| 1. |
- Murari, A., et al.
(author)
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A control oriented strategy of disruption prediction to avoid the configuration collapse of tokamak reactors
- 2024
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In: Nature Communications. - 2041-1723 .- 2041-1723. ; 15:1
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Journal article (peer-reviewed)abstract
- The objective of thermonuclear fusion consists of producing electricity from the coalescence of light nuclei in high temperature plasmas. The most promising route to fusion envisages the confinement of such plasmas with magnetic fields, whose most studied configuration is the tokamak. Disruptions are catastrophic collapses affecting all tokamak devices and one of the main potential showstoppers on the route to a commercial reactor. In this work we report how, deploying innovative analysis methods on thousands of JET experiments covering the isotopic compositions from hydrogen to full tritium and including the major D-T campaign, the nature of the various forms of collapse is investigated in all phases of the discharges. An original approach to proximity detection has been developed, which allows determining both the probability of and the time interval remaining before an incoming disruption, with adaptive, from scratch, real time compatible techniques. The results indicate that physics based prediction and control tools can be developed, to deploy realistic strategies of disruption avoidance and prevention, meeting the requirements of the next generation of devices.
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| 2. |
- 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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| 8. |
- Jmerik, V.N., et al.
(author)
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Optically pumped lasing at 300.4 nm in AlGaN MQW structures grown by plasma-assisted molecular beam epitaxy on c-Al2O3
- 2010
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In: PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE. - : WILEY-V C H VERLAG GMBH. - 1862-6300. ; 207:6, s. 1313-1317
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Journal article (peer-reviewed)abstract
- We have demonstrated optically pumped room-temperature pulse lasing at 300.4 nm from an AlGaN-based multiple-quantum-well (MQW) structure grown by plasma-assisted molecular beam epitaxy on a c-sapphire substrate. The lasing was achieved at the threshold peak power of similar to 12 MW/cm(2). The MQW structure involved AlGaN/AlN short-period super-lattices to decrease the threading dislocation densities from 10(11) down to 10(9)-10(10) cm(-2). Studies of time-resolved photoluminescence (TRPL) spectra and cw PL temperature dependences (10-300K) of different MQW structures, as well as numerical calculations of the optical gain and confinement in the laser structure allowed us to conclude about the optimum design of AlGaN-based MQW structures for the lower threshold UV lasing.
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| 9. |
- Shubina, Tatiana, et al.
(author)
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Recombination dynamics and lasing in ZnO/ZnMgO single quantum well structures
- 2007
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 91:20
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Journal article (peer-reviewed)abstract
- We report a time-resolved study of the recombination dynamics in molecular beam epitaxy grown ZnOZnMgO single quantum wells (SQWs) of 1.0-4.5 nm width. The SQWs exhibit different emission properties, depending on both the well width and defect density. Stimulated emission has been achieved at room temperature in a separate confinement double heterostructure having a 3 nm wide SQW as an active region. It has been found that a critical parameter for the lasing is the inhomogeneous broadening of both QW and barrier emission bands. © 2007 American Institute of Physics.
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| 10. |
- Bourguignon, J., et al.
(author)
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Chiral ditopic receptors. Application to palladium-catalyzed allylic alkylation
- 2003
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In: Tetrahedron. - : Elsevier BV. - 0040-4020 .- 1464-5416. ; 59:48, s. 9583-9589
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Journal article (peer-reviewed)abstract
- Chiral pyridinooxazoline, quinolinooxazoline, bis(oxazolino)pyridine (pybox), and bisoxazoline (box) derivatives containing crown ether residues were prepared. Some of the ligands were assessed in substrate binding studies and in palladium catalyzed allylic alkylations.
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| 11. |
- Bremberg, U, et al.
(author)
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Rapid and stereoselective C-C, C-O, C-N and C-S couplings via microwave accelerated palladium-catalyzed allylic substitutions
- 2000
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In: Synthesis (Stuttgart). - Uppsala Univ, Uppsala Biomed Ctr, Dept Organ Pharmaceut Chem, SE-75123 Uppsala, Sweden. Royal Inst Technol, Dept Chem, SE-10044 Stockholm, Sweden.. - 0039-7881 .- 1437-210X. ; :7, s. 1004-1008
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Journal article (peer-reviewed)abstract
- Palladium-catalyzed substitution of cyclohex-2-en-1-yl ethyl carbonate with neutral C-, O-, and N-nucleophiles was achieved in 1-2 minutes using microwave flash hearing. Enantioselectivities up to 96% were observed. Ionic nucleophiles tended to result in lower ee. With S-nucleophiles problems with the stability of the nucleophile were encountered.
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| 13. |
- Lundgren, Stina, et al.
(author)
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Polymer-Supported Pyridine-Bis(oxazoline). Application to Ytterbium Catalyzed Silylcyanation of Benzaldehyde
- 2003
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In: Organic Letters. - : American Chemical Society (ACS). - 1523-7060 .- 1523-7052. ; 5:20, s. 3663-3665
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Journal article (peer-reviewed)abstract
- Terminal acetylenes containing hydroxy and carboxylic acid groups were subjected to Sonogashira coupling with 4-bromo-2,6-bis[(R)-4-phenyloxazolin-2-yl]pyridine and the resulting pybox derivatives were immobilized on Tentagel resins. Ytterbium(ill) chloride complexes of the polymeric ligands catalyzed the addition of trimethylsilyl cyanide to benzaldehyde with 80-81% ee. The ligands were reused more than 30 times without any loss in selectivity or activity, and the metal complexes could be recovered and reused at least four times, although with slightly decreasing activity.
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| 14. |
- Lutsenko, S., et al.
(author)
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Microwave-mediated ruthenium-catalyzed asymmetric hydrogen transfer
- 2001
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In: Tetrahedron. - 0957-4166 .- 1362-511X. ; 12:18, s. 2529-2532
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Journal article (peer-reviewed)abstract
- Ru-catalyzed hydrogen transfer from propan-2-ol to acetophenone under microwave conditions using monotosylated (R,R)-diphenylethylenediamine as the chiral source afforded (R)-1-phenylethanol in >90% yield and 82% e.e. within 9 min, while use of ephedrine or norephedrine gave the same compound in high yield with 70 and 46% e.e., respectively. t-Butylphenylketone was reduced to (R)-2,2-dimethyl-1-phenyl-1-propanoI under the same conditions in close to quantitative yield, although with low enantioselectivity.
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| 15. |
- Lutsenko, S., et al.
(author)
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Preparation of L-threoninol and its bisoxazoline derivative
- 2003
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In: Synthetic Communications. - : Informa UK Limited. - 0039-7911 .- 1532-2432. ; 33:4, s. 661-666
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Journal article (peer-reviewed)abstract
- (R,R)-Threoninol was prepared in one step from L-threonine in 86% isolated yield. The product was regioselectively transformed into 2,2-bis[(4R,5R)-4-(hydroxymethyl)-5-methyl-1,3-oxazolin-2-yl]propane in 42% isolated yield.
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