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Weiszflog, Matthias
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Publications (10 of 66) Show all publications
Kazakov, Y. O. O., Possnert, G., Sjöstrand, H., Skiba, M., Weiszflog, M., Andersson Sundén, E., . . . Kazantzidis, V. (2017). Efficient generation of energetic ions in multi-ion plasmas by radio-frequency heating. Nature Physics, 13(10), 973-978
Open this publication in new window or tab >>Efficient generation of energetic ions in multi-ion plasmas by radio-frequency heating
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2017 (English)In: Nature Physics, ISSN 1745-2473, E-ISSN 1745-2481, Vol. 13, no 10, p. 973-978Article in journal (Refereed) Published
Abstract [en]

We describe a new technique for the efficient generation of high-energy ions with electromagnetic ion cyclotron waves in multi-ion plasmas. The discussed three-ion scenarios are especially suited for strong wave absorption by a very low number of resonant ions. To observe this effect, the plasma composition has to be properly adjusted, as prescribed by theory. We demonstrate the potential of the method on the world-largest plasma magnetic confinement device, JET (Joint European Torus, Culham, UK), and the high-magnetic-field tokamak Alcator C-Mod (Cambridge, USA). The obtained results demonstrate efficient acceleration of He-3 ions to high energies in dedicated hydrogendeuterium mixtures. Simultaneously, effective plasma heating is observed, as a result of the slowing-down of the fast He-3 ions. The developed technique is not only limited to laboratory plasmas, but can also be applied to explain observations of energetic ions in space-plasma environments, in particular, He-3-rich solar flares.

National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-359272 (URN)10.1038/NPHYS4167 (DOI)000412181200018 ()
Note

For a complete list of authors see http://dx.doi.org/10.1038/NPHYS4167

Available from: 2018-09-05 Created: 2018-09-05 Last updated: 2018-09-05Bibliographically approved
Litaudon, X., Abduallev, S., Abhangi, M., Abreu, P., Afzal, M., Aggarwal, K. M., . . . Zychor, I. (2017). Overview of the JET results in support to ITER. Nuclear Fusion, 57(10), Article ID 102001.
Open this publication in new window or tab >>Overview of the JET results in support to ITER
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2017 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 57, no 10, article id 102001Article in journal (Refereed) Published
Abstract [en]

The 2014-2016 JET results are reviewed in the light of their significance for optimising the ITER research plan for the active and non-active operation. More than 60 h of plasma operation with ITER first wall materials successfully took place since its installation in 2011. New multi-machine scaling of the type I-ELM divertor energy flux density to ITER is supported by first principle modelling. ITER relevant disruption experiments and first principle modelling are reported with a set of three disruption mitigation valves mimicking the ITER setup. Insights of the L-H power threshold in Deuterium and Hydrogen are given, stressing the importance of the magnetic configurations and the recent measurements of fine-scale structures in the edge radial electric. Dimensionless scans of the core and pedestal confinement provide new information to elucidate the importance of the first wall material on the fusion performance. H-mode plasmas at ITER triangularity (H = 1 at beta(N) similar to 1.8 and n/n(GW) similar to 0.6) have been sustained at 2 MA during 5 s. The ITER neutronics codes have been validated on high performance experiments. Prospects for the coming D-T campaign and 14 MeV neutron calibration strategy are reviewed.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2017
Keywords
JET, plasma, fusion, ITER
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-340063 (URN)10.1088/1741-4326/aa5e28 (DOI)000416419100001 ()
Available from: 2018-01-25 Created: 2018-01-25 Last updated: 2018-04-23Bibliographically approved
Haglund, J., Melander, E., Weiszflog, M. & Andersson, S. (2017). University physics students’ ideas of thermal radiation expressed in open laboratory activities using infrared cameras. Research in Science & Technological Education, 35(3), 349-367
Open this publication in new window or tab >>University physics students’ ideas of thermal radiation expressed in open laboratory activities using infrared cameras
2017 (English)In: Research in Science & Technological Education, ISSN 0263-5143, E-ISSN 1470-1138, Vol. 35, no 3, p. 349-367Article in journal (Refereed) Published
Abstract [en]

Background

University physics students were engaged in open-ended thermodynamics laboratory activities with a focus on understanding a chosen phenomenon or the principle of laboratory apparatus, such as thermal radiation or a heat pump. Students had access to handheld infrared (IR) cameras for their investigations.

