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  • 1. Airila, M. I.
    et al.
    Aho-Mantila, L.
    Brezinsek, S.
    Coad, J. P.
    Kirschner, A.
    Likonen, J.
    Matveev, D.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Strachan, J. D.
    Widdowson, A.
    Wiesen, S.
    ERO modelling of local deposition of injected C-13 tracer at the outer divertor of JET2009In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T138, p. 014021-Article in journal (Refereed)
    Abstract [en]

    The 2004 tracer experiment of JET with the injection of (CH4)-C-13 into H-mode plasma at the outer divertor has been modelled with the Monte Carlo impurity transport code ERO. EDGE2D solutions for inter-ELM and ELM-peak phases were used as plasma backgrounds. Local two-dimensional (2D) deposition patterns at the vertical outer divertor target plate were obtained for comparison with post-mortem surface analyses. ERO also provides emission profiles for comparison with radially resolved spectroscopic measurements. Modelling indicates that enhanced re-erosion of deposited carbon layers is essential in explaining the amount of local deposition. Assuming negligible effective sticking of hydrocarbons, the measured local deposition of 20-34% is reproduced if re-erosion of deposits is enhanced by a factor of 2.5-7 compared to graphite erosion. If deposits are treated like the substrate, the modelled deposition is 55%. Deposition measurements at the shadowed area around injectors can be well explained by assuming negligible re-erosion but similar sticking behaviour there as on plasma-wetted surfaces.

  • 2.
    Akhmedov, Evgeny
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Frigerio, M.
    Duality in left-right symmetric seesaw2006In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T127, p. 59-61Article in journal (Refereed)
    Abstract [en]

    We perform a reconstruction of the mass matrix of heavy right-handed Majorana neutrinos in the framework of the left - right symmetric type I + II seesaw mechanism. An intriguing pairwise duality relation between different solutions is shown to exist.

  • 3. Alegre, Daniel
    et al.
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Gasior, Pawel
    Kubkowska, Monika
    Kowalska-Strzeciwilk, Ewa
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Tabares, Francisco L.
    Study of correlation of deuterium content in a-C:D dust induced by laser irradiation from the co-deposited surface with the grain size and velocity2014In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T161, p. 014010-Article in journal (Refereed)
    Abstract [en]

    In the study described here, the laser ablation method was applied to clean thick (40-60 m) a-C: D co-deposits on the ALT-II limiter blade from the TEXTOR tokamak, and at the same time to characterize the ejected particles formed during ablation and measure the amount of fuel carried by them. Ablation was accomplished by similar to 3.5 ns, 0.5 J Nd: YAG laser pulses in either vacuum or an O-2 atmosphere at different pressures. Fast camera tracking of the process provided an estimate of the population and velocity of up to 100ms(-1) for larger dust particles. In the same experiment, the dust particles were caught using ultra-light Si aerogel collectors placed in front of the ablation target. SEM analysis of aerogel surfaces verified the speed estimate, providing the trapped particles' size distribution and particle yield during ablation. The D/C atomic concentration ratio was measured with the 3HE ion beam nuclear reaction analysis method in deposited layers before ablation and with a micro-ion beam in individual particles on aerogel collectors. This indicated that most of the D was thermally released during ablation, leaving no more than 5% of its original amount in the particles. The effect of ablation conditions on the acceleration of ejected particles, their population, composition and D content is the main subject of this paper.

  • 4. Al-Zoubi, Noura
    et al.
    Li, Xiaoqing
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Schonecker, Stephan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Uppsala University, Uppsala, Sweden .
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Uppsala University, Uppsala, Sweden; Wigner Research Center for Physics, Budapest, Hungary .
    Influence of manganese on the bulk properties of Fe-Cr-Mn alloys: a first-principles study2014In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 89, no 12, p. 125702-Article in journal (Refereed)
    Abstract [en]

    We investigate the effect of manganese on lattice stability and magnetic moments of paramagnetic Fe-Cr-Mn steel alloys along the Bain path connecting the body-centered cubic (bcc) and face-centered cubic (fcc) structures. The calculations are carried out using the ab initio exact muffin-tin orbital method, in combination with the coherent potential approximation, and the paramagnetic phase is modeled by the disordered local magnetic moment scheme. For all Fe-Cr-Mn alloys considered here, the local magnetic moments on Fe atoms have the minimum values for the fcc structure and the maximum values for the bcc structure, whereas the local magnetic moments on Mn have almost the same value along the constant-volume Bain path. Our results show that Mn addition to paramagnetic Fe-Cr solid solution stabilizes the bcc structure. However, when considering the paramagnetic fcc phase relative to the ferromagnetic bcc ground state, then Mn turns out to be a clear fcc stabilizer, in line with observations.

  • 5. Antoni, V.
    et al.
    Drake, James R.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Spada, E.
    Spolaore, M.
    Vianello, N.
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Cavazzana, R.
    Cecconello, Marco
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Martines, E.
    Serianni, G.
    Coherent structures and anomalous transport in reversed field pinch plasmas2006In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T122, p. 1-7Article in journal (Refereed)
    Abstract [en]

    The results leading to the identification of coherent structures emerging from the background turbulence in the edge region of the reversed field pinch experiments EXTRAP-T2R and RFX are reviewed. These structures have traits of vortices in velocity field and blobs in density, and the reconstruction of their spatial structure and of their time evolution is discussed focusing on the analysis tools applied. The role of these structures in the particle anomalous transport is addressed, showing that their collisions can contribute up to 50% the total particle losses. This process is shown to be responsible for bursts in particle flux and it is found to set a characteristic collision time, which is in agreement with the statistical properties of laminar times for particle flux bursts.

  • 6. Behringer, Hans
    et al.
    Eichhorn, Ralf
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
    Wallin, Stefan
    Dynamics of biomolecular processes PREFACE2013In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 87, no 5, p. 058501-Article in journal (Other academic)
  • 7.
    Bennett, Kochise
    et al.
    Univ Calif Irvine, Dept Chem, Irvine, CA 92697 USA.;Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA..
    Zhang, Yu
    Univ Calif Irvine, Dept Chem, Irvine, CA 92697 USA..
    Kowalewski, Markus
    Univ Calif Irvine, Dept Chem, Irvine, CA 92697 USA..
    Hua, Weijie
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Univ Calif Irvine, Dept Chem, Irvine, CA 92697 USA.;KTH Royal Inst Technol, Sch Biotechnol, Dept Theoret Chem & Biol, S-10691 Stockholm, Sweden..
    Mukamel, Shaul
    Univ Calif Irvine, Dept Chem, Irvine, CA 92697 USA.;Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA.;Freiburg Inst Adv Studies FRIAS, Freiburg, Germany..
    Multidimensional resonant nonlinear spectroscopy with coherent broadband x-ray pulses2016In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T169, article id 014002Article in journal (Refereed)
    Abstract [en]

    New x-ray free electron laser (XFEL) and high harmonic generation (HHG) light sources are capable of generating short and intense pulses that make x-ray nonlinear spectroscopy possible. Multidimensional spectroscopic techniques, which have long been used in the nuclear magnetic resonance, infrared, and optical regimes to probe the electronic structure and nuclear dynamics of molecules by sequences of short pulses with variable delays, can thus be extended to the attosecond x-ray regime. This opens up the possibility of probing core-electronic structure and couplings, the real-time tracking of impulsively created valence-electronic wavepackets and electronic coherences, and monitoring ultrafast processes such as nonadiabatic electron-nuclear dynamics near conical-intersection crossings. We survey various possible types of multidimensional x-ray spectroscopy techniques and demonstrate the novel information they can provide about molecules.

