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  • 151.
    Carlsson, Kjell
    et al.
    KTH, Superseded Departments, Physics.
    Liljeborg, A.
    Andersson, R. M.
    Brismar, Hjalmar
    Confocal pH imaging of microscopic specimens using fluorescence lifetimes and phase fluorometry: influence of parameter choice on system performance2000In: Journal of Microscopy, ISSN 0022-2720, E-ISSN 1365-2818, Vol. 199, p. 106-114Article in journal (Refereed)
    Abstract [en]

    We investigate the performance of confocal pH imaging when using phase fluorometry and fluorophores with pH-dependent lifetimes. In these experiments, the specimen is illuminated by a laser beam, whose intensity is sinusoidally modulated. The lifetime-dependent phase shift in the fluorescent signal is detected by a lock-in amplifier, and converted into a pH value through a calibration procedure. A theoretical investigation is made of how the different system parameters will influence the results concerning sensitivity and noise. Experiments carried out with the fluorophore SNAFL-2 support these theoretical predictions. It is found that, under realistic experimental conditions, we can expect a pH change of 0.1 units to be easily detected in an 8-bit digital image. However, the pixel-to-pixel root mean square noise is often of the order of one pH unit. This comparatively high level of noise has its origin in photon quantum noise. pH measurements on living cells show a systematic deviation from expected values. This discrepancy appears to be the result of fluorophore interaction with various cell constituents, and is the subject of further investigation.

  • 152.
    Carlsund-Levin, Christina
    KTH, Superseded Departments, Physics.
    Numerical studies of resonances using complex scaling2000Doctoral thesis, comprehensive summary (Other scientific)
  • 153.
    Cartling, Bo
    KTH, Superseded Departments, Physics.
    Control of neural information transmission by synaptic dynamics2002In: Journal of Theoretical Biology, ISSN 0022-5193, E-ISSN 1095-8541, Vol. 214, no 2, p. 275-292Article in journal (Refereed)
    Abstract [en]

    The computational processing of a neural system is strongly influenced by the dynamical characteristics of the information transmission between neurons. In this work, the control of neural information transmission by synaptic dynamics is investigated by means of a master-equation-based stochastic model of pre-synaptic release of neurotransmitter-containing vesicles. The model incorporates facilitation of vesicle fusion with the pre-synaptic membrane due to intracellular calcium ions and depletion of readily releasable vesicles. The message to be transmitted is coded by the pre-synaptic firing sequence, and the received signal corresponds to the post-synaptic membrane potential response. At the sending end, the stochastic character of the vesicle release contributes to the entropy of the probability distribution of the number of vesicles released and represents noise with respect to information transmission. At the receiving end, the generation of post-synaptic membrane potentials is influenced by the temporal behaviour of ionic currents and membrane charging and is determined by means of a low-dimensional model. The rate and temporal types of neural coding are compatible with limiting cases of the synaptic information transmission as a function of initial vesicle release probability and pre-synaptic firing rate. The effects of the nonlinear dependencies of the vesicle release probability on intracellular calcium concentration and number of available vesicles are analysed. The model is compared with phenomenological and reduced models, a principal advantage being the capability of also determining fluctuations of dynamic variables.

  • 154.
    Cartling, Bo
    KTH, Superseded Departments, Physics.
    Neuromodulatory control of neocortical microcircuits with activity-dependent short-term synaptic depression2004In: Journal of biological physics (Print), ISSN 0092-0606, E-ISSN 1573-0689, Vol. 30, no 3, p. 261-284Article in journal (Refereed)
    Abstract [en]

    A biophysical model of a neocortical microcircuit system is formulated and employed in studies of neuromodulatory control of dynamics and function. The model is based on recent observations of reciprocal connections between pyramidal cells and inhibitory interneurons and incorporates a new type of activity-dependent short-term depression of synaptic couplings recently observed. The model neurons are of a low-dimensional type also accounting for neuronal adaptation, i.e. the coupling between neuronal activity and excitability, which can be regulated by various neuromodulators in the brain. The results obtained demonstrate a capacity for neuromodulatory control of dynamical mode linked to functional mode. The functional aspects considered refer to the observed resolution of multiple objects in working memory as well as the binding of different features for the perception of an object. The effects of neuromodulators displayed by the model are in accordance with many observations on neuromodulatory influence on cognitive functions and brain disorders.

  • 155.
    Cartling, Bo
    KTH, Superseded Departments, Physics.
    Stochastic and reduced biophysical models of synaptic transmission2000In: Journal of biological physics (Print), ISSN 0092-0606, E-ISSN 1573-0689, Vol. 26, no 2, p. 113-131Article in journal (Refereed)
    Abstract [en]

    Stochastic and reduced biophysical models of synaptic transmission are formulated and evaluated. The synaptic transmission involves presynaptic facilitation of neurotransmitter release, depletion and recovery of the presynaptic pool of readily releasable vesicles containing neurotransmitter molecules and saturation of postsynaptic receptors of both fast non-NMDA and slow NMDA types. The models are shown to display the principal dynamical characteristics experimentally observed of synaptic transmission. The two main types of neural coding, i.e. rate and temporal coding, can be distinguished by means of different dynamical properties of synaptic transmission determined by initial neurotransmitter release probability and presynaptic firing rate. From the temporal evolution of the postsynaptic membrane potential response to a train of presynaptic action potentials at a sustained firing rate, in particular the steady-state amplitude and steady-state average level of postsynaptic membrane potentials are determined as functions of both initial release probability and presynaptic firing rate. The models are applicable to studies of the primary stages of learning processes and can be extended to incorporate short-term and long-term potentiation in memory consolidation processes.

  • 156.
    Cecconello, Marco
    et al.
    KTH, Superseded Departments, Alfvén Laboratory.
    Brzozowski, Jerzy
    KTH, Superseded Departments, Alfvén Laboratory.
    Gravestijn, Robert
    KTH, Superseded Departments, Physics.
    Murari, A
    Total radiation losses studies in EXTRAP T2R2001In: Proceedings of the 28th European Physical Society Conference on Controlled Fusion and Plasma Physics, Madeira, 2001Conference paper (Other academic)
  • 157.
    Cecconello, Marco
    et al.
    KTH, Superseded Departments, Alfvén Laboratory.
    Malmberg, Jenny A.
    KTH, Superseded Departments, Alfvén Laboratory.
    Spizzo, G.
    Chapman, B. E.
    Gravestjin, Robert M.
    KTH, Superseded Departments, Physics.
    Franz, P.
    Piovesan, P.
    Martin, P.
    Drake, James R.
    KTH, Superseded Departments, Alfvén Laboratory.
    Current profile modification experiments in EXTRAP T2R2004In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 46, no 1, p. 145-161Article in journal (Refereed)
    Abstract [en]

    Pulsed poloidal current drive (PPCD) experiments have been conducted in the resistive shell EXTRAP T2R reversed-field pinch experiment. During the current profile modification phase, the fluctuation level of the m = 1 internally resonant tearing modes decreases, and the velocity of these modes increases. The m = 0 modes are not affected during PPCD, although termination occurs with a burst in the m = 0 amplitude. The PPCD phase is characterized by an increase in the central electron temperature (up to 380 eV) and in the soft x-ray signal. Spectroscopic observations confirm an increase in the central electron temperature. During PPCD, the plasma poloidal beta increases to 14%, and the estimated energy confinement time doubles, reaching 380 mus. The reduction in the fluctuation level and the corresponding increase in the energy confinement time are qualitatively consistent with a reduction in parallel transport along stochastic magnetic field lines.

