| 1. |
- Batistoni, P., et al.
(författare)
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Technological exploitation of Deuterium-Tritium operations at JET in support of ITER design, operation and safety
- 2016
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Ingår i: Fusion engineering and design. - : ELSEVIER SCIENCE SA. - 0920-3796 .- 1873-7196. ; 109, s. 278-285
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Tidskriftsartikel (refereegranskat)abstract
- Within the framework of the EUROfusion programme, a work-package of technology projects (WPJET3) is being carried out in conjunction with the planned Deuterium-Tritium experiment on JET (DTE2) with the objective of maximising the scientific and technological return of DT operations at JET in support of ITER. This paper presents the progress since the start of the project in 2014 in the preparatory experiments, analyses and studies in the areas of neutronics, neutron induced activation and damage in ITER materials, nuclear safety, tritium retention, permeation and outgassing, and waste production in preparation of DTE2.
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| 2. |
- Beal, J., et al.
(författare)
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Deposition in the inner and outer corners of the JET divertor with carbon wall and metallic ITER-like wall
- 2016
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Ingår i: Physica Scripta. - : IOP PUBLISHING LTD. - 0031-8949 .- 1402-4896. ; T167
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Tidskriftsartikel (refereegranskat)abstract
- Rotating collectors and quartz microbalances (QMBs) are used in JET to provide time-dependent measurements of erosion and deposition. Rotation of collector discs behind apertures allows recording of the long term evolution of deposition. QMBs measure mass change via the frequency deviations of vibrating quartz crystals. These diagnostics are used to investigate erosion/deposition during JET-C carbon operation and JET-ILW (ITER-like wall) beryllium/tungsten operation. A simple geometrical model utilising experimental data is used to model the time-dependent collector deposition profiles, demonstrating good qualitative agreement with experimental results. Overall, the JET-ILW collector deposition is reduced by an order of magnitude relative to JET-C, with beryllium replacing carbon as the dominant deposit. However, contrary to JET-C, in JET-ILW there is more deposition on the outer collector than the inner. This reversal of deposition asymmetry is investigated using an analysis of QMB data and is attributed to the different chemical properties of carbon and beryllium.
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| 3. |
- Bernardo, J., et al.
(författare)
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Ion temperature and toroidal rotation in JET's low torque plasmas
- 2016
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 87:11
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports on the procedure developed as the best method to provide an accurate and reliable estimation of the ion temperature T-i and the toroidal velocity v(phi) from Charge-eXchange Recombination Spectroscopy (CXRS) data from intrinsic rotation experiments at the Joint European Torus with the carbon wall. The low impurity content observed in such plasmas, resulting in low active CXRS signal, alongside low Doppler shifts makes the determination of Ti and v(phi) particularly difficult. The beam modulation method will be discussed along with the measures taken to increase photon statistics and minimise errors from the absolute calibration and magneto-hydro-dynamics effects that may impact the CXRS passive emission.
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| 4. |
- Borodin, D., et al.
(författare)
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Improved ERO modelling for spectroscopy of physically and chemically assisted eroded beryllium from the JET-ILW
- 2016
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Ingår i: Nuclear Materials and Energy. - : ELSEVIER. - 2352-1791. ; 9, s. 604-609
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Tidskriftsartikel (refereegranskat)abstract
- Physical and chemical assisted physical sputtering were characterised by the Be I and Be II line and BeD band emission in the observation chord measuring the sightline integrated emission in front of the inner beryllium limiter at the torus midplane. The 3D local transport and plasma-surface interaction Monte-Carlo modelling (ERO code [18]) is a key for the interpretation of the observations in the vicinity of the shaped solid Be limiter. The plasma parameter variation (density scan) in limiter regime has provided a useful material for the simulation benchmark. The improved background plasma parameters input, the new analytical expression for particle tracking in the sheath region and implementation of the BeD release into ERO has helped to clarify some deviations between modelling and experiments encountered in the previous studies [4,5]. Reproducing the observations provides additional confidence in our 'ERO-min' fit for the physical sputtering yields for the plasma-wetted areas based on simulated data.
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| 5. |
- Borodkina, I., et al.
