The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
G De Temmerman - One of the best experts on this subject based on the ideXlab platform.
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Power deposition on misaligned castellated tungsten blocks in the Magnum-PSI and Pilot-PSI Linear Devices
Nuclear Fusion, 2017Co-Authors: T.w. Morgan, G De Temmerman, M.a. Van Den Berg, S. Bardin, D.u.b. Aussems, R.a. PittsAbstract:For the final design of the ITER divertor it is important to determine whether shaping of each tungsten monoblock to eliminate leading edges is required or not. In order to aid this decision, two experiments were performed in DIFFER's Linear plasma Devices to study heat loads on misaligned water cooled blocks at glancing incidence. First, a series of tungsten blocks were exposed to a high parallel heat flux (26 MW ) hydrogen plasma beam in the Magnum-PSI Linear Device. The blocks were exposed at an oblique angle between and with respect to the plasma beam, approaching the low angle of incidence expected in the ITER divertor strike-point regions. One block was vertically misaligned with respect to the others by a value between 0 and mm, and the surface temperature evolution monitored. This was compared to a finite element thermo-mechanical model of the system, to investigate any discrepancies between the two. The importance of Larmor orbit smoothing effects could also be considered, as the Larmor radius was larger than half the misalignment height. Next, a row of identical tungsten blocks were exposed at an angle of to ~500–700 μs pulsed hydrogen plasmas of peak power between 275–625 MW in the Pilot-PSI Linear Device, to simulate the effect of edge localized mode (ELM) transients. One block was misaligned with respect to the others by 1 mm. In all cases, the model and experiment were found to be in excellent agreement (to ~1%), demonstrating clearly that an optical approximation for plasma power loading on misaligned edges is appropriate. A simple model including Larmor smoothing was applied, the results of which give a similar prediction to the optical approximation for the temperature of the misaligned edges, within the error of the temperature measurements, though a small decrease in edge temperature is calculated. Therefore it can be concluded that the application of the optical approximation is generally appropriate as an input physics assumption for the study of shaping alternatives.
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dust remobilization in fusion plasmas under steady state conditions
Plasma Physics and Controlled Fusion, 2016Co-Authors: Panagiotis Tolias, S Ratynskaia, M De Angeli, G De Temmerman, D Ripamonti, G Riva, I Bykov, A Shalpegin, Ladislas VignitchoukAbstract:The first combined experimental and theoretical studies of dust remobilization by plasma forces are reported. The main theoretical aspects of remobilization in fusion Devices under steady state conditions are analyzed. In particular, the dominant role of adhesive forces is highlighted and generic remobilization conditions—direct lift-up, sliding, rolling—are formulated. A novel experimental technique is proposed, based on controlled adhesion of dust grains on tungsten samples combined with detailed mapping of the dust deposition profile prior and post plasma exposure. Proof-of-principle experiments in the TEXTOR tokamak and the EXTRAP-T2R reversed-field pinch are presented. The versatile environment of the Linear Device Pilot-PSI allowed for experiments with different magnetic field topologies and varying plasma conditions that were complemented with camera observations.
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A high-repetition rate edge localised mode replication system for the Magnum-PSI and Pilot-PSI Linear Devices
Plasma Physics and Controlled Fusion, 2014Co-Authors: G De Temmerman, T.w. Morgan, M.a. Van Den Berg, S. Bardin, H. J. Van Der Meiden, T M De Kruif, J. Scholten, W Melissen, B. J. M. KrijgerAbstract:A high-power edge-localized mode (ELM) striking onto divertor components presents one of the strongest lifetime and performance challenges for plasma facing components in future fusion reactors. A high-repetition-rate ELM replication system has been constructed and was commissioned at the Magnum-PSI Linear Device to investigate the synergy between steady state plasma exposure and the large increase in heat and particle flux to the plasma facing surface during repeated ELM transients in conditions aiming to mimic as closely as possible those in the ITER divertor. This system is capable of increasing the electron density and temperature from ~1 × 1020 m−3 to ~1 × 1021 m−3 and from 1 to 5 eV respectively, leading to a heat flux increase at the surface to ~130 MW m−2. By combining Thomson scattering measurements with heat fluxes determined using the THEODOR code, the sheath heat transmission factor during the pulses was determined to be ≈7.7, in agreement with sheath theory. The heat flux is found to be Linearly dependent upon the strength of the magnetic field at the target position, and, by adapting the system to Pilot-PSI, tests at 1.6 T showed heat fluxes of more than 600 MW m−2. This gives confidence that with the installation of a 2.5 T superconducting magnetic solenoid at Magnum-PSI the heat flux will reach the ITER-relevant gigawatt per square metre heat flux regime.
