| 1. |
- 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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| 2. |
- Chernikova, Dina, 1982, et al.
(författare)
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Experimental and numerical investigations of radiation characteristics of Russian portable/compact pulsed neutron generators: ING-031 ING-07, ING-06 and ING-10-20-120
- 2014
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 746, s. 74-86
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Tidskriftsartikel (refereegranskat)abstract
- The present paper discusses results of full-scale experimental and numerical investigations of influence of construction materials of portable pulsed neutron generators ING-031, ING-07, ING-06 and ING-10-20-120 (VNIIA, Russia) to their radiation characteristics formed during and after an operation (shutdown period). In particular, it is shown that an original monoenergetic isotropic angular distribution of neutrons emitted by TiT target changes into the significantly anisotropic angular distribution with a broad energy spectrum stretching to the thermal region. Along with the low energetic neutron part, a significant amount of photons appears during the operation of generators. In the pulse mode of operation of neutron generator, a presence of the construction materials leads to the "tailing" of the original neutron pulse and the appearance of an accompanying photon pulse at similar to 3 ns after the instant neutron pulse. In addition to that, reactions of neutron capture and inelastic scattering lead to the creation of radioactive nuclides, such as Co-58, Cu-62, Cu-64 and F-18, which form the so-called activation radiation. Thus, the selection of a portable neutron generator for a particular type of application has to be clone considering radiation characteristics of the generator itself. This paper will be of interest to users of neutron generators, providing them with valuable information about limitations of a specific generator and with recommendations for improving the design and performance of the generator as a whole. (c) 2014 Elsevier B.V. All rights reserved.
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| 3. |
- Minamisawa, R. A., et al.
(författare)
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Characterization of a n+3C/n-4H SiC heterojunction diode
- 2016
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 108:14, s. 143502-
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Tidskriftsartikel (refereegranskat)abstract
- We report on the fabrication of n+3C/n-4H SiC heterojunction diodes (HJDs) potentially promising the ultimate thermal stability of the junction. The diodes were systematically analyzed by TEM, X-ray diffraction, AFM, and secondary ion mass spectroscopy, indicating the formation of epitaxial 3C-SiC crystal on top of 4H-SiC substrate with continuous interface, low surface roughness, and up to similar to 7 x 10(17) cm(-3) dopant impurity concentration. The conduction band off-set is about 1 V as extracted from CV measurements, while the valence bands of both SiC polytypes are aligned. The HJDs feature opening voltage of 1.65 V, consistent with the barrier height of about 1.5 eV extracted from CV measurement. We finally compare the electrical results of the n+3C/n-4H SiC heterojunction diodes with those featuring Si and Ge doped anodes in order to evaluate current challenges involved in the fabrication of such devices. (C) 2016 AIP Publishing LLC.
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| 4. |
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| 5. |
- Schulte, EC, et al.
(författare)
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High energy angular distribution measurements of the exclusive deuteron photodisintegration reaction
- 2002
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Ingår i: Physical Review C (Nuclear Physics). - : American Physical Society. - 0556-2813 .- 1089-490X. ; 66:4
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Tidskriftsartikel (refereegranskat)abstract
- The first complete measurements of the angular distributions of the two-body deuteron photodisintegration differential cross section at photon energies above 1.6 GeV were performed at the Thomas Jefferson National Accelerator Facility. The results show a persistent forward-backward asymmetry up to E-gamma=2.4 GeV, the highest-energy measured in this experiment. The Hard Rescattering and the Quark-Gluon string models are in fair agreement with the results.
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| 6. |
- Wijesooriya, K, et al.
(författare)
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Polarization measurements in high-energy deuteron photodisintegration
- 2001
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 86:14, s. 2975-2979
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Tidskriftsartikel (refereegranskat)abstract
- We present measurements of the recoil proton polarization for the d(γ⃗,p⃗)n reaction at θc.m. = 90° for photon energies up to 2.4 GeV. These are the first data in this reaction for polarization transfer with circularly polarized photons. The induced polarization py vanishes above 1 GeV, contrary to meson-baryon model expectations, in which resonances lead to large polarizations. However, the polarization transfer Cx does not vanish above 1 GeV, inconsistent with hadron helicity conservation. Thus, we show that the scaling behavior observed in the d(γ,p)ncross sections is not a result of perturbative QCD. These data should provide important tests of new nonperturbative calculations in the intermediate energy regime.
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| 7. |
- Wijesooriya, K, et al.
(författare)
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Polarization measurements in neutral pion photoproduction
- 2002
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 66:3
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Tidskriftsartikel (refereegranskat)abstract
- We present measurements of the recoil proton polarization for the H-1((γ) over right arrow,(p) over right arrow)pi(0) reaction for theta(c.m.)(pi) = 60degrees-135degrees and for photon energies up to 4.1 GeV. These are the first data in this reaction for polarization transfer with circularly polarized photons. Various theoretical models are compared with the results. No evidence for hadron helicity conservation is observed. Models that employ factorization are not favored. It appears from the strong angular dependence of the induced polarization at photon energies of 2.5 and 3.1 GeV that a relatively high spin resonance or background amplitude might exist in this energy region.
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| 8. |
- Afanas'ev, Victor P., et al.
(författare)
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Study of NbN Ultra-thin Films for THz Hot-electron Bolometers
- 2014
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Ingår i: 25th International Sympsoium on Space Terahertz Technology, ISSTT 2014; Moscow; Russian Federation; 27 April 2014 through 30 April 2014. ; , s. 141-143
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Konferensbidrag (refereegranskat)abstract
- Hot-electron bolometer (HEB) mixers based on superconducting ultra-thin NbN films are largely used for THz spectroscopy for space and ground-based observations. Performance of the HEB mixers directly depends on the details of the structure and composition of thin film surface, as well as the nitrogen composition and its depth distribution. In this work, we present the study of the composition and the surface oxidation state of NbN films grown at two different temperatures and of 5 and 10 nm thickness.
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| 9. |
- Krause, Sascha, 1989, et al.
(författare)
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Ambient temperature growth of mono- and polycrystalline NbN nanofilms and their rigorous composition and surface analysis
- 2015
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Ingår i: European Conference on Applied Superconductivity.
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Konferensbidrag (refereegranskat)abstract
- This paper reflects on the rigorous investigation of high-quality 5nm thin NbN films which were deposited by means of reactive DC magnetron sputtering at ambient temperatures. Monocrystalline NbN films have been epitaxially grown onto hexagonal GaN buffer-layers (0002) and showing a distinct, low defect interface as confirmed from HRTEM. The critical temperature (Tc) of those films reached 10.4K. Furthermore, a poly-crystalline structure was observed on films grown onto Si (100) substrates, exhibiting a Tc of 8.1K albeit a narrow transition from the normal to the superconducting state. The deposition at ambient temperatures offers major advantages from a processing point of view and motivates the in-depth characterization and comparison of present films with high quality films grown at elevated temperatures. X-ray photoelectron spectroscopy and reflected electron energy loss spectroscopy verified that the composition of NbN did not differ irrespectively of applied substrate heating. Moreover, the native oxide layer at the surface of NbN has been identified as NbO2 and thus is in contrast to the Nb2O5, usually being formed at the surface of Nb when exposed to air. These findings are of great significance since it was proven the possibility of growing epitaxial NbN onto GaN buffer layer in the absence of high temperatures hence paving the way to employ NbN in more advanced fabrication processes involving a higher degree of complexity. Particularly low-noise THz receiver could benefit from the eased integration of e.g IF circuitry or general multi-layer structures which take advantage of lift-off techniques.
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