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- 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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- Coburn, J., et al.
(författare)
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Energy deposition and melt deformation on the ITER first wall due to disruptions and vertical displacement events
- 2022
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 62:1
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Tidskriftsartikel (refereegranskat)abstract
- An analysis workflow has been developed to assess energy deposition and material damage for ITER vertical displacement events (VDEs) and major disruptions (MD). This paper describes the use of this workflow to assess the melt damage to be expected during unmitigated current quench (CQ) phases of VDEs and MDs at different points in the ITER research plan. The plasma scenarios are modeled using the DINA code with variations in plasma current I (p), disruption direction (upwards or downwards), Be impurity density n (Be), and diffusion coefficient chi. Magnetic field line tracing using SMITER calculates time-dependent, 3D maps of surface power density q (perpendicular to) on the Be-armored first wall panels (FWPs) throughout the CQ. MEMOS-U determines the temperature response, macroscopic melt motion, and final surface topology of each FWP. Effects of Be vapor shielding are included. Scenarios at the baseline combination of I (p) and toroidal field (15 MA/5.3 T) show the most extreme melt damage, with the assumed n (Be) having a strong impact on the disruption duration, peak q (perpendicular to) and total energy deposition to the first wall. The worst-cases are upward 15 MA VDEs and MDs at lower values of n (Be), with q (perpendicular to,max) = 307 MW m(-2) and maximum erosion losses of similar to 2 mm after timespans of similar to 400-500 ms. All scenarios at 5 MA avoided melt damage, and only one 7.5 MA scenario yields a notable erosion depth of 0.25 mm. These results imply that disruptions during 5 MA, and some 7.5 MA, operating scenarios will be acceptable during the pre-fusion power operation phases of ITER. Preliminary analysis shows that localized melt damage for the worst-case disruption should have a limited impact on subsequent stationary power handling capability.
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- Coburn, J., et al.
(författare)
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Reassessing energy deposition for the ITER 5 MA vertical displacement event with an improved DINA model
- 2021
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Ingår i: Nuclear Materials and Energy. - : Elsevier BV. - 2352-1791. ; 28
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Tidskriftsartikel (refereegranskat)abstract
- The beryllium (Be) main chamber wall interaction during a 5 MA/1.8 T upward, unmitigated VDE scenario, first analysed in [J. Coburn et al., Phys. Scr. T171 (2020) 014076] for ITER, has been re-evaluated using the latest energy deposition analysis software. Updates to the DINA disruption model are summarized, including an improved numerical convergence for the OD power balance, limitations on the safety factor within the plasma core, and the choice to maintain a constant plasma + halo poloidal cross-section. Such updates result in a broad halo region and higher radiated power fractions compared to previous models. The new scenario lasts for similar to 75 ms and deposits similar to 29 MJ of energy, with the radial distribution of parallel heat flux q parallel to(r) resembling an exponential falloff with an effective lambda(q) = 75 -198 mm. A maximum halo width w(h) of 0.52 m at the outboard midplane is observed. SMITER field line tracing and energy deposition simulations calculate a q(perpendicular to,max) of similar to 83 MW/m(2) on the upper first wall panels (FWP). Heat transfer calculations with the MEMOS-U code show that the FWP surface temperature reaches similar to 1000 K, well below the Be melt threshold. Variations of this 5 MA scenario with Be impurity densities from 0 to 3.10(19) m(-3) also remain below the melt threshold despite differences in energy deposition and duration. These results are in contrast to the early study which predicted melt damage to the first wall [J. Coburn et al., Phys. Scr. T171 (2020) 014076], and emphasize the importance of accurate models for the halo width w(h) and the heat flux distribution q parallel to(r) within that halo width. The 2020 halo model in DINA has been compared with halo current experiments on COMPASS, JET, and Alcator C-Mod, and the preliminary results build confidence in the broad halo width predictions. Results for the 5 MA VDE are compared with those for a 15 MA equivalent, generated using the new DINA model. At the higher current, significant melting of the upper FWP is to be expected.
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- Gryczynski, Z., et al.
(författare)
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Minimization of detection volume by surface-plasmon-coupled emission
- 2006
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Ingår i: Analytical Biochemistry. - : Elsevier BV. - 0003-2697 .- 1096-0309. ; 356:1, s. 125-131
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Tidskriftsartikel (refereegranskat)abstract
- We report theoretical predictions and experimental observations of the reduced detection volume with the use of surface-plasmon-coupled emission (SPCE). The effective fluorescence volume (detection volume) in SPCE experiments depends on two near-field factors: the depth of evanescent wave excitation and a distance-dependent coupling of excited fluorophores to the surface plasmons. With direct excitation of the sample (reverse Kretschmann excitation) the detection volume is restricted only by the distance-dependent coupling of the excitation to the surface plasmons. However, with the excitation through the glass prism at surface plasmon resonance angle (Kretschmann configuration), the detection volume is a product of evanescent wave penetration depth and distance-dependent coupling. In addition, the detection volume is further reduced by a metal quenching of excited fluorophores at a close proximity (below 10 nm). The height of the detected volume size is 40-70 nm, depending on the orientation of the excited dipoles. We show that, by using the Kretschmann configuration in a microscope with a high-numerical-aperture objective (1.45) together with confocal detection, the detection volume can be reduced to 1-2 attoL. The strong dependence of the coupling to the surface plasmons on the orientation of excited dipoles can be used to study the small conformational changes of macromolecules.
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- Klitgaard, S., et al.
(författare)
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Long wavelength depolarized light scattering from silver nanoparticles
- 2007
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 443:1-3, s. 1-5
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Tidskriftsartikel (refereegranskat)abstract
- We report the depolarized light scattering from heterodisperse silver nanoparticles. The profile of the wavelength dependent anisotropy of the colloidal solution of silver nanoparticles extends to the red and near-infrared (NIR) spectral region. For long wavelengths, above 600 nm, the anisotropy drops below 0.5. The presence of such a strong orthogonal component in the scattering opens new opportunities for imaging in dispersive media when polarizers can be used to suppress the background. The anisotropy profile of the scattering of heterodisperse silver nanoparticles can be satisfactorily explained by a theory based on interference between two surface plasmon resonances. (c) 2007 Elsevier B.V. All rights reserved.
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- Matveeva, E. G., et al.
(författare)
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Red blood cells do not attenuate the SPCE fluorescence in surface assays
- 2007
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 388:5-6, s. 1127-1135
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Tidskriftsartikel (refereegranskat)abstract
- We describe the positive effect of surface plasmon-coupled fluorescence emission (SPCE) on the detection of a signal from a surface immunoassay in highly absorbing or/and scattering samples. A model immunoassay using fluorescently labeled anti-rabbit antibodies that bind to rabbit immunoglobulin on a silver surface was performed, and the signal was detected in the presence of various highly absorbing and/or scattering solutions or suspensions, such as hemoglobin solution, plastic beads, and red blood cells. The results showed that a highly absorbing solution consisting of small molecules (dye, hemoglobin) attenuates the SPCE signal approximately 2-3-fold. In contrast, suspensions with the same absorption containing large particles (large beads, red blood cell suspension) attenuate the SPCE signal only slightly, approximately 5-10%. Also, a suspension of large undyed, highly scattering beads does not reduce the SPCE signal. The effects on the immunoassay signal of the sample background absorption and scattering, the size of the background particles, and the geometry of the experimental set-up are discussed. We believe that SPCE is a promising technique in the development of biosensors utilized for surface-based assays, as well as any assays performed directly in highly absorbing and/or scattering solutions without washing or separation procedures.
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