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  • 101. Birch, J.
    et al.
    Eriksson, F.
    Johansson, G. A.
    Hertz, Hans M.
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Recent advances in ion-assisted growth of Cr/Sc multilayer X-ray mirrors for the water window2002Ingår i: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 68, nr 3, s. 275-282Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cr/Sc multilayer X-ray mirrors intended for normal incidence reflection in the water window wavelength range, lambda=[2.4-4.4 nm], have been grown by ion-assisted sputter deposition and characterized using soft and hard X-ray reflectivity. By extracting low-energy ions, with energies, E-ion, ranging from 9 to 113 eV and with ion-to-metal flux ratios, Phi, between 0.76 and 23.1, from the sputtering plasma to the growing film, the nano-structure of the multilayer interfaces could be modified. A significantly increased soft X-ray reflectivity, using lambda = 3.374 nm, for Cr/Sc multilayers with layer thicknesses in the range 0.4-2.8 nm, was obtained when high ion-to-metal flux ratios, Phi(Cr) = 7.1 and Phi(Sc) = 23.1, and low energy ions, E-ion = 9eV, were used. An experimental reflectivity of 5.5% was obtained at 76degrees for a multilayer with 400 bi-layers. Simulations of the reflectivity data showed that the interface widths are < 0.425 nm. It could be concluded that roughness of low spatial frequency is reduced at lower ion energies than the high spatial frequency which was eliminated at the expense of intermixing at the interfaces at higher ion energies. The predicted performance of normal incidence multilayer mirrors grown at optimum conditions and designed for lambda = 3.374 and 3.115 nm indicates possible reflectivities of 6.5% and 14%, respectively.

  • 102.
    Biverot, Hans
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Multi-user retinal displays with two components. New degrees of freedom.2001Doktorsavhandling, monografi (Övrigt vetenskapligt)
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  • 103.
    Bjurshagen, Stefan
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Diode-pumped Nd: YAG lasers for generation of blue light by frequency doubling2004Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Quasi-three-level lasers in neodymium-doped crystals such asNd:YAG, Nd:YLF and Nd:YVO4have received a great deal of interest becausethey allow generation of blue light by frequency doubling. Forsolid-state blue laser sources, there exist numerousapplications as in high-density optical data storage, colourdisplays, submarine communication and biologicalapplications.

    Efficient lasing on quasi-three-level transitions at 900-950nm in Nd-doped crystals is considerably more difficult toachieve than on the stronger four-level transitions at 1-1.1µm. The problems with these quasi-three-level transitionsare a significant reabsorption loss at room temperature and avery small stimulated emission cross section. This requires atight focusing of the pump light, which is achieved byend-pumping with high-intensity diode lasers.

    n this thesis, progress in diode-pumped solid-state lasersfor generation of blue light by frequency doubling has beenmade. Nd:YAG lasers at the 946 nm transition have been builtand a maximum power of 7.0 W was obtained. By inserting a thinquartz etalon in the laser cavity, the938.5 nm laser linecould be selected. An output power of 3.9 W was obtained.

    By using nonlinear crystals, frequency-doubling of laserlight at both 946 nm and 938.5 nm by second harmonic generation(SHG) was achieved. SHG of the 946 nm transition gives bluelight at 473 nm. Efficient generation of blue light has beenachieved in periodically poled KTP, both in single-passextra-cavity and intracavity configurations. More than 0.5 Wwas obtained at 473 nm by intracavity doubling. Intracavity SHGof the 938.5 nm transition gave slightly more than 200 mW at469 nm.

    The influence of energy-transfer upconversion (ETU) is adetrimental effect in Nd-doped lasers. An analytical model hasbeen developed for continuous wave quasi-three-level lasersincluding the influence of ETU. The results of the generaloutput modelling are applied to a laser with Gaussian beams,and rigorous numerical calculations have been done to study theinfluence of ETU on threshold, output power, spatialdistribution of population-inversion density and fractionalthermal loading. The model is applied to a laser operating at946 nm in Nd:YAG, where thermal lensing and the dependency oflaser-beam size are investigated in particular. A simple modelfor the degradation of laser beam quality from a transversallyvarying saturated gain is also proposed, which is in very goodagreement with measurements of the laser in a plane-planecavity.

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  • 104.
    Bjurshagen, Stefan
    et al.
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Evekull, D.
    Acreo AB, Kista.
    Koch, R.
    Acreo AB, Kista.
    Efficient generation of blue light by frequency doubling of a Nd:YAG laser operating on 4F3/2 → 4I9/2 transitions2003Ingår i: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 76, nr 2, s. 135-141Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Efficient room-temperature operation of F-4(3/2) --> I-4(9/2) transitions in diode-end-pumped Nd:YAG lasers at 946 nm and 938.5 nm is reported. 7.0-W continuous-wave output power at 946 nm and 3.9 W at 93 8.5 nm have been obtained. An analytical model has been developed for the quasi-three-level laser including the influence of energy-transfer upconversion. Frequency doubling of these transitions in periodically poled KTP generated blue light at 473 nm and 469 nm. Both single-pass extra-cavity as well as intracavity schemes have been investigated.

  • 105.
    Bjurshagen, Stefan
    et al.
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Evekull, D.
    Acreo AB, Kista.
    Koch, R.
    Acreo AB, Kista.
    Generation of blue light at 469 nm by efficient frequency doubling of a diode-pumped Nd:YAG laser2002Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 38, nr 7, s. 324-325Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Efficient operation of a diode-pumped Nd: YAG laser at 938.5 nm is reported. A continuous wave output power of 3.9 W is obtained. Single-pass frequency doubling in periodically poled KTP delivered a power of 88 mW at 469 nm. By intracavity frequency doubling an output of 200 mW in the blue region is achieved.