(författare)
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An Analytical Expression for the Electric Field and Particle Tracing in Modelling of Be Erosion Experiments at the JET ITER-like Wall
- 2016
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Ingår i: Contributions to Plasma Physics. - : WILEY-V C H VERLAG GMBH. - 0863-1042 .- 1521-3986. ; 56:6-8, s. 640-645
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Tidskriftsartikel (refereegranskat)abstract
- A new analytical approximation for the electric potential profile in the presence of an oblique magnetic field and the analytical solution for the particle motion just before the impact with a plasma-facing surface are presented. These approximations are in good agreement with fluid solutions and the corresponding PIC simulations. These expressions were applied to provide effective physical erosion yields for Be, which have in a second step been used in ERO code simulations of spectroscopy at Be limiters of the JET ITER-like wall. These new analytical expressions lead to an increase of the effective physical sputtering yields of Be by deuteron impact up to 30% in comparison with earlier pure numerical simulations. (
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| 6. |
- Bourdelle, C., et al.
(författare)
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Core turbulent transport in tokamak plasmas : bridging theory and experiment with QuaLiKiz
- 2016
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP PUBLISHING LTD. - 0741-3335 .- 1361-6587. ; 58:1
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Tidskriftsartikel (refereegranskat)abstract
- Nonlinear gyrokinetic codes allow for detailed understanding of tokamak core turbulent transport. However, their computational demand precludes their use for predictive profile modeling. An alternative approach is required to bridge the gap between theoretical understanding and prediction of experiments. A quasilinear gyrokinetic model, QuaLiKiz (Bourdelle et al 2007 Phys. Plasmas 14 112501), is demonstrated to be rapid enough to ease systematic interface with experiments. The derivation and approximation of this approach are reviewed. The quasilinear approximation is proven valid over a wide range of core plasma parameters. Examples of profile prediction using QuaLiKiz coupled to the CRONOS integrated modeling code (Artaud et al 2010 Nucl. Fusion 50 043001) are presented. QuaLiKiz is being coupled to other integrated modeling platforms such as ETS and JETTO. QuaLiKiz quasilinear gyrokinetic turbulent heat, particle and angular momentum fluxes are available to all users. It allows for extensive stand-alone interpretative analysis and for first principle based integrated predictive modeling.
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| 7. |
- Boyer, Helen, et al.
(författare)
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JET Tokamak, preparation of a safety case for tritium operations
- 2016
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Ingår i: Fusion engineering and design. - : ELSEVIER SCIENCE SA. - 0920-3796 .- 1873-7196. ; 109, s. 1308-1312
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Tidskriftsartikel (refereegranskat)abstract
- A new Safety Case is required to permit tritium operations on JET during the forthcoming DTE2 campaign. The outputs, benefits and lessons learned associated with the production of this Safety Case are presented. The changes that have occurred to the Safety Case methodology since the last JET tritium Safety Case are reviewed. Consideration is given to the effects of modifications, particularly ITER related changes, made to the JET and the impact these have on the hazard assessments as well as normal operations. Several specialized assessments, including recent MELCOR modelling, have been undertaken to support the production of this Safety Case and the impact of these assessments is outlined. Discussion of the preliminary actions being taken to progress implementation of this Safety Case is provided, highlighting new methods to improve the dissemination of the key Safety Case results to the plant operators. Finally, the work required to complete this Safety Case, before the next tritium campaign, is summarized. (C) 2016 EURATOM. Published by Elsevier B.V. All rights reserved.
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| 8. |
- Bravenec, R., et al.
(författare)
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Benchmarking the GENE and GYRO codes through the relative roles of electromagnetic and E x B stabilization in JET high-performance discharges
- 2016
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Ingår i: Plasma Physics and Controlled Fusion. - : Institute of Physics Publishing (IOPP). - 0741-3335 .- 1361-6587. ; 58:12
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Tidskriftsartikel (refereegranskat)abstract
- Nonlinear gyrokinetic simulations using the GENE code have previously predicted a significant nonlinear enhanced electromagnetic stabilization in certain JET discharges with high neutral-beam power and low core magnetic shear (Citrin et al 2013 Phys. Rev. Lett. 111 155001, 2015 Plasma Phys. Control. Fusion 57 014032). This dominates over the impact of E x B flow shear in these discharges. Furthermore, fast ions were shown to be a major contributor to the electromagnetic stabilization. These conclusions were based on results from the GENE gyrokinetic turbulence code. In this work we verify these results using the GYRO code. Comparing results (linear frequencies, eigenfunctions, and nonlinear fluxes) from different gyrokinetic codes as a means of verification (benchmarking) is only convincing if the codes agree for more than one discharge. Otherwise, agreement may simply be fortuitous. Therefore, we analyze three discharges, all with a carbon wall: a simplified, two-species, circular geometry case based on an actual JET discharge; an L-mode discharge with a significant fast-ion pressure fraction; and a low-triangularity high-beta hybrid discharge. All discharges were analyzed at normalized toroidal flux coordinate rho = 0.33 where significant ion temperature peaking is observed. The GYRO simulations support the conclusion that electromagnetic stabilization is strong, and dominates E x B shear stabilization.
