| 1. |
- Joffrin, E., et al.
(author)
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Overview of the JET preparation for deuterium-tritium operation with the ITER like-wall
- 2019
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In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 59:11
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Research review (peer-reviewed)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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| 2. |
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Overview of the JET results
- 2015
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In: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 55:10
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Journal article (peer-reviewed)
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| 3. |
- Bombarda, F., et al.
(author)
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Runaway electron beam control
- 2019
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In: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 1361-6587 .- 0741-3335. ; 61:1
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Journal article (peer-reviewed)
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| 4. |
- Krasilnikov, A., et al.
(author)
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Evidence of 9 Be + p nuclear reactions during 2ω CH and hydrogen minority ICRH in JET-ILW hydrogen and deuterium plasmas
- 2018
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In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 58:2
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Journal article (peer-reviewed)abstract
- The intensity of 9Be + p nuclear fusion reactions was experimentally studied during second harmonic (2ω CH) ion-cyclotron resonance heating (ICRH) and further analyzed during fundamental hydrogen minority ICRH of JET-ILW hydrogen and deuterium plasmas. In relatively low-density plasmas with a high ICRH power, a population of fast H+ ions was created and measured by neutral particle analyzers. Primary and secondary nuclear reaction products, due to 9Be + p interaction, were observed with fast ion loss detectors, γ-ray spectrometers and neutron flux monitors and spectrometers. The possibility of using 9Be(p, d)2α and 9Be(p, α)6Li nuclear reactions to create a population of fast alpha particles and study their behaviour in non-active stage of ITER operation is discussed in the paper.
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| 5. |
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- 2018
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In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 58:1
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Research review (peer-reviewed)
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- 2018
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In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 58:9
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Journal article (peer-reviewed)
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| 27. |
- Meyer, H., et al.
(author)
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Overview of progress in European medium sized tokamaks towards an integrated plasma-edge/wall solution
- 2017
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In: Nuclear Fusion. - : Institute of Physics Publishing (IOPP). - 0029-5515 .- 1741-4326. ; 57:10
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Journal article (peer-reviewed)abstract
- Integrating the plasma core performance with an edge and scrape-off layer (SOL) that leads to tolerable heat and particle loads on the wall is a major challenge. The new European medium size tokamak task force (EU-MST) coordinates research on ASDEX Upgrade (AUG), MAST and TCV. This multi-machine approach within EU-MST, covering a wide parameter range, is instrumental to progress in the field, as ITER and DEMO core/pedestal and SOL parameters are not achievable simultaneously in present day devices. A two prong approach is adopted. On the one hand, scenarios with tolerable transient heat and particle loads, including active edge localised mode (ELM) control are developed. On the other hand, divertor solutions including advanced magnetic configurations are studied. Considerable progress has been made on both approaches, in particular in the fields of: ELM control with resonant magnetic perturbations (RMP), small ELM regimes, detachment onset and control, as well as filamentary scrape-off-layer transport. For example full ELM suppression has now been achieved on AUG at low collisionality with n = 2 RMP maintaining good confinement H-H(98,H-y2) approximate to 0.95. Advances have been made with respect to detachment onset and control. Studies in advanced divertor configurations (Snowflake, Super-X and X-point target divertor) shed new light on SOL physics. Cross field filamentary transport has been characterised in a wide parameter regime on AUG, MAST and TCV progressing the theoretical and experimental understanding crucial for predicting first wall loads in ITER and DEMO. Conditions in the SOL also play a crucial role for ELM stability and access to small ELM regimes.
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| 28. |
- Meyer, H., et al.
(author)
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Overview of progress in European medium sized tokamaks towards an integrated plasma-edge/wall solution
- 2017
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In: Nuclear Fusion. - : Institute of Physics Publishing (IOPP). - 0029-5515 .- 1741-4326. ; 57:10
-
Journal article (peer-reviewed)abstract
- Integrating the plasma core performance with an edge and scrape-off layer (SOL) that leads to tolerable heat and particle loads on the wall is a major challenge. The new European medium size tokamak task force (EU-MST) coordinates research on ASDEX Upgrade (AUG), MAST and TCV. This multi-machine approach within EU-MST, covering a wide parameter range, is instrumental to progress in the field, as ITER and DEMO core/pedestal and SOL parameters are not achievable simultaneously in present day devices. A two prong approach is adopted. On the one hand, scenarios with tolerable transient heat and particle loads, including active edge localised mode (ELM) control are developed. On the other hand, divertor solutions including advanced magnetic configurations are studied. Considerable progress has been made on both approaches, in particular in the fields of: ELM control with resonant magnetic perturbations (RMP), small ELM regimes, detachment onset and control, as well as filamentary scrape-off-layer transport. For example full ELM suppression has now been achieved on AUG at low collisionality with n = 2 RMP maintaining good confinement H-H(98,H-y2) approximate to 0.95. Advances have been made with respect to detachment onset and control. Studies in advanced divertor configurations (Snowflake, Super-X and X-point target divertor) shed new light on SOL physics. Cross field filamentary transport has been characterised in a wide parameter regime on AUG, MAST and TCV progressing the theoretical and experimental understanding crucial for predicting first wall loads in ITER and DEMO. Conditions in the SOL also play a crucial role for ELM stability and access to small ELM regimes.