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Deuterium retention and release in tungsten co-deposited layers
Journal of Nuclear Materials, 2009Co-Authors: R.p. Doerner, G De TemmermanAbstract:Abstract A systematic study of the influence of the deposition conditions on the deuterium retention in co-deposited tungsten layers formed both by magnetron sputtering and in the PISCES-B Linear Device has been carried out. Experimental parameters such as the tungsten deposition rate, the incident particle energy and the substrate temperature are shown to affect the level of deuterium retention in the layers. A decreased retention for increased substrate temperature and deposition rates, and an increased retention for increasing incident deuterium particle energy are observed. A scaling equation is proposed to describe the influence of the conditions during the co-deposition process (surface temperature, incident particle energy and deposition flux) on the deuterium retention. In addition, the desorption kinetics of deuterium has been studied by TDS. Two desorption stages at 473–573 K and at 1073 K have been observed.
T.w. Morgan - One of the best experts on this subject based on the ideXlab platform.
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Power deposition on misaligned castellated tungsten blocks in the Magnum-PSI and Pilot-PSI Linear Devices
Nuclear Fusion, 2017Co-Authors: T.w. Morgan, G De Temmerman, M.a. Van Den Berg, S. Bardin, D.u.b. Aussems, R.a. PittsAbstract:For the final design of the ITER divertor it is important to determine whether shaping of each tungsten monoblock to eliminate leading edges is required or not. In order to aid this decision, two experiments were performed in DIFFER's Linear plasma Devices to study heat loads on misaligned water cooled blocks at glancing incidence. First, a series of tungsten blocks were exposed to a high parallel heat flux (26 MW ) hydrogen plasma beam in the Magnum-PSI Linear Device. The blocks were exposed at an oblique angle between and with respect to the plasma beam, approaching the low angle of incidence expected in the ITER divertor strike-point regions. One block was vertically misaligned with respect to the others by a value between 0 and mm, and the surface temperature evolution monitored. This was compared to a finite element thermo-mechanical model of the system, to investigate any discrepancies between the two. The importance of Larmor orbit smoothing effects could also be considered, as the Larmor radius was larger than half the misalignment height. Next, a row of identical tungsten blocks were exposed at an angle of to ~500–700 μs pulsed hydrogen plasmas of peak power between 275–625 MW in the Pilot-PSI Linear Device, to simulate the effect of edge localized mode (ELM) transients. One block was misaligned with respect to the others by 1 mm. In all cases, the model and experiment were found to be in excellent agreement (to ~1%), demonstrating clearly that an optical approximation for plasma power loading on misaligned edges is appropriate. A simple model including Larmor smoothing was applied, the results of which give a similar prediction to the optical approximation for the temperature of the misaligned edges, within the error of the temperature measurements, though a small decrease in edge temperature is calculated. Therefore it can be concluded that the application of the optical approximation is generally appropriate as an input physics assumption for the study of shaping alternatives.