  • 8.
    Bergsåker, B. Henric M.
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. EUROfusion Consortium, Culham Science Centre, JET, Abingdon, United Kingdom.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. EUROfusion Consortium, Culham Science Centre, JET, Abingdon, United Kingdom.
    Zhou, Yushan
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. EUROfusion Consortium, Culham Science Centre, JET, Abingdon, United Kingdom.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. EUROfusion Consortium, Culham Science Centre, JET, Abingdon, United Kingdom.
    Possnert, G.
    Likonen, J.
    Pettersson, J.
    Koivuranta, S.
    Widdowson, A. M.
    Deep deuterium retention and Be/W mixing at tungsten coated surfaces in the JET divertor2016In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T167, article id 014061Article in journal (Refereed)
    Abstract [en]

    Surface samples from a full poloidal set of divertor tiles exposed in JET through operations 2010-2012 with ITER-like wall have been investigated using SEM, SIMS, ICP-AES analysis and micro beam nuclear reaction analysis (μ-NRA). Deposition of Be and retention of D is microscopically inhomogeneous. With careful overlaying of μ-NRA elemental maps with SEM images, it is possible to separate surface roughness effects from depth profiles at microscopically flat surface regions, without pits. With (3He, p) μ-NRA at 3-5 MeV beam energy the accessible depth for D analysis in W is about 9 μm, sufficient to access the W/Mo and Mo/W interfaces in the coatings and beyond, while for Be in W it is about 6 μm. In these conditions, at all plasma wetted surfaces, D was found throughout the whole accessible depth at concentrations in the range 0.2-0.7 at% in W. Deuterium was found to be preferentially trapped at the W/Mo and Mo/W interfaces. Comparison is made with SIMS profiling, which also shows significant D trapping at the W/Mo interface. Mixing of Be and W occurs mainly in deposited layers.

  • 9.
    Bergsåker, Henric
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Bykov, Igor
    Zhou, Yushan
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Possnert, G
    Likonen, J
    Pettersson, J
    Koivuranta, S
    Widdowson, A.M.
    contributors, JET
    Deep deuterium retention and Be/W mixingat tungsten coated surfaces in the JETdivertor2016In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896Article in journal (Refereed)
    Abstract [en]

    Surface samples from a full poloidal set of divertor tiles exposed in JET through operations2010–2012 with ITER-like wall have been investigated using SEM, SIMS, ICP-AES analysisand micro beam nuclear reaction analysis (μ-NRA). Deposition of Be and retention of D ismicroscopically inhomogeneous. With careful overlaying of μ-NRA elemental maps with SEMimages, it is possible to separate surface roughness effects from depth profiles at microscopicallyflat surface regions, without pits. With (3He, p) μ-NRA at 3–5 MeV beam energy the accessibledepth for D analysis in W is about 9 μm, sufficient to access the W/Mo and Mo/W interfaces inthe coatings and beyond, while for Be in W it is about 6 μm. In these conditions, at all plasmawetted surfaces, D was found throughout the whole accessible depth at concentrations in therange 0.2–0.7 at% in W. Deuterium was found to be preferentially trapped at the W/Mo andMo/W interfaces. Comparison is made with SIMS profiling, which also shows significant Dtrapping at the W/Mo interface. Mixing of Be and W occurs mainly in deposited layers.

  • 10.
    Björk, Gunnar
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Grassl, Markus
    de la Hoz, Pablo
    Leuchs, Gerd
    Sanchez-Soto, Luis L.
    Stars of the quantum Universe: extremal constellations on the Poincare sphere2015In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 90, no 10, article id 108008Article in journal (Refereed)
    Abstract [en]

    The characterization of the polarization properties of a quantum state requires the knowledge of the joint probability distribution of the Stokes variables. This amounts to assessing all the moments of these variables, which are aptly encoded in a multipole expansion of the density matrix. The cumulative distribution of these multipoles encapsulates in a handy manner the polarization content of the state. We work out the extremal states for that distribution, finding that SU(2) coherent states are maximal to any order, so they are the most polarized allowed by quantum theory. The converse case of pure states minimizing that distribution, which can be seen as the most quantum ones, is investigated for a diverse range of number of photons. Exploiting the Majorana representation, the problem appears to be closely related to distributing a number of points uniformly over the surface of the Poincare sphere.

  • 11.
    Björk, Gunnar
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Man'ko, Margarita
    20th Central European Workshop on Quantum Optics Preface2014In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T160, p. 010301-Article in journal (Refereed)
  • 12.
    Björk, Gunnar
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Soderholm, J.
    Trifonov, A.
    Tsegaye, T.
    A theory of the relative phase and number difference of two quantized harmonic oscillators2002In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T102, p. 133-146Article in journal (Refereed)
    Abstract [en]

    We present a comprehensive and self-consistent theory of relative-phase measurements and the associated Hermitian relative-phase operator of two harmonic oscillators. We find that since Nature does not favor any particular initial condition of the two oscillators, the relative-phase operator is not unique. We show that the relative-phase eigenstates; are maximally entangled. Therefore. most relative-phase operators lack a classical correspondence, even in the high-excitation limit. Furthermore, we find that the relative phase and the excitation number difference are noncommuting, noncanonical observables and we derive a commutation relation.

  • 13.
    Blennow, Mattias
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Edsjö, Joakim
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Neutrinos from WIMP annihilations in the Sun including neutrino oscillations2006In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T127, p. 19-21Article in journal (Refereed)
    Abstract [en]

    The prospects for detecting neutrinos from the Sun arising from dark matter annihilations in the core of the Sun are reviewed. Emphasis is placed on new work investigating the effects of neutrino oscillations on the expected neutrino fluxes.