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| 29. |
- Bonnefoy, M., et al.
(author)
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First light of the VLT planet finder SPHERE IV. Physical and chemical properties of the planets around HR8799
- 2016
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 587
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Journal article (peer-reviewed)abstract
- Context. The system of four planets discovered around the intermediate-mass star HR8799 offers a unique opportunity to test planet formation theories at large orbital radii and to probe the physics and chemistry at play in the atmospheres of self-luminous young (similar to 30 Myr) planets. We recently obtained new photometry of the four planets and low-resolution (R similar to 30) spectra of HR8799 d and e with the SPHERE instrument (Paper III).Aims. In this paper (Paper IV), we aim to use these spectra and available photometry to determine how they compare to known objects, what the planet physical properties are, and how their atmospheres work.Methods. We compare the available spectra, photometry, and spectral energy distribution (SED) of the planets to field dwarfs and young companions. In addition, we use the extinction from corundum, silicate (enstatite and forsterite), or iron grains likely to form in the atmosphere of the planets to try to better understand empirically the peculiarity of their spectrophotometric properties. To conclude, we use three sets of atmospheric models (BT-SETTL14, Cloud-AE60, Exo-REM) to determine which ingredients are critically needed in the models to represent the SED of the objects, and to constrain their atmospheric parameters (T-eff, log g, M/H).Results. We find that HR8799d and e properties are well reproduced by those of L6-L8 dusty dwarfs discovered in the field, among which some are candidate members of young nearby associations. No known object reproduces well the properties of planets b and c. Nevertheless, we find that the spectra and WISE photometry of peculiar and/or young early-T dwarfs reddened by submicron grains made of corundum, iron, enstatite, or forsterite successfully reproduce the SED of these planets. Our analysis confirms that only the Exo-REM models with thick clouds fit (within 2 sigma) the whole set of spectrophotometric datapoints available for HR8799 d and e for T-eff = 1200 K, log g in the range 3.0-4.5, and M/H = +0.5. The models still fail to reproduce the SED of HR8799c and b. The determination of the metallicity, log g, and cloud thickness are degenerate.Conclusions. Our empirical analysis and atmospheric modelling show that an enhanced content in dust and decreased CIA of H-2 is certainly responsible for the deviation of the properties of the planet with respect to field dwarfs. The analysis suggests in addition that HR8799c and b have later spectral types than the two other planets, and therefore could both have lower masses.
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| 30. |
- Moro, Fabio, et al.
(author)
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Nuclear analysis of the ITER radial neutron camera architectural options
- 2017
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In: Fusion engineering and design. - : ELSEVIER SCIENCE SA. - 0920-3796 .- 1873-7196. ; 123, s. 1033-1038
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Journal article (peer-reviewed)abstract
- The ITER Radial Neutron Camera (RNC) is a multichannel detection system hosted in the Equatorial Port Plug 1 (EPP 1) designed to provide information on the neutron source total strength arid emissivity profiles. It consists of two sub-systems: the ex-port line-of-sights (LOSs), covering the plasma core, embedded in a massive shielding block located in the Port Interspace, and the in-port LOSs distributed in two removable cassettes integrated inside the Port Plug. Presently, the RNC layout development process is undergoing a System Level Design phase: several preliminary architectural options based on a System Engineering work have been defined: a detailed nuclear analysis of these options has been performed through radiation transport calculations with the MCNP Monte Carlo code. The radiation environment at the detectors positions has been fully characterized through the evaluation of the expected neutron spectra and the secondary gamma background and the analysis of the 3D radiation maps. MoreOver, the impact of a reduced ex-port shielding block on the neutron and gamma spectra has been investigated. The results of the present study provide guidelines for the development of the RNC final design and the necessary data for the measurement performance analysis.