  • 106.
    Bjurshagen, Stefan
    et al.
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Koch, R.
    Acreo AB, Kista.
    Modeling of energy-transfer upconversion and thermal effects in end-pumped quasi-three-level lasers2004Ingår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 43, nr 24, s. 4735-4767Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An analytical model of cw quasi-three-level lasers that includes the influence of energy-transfer upconversion (ETU) has been developed. The results of the general output modeling were applied to a laser with Gaussian beams, and rigorous numerical calculations have been made to study the influence of ETU on threshold, output power, spatial distribution of population-inversion density, and fractional thermal loading. The model was applied to a laser operating at 946 nm in Nd:YAG, where the dependence of laser-beam size on laser performance was investigated in particular. A simple model for the degradation of laser-beam quality from a transversally varying saturated gain is proposed that is in good agreement with measurements of the laser in a plane-plane cavity.

  • 107.
    Björkqvist, Magnus
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Electronic structure of semiconductor surfaces: reconstructions and surface reactions1997Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
  • 108.
    Björnängen, Therese
    KTH, Tidigare Institutioner (före 2005), Fysik.
    In-plane transport measurements of YBa_2Cu_3O_{7-d} above and below the critical temperature2001Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 109.
    Björnängen, Therese
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Resistive studies of vortices and fluctuations in single crystal YBa2Cu3O7-2004Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    High-temperature superconductors have been intensely studiedsince the discovery, almost 20 years ago. Their layeredstructure, extreme type-II behavior, large anisotropy, andstrong fluctuations have led to a large number of new andinteresting problems. In this work the resistive transitionhave been studied in YBa2Cu3O7-δsingle crystals, from the superconductingfluctuations above Tcdown to the vortex matter near the onset of resistivity.Superconducting fluctuations above Tcare suitably studied by measuring themagnetoconductivity Δσ = 1/ρ(B)-1/ρ(0).Such experiments were performed on untwinned, optimally dopedsamples, forI||ab. ForH||c, fluctuations in the CuO-chains was not important, andfluctuations in the CuO2 planes seemed isotropic. The in-planecoherence length anisotropy was determined to be close tounity. ForH||ab, Δσbdepended on the field direction, indicating an effect ofthe chains on the magnetoconductivity in thisconfiguration.

    The nature of the vortex phase below Tccan be examined through vortex-correlation measurements.Using a modified pseudo-flux transformer (PFT) geometry forin-plane experiments, the magnetic field could be appliedparallel to both the a, b, and c axis. A strong Lorentz forcewas detected, and observed to be a requirement for the meltingstep feature. The resistive anisotropy close to Tcwas strongly field and temperature dependent, which wasexplained by an almost isotropic fluctuation contribution.

    The effect of anisotropy on vortex-liquid correlation infieldsH||ab, was studied byc-axis transport measurements in oxygen-deficientsamples, using a PFT configuration. Increasing disordersuppressed both longitudinal and transverse correlation. Inheavily underdoped samples, vortex correlation was enhanced formagnetic fields exactly aligned with theabplane because of the strong anisotropy. Also, thesolid-to-liquid transition temperature became nearly fieldindependent.

    Attempts were also made to connect the fluctuation regime ofthe resistive transition with the vortex region,by accountingfor critical fluctuations close to the transition.

    Keywords:high-temperature superconductors, YBa2Cu3O7-δ, untwinned YBCO, oxygen deficiency,superconducting fluctuations, magnetoconductivity, in-planeanisotropy, vortex liquid, vortex solid, vortex correlation

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  • 110. Blanco, A
    et al.
    Carolino, N
    Correia, C M B A
    Ferreira-Marques, R
    Fonte, P
    Gobbi, A
    Gonzalez-Diaz, D
    Lopes, M I
    Lopes, L
    Macedo, M P
    Mangiarotti, A
    Peskov, Vladimir
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Policarpo, A
    Progress in timing Resistive Plate Chambers2004Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 535, nr 1-2, s. 272-276Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Timing RPCs are Resistive Plate Chambers made with glass and metal electrodes separated by precision spacers. Typical gas gaps are a few hundred micrometers wide. Such counters were introduced in 1999 and have since reached timing accuracies below 50 ps sigma with efficiencies above 99% for MIPs. Applications in high-energy physics have already taken place with several more under study. Some recent developments include the extension of the counting rate capability by over one order of magnitude, to 25 kHz/cm(2), with time resolutions below 100 ps sigma. A prototype RPC-based Positron Emission Tomograph yielded a reconstructed point-source resolution of 0.6 mm FWHM and a modified timing RPC design, featuring 50 mum pitch anode strips, allowed to reach extremely good position resolution for hard X-rays in digital readout mode. An analytically solvable model has allowed us to clarify the basic factors influencing the time resolution.

  • 111. Blazhev, A.
    et al.
    Gorska, M.
    Grawe, H.
    Nyberg, J.
    Palacz, M.
    Caurier, E.
    Cederwall, Bo
    KTH, Tidigare Institutioner (före 2005), Fysik.
    et al,
    Observation of a core-excited E4 isomer in Cd-982004Ingår i: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 69, nr 6Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A core-excited I-pi=(12(+)) spin-gap isomer was identified in Cd-98 in an experiment at EUROBALL IV. It was found to feed the known I-pi=(8(+)) seniority isomer by an E4 transition. Half-lives of T-1/2=0.23 ((+4)(-3)) mus and 0.17 ((+6)(-4)) mus were measured for the two states at E-x=6635 keV and 2428 keV, respectively. From the excitation energy of the core-excited isomer a Sn-100 shell gap of 6.46(15) MeV is inferred. The measured E4 and E2 strengths, Sn-100 core excitations and the origin of empirical polarization charges are discussed in the framework of large-scale shell model calculations. An E2 polarization charge for protons of deltae(pi)

  • 112.
    Blennow, Mattias
    et al.
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Ohlsson, Tommy
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Exact series solution to the two flavor neutrino oscillation problem in matter2004Ingår i: Journal of Mathematical Physics, ISSN 0022-2488, E-ISSN 1089-7658, Vol. 45, nr 11, s. 4053-4063Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we present a real nonlinear differential equation for the two flavor neutrino oscillation problem in matter with an arbitrary density profile. We also present an exact series solution to this nonlinear differential equation. In addition, we investigate numerically the convergence of this solution for different matter density profiles such as constant and linear profiles as well as the Preliminary Reference Earth Model describing the Earth's matter density profile. Finally, we discuss other methods used for solving the neutrino flavor evolution problem.