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| 9. |
- Brezinsek, S., et al.
(författare)
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Characterisation of the deuterium recycling at the W divertor target plates in JET during steady-state plasma conditions and ELMs
- 2016
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Ingår i: Physica Scripta. - : IOP PUBLISHING LTD. - 0031-8949 .- 1402-4896. ; T167
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Tidskriftsartikel (refereegranskat)abstract
- Experiments in the JET tokamak equipped with the ITER-like wall (ILW) revealed that the inner and outer target plate at the location of the strike points represent after one year of operation intact tungsten (W) surfaces without any beryllium (Be) surface coverage. The dynamics of near-surface retention, implantation, desorption and recycling of deuterium (D) in the divertor of plasma discharges are determined by W target plates. As the W plasma-facing components (PFCs) are not actively cooled, the surface temperature (T-surface) is increasing with plasma exposure, varying the balance between these processes in addition to the impinging deuteron fluxes and energies. The dynamic behaviour on a slow time scale of seconds was quantified in a series of identical L-mode discharges (JET Pulse Number (JPN)#81938-73) by intra-shot gas analysis providing the reduction of deuterium retention in W PFCs by 1/3 at a base temperature (T-base) range at the outer target plate between 65 degrees C and 150 degrees C equivalent to a T-surface span of 150 degrees C and 420 degrees C. The associated recycling and molecular D desorption during the discharge varies only at lowest temperatures moderately, whereas desorption between discharges rises significantly with increasing T-base. The retention measurements represent the sum of inner and outer divertor interaction at comparable T-surface. The dynamic behaviour on a fast time scale of ms was studied in a series of identical H-mode discharges (JPN #83623-83974) and coherent edge-localized mode (ELM) averaging. High energetic ELMs of about 3 keV are impacting on the W PFCs with fluxes of 3 x 10(23) D+ s(-1) m(-2) which is about four times higher than inter-ELM ion fluxes with an impact energy of about E-im = 200 eV. This intra-ELM ion flux is associated with a high heat flux of about 60 MW m(-2) to the outer target plate which causes T-surface rise by Delta T = 100 K per ELM covering finally the range between 160 degrees C and 1400 degrees C during the flat-top phase. ELM-induced desorption from saturated near-surface implantation regions as well as deep ELM-induced deuterium implantation areas under varying baseline temperature takes place. Subsequent refuelling by intra-ELM deuteron fluxes occurs and a complex interplay between deuterium fuelling and desorption can be observed in the temporal ELM footprint of the surface temperature (IR thermography), the impinging deuteron flux (Langmuir probes), and the Balmer radiation (emission spectroscopy) as representative for the deuterium recycling flux. In contrast to JET-C, a pronounced second peak, similar or equal to 8 ms delayed with respect to the initial ELM crash, in the D-alpha radiation and the ion flux has been observed. The peak can be related to desorption of implanted energetic intra-ELM D+ diffusing to the W surface, and performing local recycling.
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| 10. |
- Budny, R. V., et al.
(författare)
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Core fusion power gain and alpha heating in JET, TFTR, and ITER
- 2016
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Ingår i: Nuclear Fusion. - : IOP PUBLISHING LTD. - 0029-5515 .- 1741-4326. ; 56:5
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Tidskriftsartikel (refereegranskat)abstract
- Profiles of the ratio of fusion power and the auxiliary heating power (MT are calculated for the TFTR and JET discharges with the highest neutron emission rates, and arc predicted for ITER. Core values above 1.3 for JET and 0.8 for TFTR are obtained, Values above 20 are predicted for ITER baseline plasmas.
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