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| 31. |
- Riva, M., et al.
(author)
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High-Priority Prototype Testing in Support of System-Level Design Development of the ITER Radial Neutron Camera
- 2018
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In: IEEE Transactions on Plasma Science. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0093-3813 .- 1939-9375. ; 46:5, s. 1291-1297
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Journal article (peer-reviewed)abstract
- This paper describes the high-priority testing activities supporting the ITER radial neutron camera (RNC) design, performed by a consortium of European institutes within a framework contract placed by fusion for energy, the ITER European Domestic Agency. The main role of the RNC is to measure the uncollided 14- and 2.5-MeV neutrons from deuterium-tritium and deuterium-deuterium fusion reactions through an array of flux monitors/spectrometers located in collimated lines of sight viewing the plasma through the ITER equatorial port plug #1. The line-integrated neutron fluxes will be used to evaluate, through reconstruction techniques, the radial profile of the neutrons emitted per unit time and volume (neutron emissivity) and, therefore, the neutron yield and the alpha particles' birth profile. The activity of high-priority testing is dedicated to the preparation and the design of experimental test environment, the conduction of appropriate tests and reporting of test results for the high-priority prototypes, clarifying or verifying the expected key function and system behavior, and enhancing learning on specific issues (potential showstoppers).
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| 32. |
- Cecconello, Marco, et al.
(author)
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Neural network implementation for ITER neutron emissivity profile recognition
- 2017
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In: Fusion engineering and design. - : ELSEVIER SCIENCE SA. - 0920-3796 .- 1873-7196. ; 123, s. 637-640
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Journal article (peer-reviewed)abstract
- The ITER Radial Neutron Camera (RNC) is a neutron diagnostic intended for the measurement of the neutron emissivity radial profile and the estimate of the total fusion power. This paper presents a proof of-principle method based on neural networks to estimate the neutron emissivity profile in different ITER scenarios and for different RNC architectures. The design, optimization and training of the implemented neural network is presented together with a decision algorithm to select, among the multiple trained neural networks, which one provides the inverted neutron emissivity profile closest to the input one. Examples are given for a selection of ITER scenarios and RNC architectures. The results from this study indicate that neural networks for the neutron emissivity recognition in ITER can achieve an accuracy and precision within the spatial and temporal requirements set by ITER for such a diagnostic.
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| 33. |
- Cecconello, Marco, et al.
(author)
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Strategy and guidelines for the calibration of the ITER Radial Neutron Camera
- 2019
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In: Fusion engineering and design. - : ELSEVIER SCIENCE SA. - 0920-3796 .- 1873-7196. ; 146, s. 2049-2052
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Journal article (peer-reviewed)abstract
- A calibration procedure is proposed for ITER Radial Neutron Camera that relies on embedded sources, reference ITER pulses and cross-calibration with ITER fission chambers and activation system coupled to Monte Carlo simulations of radiation transport. The proposed procedure would allow to measure the neutron emissivity profile and of the fusion power with 10 % accuracy and precision, a time resolution of 10 ms and a spatial resolution of a/10 for ITER entire life-time.
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| 34. |
- Cruz, N., et al.
(author)
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Real-time software tools for the performance analysis of the ITER Radial Neutron Camera
- 2017
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In: Fusion engineering and design. - : ELSEVIER SCIENCE SA. - 0920-3796 .- 1873-7196. ; 123, s. 1001-1005
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Journal article (peer-reviewed)abstract
- The Radial Neutron Camera (RNC) diagnostic is a neutron detection system with multiple collimators aiming at characterizing the neutron emission that will be produced by the ITER tokamak. The RNC plays a primary role for basic and advanced plasma control measurements and acts as backup for system machine protection measurements. During the RNC system level design phase the following real-time data processing algorithms were developed to assess RNC data throughput needs and measurement performances: (i) real-time data compression block (ii) real-time calculation of the neutron emissivity radial profile, based on Tikhonov regularization, starting from the line-integrated measurements, the line-of-sight geometry and using the magnetic flux information [1] (iii) real-time calculation of the neutron emissivity profile using a priori trained neural networks, the line-integrated measurements and the magnetic flux information (the best output from different neural networks being evaluated by a figure of merit that maps the neutron emissivity profile to the original line-integrated measurements) [21]. This paper presents results for the processing times of the various algorithms and their minimum control cycle for different conditions, such as number of lines of sight, number of magnetic flux surfaces and measurement error on the line integrated RNC measurements.
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