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  • 113.
    Blennow, Mattias
    et al.
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Ohlsson, Tommy
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Snellman, Håkan
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Day-night effect in solar neutrino oscillations with three flavors2004Ingår i: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 69, nr 7, s. 073006-1-073006-9Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigate the effects of a nonzero leptonic mixing angle theta(13) on the solar neutrino day-night asymmetry. Using a constant matter density profile for the Earth and well-motivated approximations, we derive analytical expressions for the nu(e) survival probabilities for solar neutrinos arriving directly at the detector and for solar neutrinos which have passed through the Earth. Furthermore, we numerically study the effects of a nonzero theta(13) on the day-night asymmetry at detectors and find that they are small. Finally, we show that if the uncertainties in the parameters theta(12) and Deltam(2) as well as the uncertainty in the day-night asymmetry itself were much smaller than they are today, this effect could, in principle, be used to determine theta(13).

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  • 114.
    Blom, Jonas
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Topics in dynamical systems1999Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
  • 115.
    Blom, Martin
    et al.
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Minakata, H
    Unity of CP and T violation in neutrino oscillations2004Ingår i: New Journal of Physics, E-ISSN 1367-2630, Vol. 6, s. 130-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In a previous work, a simultaneous P-CP[P] and P-T [P] biprobability plot was proposed as a useful tool for a unified graphical description of CP and T violation in neutrino oscillations. The diamond-shaped structure of the plot is understood as a consequence of the approximate CP-CP and T-CP relations obeyed by the oscillation probabilities. In this paper, we take a step forward towards a deeper understanding of the unified graphical representation by showing that these two relations are identical in their content, suggesting a truly unifying view of CP and T violation in neutrino oscillations. We suspect that the unity reflects the underlying CPT theorem. We also present a calculation of corrections to the CP-CP and the T-CP relations to leading order in Deltam(21)(2)/Deltam(31)(2) and s(13)(2).

  • 116. Boezio, M.
    et al.
    Bonvicini, V.
    Mocchiutti, E.
    Schiavon, P.
    Vacchi, A.
    Carlson, Per
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Lund, Jens
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Lundquist, Johan
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Pearce, Mark
    KTH, Tidigare Institutioner (före 2005), Fysik.
    al, et
    The space experiment PAMELA2004Ingår i: Nuclear Physics B - Proceedings Supplements, 2004, Vol. 134, s. 39-46Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present in this paper a status report of the space experiment PAMELA. PAMELA is a satellite-borne experiment which primarily aims to measure the antiproton and positron spectra in the cosmic radiation over a large energy range (from 80 MeV up to 190 GeV for antiprotons and from 50 MeV up to 270 GeV for positrons) and to search for antinuclei with a sensitivity of the order of 10(-8) in the antihelium/ helium ratio. In addition, it will measure the light nucleax component of cosmic rays and investigate phenomena connected with Solar and Earth physics. The apparatus will be installed onboard the polar orbiting Resurs DK1 satellite, which will be launched into space by a Soyuz TM2 rocket in 2004 from Baikonur cosmodrome in Kazakhstan, for a 3 year long mission. PAMELA consists of: a time of flight system, a transition radiation detector, a magnetic spectrometer, an anticoincidence detector, an electromagnetic imaging calorimeter, a shower tail catcher scintillator and a neutron detector.

  • 117. Boezio, M.
    et al.
    Pearce, Mark
    KTH, Tidigare Institutioner (före 2005), Fysik.
    The Pamela, Collaboration
    Imaging dark matter with the Pamela experiment2001Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 471, nr 02-jan, s. 184-187Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The search for dark matter is a fundamental issue for astroparticle physics. A satellite-borne experiment ('Pamela') is under construction and will study cosmic rays whilst executing a polar orbit at an altitude of 690 km. The experiment comprises a transition radiation detector; a magnetic spectrometer, incorporating silicon tracking and surrounded by an anti-coincidence shield; an electromagnetic imaging calorimeter and a time-of-flight trigger system. This combination of detectors is particularly apt for the study of the antiproton component of cosmic rays from 100 MeV up to a few 100 GeV and will provide important new information for dark matter searches.

  • 118.
    Boezio, Mirko
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Positrons and electrons in the cosmic radiation measured by the CAPRICE94 experiment1998Doktorsavhandling, monografi (Övrigt vetenskapligt)
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  • 119. Bongi, M
    et al.
    Adriani, O
    Ambriola, A
    Bakaldin, A
    Barbarino, G C
    Basili, A
    Bazilevskaja, G
    Bellotti, R
    Bencardino, R
    Boezio, M
    Bogomolov, E A
    Bonechi, L
    Bongiorno, L
    Bonvicini, V
    Boscherini, M
    Cafagna, F S
    Campana, D
    Carlson, Per
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Casolino, M
    Castellini, G
    Circella, M
    De Marzo, C N
    De Pascale, M P
    Furano, G
    Galper, A M
    Giglietto, N
    Grigorjeva, A
    Koldashov, S V
    Korotkov, M G
    Krut'kov, S Y
    Lund, Jens
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Lundquist, J
    Menicucci, A
    Menn, W
    Mikhailov, V V
    Minori, M
    Mirizzi, N
    Mitchell, J W
    Mocchiutti, E
    Morselli, A
    Mukhametshin, R
    Orsi, Silvio
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Osteria, G
    Papini, P
    Pearce, Mark
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Picozza, P
    Ricci, M
    Ricciarini, S B
    Romita, M
    Rossi, G
    Russo, S
    Schiavon, P
    Simon, M
    Sparvoli, R
    Spillantini, P
    Spinelli, P
    Stochaj, S J
    Stozhkov, Y
    Straulino, S
    Streitmatter, R E
    Taccetti, F
    Vacchi, A
    Vannuccini, E
    Vasilyev, G I
    Voronov, S A
    Wischnewski, R
    Yurkin, Y
    Zampa, G
    Zampa, N
    PAMELA: A satellite experiment for antiparticles measurement in cosmic rays2004Ingår i: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 51, nr 3, s. 854-859Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    PAMELA is a satellite-borne experiment that will study the antiproton and positron fluxes in cosmic rays in a wide range of energy (from 80 MeV up to 190 GeV for antiprotons and from 50 MeV up to 270 GeV for positrons) and with high statistics, and that will measure the antihelium/helium ratio with a sensitivity of the order of 10(-8). The detector will fly on-board a polar orbiting Resurs DK1 satellite, which will be launched into space by a Soyuz rocket in 2004 from Baikonur cosmodrome in Kazakhstan, for a 3-year-long mission. Particle identification and energy measurements are performed in the PAMELA apparatus using the following subdetectors: a magnetic spectrometer made up of a permanent magnet equipped with double-sided microstrip silicon detectors, an electromagnetic imaging calorimeter composed of layers of tungsten absorber and silicon detectors planes, a transition radiation detector made of straw tubes interleaved with carbon fiber radiators, a plastic scintillator time-of-flight and trigger system, a set of anticounter plastic scintillator detectors, and a neutron detector. The features of the detectors and the main results obtained in beam test sessions are presented.