  • 158.
    Cecconello, Marco
    et al.
    KTH, Superseded Departments, Alfvén Laboratory.
    Malmberg, Jenny-Ann
    KTH, Superseded Departments, Alfvén Laboratory.
    Spizzo, G
    Gravestijn, Robert
    KTH, Superseded Departments, Physics.
    Franz, P
    Martin, P
    Chapman, B
    Drake, James Robert
    KTH, Superseded Departments, Alfvén Laboratory.
    Current profile control experiments in EXTRAP T2RManuscript (preprint) (Other academic)
  • 159.
    Cederkäll, Joakim
    KTH, Superseded Departments, Physics.
    Nuclear structure close to<SUP>100</SUP>Sn1998Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The nuclear structure of neutron deficient isotopes in thevicinity of the douhle shell closure at1ooSn has been experimentally investigated by meansof y-spectroscopic meth ods. Experimental information onexcit,ed st,ates in nuclei in the vicinity of1ooSn has been scarce until recently. Theexperiments reported in this thesis have utilized multidetectorsystems comprising high resolution Compton suppressed germaniumspectrometers, neutron detectors and charged particle detectorsto identify residues from heavy-ion induced fusion-evaporationreactions. The first in-beam observation of excited states in1o6,1o7,1o8,Sb as well as in the one-hole two-particlenucleus1ooIn and the two-hole one particle nucleus99Cd is reported. The experimental information onexcited states in a number of other isotopes has beenconsiderably extended. The results thus provide new informationthat is vital for the interpretation of nuclear structure usingthe nuclear shell model.

    Keywords:y-ray spectroscopy far from stabilit.y,fusion-evaporation reactions, multidetector arrays, nuclearshell model.

  • 160.
    Cederström, Björn
    KTH, Superseded Departments, Physics.
    A multi-prism lens for hard X-Rays2002Doctoral thesis, monograph (Other scientific)
    Abstract [en]

    This thesis describes a new type of refractive lens for hardx-rays. It is shown that a linear array of prisms, slightlyinclined with respect to the optical axis, will form a linefocus at a certain distance from the lens. Hence, the namemulti-prism lens. These lenses are free from sphericalaberration and are similar to planar parabolic compoundrefractive lenses in terms of performance. However, theydistinguish themselves in that only planar surfaces need to befabricated. A special feature is that the focal length can beeasily varied by adjusting the inclination angle.

    Theoretical calculations, based on geometrical and physicaloptics, are used to characterize the lenses. Aberrations arediscussed, as well as the sensitivity to fabricationimperfections, and insufficient flatness is identified as apotential problem. Ray-tracing is used to test theapproximations and assumptions used in the theory. Applicationsin x-ray microscopy and mammography are discussed.

    Lenses have been made of beryllium, silicon, epoxy anddiamond using different methods. Results from measurements ofsurface roughness and figure error show that the imperfectionsof the silicon and epoxy lenses should have a small impact,while the beryllium lenses should suffer from strongscattering. Experiments were performed at the EuropeanSynchrotron Radiation Facility and sub-µm focal linewidths, close to theoretical expectations, were measured forsilicon and epoxy lenses at 30 keV and 14 keV, respectively.Insertion gains up to 40 were reached. Two crossed lenses wereused to obtain focusing in two dimensions and a point focus.The smallest measured focal spot size was 1.0 µm by 5 .4µm, and an insertion gain exceeding 100 was achieved usingepoxy lenses.

    The diamond lenses suffered from voids in the materialformed in the chemical vapor deposition process, butnevertheless provided focal lines less than 2 µm in width,albeit at at relatively low insertion gain of 13. Due to theirexcellent thermal properties, these lenses are put forward ascandidates for optics at the next generationultra-high-intensity synchrotron beams and x-ray free electronlasers.

    Keywords:x-ray, optics, refractive, lens, mammography,synchrotron.

  • 161.
    Cederström, Björn
    KTH, Superseded Departments, Physics.
    Refractive Optics for Hard X-rays2001Licentiate thesis, monograph (Other scientific)
  • 162.
    Cederström, Björn
    et al.
    KTH, Superseded Departments, Physics.
    Cahn, R. N.
    Danielsson, Mats
    KTH, Superseded Departments, Physics.
    Lundqvist, M.
    Nygren, D. R.
    Focusing hard X-rays with old LPs2000In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 404, no 6781, p. 951-951Article in journal (Refereed)
  • 163.
    Cederwall, Bo
    et al.
    KTH, Superseded Departments, Physics.
    Bäck, Torbjörn
    KTH, Superseded Departments, Physics.
    Bark, R
    Tormanen, S
    Odegard, S
    King, L
    Simpson, J
    Page, D
    Amzal, N
    Cullen, M
    Greenlees, T
    Keenan, A
    Lemmon, R
    Cocks, C
    Helariutta, K
    Jones, M
    Julin, R
    Juutinen, S
    Kettunen, H
    Kankaanpaa, H
    Kuusiniemi, P
    Leino, M
    Muikku, M
    Rahkila, P
    Savelius, A
    Uusitalo, J
    Magierski, P
    Wyss, Ramon
    KTH, Superseded Departments, Physics.
    Collective rotational-vibrational transition in the very neutron-deficient nuclei (171,172)-Pt1998In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 443, no 1-4, p. 69-76Article in journal (Refereed)
    Abstract [en]

    Excited states have been identified for the first time in very neutron deficient Pt-171.172 nuclei using the recoil-or-decay tagging technique. The ground-state band in Pt-172 has been established up to I-pi = 8+. A similar level sequence, presumably built on the I-pi = 13/2(+) state, is observed for Pt-171. The data are compared with theoretical calculations based on the mean field approach and the random phase approximation and are put into the context of the systematics of platinum isotopes. (C) 1998 Elsevier Science B.V. All rights reserved.