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A high-repetition rate edge localised mode replication system for the Magnum-PSI and Pilot-PSI Linear Devices
Plasma Physics and Controlled Fusion, 2014Co-Authors: G De Temmerman, T.w. Morgan, M.a. Van Den Berg, S. Bardin, H. J. Van Der Meiden, T M De Kruif, J. Scholten, W Melissen, B. J. M. KrijgerAbstract:A high-power edge-localized mode (ELM) striking onto divertor components presents one of the strongest lifetime and performance challenges for plasma facing components in future fusion reactors. A high-repetition-rate ELM replication system has been constructed and was commissioned at the Magnum-PSI Linear Device to investigate the synergy between steady state plasma exposure and the large increase in heat and particle flux to the plasma facing surface during repeated ELM transients in conditions aiming to mimic as closely as possible those in the ITER divertor. This system is capable of increasing the electron density and temperature from ~1 × 1020 m−3 to ~1 × 1021 m−3 and from 1 to 5 eV respectively, leading to a heat flux increase at the surface to ~130 MW m−2. By combining Thomson scattering measurements with heat fluxes determined using the THEODOR code, the sheath heat transmission factor during the pulses was determined to be ≈7.7, in agreement with sheath theory. The heat flux is found to be Linearly dependent upon the strength of the magnetic field at the target position, and, by adapting the system to Pilot-PSI, tests at 1.6 T showed heat fluxes of more than 600 MW m−2. This gives confidence that with the installation of a 2.5 T superconducting magnetic solenoid at Magnum-PSI the heat flux will reach the ITER-relevant gigawatt per square metre heat flux regime.
M.a. Van Den Berg - One of the best experts on this subject based on the ideXlab platform.
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Power deposition on misaligned castellated tungsten blocks in the Magnum-PSI and Pilot-PSI Linear Devices
Nuclear Fusion, 2017Co-Authors: T.w. Morgan, G De Temmerman, M.a. Van Den Berg, S. Bardin, D.u.b. Aussems, R.a. PittsAbstract:For the final design of the ITER divertor it is important to determine whether shaping of each tungsten monoblock to eliminate leading edges is required or not. In order to aid this decision, two experiments were performed in DIFFER's Linear plasma Devices to study heat loads on misaligned water cooled blocks at glancing incidence. First, a series of tungsten blocks were exposed to a high parallel heat flux (26 MW ) hydrogen plasma beam in the Magnum-PSI Linear Device. The blocks were exposed at an oblique angle between and with respect to the plasma beam, approaching the low angle of incidence expected in the ITER divertor strike-point regions. One block was vertically misaligned with respect to the others by a value between 0 and mm, and the surface temperature evolution monitored. This was compared to a finite element thermo-mechanical model of the system, to investigate any discrepancies between the two. The importance of Larmor orbit smoothing effects could also be considered, as the Larmor radius was larger than half the misalignment height. Next, a row of identical tungsten blocks were exposed at an angle of to ~500–700 μs pulsed hydrogen plasmas of peak power between 275–625 MW in the Pilot-PSI Linear Device, to simulate the effect of edge localized mode (ELM) transients. One block was misaligned with respect to the others by 1 mm. In all cases, the model and experiment were found to be in excellent agreement (to ~1%), demonstrating clearly that an optical approximation for plasma power loading on misaligned edges is appropriate. A simple model including Larmor smoothing was applied, the results of which give a similar prediction to the optical approximation for the temperature of the misaligned edges, within the error of the temperature measurements, though a small decrease in edge temperature is calculated. Therefore it can be concluded that the application of the optical approximation is generally appropriate as an input physics assumption for the study of shaping alternatives.