  • 120. Bonvicini, V.
    et al.
    Barbiellinia, G.
    Boezio, M.
    Mocchiutti, E.
    Schiavon, P.
    Lund, J.
    Pearce, Mark
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Vignoli, V.
    et al,
    The PAMELA experiment in space2001Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 461, nr 03-jan, s. 262-268Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We provide in this paper a status report of the space experiment PAMELA. PAMELA aims primarily to measure the flux of antiparticles, namely antiprotons and positrons, in cosmic rays with unprecedented statistics over a large energy range. Tn addition, it will measure the light nuclear components of cosmic rays, investigate phenomena connected to Solar and Earth physics and it will search for cosmic ray antinuclei with sensitivity better than 10(-7) in the He/He ratio. PAMELA consists of a magnet spectrometer, a transition radiation detector, an imaging calorimeter, a time of flight system and an anticoincidence detector. The apparatus will be installed on board of the Russian satellite of the Resurs type in a polar orbit at about 680 km of altitude. The launch is foreseen for late 2002/early 2003.

  • 121. Bonvicini, V.
    et al.
    Boezio, M.
    Haslum, Eva
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Matveev, D.
    Pearce, Mark
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Vacchi, A.
    Zampa, G.
    Zampa, N.
    New concepts in silicon calorimetry for space experiments2004Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 518, nr 1-2, s. 186-187Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the framework of the INFN R&D project CASIS, we have designed a new double-sided silicon strip detector with parallel strips, optimised for calorimetry. The idea is to read out p and n strips with two types of electronics, having different sensitivities and ranges, in order to increase the overall dynamic range by covering different signal regions. We present results from a test beam we performed at TSL (Uppsala, Sweden) with N, O and Ne ions with energies above 40 MeV/n. The design of a new front-end integrated circuit, with ultra-large dynamic range (more than 10,000 MIP) is under way and the first prototypes will be produced by the end of 2003.

  • 122.
    Bornefalk, Hans
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Use of phase and certainty information in automatic detection of stellate patterns in mammograms: IMAGE PROCESSING, PTS 1-32004Ingår i: MEDICAL IMAGING 2004: IMAGE PROCESSING, PTS 1-3 / [ed] Fitzpatrick, JM; Sonka, M, BELLINGHAM: SPIE-INT SOC OPTICAL ENGINEERING , 2004, Vol. 5370, s. 97-107Konferensbidrag (Refereegranskat)
    Abstract [en]

    Detection of stellate patterns is a very important step in computer-aided detection schemes designed for mammography. We introduce a new way of finding these regions based on the use of quadrature filters. The method allows extraction of a certainty measure for each orientation estimate. This makes the method of finding the areas the spicules seem to emanate from more robust than simply basing it on the orientation estimates themselves. The local phase extracted from the filter outputs allows us to discriminate between orientation estimates from edges and dark lines from those generated by bright line structures, i.e. spicules. This makes the method more specific. We also show how the method can be modified for finding non-spiculated masses in digitized mammograms.

  • 123. Boudrioua, A.
    et al.
    Loulergue, J. C.
    Laurell, Fredrik
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Moretti, P.
    Nonlinear optical properties of (H+,He+)-implanted planar waveguides in z-cut lithium niobate: annealing effect2001Ingår i: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 18, nr 12, s. 1832-1840Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Reflection second-harmonic generation from the polished waveguide end face was used to investigate the nonlinear properties of LiNbO3-implanted waveguides fabricated by use of 2-MeV He+ and 1.5-Mev H+ beams. Results were compared with waveguides obtained by protonic exchange in benzoic acid, In contrast to the exchanged sample where the nonlinearity is strongly reduced, the implanted samples showed that the guiding region presents rather the same response as the substrate. The area where the optical barrier is located showed a strongly enhanced second-harmonic signal that was likely to be due to structural modifications in this area. Moreover, the investigation of the annealing effect showed strong interaction of protons with the lattice compared with that of He+ ions.

  • 124. Bowen, A.
    et al.
    Gulacsi, M.
    Rosengren, Anders
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Finite temperature correlation functions of one-dimensional interacting electron systems2000Ingår i: Australian journal of physics (Print), ISSN 0004-9506, E-ISSN 1446-5582, Vol. 53, nr 4, s. 553-566Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The well-known bosonisation method of one-dimensional electron systems is extended to finite temperatures. As an example, the correlation functions of the non-interacting case are explicitly calculated. The presentation is pedagogical and is intended to be accessible to graduate students or physicists who are not experts in this field.

  • 125. Brahme, A.
    et al.
    Danielsson, Mats
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Iacobaeus, C.
    Ostling, J.
    Peskov, V.
    Wallmark, M.
    Evaluation of a GEM and CAT-based detector for radiation therapy beam monitoring2000Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 454, nr 1, s. 136-141Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We are developing a radiation therapy beam monitor for the Karolinska Institute. This monitor will consist of two consecutive detectors confined in one gas chamber: a keV-photon detector, which will allow diagnostic quality visualization of the patient, and a MeV-photon detector, that will measure the absolute intensity of the therapy beam and its position with respect to the patient. Both detectors are based on highly radiation resistant gas and solid photon to electron converters, combined with GEMs and a CAT as amplification structures. We have performed systematic studies of the high-rate characteristics of the GEM and the CAT, as well as tested the electron transfer through these electron multipliers and various types of converters. The tests show that the GEM and the CAT satisfy all requirements for the beam monitoring system. As a result of these studies we successfully developed and tested a full section of the beam monitor equipped with a MeV-photon converter placed between the GEM and the CAT.