  • 164.
    Cederwall, Bo
    et al.
    KTH, Superseded Departments, Physics.
    Bäck, Torbjörn
    KTH, Superseded Departments, Physics.
    Wyss, Ramon
    KTH, Superseded Departments, Physics.
    Johnson, Arne
    KTH, Superseded Departments, Physics.
    Cederkäll, Joakim
    KTH, Superseded Departments, Physics.
    Devlin, M
    Elson, J
    LaFosse, R
    Lerma, F
    Sarantites, G
    Clark, M
    Fallon, P
    Lee, Y
    Macchiavelli, O
    Macleod, W
    Favoured superdeformed states in 89TC1999In: European Physical Journal A, ISSN 1434-6001, E-ISSN 1434-601X, Vol. 6, no 3, p. 251-255Article in journal (Refereed)
    Abstract [en]

    A superdeformed band consisting of a cascade of ten gamma-ray transitions has been identified and assigned to the nucleus Tc-89, close to the proton dripline. The quadrupole moment of the band (Q(t) = 6.7(-2.3)(+3.0) eb, as measured by the Residual Doppler Shift Method) as well as a large dynamic moment of inertia point to a highly elongated shape. With a relative population of approximately 15% of the gamma-ray flux in the Tc-89 exit channel, thp band is among the most intense superdeformed bands observed to date.

  • 165. Chakraborty, P. B.
    et al.
    Henelius, Patrik
    KTH, Superseded Departments, Physics.
    Kjonsberg, H.
    Sandvik, A. W.
    Girvin, S. M.
    Theory of the magnetic phase diagram of LiHoF42004In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 70, no 14Article in journal (Refereed)
    Abstract [en]

    The properties of LiHoF4 are believed to be well described by a long-range dipolar Ising model. We go beyond mean-field theory and calculate the phase diagram of the Ising model in a transverse field using a quantum Monte Carlo method. The relevant Ising degrees of freedom are obtained using a nonperturbative projection onto the low-lying crystal-field eigenstates. We explicitly take the domain structure into account, and the strength of the near-neighbor exchange interaction is obtained as a fitting parameter. The on-site hyperfine interaction is approximately taken into account through a renormalization of the transverse applied magnetic field. Finally, we propose a spectroscopy experiment to precisely measure the most important parameter controlling the location of the phase boundary.

  • 166. Charlton, D. G.
    et al.
    Dowell, J. D.
    Homer, R. J.
    Jovanovic, P.
    Kenyon, I. R.
    Mahout, G.
    Shaylor, H. R.
    Wilson, J. A.
    Rudge, A.
    Fopma, J.
    Mandic, I.
    Nickerson, R. B.
    Shield, P.
    Wastie, R.
    Weidberg, A. R.
    Eek, L. O.
    Go, A.
    Lund-Jensen, Bengt
    KTH, Superseded Departments, Physics.
    Pearce, Mark
    KTH, Superseded Departments, Physics.
    Soderqvist, J.
    Morrissey, M.
    White, D. J.
    System tests of radiation hard optical links for the ATLAS semiconductor tracker2000In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 443, no 03-feb, p. 430-446Article in journal (Refereed)
    Abstract [en]

    A prototype optical data and Timing Trigger and Control transmission system based on LEDs and PIN-diodes has been constructed. The system would be suitable in terms of radiation hardness and radiation length for use in the ATLAS SemiConductor Tracker. Bit error rate measurements were performed for the data links and for the links distributing the Timing, Trigger and Control data from the counting room to the front-end modules. The effects of cross-talk between the emitters and receivers were investigated. The advantages of using Vertical Cavity Surface Emitting Lasers (VCSELs) instead of LEDs are discussed.

  • 167.
    Chauvin, Maxime
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Florén, Hans-Gustav
    Friis, Mette
    Jackson, Miranda
    Kamae, Tuneyoshi
    Kataoka, Jun
    Kawano, Takafumi
    Kiss, Mózsi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Mikhalev, Victor
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Mizuno, Tsunefumi
    Ohashi, Norie
    Stana, Theodor
    Tajima, Hiro
    Takahashi, Hiromitsu
    Uchida, Nagomi
    Pearce, Mark
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics. KTH, Superseded Departments (pre-2005), Physics.
    Accretion geometry of the black-hole binary Cygnus X-1 from X-ray polarimetryIn: Nature Astronomy, ISSN 2397-3366Article in journal (Refereed)
  • 168. Chen, M. X.
    et al.
    Perzon, E.
    Andersson, M. R.
    Marcinkevicius, Saulius
    KTH, Superseded Departments, Physics.
    Jonsson, S. K. M.
    Fahlman, M.
    Berggren, M.
    1 micron wavelength photo- and electroluminescence from a conjugated polymer2004In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 84, no 18, p. 3570-3572Article in journal (Refereed)
    Abstract [en]

    We report photo- and electroluminescence from an alternating conjugated polymer consisting of fluorene units and low-band gap donor-acceptor-donor (D-A-D) units. The D-A-D segment includes two electron-donating thiophene rings combined with a thiadiazolo-quinoxaline unit, which is electron withdrawing to its nature. The resulting polymer is conjugated and has a band gap of 1.27 eV. The corresponding electro- and photoluminescence spectra both peak at approximately 1 mum. Light-emitting diodes, based on a single layer of the polymer, demonstrated external quantum efficiencies from 0.03% to 0.05%.

  • 169. Chen, W.
    et al.
    Cameron, S.
    Göthelid, M.
    Hammar, M.
    KTH, Superseded Departments, Physics.
    Paul, J.
    Redox properties of titanium oxides on Pt3Ti1995In: Journal of Physical Chemistry, ISSN 00223654 (ISSN), Vol. 99, no 34, p. 12892-12895Article in journal (Refereed)
    Abstract [en]

    The morphology and electronic structure of surface-segregated titanium oxides on Pt3Ti(111) are presented. Core level photoemission spectra at grazing emission reveal two states of oxidation: a dominant and reducible four-valent oxide together with a small amount of a three-valent oxide is produced by oxidation in O2 at and below 400°C; an irreducible three-valent oxide by oxidation in O2 at and above 450°C. The ratio between the active four-valent and the inactive three-valent oxides decreases with increasing oxidation temperature. The probability for reduction by CO is almost unity for the Ti4+ oxide, and the conclusion must be that the four-valent oxide plays an active role for catalytic reactions. Scanning tunneling measurements relate these observations to changes in the dispersion and nucleation of the oxide overlayer. The four-valent oxide grows as islands with remaining areas open for CO adsorption while the three-valent oxide spreads on and blocks the crystal surface. Photoemission spectra relate these dispersion effects to an electronic interaction between the Ti3+ oxide and adjacent Pt atoms. The above observations are in accordance with the common picture of dispersion effects in titania-supported SMSI catalysts and prove that interfacial energies play a crucial role whether the dominant phase is metallic or an oxide. © 1995 American Chemical Society.

