. We also compared the results in this simulator with the established MIST simulator with an artificial environment and no haptic feedback. There was a significant improvement after 1 hour of training regarding time, movement economy and total score. The results in the two simulators were highly correlated. In Paper II, novices participated in a study with experimental design: a randomized, posttest only, control group design. We analyzed the importance of visual-spatial components in a simulator context. Performance in a virtual arthroscopy simulator did not improve after training in other simulators with different visual-spatial components. The performance in the arthroscopy simulator was not significantly correlated with the MIST simulator. In Paper III, novices participated in a study with self-controlled design, which was modified to provide a combination of self-controls and concurrent experimental treatments. We analyzed the correlations between high-level visualspatial ability test scores and performance measures in two simulator tasks differing in spatial complexity. The performance in the most spatial complex simulator task significantly correlated with high-level visual-spatial ability while such ability-performance relationships were not found for the less spatial complex simulator task. In Paper IV, surgical residents participated in a randomized study with cross-over design to analyze the effect of early exposure to haptic feedback during early phases of image guided surgical simulator training. After two hours of training the group who had started with haptic feedback performed significantly better on two diathermy tasks compared to the group who had started without haptic feedback. The results show that the use of surgical simulators as a pedagogical tool in medical student training is promising with steep learning curves. Performance in one visual-spatial context (VR arthroscopy) did not improve after one hour of training on virtual tasks with different context. However, it cannot be excluded, that experienced trainees could improve their performance, as perceived similarity between different situations is influenced by many psychological factors, such as the knowledge or expertise of the person performing the task. A training curriculum in advanced image guided surgical simulators should aim at task and context specificity in order to maximize transfer. However, construction of simulator tasks should be based on task analysis to select essential components and invariant relationships for transfer to the real task. High-level visual-spatial ability is important to possess for surgical novices in the early training phase of a visual-spatial complex simulator task. Our findings further indicate that haptic feedback enhances performance in the early training phase of skill acquisition in image guided surgical simulator training. This is important to consider when designing a multi-modal simulator based curriculum for image guided surgical training.
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| 40. |
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| 41. |
- Tegnered, Daniel, 1987, et al.
(författare)
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Comparative gyrokinetic analysis of JET baseline H-mode core plasmas with carbon wall and ITER-like wall
- 2016
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 0741-3335 .- 1361-6587. ; 58:4
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Tidskriftsartikel (refereegranskat)abstract
- Following the change of plasma facing components at JET from a carbon wall (CW) to a metal ITER-like wall (ILW) a deterioration of global confinement has been observed for H-mode baseline experiments. The deterioration has been correlated with a degradation of pedestal confinement with lower electron temperatures at the top of the edge barrier region. In order to investigate the change in core confinement, heat transport due to Ion Temperature Gradient (ITG)/Trapped Electron Mode (TEM) turbulence is investigated using the gyrokinetic code GENE. Two pairs of CW and ILW discharges that are matched according to several global parameters are simulated at mid radius. The simulations included effects of collisions, finite beta, realistic geometries, and impurities. A sensitivity study is performed with respect to the key dimensionless parameters in the matched pairs. The combined effect of the relative change in these parameters is that the ITG mode is destabilized in the ILW discharges compared to the CW discharges. This is also reflected in nonlinear simulations where the ILW discharges show higher normalized ion and electron heat fluxes and larger stiffness. The ion energy confinement time within rho = 0.5 is found to be comparable while the electron confinement time is shorter for the ILW discharges. The core confinement in the ILW discharges is expected to improve if the edge pedestal is recovered since that would favourably change the key plasma parameters that now serve to destabilize them.
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| 42. |
- Tegnered, Daniel, 1987, et al.
(författare)
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Gyrokinetic simulations of particle transport in pellet fuelled JET discharges
- 2017
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP PUBLISHING LTD. - 0741-3335 .- 1361-6587. ; 59:10
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Tidskriftsartikel (refereegranskat)abstract
- Pellet injection is a likely fuelling method of reactor grade plasmas. When the pellet ablates, it will transiently perturb the density and temperature profiles of the plasma. This will in turn change dimensionless parameters such as a/L-n, a/L-T and plasma beta. The microstability properties of the plasma then changes which influences the transport of heat and particles. In this paper, gyrokinetic simulations of a JET L-mode pellet fuelled discharge are performed. The ion temperature gradient/trapped electron mode turbulence is compared at the time point when the effect from the pellet is the most pronounced with a hollow density profile and when the profiles have relaxed again. Linear and nonlinear simulations are performed using the gyrokinetic code GENE including electromagnetic effects and collisions in a realistic geometry in local mode. Furthermore, global nonlinear simulations are performed in order to assess any nonlocal effects. It is found that the positive density gradient has a stabilizing effect that is partly counteracted by the increased temperature gradient in the this region. The effective diffusion coefficients are reduced in the positive density region region compared to the intra pellet time point. No major effect on the turbulent transport due to nonlocal effects are observed.
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