Purpose

The purpose of the research was to explore students’ interactions with reformed thermodynamics laboratory activities. It was guided by the research question: How do university physics students make use of IR cameras in the investigation of the interaction of thermal radiation?

Sample

The study was conducted with a class of first-year university physics students in Sweden. The interaction with the activities of four of the students was selected for analysis. The four students are males.

Design and methods

We used a qualitative, interpretive approach to the study of students’ interaction.  The primary means of data collection was video recording of students’ work with the laboratory activities and their subsequent presentations. The analysis focused on how IR cameras helped students notice phenomena relating to thermal radiation, with comparison to previous research on students’ conceptions of thermal radiation.

Results

When using the IR camera students attended to the reflection of thermal radiation on shiny surfaces, such as polished metals, windows or a white-board, and emissive properties of surfaces of different types. In this way, they went beyond using the technology as a temperature probe. Students were able to discuss merits and shortcomings of IR cameras in comparison with digital thermometers.

Conclusions

With the help of IR cameras, university physics students attend to thermal phenomena that would otherwise easily go unnoticed.

Place, publisher, year, edition, pages
Routledge, 2017
Keywords
Infrared cameras; Thermal radiation; Open laboratory exercises; Physics education
National Category
Physical Sciences
Research subject
Physics with specialization in Physics Education
Identifiers
urn:nbn:se:uu:diva-326285 (URN)10.1080/02635143.2017.1318362 (DOI)000404933100007 ()
Available from: 2017-07-05 Created: 2017-07-05 Last updated: 2017-11-20Bibliographically approved
Melander, E., Haglund, J., Weiszflog, M. & Andersson, S. (2016). More than meets the eye: Infrared cameras in open-ended university thermodynamics labs. Physics Teacher, 54(9), 528-531
Open this publication in new window or tab >>More than meets the eye: Infrared cameras in open-ended university thermodynamics labs
2016 (English)In: Physics Teacher, ISSN 0031-921X, E-ISSN 1943-4928, Vol. 54, no 9, p. 528-531Article in journal (Refereed) Published
Abstract [en]

Educational research has found that students have challenges understanding thermal science. Undergraduate physics students have difficulties differentiating basic thermal concepts, such as heat, temperature, and internal energy. Engineering students have been found to have difficulties grasping surface emissivity as a thermal material property. One potential source of students’ challenges with thermal science is the lack of opportunity to visualize energy transfer in intuitive ways with traditional measurement equipment. Thermodynamics laboratories have typically depended on point measures of temperature by use of thermometers (detecting heat conduction) or pyrometers (detecting heat radiation). In contrast, thermal imaging by means of an infrared (IR) camera provides a real-time, holistic image. Here we provide some background on IR cameras and their uses in education, and summarize five qualitative investigations that we have used in our courses.

Keywords
infrared cameras; thermodynamics; physics education research; laboratory
National Category
Didactics Physical Sciences
Research subject
Physics with specialization in Physics Education
Identifiers
urn:nbn:se:uu:diva-306683 (URN)10.1119/1.4967889 (DOI)000388753500005 ()
Available from: 2016-11-02 Created: 2016-11-01 Last updated: 2017-11-29Bibliographically approved
Eriksson, J., Nocente, M., Binda, F., Cazzaniga, C., Conroy, S., Ericsson, G., . . . Weiszflog, M. (2015). Dual sightline measurements of MeV range deuterons with neutron and gamma-ray spectroscopy at JET. Nuclear Fusion, 55(12), Article ID 123026.
Open this publication in new window or tab >>Dual sightline measurements of MeV range deuterons with neutron and gamma-ray spectroscopy at JET
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2015 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 55, no 12, article id 123026Article in journal (Refereed) Published
Abstract [en]