  • 170. Chen, W.
    et al.
    Severin, L.
    Göthelid, M.
    Hammar, M.
    KTH, Superseded Departments, Physics.
    Cameron, S.
    Paul, J.
    Electronic and geometric structure of clean Pt3Ti(111)1994In: Physical Review B, ISSN 01631829 (ISSN), Vol. 50, no 8, p. 5620-5627Article in journal (Refereed)
    Abstract [en]

    Photoemission spectra and scanning tunneling microscopy (STM) images of the clean Pt3Ti(111) surface are presented. Grazing-emission core-level spectra show that the topmost layer is pure platinum, modified compared with the Pt(111) surface. The Pt 4f levels at the surface are shifted 0.4 eV toward the Fermi level relative to bulk Pt3Ti while the Pt 4f and Ti 2p levels in the bulk are shifted 0.4 and 1.3 eV to higher binding energy relative to pure bulk platinum and titanium, respectively, Tunneling measurements show a surface with only metallic atoms and a small p(2×2) buckling. Our observations of molecularly adsorbed CO are not compatible with metallic titanium atoms at the surface and the STM data thus indirectly confirm that only platinum atoms are present in the topmost layer. Linear muffin-tin-orbital calculations of the bulk band structure and valence-band photoemission spectra reveal highly hybridized electron states between the Pt d and Ti d levels. The calculations give a minor charge transfer from Ti to Pt, 0.37 electrons per Ti atom, but the large core-level shifts reflect the stability of the alloy and the response to the excitation rather than the amount of charge transfer. The observed segregation of platinum to the surface and the altered electronic structure of the topmost layer, due to interaction with the underlying alloy, are in full agreement with earlier conclusions based on low-energy electron-diffraction measurements and on the chemical properties of the surface. © 1994 The American Physical Society.

  • 171.
    Chmill, Valery
    KTH, Superseded Departments, Physics.
    Investigation of GaAs structures for microstrip detectors2003Licentiate thesis, monograph (Other scientific)
    Abstract [en]

    The performance of Gallium Arsenide p-i-n detectors afterneutron irradiation has been studied. The detectors have beenirradiated with » 6 MeV neutrons at various neutronfluences up to approximately 6 ¢ 1014 n/cm2, protons andmixed beam up to 1015 p/cm2. Results are presented for thee®ect on leakage currents and charge collectione±ciencies for alpha particles irradiation and minimumionizing electrons. The signal from minimum ionizing electronswas well separated from the noise even at the highest neutronexposures achieved, therefore the diodes are still operationalas detectors. Saturation of damage is observed in both the I-Vcharacteristics and charge collection measurements. Theoperation of detectors at the LHC is most challenging in termsof radiation damage. Detectors for tracking applications insidethe inner cavity of an electromagnetic calorimeter and close tothe interaction point will receive charged particle doses inthe range of 11 Mrad and fast neutron fluences 1014 n/cm2during the lifetime of an experiment. Gallium Arsenidedetectors have been shown to be radiation resistant to neutronirradiation for fluences up to 1015 n/cm2 and consequently theuse of GaAs detectors as a part of the inner tracker has beenproposed by the ATLAS collaboration. For this work detectorswere irradiated in the Protvino I-100 Injector, U-70Accelerator and Neutrino decay channel at CERN. Allexperimental measurements was done within the RD8collaboration.

  • 172. Cho, C. R.
    et al.
    Grishin, Alexander M.
    KTH, Superseded Departments, Physics.
    Background oxygen effects on pulsed laser deposited Na0.5K0.5NbO3 films: From superparaelectric state to ferroelectricity2000In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 87, no 9, p. 4439-4448Article in journal (Refereed)
    Abstract [en]

    Ambient oxygen pressure in a pulsed laser deposition process has been observed to have a critical influence on the compositional, crystalline, and electrical properties of Na0.5K0.5NbO3 (NKN) thin films grown onto polycrystalline Pt80Ir20 and SiO2 (native oxide)/Si(111) substrates. Films prepared at high oxygen pressure (similar to 400 mTorr) were found to be single phase and highly c-axis oriented. X-ray diffraction theta-2 theta scans and rocking curve data show a strong effect of NKN film self-assembling along the [001] direction regardless of the substrate texture. The high dielectric permittivity of 550, low dissipation factor of less than 3%, and high remanent polarization of 12 mu C/cm(2) indicate the high ferroelectric quality of the fabricated film. The role of the high-energy component of the erosion products has been proven to be crucial to film performance. On the other hand, films grown at low oxygen pressure (similar to 10 mTorr) have been found to be mixed phases of ferroelectric NKN and paraelectric potassium niobates. These films have shown superparaelectric behavior: 5% tunability at an electric field of 100 kV/cm, losses as low as 0.3%, and excellent stability to temperature and frequency changes.

  • 173.
    Cho, Choong-Rae
    KTH, Superseded Departments, Physics.
    Ferroelectric Na0.5K0.5NbO3 Thin Films: Processing, Physical Properties and Applications2001Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis presents the results on the fabrication offerroelectric Na0.5K0.5NbO3(NKN) thin films by pulsed laser deposition (PLD)technique, comprehensive characterization of film properties,and various applications of NKN films. To preparestoichiometric single phase ferroelectric NKN films andovercome high volatility of Na and K constituents through thecomplete thermalization of plasma plume and forming a shockwave, NKN ceramic target was ablated at sufficiently highambient oxygen pressure. On the other hand, Na deficient filmsdeposited at low ambient pressure exhibited superparaelectricbehavior with very low frequency dispersion and uniquetemperature stability in the range 77 K to 420 K. Highly polaraxis oriented textures (XRD reflection ratio>100) areobserved in the films on polycrystalline Pt80Ir20, amorphous SiO2/Si, hexagonal Al2O3and trigonal quartz substrates. Smooth filmssurface (average roughness = 6 Å), significantly narrowermosaic broadenings than those in substrates (more than 6times), and abnormally large grain sizes (up to several µm2) indicateself-asembling phenomenon. From the analysis of bi-axialtextures observed in NKN films on MgO substrates, effect of theself-assembling has been attributed to strong interactionbetween NbO6octahedra and two-dimensional film growthmode.

    Superior crystalline properties correlate with highperformances of electrical properties. High remnantpolarization of µC/cm2, low dielectric loss less than 1 %, highresistivity in the order of 1010Ω -cm, very low leakage currents, and highbreakdown voltages (>500 kV/cm) are observed in NKN films.Polarization fatigue resistant properties in Au/NKN/Ptstructures and wide memory window with long retention time inAu/NKN/SiO2/Si/Au MFIS-diode, as well as high degree ofpreferential orientations indicate NKN is a suitable materialfor next generation ferroelectric non-volatile memories. Highvoltage tunability (>40 %) with very low loss (<1 %)observed in NKN varactors both at radio and microwavefrequencies evidence this material is a promising candidate forvarious voltage tunable microwave devices. Considerable voltagetunability combined by high piezoelectricity in polar-axisoriented NKN films on various substrates suggest novel voltagetunable acoustic wave devices.

