| 51. |
- Nocente, M., et al.
(författare)
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Fast ion energy distribution from third harmonic radio frequency heating measured with a single crystal diamond detector at the Joint European Torus
- 2015
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Ingår i: Review of Scientific Instruments. - : AMER INST PHYSICS. - 0034-6748 .- 1089-7623. ; 86:10
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Tidskriftsartikel (refereegranskat)abstract
- Neutron spectroscopy measurements with a single crystal diamond detector have been carried out at JET, for the first time in an experiment aimed at accelerating deuterons to MeV energies with radio frequency heating at the third harmonic. Data are interpreted by means of the expected response function of the detector and are used to extract parameters of the highly non-Maxwellian distribution function generated in this scenario. A comparison with observations using a time of flight and liquid scintillator neutron spectrometers is also presented. The results demonstrate the capability of diamond detectors to contribute to fast ion physics studies at JET and are of more general relevance in view of the application of such detectors for spectroscopy measurements in the neutron camera of next step tokamak devices.
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| 52. |
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| 53. |
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| 54. |
- Salewski, M., et al.
(författare)
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Bayesian Integrated Data Analysis of Fast-Ion Measurements by Velocity-Space Tomography
- 2018
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Ingår i: Fusion science and technology. - : TAYLOR & FRANCIS INC. - 1536-1055 .- 1943-7641. ; 74:1-2, s. 23-36
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Tidskriftsartikel (refereegranskat)abstract
- Bayesian integrated data analysis combines measurements from different diagnostics to jointly measure plasma parameters of interest such as temperatures, densities, and drift velocities. Integrated data analysis of fast-ion measurements has long been hampered by the complexity of the strongly non-Maxwellian fast-ion distribution functions. This has recently been overcome by velocity-space tomography. In this method two-dimensional images of the velocity distribution functions consisting of a few hundreds or thousands of pixels are reconstructed using the available fast-ion measurements. Here we present an overview and current status of this emerging technique at the ASDEX Upgrade tokamak and the JET toamak based on fast-ion D-alpha spectroscopy, collective Thomson scattering, gamma-ray and neutron emission spectrometry, and neutral particle analyzers. We discuss Tikhonov regularization within the Bayesian framework. The implementation for different types of diagnostics as well as the uncertainties are discussed, and we highlight the importance of integrated data analysis of all available detectors.
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| 55. |
- Weisen, H., et al.
(författare)
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The 'neutron deficit' in the JET tokamak
- 2017
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 57:7
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Tidskriftsartikel (refereegranskat)abstract
- The measured D-D neutron rate of neutral beam heated JET baseline and hybrid H-modes in deuterium is found to be between approximately 50% and 100% of the neutron rate expected from the TRANSP code, depending on the plasma parameters. A number of candidate explanations for the shortfall, such as fuel dilution, errors in beam penetration and effectively available beam power have been excluded. As the neutron rate in JET is dominated by beamplasma interactions, the ` neutron deficit' may be caused by a yet unidentified form of fast particle redistribution. Modelling, which assumes fast particle transport to be responsible for the deficit, indicates that such redistribution would have to happen at time scales faster than both the slowing down time and the energy confinement time. Sawteeth and edge localised modes are found to make no significant contribution to the deficit. There is also no obvious correlation with magnetohydrodynamic activity measured using magnetic probes at the tokamak vessel walls. Modelling of fast particle orbits in the 3D fields of neoclassical tearing modes shows that realistically sized islands can only contribute a few percent to the deficit. In view of these results it appears unlikely that the neutron deficit results from a single physical process in the plasma.
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| 56. |
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| 57. |
- Beaton, Dorcas E, et al.
(författare)
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OMERACT Filter Evidence Supporting the Measurement of At-work Productivity Loss as an Outcome Measure in Rheumatology Research.
- 2016
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Ingår i: Journal of Rheumatology. - : The Journal of Rheumatology. - 0315-162X .- 1499-2752. ; 43:1, s. 214-222
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Tidskriftsartikel (refereegranskat)abstract
- Indicators of work role functioning (being at work, and being productive while at work) are important outcomes for persons with arthritis. As the worker productivity working group at OMERACT (Outcome Measures in Rheumatology), we sought to provide an evidence base for consensus on standardized instruments to measure worker productivity [both absenteeism and at-work productivity (presenteeism) as well as critical contextual factors].
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| 58. |
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| 59. |
- Ceberg, S., et al.
(författare)
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FLASH radiotherapy and the associated dosimetric challenges
- 2023
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Ingår i: Journal of Physics: Conference Series. ; 2630
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Konferensbidrag (refereegranskat)abstract
- At Lund University and Skåne University Hospital in Lund, Sweden, we have, as the first clinic, modified a clinical Elekta Precise linear accelerator for convertible delivery of ultrahigh dose rate (FLASH) irradiation. Whereas recently published reviews highlighted the need for standardised protocols for ultra-high dose rate beam dosimetry to be able to determine the true potential of FLASH irradiation, several dosimetry studies as well as in-vitro and in-vivo experiments have been carried out at our unit. Dosimetric procedures for verification of accurate dose delivery of FLASH irradiation to cell cultures, zebrafish embryos and small animals have been established using radiochromic films and thermo-luminescent dosimeters. Also, recently the first experience of electron FLASH radiotherapy (FLASH-RT) in canine patients in our clinical setting was published. Our research facilities also include a laboratory for 3D polymer gel manufacturing. Recently, we started investigating the feasibility of a NIPAM polymer gel dosimeter for ultra-high dose rate dosimetry. Furthermore, in the bunker of the modified Elekta linear accelerator, a Surface Guided Radiotherapy (SGRT) system is accessible. The CatalystTM system (C-Rad Positioning, Uppsala, Sweden) provides optical surface imaging for patient setup, real-time motion monitoring and breathing adapted treatment. Aiming at treating patients using ultra-high dose rates, a real-time validation of the alignment between the beam and the target is crucial as the dose is delivered in a fraction of a second. Our research group has during the last decade investigated and developed SGRT workflows which improved patient setup and breathing adapted treatment for several cancer patient groups. Recently, we also started investigating the feasibility of a real-time motion monitoring system for surface guided FLASH-RT. Both FLASH related studies; 3D polymer gel dosimetry and surface guided FLASH-RT are to our knowledge the first of their kind. Following an introduction to the field of FLASH and the associated dosimetric challenges, we here aim to present the two ongoing studies including some preliminary results.
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| 60. |
- Hakola, A., et al.
(författare)
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Global migration of impurities in tokamaks
- 2013
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 0741-3335 .- 1361-6587. ; 55:12
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Tidskriftsartikel (refereegranskat)abstract
- The migration of impurities in tokamaks has been studied with the help of tracer-injection (C-13 and N-15) experiments in JET and ASDEX Upgrade since 2001. We have identified a common pattern for the migrating particles: scrape-off layer flows drive impurities from the low-field side towards the high-field side of the vessel. Migration is also sensitive to the density and magnetic configuration of the plasma, and strong local variations in the resulting deposition patterns require 3D treatment of the migration process. Moreover, re-erosion of the deposited particles has to be taken into account to properly describe the migration process during steady-state operation of the tokamak.
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