  • 14.
    Blom, Hans
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Bates, Mark
    Nanoscopy-imaging life at the nanoscale: a Nobel Prize achievement with a bright future2015In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 90, no 10, article id 108010Article in journal (Refereed)
    Abstract [en]

    A grand scientific prize was awarded last year to three pioneering scientists, for their discovery and development of molecular 'ON-OFF' switching which, when combined with optical imaging, can be used to see the previously invisible with light microscopy. The Royal Swedish Academy of Science announced on October 8th their decision and explained that this achievement-rooted in physics and applied in biology and medicine-was awarded with the Nobel Prize in Chemistry for controlling fluorescent molecules to create images of specimens smaller than anything previously observed with light. The story of how this noble switch in optical microscopy was achieved and how it was engineered to visualize life at the nanoscale is highlighted in this invited comment.

  • 15. Borodkina, I.
    et al.
    Borodin, D.
    Brezinsek, S.
    Tsvetkov, I. V.
    Kurnaev, V. A.
    Guillemaut, C.
    Maslov, M.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Intra-ELM tungsten sputtering in JET ITER-like wall: analytical studies of Be impurity and ELM type influence2017In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T170, article id 014065Article in journal (Refereed)
    Abstract [en]

    The W source strength in JET H-mode discharges depends on the W sputtering in the inter and the intra-ELM phase due to impinging hydrogenic ions (D or H) and impurities (mainly Be). The analytical approach for interpretation of the Langmuir probe measurements is applied to model the ELM ion parallel transport and the W sputtering flux in intra-ELM and inter-ELM conditions in JET-ITER-like wall (ILW) hydrogen and deuterium plasmas. The impact of the Be ion charge and the Be concentration in the impinging ion flux on the W sputtering was estimated. Be2+ concentrations of 0.5% and 1% in the impinging ion flux increases the W sputtering fluence per ELM by 20%-30% and 35%-55% correspondingly with respect to pure deuterium plasma; the charge state of Be ions has no substantial effect on W sputtering in the intra-ELM phase. The analysis of JET ELMy H-mode discharges in hydrogen with different types of ELMs is presented. The W sputtering source under inter-and intra-ELM conditions is estimated using the analytical approach and validated by optical emission spectroscopy in these discharges. The intra-ELM W sputtering flux increases 2-4 times in comparison to the inter-ELM flux.

  • 16. Boström, M.
    et al.
    Thiyam, Priyadarshini
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Persson, C.
    Parsons, D. F.
    Buhmann, S. Y.
    Brevik, I.
    Sernelius, Bo E.
    Non-perturbative theory of dispersion interactions2015In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 90, no 3, article id 035405Article in journal (Refereed)
    Abstract [en]

    Some open questions exist with fluctuation-induced forces between extended dipoles. Conventional intuition derives from large-separation perturbative approximations to dispersion force theory. Here, we present a full non-perturbative theory. In addition, we discuss how one can take into account finite dipole size corrections. It is of fundamental value to investigate the limits of validity of the perturbative dispersion force theory.

  • 17.
    Brenning, Nils
    et al.
    KTH, Superseded Departments, Alfvén Laboratory.
    Fälthammar, Carl-Gunne
    KTH, Superseded Departments, Alfvén Laboratory.
    Dynamic trapping and skidding of dense plasma clouds2004In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 70, no 03-feb, p. 153-156Article in journal (Refereed)
    Abstract [en]

    We investigate the possibility that the mechanism dynamic trapping can play a role in decoupling dense plasma clouds injected in a thinner ambient plasma, by establishing strong magnetic-field-aligned electric fields in the vicinity or in the edge of the cloud. Dynamic trapping has previously been shown to allow such fields to be established and maintained on the time scale of ion motion, also for arbitrarily low current densities. A model is presented of how such fields could arise and decouple injected plasma clouds, a mechanism which we call dynamic decoupling. A dimensionless parameter. the dynamic decoupling factor F-DD, is derived which gives an estimate of the importance of the process. One possible application is the CRRES ionospheric injection experiments where anomalous skidding has recently been reported. However. the dynamic decoupling mechanism might also play a role in naturally occurring situations, e.g. the impulsive penetration of plasmoids from the solar wind into the Earth's magnetosphere.

  • 18. Brezinsek, Sebastijan
    et al.
    Wirtz, Marius
    Dorrow-Gesprach, Daniel
    Loewenhoff, Thorsten
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    16th International Conference on Plasma-Facing Materials and Components for Fusion Applications2017In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T170, article id 010201Article in journal (Refereed)
  • 19.
    Bäck, Torbjörn
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Cederwall, Bo
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Moradi, Farnaz Ghazi
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Johnson, Arne
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Wyss, Ramon
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Wadsworth, R.
    The B(E2;0(gs)(+) -> 2(+)) systematics of Sn and Te isotopes in light of data in the light Sn region including a recent measurement in Te-108 using the combined recoil-decay-tagging-recoil-distance Doppler technique2012In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T150, p. 014003-Article in journal (Refereed)
    Abstract [en]

    An experimental technique combining the well-established alpha/p-decay-recoil-tagging method with a differential plunger has recently been successful in producing results in the neutron-deficient region near Sn-100. This experimental technique is briefly presented here and the result of a recent measurement for Te-108 is put in the context of the systematics of B(E-2) values for the Te and Sn isotopic chains. New state-of-the-art shell-model calculations are presented for the Sn data, and possible explanations for the unusually large B(E-2) values for the Sn isotopes near the N = 50 shell closure are given.

  • 20.
    Bäcklund, Anna
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Bengtsson, Ingemar
    Four remarks on spin coherent states2014In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T163Article in journal (Refereed)
    Abstract [en]

    We discuss how to recognize the constellations seen in the Majorana representation of quantum states. Then we give explicit formulae for the metric and symplectic form on SU (2) orbits containing general number states. Their metric and symplectic areas differ unless the states are coherent. Finally we discuss some patterns that arise from the Lieb-Solovej map, and for dimensions up to nine we find the location of those states that maximize the Wehrl-Lieb entropy.

  • 21.
    Carlsund-Levin, Christina
    et al.
    KTH, Superseded Departments, Numerical Analysis and Computer Science, NADA.
    Elander, N.
    Nunez, A.
    Scrinzi, A.
    An exterior complex rotated coupled channel description of predissociation in diatomic molecules applied to a model of the four lowest (2)Sigma(+)-states in CaH2002In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 65, no 4, p. 306-322Article in journal (Refereed)
    Abstract [en]

    The exterior complex rotated Coupled-Channel formulation of potential scattering makes it possible to calculate energies and widths for a non-adiabatic model of a diatomic molecule or quasimolecule, The structure and decay pattern of a diatomic system is in this way described in a non-perturbative way. In this contribution we use the non-adiabatic form of an empirically derived potential energy curve matrix, previously used by Martin, J. Chem. Phys. 88, 1997 (1988) [1], for the four lowest (2)Sigma(+)-states of the CaH radical to demonstrate how one can calculate term positions as well as non-radiative decay widths in a realistic case for a large range of rovibronic levels. The differences between the previously derived Born-Oppenheimer term values [1] and the present non-adiabatic results are discussed and compared with previous work.