  • 174.
    Cho, Choong-Rae
    KTH, Superseded Departments, Physics.
    Ferroelectric NaKNbO films by pulsed laser deposition1999Licentiate thesis, comprehensive summary (Other scientific)
  • 175. Cholewa, W
    et al.
    Frid, Wiktor
    KTH, Superseded Departments, Physics.
    Bednarski, Marcin
    KTH, Superseded Departments, Physics.
    Identification of loss-of-coolant accidents in LWRs by inverse models2004In: Nuclear Technology, ISSN 0029-5450, E-ISSN 1943-7471, Vol. 147, no 2, p. 216-226Article in journal (Refereed)
    Abstract [en]

    This paper describes a novel diagnostic method based on inverse models that could be applied to identification of transients and accidents in nuclear power plants. In particular, it is shown that such models could be successfully applied to identification of loss-of-coolant accidents (LOCAs). This is demonstrated for LOCA scenarios for a boiling water reactor. Two classes of inverse models are discussed: local models valid only in a selected neighborhood of an unknown element in the data set, representing a state of a considered object, and global models, in the form of partially unilateral models, valid over the whole learning data set. An interesting and useful property of local inverse models is that they can be considered as example based models, i.e., models that are spanned on particular sets of pattern data. It is concluded that the optimal diagnostic method should combine the advantages of both models, i.e., the high quality of results obtained from a local inverse model and the information about the confidence interval for the expected output provided by a partially unilateral model.

  • 176.
    Christiansson, Henrik
    KTH, Superseded Departments, Physics.
    High-order accurate calculations and bounds on effective properties of composites1997Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    A classical problem in material science has been the studyof electrostatic and elastostatic properties of compositematerials. The complexity of the microstructure of randomcomposite media makes an exact calculation of the effectiveproperties very difficult. This naturally leads to the attemptto estimate the properties from partial structural information.Considerable theoretical progress has been made in the lastdecade on the derivation of bounds. There has been relativelyless research directed towards solving the governing equationsaccurately. Such calculations could provide tests on theoriesfor well-defined model microstructures.

    This thesis considers high-order accurate calculations andbounds on some physical properties of composites. Specialattention is paid to the calculation of structural parametersthat enter certain parameter-dependent bounds. The high-orderaccurate calculations on some non-trivial microstructures areperformed with interface integral equation methods. Thecomposites are allowed to have anisotropic componentproperties.

    The main results in the thesis are:

        Estimates of the thermal and electrical conductivity ofcementite (Fe3C) over a wide range of temperatures.

        Expressions for the structural parameters ζ2and η2for a class of fiber-reinforced composites.

        Numerical calculations of the above mentioned parametersfor hundreds of millions of structures. to obtain realizableregions in the ζ2- η2plane.

        Highly accurate numerical calculations of the effectivePoisson's ratio for some fiber-reinforced composites. Aformulation of a general statement for Poisson's ratio flowdiagrams.

        Highly accurate numerical calculations of the effectiveconductivity tensor for composite films in an appliedperpendicular magnetic field. Asymptotic studies of theeffective Hall conductivity in these systems.

    Keywords:electrostatic and elastostatic properties ofcomposites, parameterdependent bounds, effective Poisson'sratio, interface integral equations, effective Hallconductivity tensor

  • 177. Claesson, A.
    et al.
    Holm, J.
    Koch, R.
    Olson, M.
    Olsson, A.
    Vieider, C.
    Ahlfeldt, H.
    Laurell, Fredrik
    KTH, Superseded Departments, Physics.
    Diode-pumped miniature lasers using microstructured silicon carriers2000In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 36, no 5, p. 433-434Article in journal (Refereed)
    Abstract [en]

    A new versatile design concept for compact diode-pumped solid-state lasers based on a microstructured silicon carrier with etched V-grooves is presented. The carrier provides efficient thermal management as well as compact integration and alignment of all active acid passive optical components. In initial experiments, an Nd:YAG laser delivered a continuous-wave output of 3W.

  • 178. Claesson, T.
    et al.
    Kerek, Andras
    KTH, Superseded Departments, Physics.
    Molnar, J.
    Novak, D.
    An X-ray computed tomography demonstrator using a CZT solid-state detector2002In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 487, no 02-jan, p. 202-208Article in journal (Refereed)
    Abstract [en]

    A demonstrator of Computed Tomography (CT) has been designed and built for educational purposes. The system is based on a solid-state CdZnTe detector and a standard PC. The mechanics of the system is controlled and data is acquired by programs written in LabVIEW. CT images are reconstructed using MATLAB programs.

  • 179.
    Clement, Christophe
    KTH, Superseded Departments, Physics.
    Electromagnetic Calorimetry for the ATLAS Experiment and Studies of R-Parity Violating Supersymmetry2001Doctoral thesis, monograph (Other scientific)
  • 180.
    Clément, Christophe
    KTH, Superseded Departments, Physics.
    Studies of the barrel presampler for the ATLAS experiment1998Licentiate thesis, monograph (Other scientific)
  • 181.
    Corlevi, Silvia
    KTH, Superseded Departments, Physics.
    Superconducting quantum circuits in a tunable electromagnetic environment2004Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis presents the results of an experimental study onsmall-capacitance Josephson junctions in a high impedanceenvironment.

    In small-capacitance Josephson junctions the charging energyEC=e2/2C becomes relevant at low temperature and thecharging effects influence the transport properties. In theobservation of single-charge effects, a fundamental role isplayed by the impedance Z(ω) of the electromagneticenvironment surrounding the junction. To detect the tunnelingof single Cooper pairs in one junction, it is essential toembed the junction in a high impedance environment at all thefrequencies, such that Z(ω)>>RQ, where RQ=h/(2e)2= 6.45 kΩ is the quantum resistance forCooper pairs. This requirement is necessary in order to avoidthe fast discharge of the junction capacitance through theexternal circuit.

    In this work the effect of the high impedance environment isstudied on Cooper pair transistors (CPT) and single junctionswith tunable coupling (SQUID). The high impedance environmentis obtained by biasing the sample under test with four SQUIDarrays. The SQUID geometry, besides the modulation of thejunctions Josephson energy (EJ), allows the tuning in situ of the effective impedanceof the environment. By applying a magnetic field perpendicularto the SQUIDs loop, the zero bias resistance of the leads (R0) can be varied over several orders of magnitude(104<R0 (Ω)<108), providing the possibility to study the samesample in different electromagnetic environments.