Observations made in a JET experiment aimed at accelerating deuterons to the MeV range by third harmonic radio-frequency (RF) heating coupled into a deuterium beam are reported. Measurements are based on a set of advanced neutron and gamma-ray spectrometers that, for the first time, observe the plasma simultaneously along vertical and oblique lines of sight. Parameters of the fast ion energy distribution, such as the high energy cut-off of the deuteron distribution function and the RF coupling constant, are determined from data within a uniform analysis framework for neutron and gamma-ray spectroscopy based on a one-dimensional model and by a consistency check among the individual measurement techniques. A systematic difference is seen between the two lines of sight and is interpreted to originate from the sensitivity of the oblique detectors to the pitch-angle structure of the distribution around the resonance, which is not correctly portrayed within the adopted one dimensional model. A framework to calculate neutron and gamma-ray emission from a spatially resolved, two-dimensional deuteron distribution specified by energy/pitch is thus developed and used for a first comparison with predictions from ab initio models of RF heating at multiple harmonics.

The results presented in this paper are of relevance for the development of advanced diagnostic techniques for MeV range ions in high performance fusion plasmas, with applications to the experimental validation of RF heating codes and, more generally, to studies of the energy distribution of ions in the MeV range in high performance deuterium and deuterium-tritium plasmas.

Keywords
fusion, tokamak, fast ions, neutron spectrometry, gamma-ray spectroscopy
National Category
Fusion, Plasma and Space Physics
Research subject
Physics with specialization in Applied Nuclear Physics
Identifiers
urn:nbn:se:uu:diva-247990 (URN)10.1088/0029-5515/55/12/123026 (DOI)000366534500028 ()
Available from: 2015-03-25 Created: 2015-03-25 Last updated: 2018-04-23Bibliographically approved
Hellesen, C., Eriksson, J., Binda, F., Conroy, S., Ericsson, G., Hjalmarsson, A., . . . Weiszflog, M. (2015). Fuel ion ratio determination in NBI heated deuterium tritium fusion plasmas at JET using neutron emission spectrometry. Nuclear Fusion, 55(2), Article ID 023005.
Open this publication in new window or tab >>Fuel ion ratio determination in NBI heated deuterium tritium fusion plasmas at JET using neutron emission spectrometry
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2015 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 55, no 2, article id 023005Article in journal (Refereed) Published
Abstract [en]

The fuel ion ratio ( n t / n d ) is of central importance for the performance and control of a future burning fusion plasma, and reliable measurements of this quantity are essential for ITER. This paper demonstrates a method to derive the core fuel ion ratio by comparing the thermonuclear and beam-thermal neutron emission intensities, using a neutron spectrometer. The method is applied to NBI heated deuterium tritium (DT) plasmas at JET, using data from the magnetic proton recoil spectrometer. The trend in the results is consistent with Penning trap measurements of the fuel ion ratio at the edge of the plasma, but there is a discrepancy in the absolute values, possibly owing to the fact that the two measurements are weighted towards different parts of the plasma. It is suggested to further validate this method by comparing it to the traditionally proposed method to estimate n t / n d from the ratio of the thermal DD and DT neutron emission components. The spectrometer requirements for measuring n t / n d at ITER are also briefly discussed.

National Category
Fusion, Plasma and Space Physics
Research subject
Physics
Identifiers
urn:nbn:se:uu:diva-244352 (URN)10.1088/0029-5515/55/2/023005 (DOI)000348843100006 ()
Available from: 2015-02-16 Created: 2015-02-16 Last updated: 2018-04-23Bibliographically approved
Romanelli, F., Abhangi, M., Abreu, P., Aftanas, M., Afzal, M., Aggarwal, K. M., . . . Zychor, I. (2015). Overview of the JET results. Paper presented at 25th Fusion Energy Conference (FEC), OCT 13-18, 2014, Govt Russian Federat, St Petersburg, RUSSIA. Nuclear Fusion, 55(10), Article ID 104001.
Open this publication in new window or tab >>Overview of the JET results