  • 22. Catarino, N.
    et al.
    Widdowson, A.
    Baron-Wiechec, A.
    Coad, J. P.
    Heinola, K.
    Rubel, Marek
    KTH.
    Alves, E.
    Time-resolved deposition in the remote region of the JET-ILW divertor: measurements and modelling2017In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T170, article id 014059Article in journal (Refereed)
    Abstract [en]

    One crucial requirement for the development of fusion power is to know where, and how much, impurities collect in the machine, and how much of the fuelling isotope tritium will be trapped therein. The most relevant information on this issue comes from the operation of the Joint European Tokamak (JET), which is the world's largest operating tokamak and has the same interior plasma-facing materials as the next step machine, ITER. Much of the information gained so far has been from post-mortem analysis of samples collected after whole campaigns involving varied types of operation. This paper describes time-resolved measurements of the deposition rate using rotating collectors (RC) placed in remote areas of the JET divertor during the 2013-2014 campaign with the ITER-like Wall (ILW). These techniques allow the effects of different types of operation to be distinguished. Rotating collectors made of silicon discs housed behind an aperture are exposed to the plasma. Each time the magnetic field coils are ramped up for a discharge the disc rotates, providing a linear relationship between the exposed region and the discharge number. Post-mortem ion beam analyses provide information on the deposit composition as a function of the discharge number. The results show that the Be deposition average for the RC in the corners of the inner and outer divertor are 4.9 x 10(16) cm(-2) and 1.8 x 10(17) cm(-2), respectively, accumulated over an average of similar to 25 pulses. Data from the rotating collector below Tile 5 in the central region of divertor indicate a Be deposition rate of 9.3 x 10(15) cm(-2), per similar to 25 pulses.

  • 23.
    Cecconello, Marco
    et al.
    KTH, Superseded Departments, Alfvén Laboratory.
    Malmberg, Jenny-Ann
    KTH, Superseded Departments, Alfvén Laboratory.
    Sallander, Eva
    KTH, Superseded Departments, Alfvén Laboratory.
    Drake, Drake James
    KTH, Superseded Departments, Alfvén Laboratory.
    Self-organisation and intermittent coherent oscillations in the EXTRAP T2 reversed field pinch2002In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 65, no 1, p. 69-75Article in journal (Refereed)
    Abstract [en]

    Many reversed-field pinch (RFP) experiments exhibit a coherent oscillatory behaviour that is characteristic of discrete dynamo events and is associated with intermittent current profile self-organisation phenomena. However, in the vast majority of the discharges in the resistive shell RFP experiment EXTRAP T2, the dynamo activity does not show global, coherent oscillatory behaviour, The internally resonant tearing modes are phase-aligned and wall-locked resulting in a large localised magnetic perturbation. Equilibrium and plasma parameters have a level of high frequency fluctuations but the average values are quasi-steady. For some discharges, however, the equilibrium parameters exhibit the oscillatory behaviour characteristic of the discrete dynamo events. For these discharges, the trend observed in the tearing mode spectra, associated with the onset of the discrete relaxation event behaviour, is a relative higher amplitude of m = 0 mode activity and relative lower amplitude of the m = 1 mode activity compared with their average values. Global plasma parameters and model profile calculations for sample discharges representing the two types of relaxation dynamics are presented.

  • 24.
    Cederwall, Bo
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    NCNP 2011: Nordic Conference on Nuclear Physics 2011 (Stockholm, Sweden, 13-17 June 2011)2012In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T150, p. 010101-Article in journal (Other academic)
  • 25. Coad, J. P.
    et al.
    Alves, E.
    Barradas, N. P.
    Baron-Wiechec, A.
    Catarino, N.
    Heinola, K.
    Likonen, J.
    Mayer, M.
    Matthews, G. F.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Widdowson, A.
    Surface analysis of tiles and samples exposed to the first JET campaigns with the ITER-like wall2014In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T159, p. 014012-Article in journal (Refereed)
    Abstract [en]

    This paper reports on the first post-mortem analyses of tiles removed from JET after the first campaigns with the ITER-like wall (ILW) during 2011-12 [1]. Tiles from the divertor have been analysed by ion beam analysis techniques and by secondary ion mass spectrometry to determine the amount of beryllium deposition and deuterium retention in the tiles exposed to the scrape-off layer. Films 10-20 mu m thick were present at the top of tile 1, but only very thin films (<1 mu m) were found in the shadowed areas and on other divertor tiles. The total amount of Be found in the divertor following the ILW campaign was a factor of similar to 9 less than the material deposited in the 2007-09 carbon campaign, after allowing for the longer operations in 2007-09.

  • 26. Coad, J. P.
    et al.
    Gruenhagen, S.
    Hole, D. E.
    Hakola, A.
    Koivuranta, S.
    Likonen, J.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Widdowson, A.
    Overview of JET post-mortem results following the 2007-9 operational period, and comparisons with previous campaigns2011In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T145, p. 014003-Article in journal (Refereed)
    Abstract [en]

    In 2010, all the plasma-facing components were removed from JET so that the carbon-based surfaces could be replaced with beryllium (Be) or tungsten as part of the ITER-like wall (ILW) project. This gives unprecedented opportunities for post-mortem analyses of these plasma-facing surfaces; this paper reviews the data obtained so far and relates the information to studies of tiles removed during previous JET shutdowns. The general pattern of erosion/deposition at the JET divertor has been maintained, with deposition of impurities in the scrape-off layer (SOL) at the inner divertor and preferential removal of carbon and transport into the corner. However, the remaining films in the SOL contain very high Be/C ratios at the surface. The first measurements of erosion using a tile profiler have been completed, with up to 200 microns erosion being recorded at points on the inner wall guard limiters.

  • 27. Coenen, J. W.
    et al.
    Matthews, G. F.
    Krieger, K.
    Iglesias, D.
    Bunting, P.
    Corre, Y.
    Silburn, S.
    Balboa, I.
    Bazylevs, B.
    Conway, N.
    Coffey, I.
    Dejarnac, R.
    Gauthier, E.
    Gaspar, J.
    Jachmich, S.
    Jepu, I.
    Makepeace, C.
    Scannell, R.
    Stamp, M.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Pitts, R. A.
    Wiesen, S.
    Widdowson, A.
    Heinola, K.
    Baron-Wiechec, A.
    Transient induced tungsten melting at the Joint European Torus (JET)2017In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T170, article id 014013Article in journal (Refereed)
    Abstract [en]