    Measurements of the current-voltage (I-V) characteristic ofa single junction with SQUID geometry allow the investigationof the influence of both the electrodynamic environment and theEJ/ECratio in the same sample. As the impedance of thebiasing leads is increased (R0>>RQ), the I-V curve of the junction exhibits a welldefined Coulomb blockade feature with a region of negativedifferential resistance, evidence of the coherent tunneling ofsingle Cooper pairs.

    Measurements on CPT samples also show how the Coulombblockade feature in the I-V curve becomes sharper as theimpedance of the environment is increased. Furthermore theyindicate how the Coulomb blockade threshold voltage is modifiedwith the DC signal applied to the gate. When the SQUID arraysare highly resistive, the gate-induced modulation of the I-Vcurve changes frome-periodic to 2e-periodic, suggesting that high impedance leadseffectively reduce non-equilibrium quasiparticle poisoning.

  • 182. Crusius, Sabine
    et al.
    Höglund, Lars
    KTH, Superseded Departments, Materials Science and Engineering.
    Knoop, Usula
    Inden, Gerhard
    KTH, Superseded Departments, Physics.
    Ågren, John
    On the growth of ferrite allotriomorphs in fe-c alloys1992In: Zeitschrift für Metallkunde, ISSN 0044-3093, Vol. 83, no 10, p. 729-738Article in journal (Refereed)
    Abstract [en]

    Different geometrical models of allotriomorphic growth of ferrite in undercooled austenite are investigated by means of numerical and analytical treatments of diffusional growth under local equilibrium. The results obtained by the numerical method are compared with analytical solutions for those cases where such solutions may be derived. An excellent agreement is obtained. The numerical method is subsequently applied to simulate the experiments by Aaronson et al. and some more recent experiments by Hougardy et al.. taking into account the concentration dependence of the diffusivity of C in austenite and the most recent thermodynamic assessment of the ferrite/austenite equilibrium. Taking into account the experimental uncertainties we conclude that the growth of allotriomorphic ferrite must be essentially controlled by long-range carbon diffusion in austenite.

  • 183. Crusius, Sabine
    et al.
    Inden, Gerhard
    KTH, Superseded Departments, Physics.
    Knoop, Ursula
    Höglund, Lars
    KTH, Superseded Departments, Materials Science and Engineering.
    Ågren, John
    On the numerical treatment of moving boundary problems1992In: Zeitschrift für Metallkunde, ISSN 0044-3093, Vol. 83, no 9, p. 673-678Article in journal (Refereed)
    Abstract [en]

    Some numerical methods for solving a Stefan problem are discussed and compared with the exact solution. The growth of a planar particle from a supersaturated solution (or solidification from a supercooled liquid) is considered. It is found that the Murray-Landis method, based on a finite difference technique to solve the diffusion equation on a contracting grid, yields a poor accuracy for high supersaturations. The enthalpy method, also based on the finite difference technique and an interpolation formula for obtaining the interface position, shows a satisfactory performance at high supersaturations but a less satisfactory one at low supersaturations. It is demonstrated that the poor accuracy of the Murray-Landis method depends on the application of a less accurate flux-balance equation for finite time increments and the procedure for displacing the grid points. A modification of the Murray-Landis method is developed and is found to have superior numerical performance.

  • 184. Dahlberg, D
    et al.
    Miller, B
    Hill, B
    Jonsson, J
    Ström, Valter
    KTH, Superseded Departments, Physics.
    Rao, K Venkat
    KTH, Superseded Departments, Physics.
    Nogués, Josep
    Schuller, K
    Measurements of the ferromagnetic/antiferromagnetic interfacial exchange energy in CO/CoO and Fe/FeF2 layers1998In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 83, no 11, p. 6893-6895Article in journal (Refereed)
    Abstract [en]

    Two measurement techniques, both relying on reversible rotations of the magnetization, have been used to determine the magnitude of the interfacial exchange energy (IEE) between ferromagnetic and antiferromagnetic (F/AF) layers. One technique is to use the anisotropic magnetoresistance to determine rotations of the magnetization away from the unidirectional easy axis, where the rotation is accomplished by applying external magnetic fields less than the effective F/AF exchange field. The second technique uses measurements of the ac susceptibility as a function of the angle between the ac field and the unidirectional exchange field. Both of the reversible process techniques result in values of the IEE larger (by as much as a factor of 10 in Co/CoO bilayers) than the traditional irreversible technique of measuring a shift in the hysteresis loop. The ac susceptibility technique was also used to measure one Fe/FeF2 bilayer. For this sample, the IEE values obtained by reversible and irreversible methods are equivalent.

  • 185.
    Danielsson, Mats
    KTH, Superseded Departments, Physics.
    A collimator arrangement for varying the exposed surface of an x-ray detector in an x-ray imaging system includes an arrangement of two relatively displaceable parts having overlapping slots producing an adjustable slot width2000Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    In an x-ray imaging system, a variable exposure of a semiconductor, gas or sensitive film x-ray detector (43) to x-rays from a source is provided by a collimator (42). The collimator is arranged as two parts (42a, 42b) that are displaceable relative to each other, each having several identical slots in different planes that overlap. Relative displacement by a motor/actuator produces a variable width slot (45) that is adjustable between fully closed and open positions.

  • 186.
    Danielsson, Mats
    KTH, Superseded Departments, Physics.
    Metod och anordning att genom etsning anordna ett blockerande medel för att förhindra laddningsdelning mellan näraliggande röntgensensorer: [Method and arrangement relating to x-ray imaging]2000Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    A detector (200) comprises a number of spaced-apart sensor strips (220) arranged on a substrate, while a blocking arrangement is in the form of strips (230) covering the spaces between the sensor strips. The blocking strips also cover parts of the sensor strips and are made of a material such as wolfram, lead etc. which can be arranged as strips directly on the sensors. AN Independent claim is included for an arrangement for detecting signals from converted photons.

  • 187.
    Danielsson, Mats
    et al.
    KTH, Superseded Departments, Physics.
    Fonte, P.
    Francke, T.
    Iacobaeus, C.
    Östling, J.
    Peskov, V.
    Novel gaseous detectors for medical imaging2004In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 518, no 1-2, p. 406-410Article in journal (Refereed)
    Abstract [en]

    We have developed and successfully tested prototypes of two new types of gaseous detectors for medical imaging purposes. The first one is called the Electronic Portal Imaging Device (EPID). It is oriented on monitoring and the precise alignment of the therapeutic cancer treatment beam (pulsed gamma radiation) with respect to the patient's tumor position. The latest will be determined from an X-ray image of the patient obtained in the time intervals between the gamma pulses. The detector is based on a sandwich of hole-type gaseous detectors (GEM and glass microcapillary plates) with metallic gamma and X-ray converters coated with CsI layers. The second detector is an X-ray image scanner oriented on mammography and other radiographic applications. It is based on specially developed by us high rate RPCs that are able to operate at rates of 10(5) HZ/mm(2) with a position resolution better than 50 mum at 1 atm. The quality of the images obtained with the latest version of this device were in most cases more superior than those obtained from commercially available detectors.