  • 126.
    Brismar, Hjalmar
    et al.
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Trepte, O
    Ulfhake, B
    Spectra and fluorescence lifetimes of lissamine rhodamine, tetramethylrhodamine isothiocyanate, texas red, and cyanine 3.18 fluorophores: influences of some environmental factors recorded with a confocal laser scanning microscope.1995Ingår i: Journal of Histochemistry and Cytochemistry, ISSN 0022-1554, E-ISSN 1551-5044, Vol. 43, nr 7Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on the spectra and fluorescence lifetimes of four commonly used fluorophores: lissamine rhodamine (LRSC); tetramethyl rhodamine isothiocyanate (TRITC); Texas Red; and cyanine 3.18 (Cy-3). Fluorescence lifetime recordings revealed that these spectrally overlapping fluorophores can be individually detected by their lifetimes, indicating that at least four fluorophores can be individually identified in discrete tissue domains by confocal microscopy. A further advantage of lifetime recordings is that fluorophores that emit light within the same wavelength band can be used and chromatic aberrations are therefore circumvented, thereby improving the spatial accuracy in imaging of multiple fluorophores. Low and high pH, respectively, tended to influence fluorophore emission spectra and fluorescence lifetime. IgG conjugation of the fluorophores tended to shift the spectra towards longer wavelengths and to change the fluorescence lifetimes. The IgG-conjugated form of the fluorophores may, when applied to tissue specimens, change the emission spectrum and lifetime. In addition, different tissue embedding procedures may influence fluorescence lifetime. These observations emphasize the importance of spectral and lifetime characterization of fluorescent probes within the chemical context in which they will be used experimentally. Changes in spectra and fluorescence lifetimes may be a useful tool to gain information about the chemical environment of the fluorophores.

  • 127.
    Brismar, Hjalmar
    et al.
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Ulfhake, B
    Fluorescence lifetime measurements in confocal microscopy of neurons labeled with multiple fluorophores.1997Ingår i: Nature Biotechnology, ISSN 1087-0156, E-ISSN 1546-1696, Vol. 15, nr 4Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In order to resolve multiple fluorophores by their lifetimes in discrete tissue domains, the labeling intensity must be sufficiently strong and the intensity-difference between the labels must not be too large, the rate of fading should be similar for all fluorophores, and the lifetimes of the fluorophores should be sufficiently discrete. We could readily distinguish Cyanine-3.18 (Cy-3), Lissamine Rhodamine (LRSC), and Texas Red when they were not colocalized in tissue profiles. Colocalization of Cy-3 and LRSC, as well as Cy3 and Texas Red, could also be distinguished, while the combination of LRSC and Texas Red was more difficult. We have used fluorescence lifetime recordings in confocal microscopy to detect different neuropeptides in neurons. We demonstrate that somatostatin and galanin are colocalized in axon profiles of the spinal cord dorsal horn.

  • 128. Bruce, A. M.
    et al.
    Simpson, J.
    Warner, D. D.
    Baktash, C.
    Barton, C. J.
    Bentley, M. A.
    Brinkman, M. J.
    Cunningham, R. A.
    Dragulescu, E.
    Frankland, L.
    Ginter, T. N.
    Gross, C. Y.
    Lemmon, R. C.
    MacDonald, B.
    O'Leary, C. D.
    Vincent, S. M.
    Wyss, Ramon
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Yu, C. H.
    Zamfir, N. V.
    Two-neutron alignment and shape changes in As-692000Ingår i: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 6202, nr 2Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The nucleus As-69 was Studied using the Ca-40(S-32,3p)As-69 reaction at a beam energy of 105 MeV. An extension of the band built on the g(9/2) orbital was observed to exhibit a band crossing at a rotational frequency of 0.511 MeV with an associated alignment of 7 (h) over bar. This alignment is interpreted as being due to a pair of g(9/2) neutrons. Total Routhian surface calculations have been carried out which confirm that the shape of this nucleus changes from oblate at low spin to a triaxial prolate shape at intermediate spin.

  • 129.
    Brunsell, Per
    et al.
    KTH, Tidigare Institutioner (före 2005), Alfvénlaboratoriet.
    Bergsåker, Henric
    KTH, Tidigare Institutioner (före 2005), Alfvénlaboratoriet.
    Cecconello, Marco
    KTH, Tidigare Institutioner (före 2005), Alfvénlaboratoriet.
    Drake, James Robert
    KTH, Tidigare Institutioner (före 2005), Alfvénlaboratoriet.
    Gravestijn, Robert
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Hedqvist, Anders
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Malmberg, Jenny A.
    KTH, Tidigare Institutioner (före 2005), Alfvénlaboratoriet.
    Initial results from the rebuilt EXTRAP T2R RFP device2001Ingår i: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 43, nr 11, s. 1457-1470Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The EXTRAP T2R thin shell reversed-field pinch (RFP) device has recently resumed operation after a major rebuild including the replacement of the graphite armour with molybdenum limiters, a fourfold increase of the shell time constant, and the replacement of the helical coil used for the toroidal field with a conventional solenoid-type coil. Wall-conditioning using hydrogen glow discharge cleaning was instrumental for successful RFP operation. Carbon was permanently removed from the walls during the first week of operation. The initial results from RFP operation with relatively low plasma currents in the range I-p = 70-100 kA are reported. RFP discharges are sustained for more than three shell times. Significant improvements in plasma parameters are observed, compared to operation before the rebuild. There is a substantial reduction in the carbon impurity level. The electron density behaviour is more shot-to-shot reproducible. The typical density is n(e) = 0.5-1 x 10(19) m(-3). Monitors of H-alpha line radiation indicate that the plasma wall interaction is more toroidally symmetric and that there is less transient gas release from the wall. The minimum loop voltage is in the range V-t = 28-35 V, corresponding to a reduction by a factor of two to three compared to the value before the rebuild.