    Melting is one of the major risks associated with tungsten (W) plasma-facing components (PFCs) in tokamaks like JET or ITER. These components are designed such that leading edges and hence excessive plasma heat loads deposited at near normal incidence are avoided. Due to the high stored energies in ITER discharges, shallow surface melting can occur under insufficiently mitigated plasma disruption and so-called edge localised modes-power load transients. A dedicated program was carried out at the JET to study the physics and consequences of W transient melting. Following initial exposures in 2013 (ILW-1) of a W-lamella with leading edge, new experiments have been performed on a sloped surface (15 degrees slope) during the 2015/2016 (ILW-3) campaign. This new experiment allows significantly improved infrared thermography measurements and thus resolved important issue of power loading in the context of the previous leading edge exposures. The new lamella was monitored by local diagnostics: spectroscopy, thermography and high-resolution photography in between discharges. No impact on the main plasma was observed despite a strong increase of the local W source consistent with evaporation. In contrast to the earlier exposure, no droplet emission was observed from the sloped surface. Topological modifications resulting from the melting are clearly visible between discharges on the photographic images. Melt damage can be clearly linked to the infrared measurements: the emissivity drops in zones where melting occurs. In comparison with the previous leading edge experiment, no runaway melt motion is observed, consistent with the hypothesis that the escape of thermionic electrons emitted from the melt zone is largely suppressed in this geometry, where the magnetic field intersects the surface at lower angles than in the case of perpendicular impact on a leading edge. Utilising both exposures allows us to further test the model of the forces driving melt motion that successfully reproduced the findings from the original leading edge exposure. Since the ILW-1 experiments, the exposed misaligned lamella has now been retrieved from the JET machine and post mortem analysis has been performed. No obvious mass loss is observed. Profilometry of the ILW-1 lamella shows the structure of the melt damage which is in line with the modell predictions thus allowing further model validation. Nuclear reaction analysis shows a tenfold reduction in surface deuterium concentration in the molten surface in comparison to the non-molten part of the lamella.

  • 28. Coreno, M.
    et al.
    Kivimaeki, A.
    de Simone, M.
    Garcia, E. Melero
    Vall-Llosera, G.
    Ruiz, J. Alvarez
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Stankiewicz, M.
    Vis-UV fluorescence studies of fragments resulting from the relaxation of molecular core hole states2007In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 76, no 3, p. C90-C95Article in journal (Refereed)
    Abstract [en]

    The absorption of soft x-ray radiation induces neutral and ionic core hole states in molecules. The relaxation of such states typically leads to a multi-step process, at the end of which photons in the visible and UV range can also be emitted from fragments. In this paper, we present results on Balmer and Lyman emission that originates from excited H atoms produced at the K-edge of the water, ammonia and methane molecules. Dissociation pathways leading to fluorescence emission are discussed.

  • 29. Corre, Y.
    et al.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Cecconello, M.
    Gravestijn, R. M.
    Hedqvist, A.
    Pegourie, B.
    Schunke, B.
    Stancalie, V.
    Radiated power and impurity concentrations in the EXTRAP-T2R reversed-field pinch2005In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 71, no 5, p. 523-531Article in journal (Refereed)
    Abstract [en]

    A numerical and experimental study of the impurity concentration and radiation in the EXTRAP-T2R device is reported. The experimental setup consists of an 8-chord bolometer system providing the plasma radiated power and a vacuum-ultraviolet spectrometer providing information on the plasma impurity content. The plasma emissivity profile as measured by the bolometric system is peaked in the plasma centre. A one dimensional Onion Skin Collisional-Radiative model (OSCR) has been developed to compute the density and radiation distributions of the main impurities. The observed centrally peaked emissivity profile can be reproduced by OSCR simulations only if finite particle confinement time and charge-exchange processes between plasma impurities and neutral hydrogen are taken into account. The neutral hydrogen density profile is computed with a recycling code. Simulations show that recycling on metal first wall such as in EXTRAP-T2R (stainless steel vacuum vessel and molybdenum limiters) is compatible with a rather high neutral hydrogen density in the plasma centre. Assuming an impurity concentration of 10% for oxygen and 3% for carbon compared with the electron density, the OSCR calculation including lines and continuum emission reproduces about 60% of the total radiated power with a similarly centrally peaked emmissivity profile. The centrally peaked emissivity profile is due to low ionisation stages and strongly radiating species in the plasma core, mainly O4+ (Be-like) and C3+ (Li-like).

  • 30. da Silva, A. F.
    et al.
    Pepe, I.
    Persson, Clas
    KTH, Superseded Departments, Materials Science and Engineering.
    de Almeida, J. S.
    Araujo, C. M.
    Ahuja, Rajeev
    Johansson, Börje
    KTH, Superseded Departments, Materials Science and Engineering.
    An, C. Y.
    Guo, J. H.
    Optical properties of oxide compounds PbO, SnO2 and TiO22004In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T109, p. 180-183Article in journal (Refereed)
    Abstract [en]

    The optical properties of the oxide compounds PbO and SnO2 have been investigated experimentally by transmission spectroscopy measurements and theoretically by a full-potential linearized augmented plane wave (FPLAPW) method. The dielectric functions of the rutile TiO2 has also been calculated. The calculated band-gap energies as well as the optical absorption were found to be in a very good qualitatively agreement with the experimental results.

  • 31.
    Dahlin, Jon-Erik
    et al.
    KTH, Superseded Departments, Alfvén Laboratory.
    Scheffel, Jan
    KTH, Superseded Departments, Alfvén Laboratory.
    Self-consistent zero-dimensional numerical simulation of a Magnetized Target Fusion Configuration2004In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 70, no 5, p. 310-316Article in journal (Refereed)
    Abstract [en]

    A self-consistent zero-dimensional model of a Magnetized Target Fusion (MTF) configuration is presented. The plasma target is a Field Reversed Configuration (FRC). Model parameters were scanned using a Monte Carlo routine in order to determine an operating point that would correspond to reactor conditions. Albeit the model being intrinsically optimistic, the highest Q-values found only slightly exceed unity. The limited performance is due to the short dwell time of the liner, preventing a large portion of the fuel to burn.

  • 32. De Backer, A.
    et al.
    Sand, A.
    Ortiz, C. J.
    Domain, C.
    Olsson, Pär
    KTH, School of Engineering Sciences (SCI), Physics, Reactor Physics.
    Berthod, E.
    Becquart, C. S.
    Primary damage in tungsten using the binary collision approximation, molecular dynamic simulations and the density functional theory2016In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T167, article id 014018Article in journal (Refereed)
    Abstract [en]

    The damage produced by primary knock-on atoms (PKA) in W has been investigated from the threshold displacement energy (TDE) where it produces one self interstitial atom-vacancy pair to larger energies, up to 100 keV, where a large molten volume is formed. The TDE has been determined in different crystal directions using the Born-Oppenheimer density functional molecular dynamics (DFT-MD). A significant difference has been observed without and with the semi-core electrons. Classical MD has been used with two different empirical potentials characterized as 'soft' and 'hard' to obtain statistics on TDEs. Cascades of larger energy have been calculated, with these potentials, using a model that accounts for electronic losses (Sand et al 2013 Europhys. Lett. 103 46003). Two other sets of cascades have been produced using the binary collision approximation (BCA): a Monte Carlo BCA using SDTrimSP (Eckstein et al 2011 SDTrimSP: Version 5.00. Report IPP 12/8) (similar to SRIM www.srim.org) and MARLOWE (RSICC Home Page. (https://rsicc.ornl.gov/codes/psr/psr1/psr-137.html) (accessed May, 2014)). The comparison of these sets of cascades gave a recombination distance equal to 12 angstrom which is significantly larger from the one we reported in Hou et al (2010 J. Nucl. Mater. 403 89) because, here, we used bulk cascades rather than surface cascades which produce more defects (Stoller 2002 J. Nucl. Mater. 307 935, Nordlund et al 1999 Nature 398 49). Investigations on the defect clustering aspect showed that the difference between BCA and MD cascades is considerably reduced after the annealing of the cascade debris at 473 K using our Object Kinetic Monte Carlo model, LAKIMOCA.