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A high-repetition rate edge localised mode replication system for the Magnum-PSI and Pilot-PSI Linear Devices
Plasma Physics and Controlled Fusion, 2014Co-Authors: G De Temmerman, T.w. Morgan, M.a. Van Den Berg, S. Bardin, H. J. Van Der Meiden, T M De Kruif, J. Scholten, W Melissen, B. J. M. KrijgerAbstract:A high-power edge-localized mode (ELM) striking onto divertor components presents one of the strongest lifetime and performance challenges for plasma facing components in future fusion reactors. A high-repetition-rate ELM replication system has been constructed and was commissioned at the Magnum-PSI Linear Device to investigate the synergy between steady state plasma exposure and the large increase in heat and particle flux to the plasma facing surface during repeated ELM transients in conditions aiming to mimic as closely as possible those in the ITER divertor. This system is capable of increasing the electron density and temperature from ~1 × 1020 m−3 to ~1 × 1021 m−3 and from 1 to 5 eV respectively, leading to a heat flux increase at the surface to ~130 MW m−2. By combining Thomson scattering measurements with heat fluxes determined using the THEODOR code, the sheath heat transmission factor during the pulses was determined to be ≈7.7, in agreement with sheath theory. The heat flux is found to be Linearly dependent upon the strength of the magnetic field at the target position, and, by adapting the system to Pilot-PSI, tests at 1.6 T showed heat fluxes of more than 600 MW m−2. This gives confidence that with the installation of a 2.5 T superconducting magnetic solenoid at Magnum-PSI the heat flux will reach the ITER-relevant gigawatt per square metre heat flux regime.
S. Bardin - One of the best experts on this subject based on the ideXlab platform.
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Power deposition on misaligned castellated tungsten blocks in the Magnum-PSI and Pilot-PSI Linear Devices
Nuclear Fusion, 2017Co-Authors: T.w. Morgan, G De Temmerman, M.a. Van Den Berg, S. Bardin, D.u.b. Aussems, R.a. PittsAbstract:For the final design of the ITER divertor it is important to determine whether shaping of each tungsten monoblock to eliminate leading edges is required or not. In order to aid this decision, two experiments were performed in DIFFER's Linear plasma Devices to study heat loads on misaligned water cooled blocks at glancing incidence. First, a series of tungsten blocks were exposed to a high parallel heat flux (26 MW ) hydrogen plasma beam in the Magnum-PSI Linear Device. The blocks were exposed at an oblique angle between and with respect to the plasma beam, approaching the low angle of incidence expected in the ITER divertor strike-point regions. One block was vertically misaligned with respect to the others by a value between 0 and mm, and the surface temperature evolution monitored. This was compared to a finite element thermo-mechanical model of the system, to investigate any discrepancies between the two. The importance of Larmor orbit smoothing effects could also be considered, as the Larmor radius was larger than half the misalignment height. Next, a row of identical tungsten blocks were exposed at an angle of to ~500–700 μs pulsed hydrogen plasmas of peak power between 275–625 MW in the Pilot-PSI Linear Device, to simulate the effect of edge localized mode (ELM) transients. One block was misaligned with respect to the others by 1 mm. In all cases, the model and experiment were found to be in excellent agreement (to ~1%), demonstrating clearly that an optical approximation for plasma power loading on misaligned edges is appropriate. A simple model including Larmor smoothing was applied, the results of which give a similar prediction to the optical approximation for the temperature of the misaligned edges, within the error of the temperature measurements, though a small decrease in edge temperature is calculated. Therefore it can be concluded that the application of the optical approximation is generally appropriate as an input physics assumption for the study of shaping alternatives.
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A high-repetition rate edge localised mode replication system for the Magnum-PSI and Pilot-PSI Linear Devices
Plasma Physics and Controlled Fusion, 2014Co-Authors: G De Temmerman, T.w. Morgan, M.a. Van Den Berg, S. Bardin, H. J. Van Der Meiden, T M De Kruif, J. Scholten, W Melissen, B. J. M. KrijgerAbstract:A high-power edge-localized mode (ELM) striking onto divertor components presents one of the strongest lifetime and performance challenges for plasma facing components in future fusion reactors. A high-repetition-rate ELM replication system has been constructed and was commissioned at the Magnum-PSI Linear Device to investigate the synergy between steady state plasma exposure and the large increase in heat and particle flux to the plasma facing surface during repeated ELM transients in conditions aiming to mimic as closely as possible those in the ITER divertor. This system is capable of increasing the electron density and temperature from ~1 × 1020 m−3 to ~1 × 1021 m−3 and from 1 to 5 eV respectively, leading to a heat flux increase at the surface to ~130 MW m−2. By combining Thomson scattering measurements with heat fluxes determined using the THEODOR code, the sheath heat transmission factor during the pulses was determined to be ≈7.7, in agreement with sheath theory. The heat flux is found to be Linearly dependent upon the strength of the magnetic field at the target position, and, by adapting the system to Pilot-PSI, tests at 1.6 T showed heat fluxes of more than 600 MW m−2. This gives confidence that with the installation of a 2.5 T superconducting magnetic solenoid at Magnum-PSI the heat flux will reach the ITER-relevant gigawatt per square metre heat flux regime.