  • 188.
    Danielsson, Mats
    et al.
    KTH, Superseded Departments, Physics.
    Lammroth, Theresa
    Rapp, Lennart
    Beam collimator arrangement for scanned-slot mammography has x-ray source, x-ray image receiver and female breast compression paddles2001Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    The apparatus comprises an x-ray source (21) and an x-ray image receiver (25). The breast (26) to be examined is placed between compression paddles (23,24) which flatten it, maximizing breast exposure to allow a sufficient contrast to be obtained. The collimator arrangement (22) can be moved to a parking position (P) when no x-ray exposure is conducted, and an active position (A) before x-ray exposure is initiated. The beam collimator is positioned between the x-ray source and the compressor paddles. An Independent claim is included for a mammography apparatus.

  • 189.
    Davis, Sergio
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Belonoshko, Anatoly
    KTH, Superseded Departments, Physics.
    Skorodumova, Natalia
    Department of Physics, Uppsala University.
    Johansson, Börje
    KTH, Superseded Departments, Materials Science and Engineering.
    Relative stability of phases of iron in the Earth's inner coreManuscript (preprint) (Other academic)
    Abstract [en]

    We have investigated the phase diagram of iron in a range close to the conditions inside the Earth’sinner core, using molecular dynamics with a semi–empirical, embedded atom interatomic potential.Our calculated melting curves for the body centered cubic (bcc) and hexagonal close packed (hcp)phases of iron are in good agreement with experimental and first–principles data. Interestingly ourmodel suggests evidence of a crossover in relative stability of these crystalline phases: the moststable phase being bcc below 315 GPa, and hcp above that point. The dependence of structuraland dynamical properties of crystallized iron on the temperature, at the pressure of the inner core,were determined.

  • 190. de Angelis, G.
    et al.
    Gadea, A.
    Farnea, E.
    Isocrate, R.
    Petkov, P.
    Marginean, N.
    Napoli, D. R.
    Dewald, A.
    Bellato, M.
    Bracco, A.
    Camera, F.
    Curien, D.
    De Poli, M.
    Fioretto, E.
    Fitzler, A.
    Kasemann, S.
    Kintz, N.
    Klug, T.
    Lenzi, S.
    Lunardi, S.
    Menegazzo, R.
    Pavan, P.
    Pedroza, J. L.
    Pucknell, V.
    Ring, C.
    Sampson, J.
    Wyss, Ramon
    KTH, Superseded Departments, Physics.
    Coherent proton-neutron contribution to octupole correlations in the neutron-deficient Xe-114 nucleus2002In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 535, no 04-jan, p. 93-102Article in journal (Refereed)
    Abstract [en]

    Gamma ray linear polarization and picosecond lifetimes have been measured for levels in the neutron deficient nucleus Xe-114 using the EUROBALL IV spectrometer and the Cologne plunger device. The EUCLIDES Si-ball was used to improve the reaction channel selectivity. The linear polarization results have, for the first time, unambiguously determined the electromagnetic character of the dipole transitions de-exciting the negative parity level sequence, providing clear evidence for enhanced octupole collectivity. The discovery of two E3 transitions and the measurement of the lifetimes of the states depopulated by these transitions have allowed a quantitative determination of the octupole collectivity in the A approximate to 112 mass region. The large measured B(E3) values, close to approximate to 70 W.u., are among the strongest observed hitherto and indicate a coherent proton-neutron contribution to the octupole moment.

  • 191. de Groot, J.
    et al.
    Hemberg, O.
    Holmberg, A.
    Hertz, Hans M.
    KTH, Superseded Departments, Physics.
    Target optimization of a water-window liquid-jet laser-plasma source2003In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 94, no 6, p. 3717-3721Article in journal (Refereed)
    Abstract [en]

    We optimize the water-window x-ray flux and debris deposition for a liquid-jet laser plasma source by varying both the target diameter and the jet material. For two target liquids, methanol and ethanol, measurements of the lambda = 3.37 nm C vi x-ray flux and the debris deposition rates are presented as function of the jet diameter. It is shown that the effective carbon debris deposition is more than I order of magnitude smaller for methanol, while the x-ray flux is reduced only similar to40%. The reduction in carbon debris deposition may be explained by reactive ion etching by oxygen from the plasma. Thus, the methanol water-window source may be operated at a 5-10X higher flux without increasing the debris deposition. The optimization potentially allows a reduction of the exposure time of compact soft x-ray microscopy or other water-window applications based on such sources without increasing damage to sensitive x-ray optics.

  • 192. de Groot, J.
    et al.
    Johansson, G. A.
    Hemberg, O.
    Hertz, Hans M.
    KTH, Superseded Departments, Physics.
    Improved liquid-jet laser-plasma source for X-ray microscopy2003In: Journal de Physique IV: Colloque, ISSN 1155-4339, E-ISSN 1764-7177, Vol. 104, p. 121-122Article in journal (Refereed)
    Abstract [en]

    We increase the x-ray flux from a liquid-jet laser-plasma x-ray source by optimizing the target geometry. A new nozzle fabrication method allows us to produce stable microscopic liquid jets with a wide range of diameters. The improved x-ray flux is demonstrated by optimizing the diameter of an ethanol liquid-jet for our 3 ns, square=532 nm Nd:YAG laser and measuring the flux at the square=3.37 rim C VI emission line. Preliminary data suggest that the x-ray flux can be increased by more than a factor of 4 compared to previous experiments. The goal is to significantly reduce the exposure time of our laser-plasma-based compact x-ray microscope by improving the source.

  • 193. de Groot, J.
    et al.
    Johansson, G. A.
    Hertz, Hans M.
    KTH, Superseded Departments, Physics.
    Capillary nozzles for liquid-jet laser-plasma x-ray sources2003In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 74, no 8, p. 3881-3882Article in journal (Refereed)
    Abstract [en]

    We describe a method to fabricate tapered glass nozzles suitable for liquid-jet-target generation in laser-plasma soft x-ray and extreme ultraviolet sources. In the method, a tapered nozzle is formed as an integral part of a flexible capillary glass tubing. The method makes use of inert materials, extending the possible choice of target liquids compared to current nozzles. It also provides flexibility as regards nozzle diameter and pressure, thereby allowing optimization of the target size and extending the range of applicability for the liquid-jet-target laser plasmas.