  • 33. de la Hoz, P.
    et al.
    Björk, Gunnar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    de Guise, H.
    Klimov, A. B.
    Leuchs, G.
    Sanchez-Soto, L. L.
    Classical polarization multipoles: paraxial versus nonparaxial2015In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 90, no 7, article id 074030Article in journal (Refereed)
    Abstract [en]

    We discuss the polarization of paraxial and nonparaxial classical light fields by resorting to a multipole expansion of the corresponding polarization matrix. It turns out that only a dipolar term contributes when one considers SU(2) (paraxial) or SU(3) (nonparaxial) as fundamental symmetries. In this latter case, one can alternatively expand in SU(2) multipoles, and then both a dipolar and a quadrupolar component contribute, which explains the richer structure of this nonparaxial instance. These multipoles uniquely determine Wigner functions, in terms of which we examine some intriguing hallmarks arising in this classical scenario.

  • 34.
    Eichhorn, Ralf
    et al.
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
    Aurell, Erik
    KTH, School of Computer Science and Communication (CSC), Computational Biology, CB. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Stochastic thermodynamics2014In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 89, no 4, p. 048001-Article in journal (Refereed)
  • 35.
    Erdal, Suvar
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Haralson, Erik
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Radamson, Henry H.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Wang, Yong-Bin
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Malm, B. Gunnar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Östling, Mikael
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    High frequency performance of SiGeCHBTs with selectively & non-selectively grown collector2004In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T114, p. 138-141Article in journal (Refereed)
    Abstract [en]

    Two high-frequency heterojunction bipolar transistor (HBT) architectures based on SiGeC have been fabricated and characterized. Different collector designs were applied either by using selective epitaxial growth doped with phosphorous or by non-selective epitaxial growth doped with arsenic. Both designs have a non-selectively deposited SiGeC base doped with boron and a poly-crystalline emitter doped with phosphorous. Both HBT designs exhibit similar electrical characteristics with a peak DC current gain of around 1600 and a BVCEO of 1.8V. The cut-off frequency (f(T)) and maximum frequency of oscillation (f(max)) vary from 40-80 GHz and 15-30 GHz, respectively, depending on lateral design relations. Good high frequency performance for a device with a selectively grown collector is demonstrated for the first time.

  • 36. Fortuna, E.
    et al.
    Rubel, Marek J.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Psoda, M.
    Andrzejczuk, M.
    Kurzydlowski, K. J.
    Miskiewicz, M.
    Philipps, V.
    Pospieszczyk, A.
    Sergienko, G.
    Spychalski, M.
    Zielinski, W.
    Plasma-induced damage of tungsten coatings on graphite limiters2007In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T128, p. 162-165Article in journal (Refereed)
    Abstract [en]

    Vaccum plasma sprayed tungsten coatings with an evaporated sandwich Re - W interlayer on graphite limiter blocks were studied after the experimental campaign in the TEXTOR tokamak. The coating morphology was modified by high-heat loads and co-deposition of species from the plasma. Co-deposits contained fuel species, carbon, boron and silicon. X-ray diffractometer phase analysis indicated the coexistence of metallic tungsten and its carbides (WC and W2C) and boride (W2B). In the Re - W layer the presence of carbon was detected in a several micrometres thick zone. In the overheated part of the limiter, the Re - W layer was transformed into a sigma phase.

  • 37. Fortuna-Zalesna, E.
    et al.
    Grzonka, J.
    Moon, Sunwoo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Widdowson, A.
    Fine metal dust particles on the wall probes from JET-ILW2017In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T170, article id 014038Article in journal (Refereed)
    Abstract [en]

    Collection and ex situ studies of dust generated in controlled fusion devices during plasma operation are regularly carried out after experimental campaigns. Herewith results of the dust survey performed in JET after the second phase of operation with the metal ITER-like wall (2013-2014) are presented. For the first-time-ever particles deposited on silicon plates acting as dust collectors installed in the inner and outer divertor have been examined. The emphasis is on analysing metal particles (Be and W) with the aim to determine their composition, size and surface topography. The most important is the identification of beryllium dust in the form of droplets (both splashes and spherical particles), flakes of co-deposits and small fragments of Be tiles. Tungsten and nickel rich (from Inconel) particles are also identified. Nitrogen from plasma edge cooling has been detected in all types of particles. They are categorized and the origin of various constituents is discussed.

  • 38. Fortuna-Zalesna, E.
    et al.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Grozonka, J.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Esser, H. G.
    Freisinger, M.
    Kreter, A.
    Kischner, A.
    Sergienko, G.
    Ström, Petter
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Dust Survey Following the Final Shutdown of TEXTOR: Metal Particles and Fuel Retention2016In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T167, article id 014059Article in journal (Refereed)
    Abstract [en]

    The work presents results of a broad TEXTOR dust survey in terms of its composition, structure, distribution and fuel content. The dust particles were collected after final shutdown of TEXTOR in December 2013. Fuel retention, as determined by thermal desorption, varied significantly, even by two orders of magnitude, dependent on the dust location in the machine. Dust structure was examined by means of scanning electron microscopy combined with energy-dispersive X-ray spectroscopy, focused ion beam and scanning transmission electron microscopy. Several categories of dust have been identified. Carbon-based stratified and granular deposits were dominating, but the emphasis in studies was on metal dust. They were found in the form of small particles, small spheres, flakes and splashes which formed “comet”-like structures clearly indicating directional effects in the impact on surfaces of plasma-facing components. Nickel-rich alloys from the Inconel liner and iron-based ones from various diagnostic holders were the main components of metal-containing dust, but also molybdenum and tungsten debris were detected. Their origin is discussed.