  • 130.
    Bäck, Torbjörn
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Spectroscopy of neutron deficient nuclei in the A=90 and A=170 mass regions2002Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
  • 131.
    Bäck, Torbjörn
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Superdeformed states in A90 nuclei1999Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 132.
    Bäck, Torbjörn
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Cederkall, J.
    Cederwall, Bo
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Johnson, Arne
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Kerek, Andras
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Klamra, Wlodzimierz
    KTH, Tidigare Institutioner (före 2005), Fysik.
    van der Marel, J.
    Molnar, J.
    Novak, D.
    Sohler, D.
    Steen, M.
    Uhlen, P.
    A TOF-PET system for educational purposes2002Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 477, nr 03-jan, s. 82-87Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A TOF-PET system has been designed and constructed for educational purposes. The aim of this system is to demonstrate the possibilities of positron emission tomography in general and the time-of-flight method in particular to the students of various courses at the Royal Institute of Technology, Stockholm, Sweden. The set-up consists of 48 small BaF2 crystals coupled to fast photomultipliers placed in a ring geometry. The signals of the photomultipliers are fed into fast constant fraction discriminators (CFD). The outputs of these are directed to a specially designed logic VME unit. which combines the CFD signals of 6 neighbouring channels to one signal by adding a different delay to each channel. The logic circuitry produces a prompt pulse for each event that serves as the start pulse for the 8-channel fast TDC. The delayed pulses act as the stop pulses for the TDC. In a computer. the measured times are converted into information about which the photomultipliers fired with the difference in the time of flight. The set-up is described and the results are presented.

  • 133.
    Bäck, Torbjörn
    et al.
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Cederkäll, Joakim
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Cederwall, Bo
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Johnson, Arne
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Kerek, Andras
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Klamra, Wlodzimierz
    van der Marel, J
    Molnar, J
    Novak, D
    Sohler, D
    Steen, M
    Uhlen, P
    An educational tool for demonstrating the TOF-PET technique2001Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 471, nr 1-2, s. 200-204Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A detector system for positron emission tomography with time-of-flight capability has been built to serve as an educational tool for undergraduate students. The set-up consists of 48 BaF2 scintillator crystals, each coupled to a fast photo-multiplier tube, mounted in a circular geometry. The analogue detector pulses are handled by fast constant fraction discriminators. A dedicated unit reduces the 48 channels to eight channels via delay-fine encoding, and the signals are then fed to an eight channel fast time-to-digital converter. A VME processor sorts the events and sends them to a workstation where the coincident events are extracted. The time resolution of the detectors together with fast VME based electronics allows for time-of-flight measurements to improve on the signal-to-noise ratio in the, reconstructed images. The system can be used for different types of exercises for the students, varying from the fundamentals of scintillator detectors to advanced image reconstruction. The set-up is described and some results are presented. (C) 2001 Elsevier Science B.V. All rights reserved.

  • 134.
    Bäck, Torbjörn
    et al.
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Cederwall, Bo
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Lagergren, Karin
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Wyss, Ramon
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Johnson, Arne
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Greenlees, P
    Jenkins, D
    Jones, P
    Joss, T
    Julin, R
    Juutinen, S
    Keenan, A
    Kettunen, H
    Kuusiniemi, P
    Leino, M
    Leppanen, P
    Muikku, M
    Nieminen, P
    Pakarinen, J
    Rahkila, P
    Uusitalo, J
    Spectroscopy of the neutron-deficient nuclide Pt-1712003Ingår i: European Physical Journal A, ISSN 1434-6001, E-ISSN 1434-601X, Vol. 17, nr 1, s. 1-5Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A number of previously unobserved gamma-rays emitted from the neutron-deficient nuclide Pt-171 have been identified using the recoil decay tagging technique. The level scheme has been updated using information from gamma-gamma coincidences and angular distribution measurements. To further confirm the assignments of the gamma-rays to Pt-171, the events were correlated with the alpha-decay of the daughter nucleus Os-167.

  • 135.
    Bäck, Torbjörn
    et al.
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Cederwall, Bo
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Lagergren, Karin
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Wyss, Ramon
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Johnson, Arne
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Karlgren, Daniel
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Greenlees, P
    Jenkins, D
    Jones, P
    Joss, T
    Julin, R
    Juutinen, S
    Keenan, A
    Kettunen, H
    Kuusiniemi, P
    Leino, M
    Leppanen, P
    Muikku, M
    Nieminen, P
    Pakarinen, J
    Rahkila, P
    Uusitalo, J
    First observation of gamma-rays from the proton emitter Au-1712003Ingår i: European Physical Journal A, ISSN 1434-6001, E-ISSN 1434-601X, Vol. 16, nr 4, s. 489-494Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Gamma-rays from the alpha- and proton-unstable nuclide Au-171 have been observed for the first time. The gamma-rays were correlated with both a proton- and an alpha-particle decay branch, confirming that the nucleus decays by alpha and proton emission from a single (11/2(-)) state. The measurement confirms the previously determined half-lives for these particle decays but the present values are of higher precision. In addition, a longer half-life than determined in previous work was measured for the proton-unstable tentative ground state. The results are discussed in relation to structures in neighbouring nuclei and compared with a Strutinsky-type TRS calculation.

  • 136.
    Bäck, Torbjörn
    et al.
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Cederwall, Bo
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Wyss, Ramon
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Johnson, Arne
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Cederkäll, Joakim
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Devlin, M
    Elson, J
    LaFosse, R
    Lerma, F
    Sarantites, G
    Clark, M
    Fallon, P
    Lee, Y
    Macchiavelli, O
    Macleod, W
    Observation of superdeformed states in Mo-881999Ingår i: European Physical Journal A, ISSN 1434-6001, E-ISSN 1434-601X, Vol. 6, nr 4, s. 391-397Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High-spin states in Mo-88 were studied using the GAMMASPHERE germanium detector array in conjunction with the MICROBALL CsI(TI) charged-particle detector system. Three gamma-ray cascades with dynamic moments of inertia showing similar characteristics to superdeformed rotational bands observed in the neighbouring A = 80 region have been identified and assigned to the nucleus Mo-88. The quadrupole moment of the strongest band, deduced by the Residual Doppler Shift Method, corresponds to a quadrupole deformation of beta(2) approximate to 0.6. This confirms the superdeformed nature of this band. The experimental data are interpreted in the framework of total routhian surface calculations. All three hands are assigned to two-quasi-particle proton configurations at superdeformed shape.