H. J. Van Der Meiden - One of the best experts on this subject based on the ideXlab platform.
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Soledge2D-Eirene simulations of the Pilot-PSI Linear plasma Device compared to experimental data
Contributions to Plasma Physics, 2018Co-Authors: K. Jesko, Y. Marandet, H. Bufferand, J.p. Gunn, H. J. Van Der Meiden, G. CiraoloAbstract:Predictions for the operation of tokamak divertors are reliant on edge plasma simulations typically utilizing a fluid plasma code in combination with a Monte Carlo code for neutral species. Pilot-PSI is a Linear Device operating with a cascaded arc plasma source that produces plasmas comparable to those expected in the ITER divertor (Te ∼ 1 eV, ne ∼ 10 21 m −3). In this study, plasma discharges in Pilot-PSI have been modelled using the Soledge2D fluid plasma code [1] coupled to the Eirene neutral Monte Carlo code. The plasma is generated using an external source of plasma density and power. These input parameters are tuned in order to match Thomson scattering (TS) measurements close to the cascaded arc source nozzle. The sensitivity of the simulations to different atomic physics models was explored. It was found that elastic collisions between ions and hydrogen molecules have a strong influence on calculated profiles. Without their inclusion, supersonic flow regimes are obtained with M ∼ 2 close to the target plate. Simulation results have been compared with experimental findings using TS close to the target and in the case of Pilot-PSI, a Langmuir probe embedded in the target. Comparison between experimental trends observed in a background pressure scan [2] and the simulations show that the inclusion of the elastic collision is mandatory for the trends to be reproduced.
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A high-repetition rate edge localised mode replication system for the Magnum-PSI and Pilot-PSI Linear Devices
Plasma Physics and Controlled Fusion, 2014Co-Authors: G De Temmerman, T.w. Morgan, M.a. Van Den Berg, S. Bardin, H. J. Van Der Meiden, T M De Kruif, J. Scholten, W Melissen, B. J. M. KrijgerAbstract:A high-power edge-localized mode (ELM) striking onto divertor components presents one of the strongest lifetime and performance challenges for plasma facing components in future fusion reactors. A high-repetition-rate ELM replication system has been constructed and was commissioned at the Magnum-PSI Linear Device to investigate the synergy between steady state plasma exposure and the large increase in heat and particle flux to the plasma facing surface during repeated ELM transients in conditions aiming to mimic as closely as possible those in the ITER divertor. This system is capable of increasing the electron density and temperature from ~1 × 1020 m−3 to ~1 × 1021 m−3 and from 1 to 5 eV respectively, leading to a heat flux increase at the surface to ~130 MW m−2. By combining Thomson scattering measurements with heat fluxes determined using the THEODOR code, the sheath heat transmission factor during the pulses was determined to be ≈7.7, in agreement with sheath theory. The heat flux is found to be Linearly dependent upon the strength of the magnetic field at the target position, and, by adapting the system to Pilot-PSI, tests at 1.6 T showed heat fluxes of more than 600 MW m−2. This gives confidence that with the installation of a 2.5 T superconducting magnetic solenoid at Magnum-PSI the heat flux will reach the ITER-relevant gigawatt per square metre heat flux regime.