  • 39. Gaarder, A.
    et al.
    Marcinkevicius, Saulius
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Barrios, C. A.
    Lourdudoss, Sebastian
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Time-resolved micro-photoluminescence studies of dopant distribution in selectively regrown GalnP: Fe around VCSELs2002In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T101, p. 89-91Article in journal (Refereed)
    Abstract [en]

    We apply time-resolved photoluminescence with 1.5 mum spatial resolution for characterization ofcarrier trap distribution in semi-insulating Ga0.51In0.49P:Fe layers regrown around GaAs/AlGaAs circular vertical cavity surface emitting laser mesas using hydride vapour phase epitaxy. The carrier trapping times are in the range from 10 to 15 ps and quite uniformly distributed throughout the burying GaInP:Fe layer, suggesting that the layer is semi-insulating everywhere. Simulations show that, in addition to the Fe dopants, the layer contains other, unintended carrier traps. The photoluminescence spectra reveal that the regrown GaInP:Fe material has several distinct regions with different band gaps. This is attributed to differences in the In/Ga composition and/or CuPt ordering of the GaInP.

  • 40.
    Garcia Carrasco, Alvaro
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Möller, S.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Kreter, A.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Wauters, T.
    Impact of ion cyclotron wall conditioning on fuel removal from plasma-facing components at TEXTOR2014In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T159, p. 014017-Article in journal (Refereed)
    Abstract [en]

    Ion cyclotron wall conditioning (ICWC) is based on low temperature and low density plasmas produced and sustained by ion cyclotron resonance (ICR) pulses in reactive or noble gases. The technique is being developed for ITER. It is tested in tokamaks in the presence of toroidal magnetic field (0.2-3.8 T) and heating power of the order of 10(5) W. ICWC with hydrogen, deuterium and oxygen-helium mixture was studied in the TEXTOR tokamak. The exposed samples were pre-characterized limiter tiles mounted on specially designed probes. The objectives were to assess the reduction of deuterium content, the uniformity of the reduction and the retention of seeded oxygen. For the last objective oxygen-18 was used as a marker. ICWC in hydrogen caused a drop of deuterium content in the tile by a factor of more than 2: from 4.5x10(18) to 1.9x10(18) D cm(-2). A decrease of the fuel content by approximately 25% was achieved by the ICWC in oxygen, while no reduction of the fuel content was measured after exposure to discharges in deuterium. These are the first data ever obtained showing quantitatively the local decrease of deuterium in wall components treated by ICWC in a tokamak. The oxygen retention in the tiles exposed to ICWC with oxygen-helium was analyzed for different orientations and radial positions with respect to plasma. An average retention of 1.38x10(16) O-18 cm(-2) was measured. A maximum of the retention, 4.4x10(16) O-18 cm(-2), was identified on a sample surface near the plasma edge. The correlation with the gas inlet and antennae location has been studied.

  • 41. Gasior, P.
    et al.
    Badziak, J.
    Czarnecka, A.
    Parys, P.
    Wolowski, J.
    Rosinski, M.
    Rubel, Marek J.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Philipps, V.
    Characterization of laser-irradiated co-deposited layers on plasma facing components from a tokamak2006In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T123, p. 99-103Article in journal (Refereed)
    Abstract [en]

    An experimental setup and ion diagnostic method for laser-induced fuel removal and decomposition of co-deposited layers on plasma facing components from tokamaks are described. Nd:YAG 3.5 ns pulse laser with a repetition rate of 10 Hz and single-pulse energy of up to 0.8J at 1.06 mu m has been used for irradiation of a graphite limiter tile from the TEXTOR tokamak. Comparative studies have been performed for a pure graphite plate as a reference target. Energy of emitted ions has been measured using a time-of-flight method. Early results show that laser pulses efficiently ablate the co-deposit removing both fuel species and heavy components such as Si, Ni, Cr, Fe and W present in the layers. Surface topography of the irradiated targets is also presented.

  • 42. Gvozdic, D. M.
    et al.
    Ekenberg, Ulf
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Superiority of p-type spin transistors2006In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T126, p. 21-26Article in journal (Refereed)
    Abstract [en]

    The spintronic device that has probably stimulated the most research interest is the Datta-Das spin transistor. The mechanism behind it, called the Rashba effect, is that an applied voltage gives rise to a spin splitting. We demonstrate that the relevant spin splitting in k-space can be made more than three orders of magnitude larger for holes than for electrons at the same electric field. This is partly achieved by utilizing the frequently neglected lattice-mismatch between GaAs and AlGaAs. We design heterostructures where this efficient Rashba effect should show up. Compared to present transistors, we conclude that electron-based spin transistors will have problems in becoming competitive but hole-based ones are much more promising.

  • 43.
    Hallén, Anders.
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Suchodolskis, Arturas
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Österman, John
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Abtin, L.
    Linnarsson, Margareta K.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Annealing of Al implanted 4H silicon carbide2006In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T126, p. 37-40Article in journal (Refereed)
    Abstract [en]

    Al ions were implanted with multiple energies up to 250 keV at elevated temperatures in n-type 4H SiC epitaxial layers to reach a surface concentration of 1 x 10(20) cm(-3). These samples were then annealed at temperatures between 1500 and 1950 degrees C. A similar 4H SiC epitaxial sample was implanted by MeV Al ions to lower doses and annealed only at 200 and 400 degrees C. After annealing, cross-sections of the samples were characterized by scanning spreading resistance microscopy (SSRM). The results show that the resistivity of high-dose Al implanted samples has not reached a saturated value, even after annealing at the highest temperature. For the MeV Al implanted sample, the activation of Al has not yet started, but a substantial annealing of the implantation induced damage can be seen from the SSRM depth profiles.

  • 44. Heinola, K.
    et al.
    Widdowson, A.
    Likonen, J.
    Alves, E.
    Baron-Wiechec, A.
    Barradas, N.
    Brezinsek, S.
    Catarino, N.
    Coad, P.
    Koivuranta, S.
    Krat, S.
    Matthews, G. F.
    Mayer, M.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. EUROfusion Consortium, Culham Science Centre, JET, Abingdon, United Kingdom.
    Contributors, J.
    Long-term fuel retention in JET ITER-like wall2016In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T167, article id 014075Article in journal (Refereed)
    Abstract [en]

    Post-mortem studies with ion beam analysis, thermal desorption, and secondary ion mass spectrometry have been applied for investigating the long-term fuel retention in the JET ITERlike wall components. The retention takes place via implantation and co-deposition, and the highest retention values were found to correlate with the thickness of the deposited impurity layers. From the total amount of retained D fuel over half was detected in the divertor region. The majority of the retained D is on the top surface of the inner divertor, whereas the least retention was measured in the main chamber on the mid-plane of the inner wall limiter. The recessed areas of the inner wall showed significant contribution to the main chamber total retention. Thermal desorption spectroscopy analysis revealed the energetic T from DD reactions being implanted in the divertor. The total T inventory was assessed to be >0.3 mg.