  • 137.
    Béland, Marie-Claude
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Gloss variation of printed paper2001Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
  • 138.
    Börjesson, Lars
    et al.
    Dept. Physics, Chalmers University of Technology.
    Phuong, H.V.
    Dept. Physics, Chalmers University of Technology.
    Jarlborg, Tomas
    Dept. de la Matière Condensée, University of Geneva.
    Andersson, Magnus
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Rapp, Östen
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Ca-Th substitution in YBa2Cu3O7-delta: Raman scattering and calculation of the electron-phonon interaction1992Ingår i: Proceedings of the Joint Nordic Spring Meeting '92 / [ed] Per-Anker Lindgård, Roskilde, Denmark: Risø National Laboratory , 1992, s. 235-235Konferensbidrag (Övrigt vetenskapligt)
  • 139.
    Cahn, R N
    et al.
    -.
    Cederström, B.
    -.
    Danielsson, Mats
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Hall, A.
    -.
    Lundqvist, M.
    -.
    Nygren, D.
    -.
    Detective quantum efficiency dependence on x-ray energy weighting in mammography1999Ingår i: Medical physics, Vol. 26, nr 12, s. 2680-2683Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An evaluation of the dependence of detective quantum efficiency (DQE) on the incident energy spectrum has been made for mammography. The DQE dependence on the energy spectrum has been evaluated for energy-integrating detectors, photon-counting detectors, and detectors that measure the energy of each photon. To isolate the effect of the x-ray energy spectrum the detector has been assumed to be ideal, i.e., all noise sources are assumed to be zero except for quantum fluctuations. The result shows that the improvement in DQE, if the energy-integrating detector is compared to a single-photon counting detector, is of the order of 10%. Comparing the energy-integrating detector and the detector measuring the energy for each photon the improvement is around 30% using a molybdenumanodespectrum typical in mammography. It is shown that the optimal weight factors to combine the data in the case the energy is measured are very well approximated if the weight factors are proportional to E&#x2212;3." style="position: relative;" tabindex="0" id="MathJax-Element-1-Frame" class="MathJax">E−3. Another conclusion is that in calculating the DQE, a detector should be compared to one that uses ideal energy weighting for each photon since this provides the best signal-to-noise ratio. This has generally been neglected in the literature.

  • 140.
    Campi, Roberta
    et al.
    KTH, Tidigare Institutioner (före 2005), Elektronik.
    Marcinkevicius, Saulius
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Landgren, Gunnar
    KTH, Tidigare Institutioner (före 2005), Elektronik.
    Studies on the carrier transport in InGaAlAdP/InGaAsP quantum well structures emitting at 1.3 μm2000Ingår i: Conference on Lasers and Electro-Optics Europe - Technical Digest, 2000, s. 141-Konferensbidrag (Refereegranskat)
    Abstract [en]

    A novel approach to improve high temperature performance in the IngaAsP lasers was examined by adding aluminum to the barrier,which allows to increase conduction band offset. To find optimal heterostructure parameters, different barrier material compositions were examined in structures with InGaAsP compressively strained wells and tensile strained InGaAlAsP barriers. The MQW structures were fabricated by low pressure MOVPE.

  • 141.
    Canalias, Carlota
    et al.
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Pasiskevicius, Valdas
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Clemens, Rosalie
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Laurell, Fredrik
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Submicron periodically poled flux-grown KTiOPO42003Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 82, nr 24, s. 4233-4235Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A submicron domain grating has been created in a bulk ferroelectric. Electron-beam lithography and electric-field poling were used to fabricate the 800 nm period grating in a 0.5-mm-thick flux-grown KTiOPO4 sample. The domain structure was characterized with an atomic force microscope and was used to demonstrate electrically amplitude adjustable Bragg reflections.

  • 142.
    Canalias, Carlota
    et al.
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Pasiskevicius, Valdas
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Fragemann, Anna
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Laurell, Fredrik
    KTH, Tidigare Institutioner (före 2005), Fysik.
    High-resolution domain imaging on the nonpolar y-face of periodically poled KTiOPO4 by means of atomic force microscopy2003Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 83, nr 4, s. 734-736Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The inverse piezoelectric effect is used to produce high-resolution images of ferroelectric domains in periodically poled KTiOPO4 crystals on their nonpolar y-face using atomic force microscopy. We demonstrate that the technique is convenient for studying the nucleation and growth of domains in a periodically poled KTiOPO4 sample.

  • 143. Carling, K. M.
    et al.
    Wahnstrom, G.
    Mattsson, T. R.
    Sandberg, Nils
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Grimvall, G.
    Vacancy concentration in Al from combined first-principles and model potential calculations2003Ingår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 67, nr 5Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a comprehensive study of vacancy formation enthalpies and entropies in aluminum. The calculations are done in the framework of the local-density and generalized-gradient approximations in the density-functional formalism. To assess anharmonic contributions to the formation free energies, we use an interatomic potential with parameters determined from density-functional-theory calculations. We find that the binding energy for the nearest-neighbor divacancy is negative, i.e., it is energetically unstable. The entropy contributions slightly stabilize the divacancy but also the binding free energy at the melting temperature is found to be negative. We show that the anharmonic atomic vibrations explain the non-Arrhenius temperature dependence of the vacancy concentration in contrast to the commonly accepted interpretation of the experimental data in terms of the monovacancy-divacancy model.

  • 144. Carling, Karin
    et al.
    Wahnström, Göran
    Mattsson, Thomas R
    Mattsson, Ann E
    Sandberg, Nils
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Grimvall, Göran
    Vacancies in metals: From first-principles calculations to experimental data2000Ingår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 85, nr 18, s. 3862-3865Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have revealed, and resolved, an apparent inability of density functional theory, within the local density and generalized gradient approximations, to describe vacancies in Al accurately and consistently. The shortcoming is due to electron correlation effects near electronic edges and we show how to correct for them. We find that the divacancy in Al is energetically unstable and we show that anharmonic atomic vibrations explain the non-Arrhenius temperature dependence of the vacancy concentration.