  • 194. Delion, D. S.
    et al.
    Liotta, Roberto
    KTH, Superseded Departments, Physics.
    Wyss, Ramon
    KTH, Superseded Departments, Physics.
    High-spin proton emitters in odd-odd nuclei and shape changes2003In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 68, no 5, p. 054603-Article in journal (Refereed)
    Abstract [en]

    We present a formalism to describe proton emission from odd-odd nuclei based on a scatteringlike approach. Special emphasis is given to the case of transitions between states with different deformations. As an example we estimate the proton half-life of the odd-odd nucleus Cu-58 . Our calculations show that the change of deformation in the decay process has a significant influence on the half life. In addition, the angular momentum coupling of proton and neutron orbitals can result in an additional K hindrance of the decay. To fully account for the observed half life in Cu-58 , we propose shape mixing of the final state.

  • 195. Delion, D. S.
    et al.
    Wyss, Ramon
    KTH, Superseded Departments, Physics.
    Karlgren, Daniel
    KTH, Superseded Departments, Physics.
    Liotta, Roberto
    KTH, Superseded Departments, Physics.
    Proton emission from triaxial nuclei2004In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 70, no 6, p. 061301-Article in journal (Refereed)
    Abstract [en]

    Proton decay from triaxially deformed nuclei is investigated. The deformation parameters corresponding to the mother nucleus are determined microscopically and the calculated decay widths are used to probe the mean-field wave function. The proton wave function in the mother nucleus is described as a resonant state in a coupled-channel formalism. The decay width, as well as the angular distribution of the decaying particle, are evaluated and their dependence upon the triaxial deformation parameters is studied in the decay of Re-161 and Bi-185. It is found that the decay width is very sensitive to the parameters defining the triaxial deformation while the angular distribution is a universal function which does not depend upon details of the nuclear structure.

  • 196. Denker, B.
    et al.
    Galagan, B.
    Ivleva, L.
    Osiko, V.
    Sverchkov, S.
    Voronina, I.
    Hellström, Jonas E.
    KTH, Superseded Departments, Physics.
    Karlsson, Gunnar
    KTH, Superseded Departments, Physics.
    Laurell, Fredrik
    KTH, Superseded Departments, Physics.
    New crystalline material for 1.5 μm lasers: Yb,Er - Activated GdCa 4O(BO3)32004In: Advanced Solid-State Photonics: Proceedings volume, Optics Info Base, Optical Society of America, 2004, Vol. 94, p. 430-434Conference paper (Refereed)
    Abstract [en]

    A new crystalline medium for 1.5 μm Yb-Er lasers is proposed: GdCa 4O(BO3)3 (GdCOB). Its melting point allows crystal growth using platinum instead of iridium crucibles. Spectroscopic and laser tests of the new material are described. A maximum CW output power of 80 mW was achieved in a monolithic microchip cavity under laser diode pumping.

  • 197.
    Denker, Boris
    et al.
    General Physics Institute, Moscow.
    Galagan, Boris
    General Physics Institute, Moscow.
    Ivleva, L.
    General Physics Institute, Moscow.
    Osiko, V.
    General Physics Institute, Moscow.
    Sverchkov, Sergey
    General Physics Institute, Moscow.
    Voronina, I.
    General Physics Institute, Moscow.
    Hellström, Jonas
    KTH, Superseded Departments, Physics.
    Karlsson, Gunnar
    KTH, Superseded Departments, Physics.
    Laurell, Fredrik
    KTH, Superseded Departments, Physics.
    Luminescent and laser properties of Yb-Er:GdCa4O(BO3)3: a new crystal for eye-safe 1.5-µm lasers2004In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 79, no 5, p. 577-581Article in journal (Refereed)
    Abstract [en]

    We present for the first time 1.5-μm laser emission in Yb-Er:GdCa 4O(BO3)3 (GdCOB). The crystals were grown by the Czochralski method from platinum crucibles. Spectroscopic and laser tests of the crystals are described. A continuous-wave output power of 80 mW was achieved in a monolithic microchip cavity under laser-diode pumping.

  • 198. Derkatch, A.
    et al.
    Lundevall, C.
    Berg, Lars-Erik
    KTH, Superseded Departments, Physics.
    Royen, P.
    Lifetime measurements of the A (2)Pi state of BaCl using laser spectroscopy2000In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 332, no 04-mar, p. 278-282Article in journal (Refereed)
    Abstract [en]

    The lowest-lying radiative state of barium chloride has been studied by laser-induced fluorescence in the near-infrared wavelength region. The A (II1/2)-I-2 and A (II3/2)-I-2 states have been investigated in time-resolved experiments using a Ti:Sapphire laser. The zero pressure radiative lifetime measured for the e-levels of BaCl was 107 +/- 4 ns for the A (II1/2)-I-2 state and 101+/-6 ns for the A (II3/2)-I-2 state. The discrepancy between the corresponding transition moments is discussed.

  • 199.
    Dinh, Truc-Nam
    et al.
    KTH, Superseded Departments, Physics.
    Konovalikhin, M. J.
    Sehgal, B. R.
    Core melt spreading on a reactor containment floor2000In: Progress in nuclear energy (New series), ISSN 0149-1970, E-ISSN 1878-4224, Vol. 36, no 4, p. 405-468Article in journal (Refereed)
    Abstract [en]

    The ex-vessel core melt spreading, cooling and stabilization is proposed for a nuclear power plant containment design. Clearly, the retention and coolability of the decay-heated core debris is very much the focal point in the proposed new and advanced designs so that, in the postulated event of a severe accident, the containment integrity is maintained and the risk of radioactivity releases is eliminated. The work reported here includes three tasks (i) to review related methodology and data base, (ii) to develop the scaling methodology and (iii) to validate the assessment methodology developed by the authors. The study is based on state-of-the-art knowledge of the melt spreading phenomenology, in particular, and, of severe accident phenomenology in general.

  • 200. Dobaczewski, J.
    et al.
    Dudek, J.
    Wyss, Ramon
    KTH, Superseded Departments, Physics.
    T=0 neutron-proton pairing correlations in the superdeformed rotational bands around Zn-602003In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 67, no 3, p. 343081-3430810Article in journal (Refereed)
    Abstract [en]

    The superdeformed bands in Cu-58, Cu-59, Zn-60, and Zn-61 are analyzed within the frameworks of the Skyrme-Hartree-Fock as well as Strutinsky-Woods-Saxon total Routhian surface methods with and without T = 1 pairing correlations between like particles. It is shown that a consistent description within these standard approaches cannot be achieved. A T = 0 neutron-proton pairing configuration mixing of signature-separated bands in Zn-60 is suggested as a possible solution to the problem.

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