  • 45.
    Hellsten, Torbjörn
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. JET Joint Undertaking, Oxfordshire OX14 3EA, UK.
    Scheffel, Jan
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Continuous Double Adiabatic Spectrum in Toroidal Plasmas1984In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 30, p. 78-Article in journal (Refereed)
    Abstract [en]

    The continuous spectrum of an anisotropic and axisymmetric toroidal plasma is investigated using the double adiabatic theory. The continuum is given by an eigenvalue problem of a fourth order system of ordinary differential equations. In contrast to the magnetohydrodynamic continuum the double adiabatic continuum may become unstable. The stability depends upon the parallel and perpendicular pressure distributions along the field lines. In absence of a toroidal magnetic field, the fourth order system decouples into two second order differential equations for which specific stability criteria are derived.

  • 46. Henry, A
    et al.
    Forsberg, U
    Linnarsson, Margareta
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Janzen, E
    Determination of nitrogen doping concentration in doped 4H-SiC epilayers by low temperature photoluminescence2005In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 72, p. 254-257Article in journal (Refereed)
    Abstract [en]

    A complete calibration of nitrogen concentration in doped 4H-SiC material is presented. This is done in the very large range of doping available today. i.e. from low 10(14) to 10(19) cm(-3). The samples are 4H-SiC films fabricated by hot-wall chemical vapour deposition. Low temperature photoluminescence is used as the experimental tool. For doping concentrations less than 8. 10(17) cm(-3), comparison between the intensity of various luminescence lines is used. whereas for doping hi,,her than 3 - 10(18) cm(-3) the energy position of an observed broad band allows the determination of the doping level.

  • 47. Herskind, B.
    et al.
    Hagemann, G. B.
    Sletten, G.
    Dossing, Th
    Hansen, C. Ronn
    Schunck, N.
    Cederwall, Bo
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Lagergren, Karin
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    et al,
    Charged particle feeding of hyperdeformed nuclei in the A=118-126 region2006In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T125, p. 108-114Article in journal (Refereed)
    Abstract [en]

    A breakthrough was recently obtained in the analysis of the so-called Hyper-Long-HyperDeformed (HLHD) experiment made at the EUROBALL-IV gamma-detector array (EB). The Ni-64 + Ni-64 double right arrow Ba-128* fusion reaction was studied at E-beam = 255 and 261 MeV, reaching the highest angular momentum that the compound nuclei can accommodate. To date no discrete HD rotational bands have been identified. However, rotational patterns in the form of ridge-structures in three-dimensional (3D) rotational mapped spectra are identified with dynamic moments of inertia J((2)) ranging from 71 to 111h(2) MeV-1 in 12 different nuclei selected by charged particle- and/or gamma-gating. The four nuclei, Te-118, Cs-124, Cs-125 and Xe-124 found with moment of inertia J((2)) >= 100h(2) MeV-1, are most likely hyperdeformed, the remaining nuclei with smaller values of J((2)), are considered to be superdeformed, in qualitative agreement with recent theoretical calculations.

  • 48. Herzberg, R-D
    et al.
    Greenlees, P. T.
    Butler, P. A.
    Jones, G. D.
    Darby, I. G.
    Eeckhaudt, S.
    Grahn, T.
    Gray-Jones, C.
    Hessberger, F. P.
    Jones, P.
    Julin, R.
    Juutinen, S.
    Ketelhut, S.
    Leino, M.
    Leppanen, A-P
    Moon, S.
    Nyman, M.
    Page, R. D.
    Pakarinen, J.
    Pritchard, A.
    Rahkila, P.
    Sandzelius, Mikael
    KTH, School of Engineering Sciences (SCI), Physics.
    Saren, J.
    Scholey, C.
    Steer, A.
    Uusitalo, J.
    Venhart, M.
    Isomer spectroscopy in No-2542006In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T125, p. 73-77Article in journal (Refereed)
    Abstract [en]

    Isomeric states in No-254 were investigated using a calorimetric method. Two different isomers were found with half-lives of T-1/2 = 266 +/- 2 ms and T-1/2 = 184 +/- 3 mu s, respectively. The dominant decay path of the 184 mu s isomer proceeds via states feeding the longer-lived 266 ms isomer. The 266 ms isomer in turn decays via a two-quasi-particle K = 3 band to the ground-state band. The full decay path was observed with the GREAT spectrometer located at the focal plane of the gas-filled separator RITU at the Accelerator Laboratory in Jyvskyl. This work sheds light on the two-quasi-particle structure in this transfermium nucleus.

  • 49. Hirai, T.
    et al.
    Linke, J.
    Sundelin, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Rubel, Marek J.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Kuehnlein, W.
    Wessel, E.
    Coad, J. P.
    Lungu, C. P.
    Matthews, G. F.
    Pedrick, L.
    Piazza, G.
    Characterization and heat flux testing of beryllium coatings on Inconel for JET ITER-like wall project2007In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T128, p. 166-170Article in journal (Refereed)
    Abstract [en]

    In order to perform a fully integrated material test, JET has launched the ITER-like wall project with the aim of installing a full metal wall during the next major shutdown. The material foreseen for the main chamber wall is bulk Be at the limiters and Be coatings on inconel tiles elsewhere. R&D process comprises global characterization ( structure, purity etc) of the evaporated films and testing of their performance under heat loads. The major results are (i) the layers have survived energy loads of 20 MJ m(-2) which is significantly above the required level of 5 - 10 MJ m(-2), (ii) melting limit of beryllium coating would be at the energy level of 30 MJ m(-2), (iii) cyclic thermal load of 10 MJ m(-2) for up to 50 cycles have not induced any noticeable damage such as flaking or detachment.

  • 50. Hirai, T.
    et al.
    Rubel, Marek J.
    KTH, Superseded Departments, Alfvén Laboratory.
    Philipps, V.
    Huber, A.
    Tanabe, T.
    Wada, M.
    Ohgo, T.
    Pospieszczyk, A.
    Sergienko, G.
    Wienhold, P.
    Testing of tungsten and tantalum limiters at the TEXTOR tokamak: Material performance and deuterium retention2003In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T103, p. 59-62Article in journal (Refereed)
    Abstract [en]

    Tungsten and tantaium were examined in the TEXTOR tokamak as test limiters in order to compare their performance under plasma operation and to recognise fuel recycling on endothermic (W) and exothermic (Ta) hydrogen absorbers. Differences have been noticed in the distribution and microstructure of co-deposits. in the fuel inventory in the bulk of metals and, in the deuterium release mechanism (ratio of molecules to atoms). As a result of poor thermal conductivity. the surface temperature of Ta during the power deposition was higher than that of W and it increased shot-by-shot because of the degradation of thermal properties due to surface modification. Results on thermal response, fuel recycling and inventory show that. as a candidate material for plasma facing components. tungsten is superior to tantalum.

123 1 - 50 of 143
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