  • 145. Carlson, P.
    et al.
    Francke, T.
    Lund-Jensen, Bengt
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Peskov, V.
    Gaseous photomultipliers with solid photocathodes for the detection of sparks, flames and dangerous gases2003Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 505, nr 02-jan, s. 207-210Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In many applications, it is necessary to detect sparks or flames in daylight conditions or in illuminated areas. Most flames emit strongly in the ultraviolet spectrum (180-280 nm), and this property can be used for reliable identification of flames. We have developed new spark and flame detectors based on gaseous photomultipliers with CsI, CuI or CsTe photocathodes. A modified version of the detector can also detect smoke and dangerous vapors. These detectors are able to perform complex monitoring and detection functions. Some of their advantages are: low cost, high sensitivity, large output signal and operation under battery power. Gaseous photomultipliers can be position sensitive and, if necessary, be used in combination with various optical systems, for example for monitoring flames from space.

  • 146. Carlson, P.
    et al.
    Iacobeaus, C.
    Francke, T.
    Lund-Jensen, Bengt
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Periale, L.
    Peskov, V.
    Rodionov, I.
    Beyond the RICH: innovative photosensitive gaseous detectors for new fields of applications2003Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 502, nr 1, s. 189-194Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have developed and successfully used several innovative designs of detectors with solid photocathodes. The main advantage of these detectors is that rather high gains (> 10(4)) can be achieved in a single multiplication step. This is possible by, for instance, exploiting the secondary electron multiplication and limiting the energy of the steamers by distributed resistivity. The single step approach also allows a very good position resolution to be achieved in some devices: 50 mum on line without applying any treatment method (like center of gravity). The main focus of our report is new fields of applications for these detectors and the optimization of their designs for such purposes.

  • 147.
    Carlsson, Camilla
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Development of a thin, soft, single segment conductance catheter for monitoring left ventricular pressure and volume2002Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Knowledge of the leftventricular (LV) pressure-volume relation, along withparameters derived from this relation, have led to newpossibilities for the characterisation of cardiac pumpfunction, in both experimental studies and clinicalsettings.

    The pressure-volume diagram is apowerful tool for visualising LV performance, but in order tobe clinically useful it is necessary to make plots continuouslyand on-line. The conductance catheter technique offers thispossibility. The conductance catheter system has experiencedgrowing interest among cardiologists, physiologists, surgeons,and anaesthesiologists around the world as a powerful newresearch tool, but the invasiveness of this technique has beena limiting factor for most clinical applications. The catheterneeds to be thinner and softer in order to make this techniquemore suitable for human use.

    This thesis reports of a newthin and soft conductance catheter for continuously and on-linemeasurements of LV pressure and volume.

    One way to reduce both cathetersize and stiffness is to decrease the number of electrodes onthe catheter. Theoretical calculations shown in this thesisproves that it is possible to obtain the same performance witha single segment catheter as with a five-segment catheter. Thethin catheter has been tested and compared to a commercialfive-segment conductance catheter in animal studies.

    We conclude that the thin singlesegment conductance catheter can measure left ventricularvolume and pessure. The regression coefficient between the twomethods is good independent of loading condition and duringbaseline conditions the catheters produce very similar volumecurves. During preload reduction the estimated volume reductionis different in the two systems.

    Our thin catheter does notdisturb the heart's normal electrophysiology, neither by thecatheter current nor by any mechanical stimuli. The resultsdemonstrates that our thin, soft, single segment conductancecatheter has performance characteristics which warrant furtherdevelopment, with the goal to make the method available forhuman use.

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  • 148.
    Carlsson, Johan
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Decay heat removal from the guard vessel by thermal radiation and natural convection2000Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 149.
    Carlsson, Johan
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Inherent Safety Features and Passive Prevention Approaches for Pb/Bi-cooled Accelerator-Driven Systems2003Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This thesis is devoted to the investigation of passivesafety and inherent features of subcritical nucleartransmutation systems - accelerator-driven systems. The generalobjective of this research has been to improve the safetyperformance and avoid elevated coolant temperatures inworst-case scenarios like unprotected loss-of-ow accidents,loss-of-heat-sink accidents, and a combination of both theseaccident initiators. The specific topics covered are emergencydecay heat removal by reactor vessel auxiliary cooling systems,beam shut-off by a melt-rupture disc, safety aspects fromlocating heat-exchangers in the riser of a pool-type reactorsystem, and reduction of pressure resistance in the primarycircuit by employing bypass routes.

    The initial part of the research was focused on reactorvessel auxiliary cooling systems. It was shown that an 80 MWthPb/Bi-cooled accelerator-driven system of 8 m height and 6 mdiameter vessel can be well cooled in the case of loss-of-owaccidents in which the accelerator proton beam is not switchedoff. After a loss-of-heat-sink accident the proton beam has tobe interrupted within 40 minutes in order to avoid fast creepof the vessel. If a melt-rupture disc is included in the wallof the beam pipe, which breaks at 150 K above the normal coreoutlet temperature, the grace period until the beam has to beshut off is increased to 6 hours. For the same vessel geometry,but an operating power of 250 MWth the structural materials canstill avoid fast creep in case the proton beam is shut offimmediately. If beam shut-off is delayed, additional coolingmethods are needed to increase the heat removal. Investigationswere made on the filling of the gap between the guard and thereactor vessel with liquid metal coolant and using water spraycooling on the guard vessel surface.

    The second part of the thesis presents examinationsregarding an accelerator-driven system also cooled with Pb/Bibut with heat-exchangers located in the risers of the reactorvessel. For a pool type design, this approach has advantages inthe case of heat-exchanger tube failures, particularly if wateris used as the secondary uid. This is because a leakage ofwater from the secondary circuit into the Pb/Bi-cooled primarycircuit leads to upward sweeping of steam bubbles, which wouldcollect in the gas plenum. In the case of heatexchangers in thedowncomer steam bubbles may be dragged into the ADS core andadd reactivity. Bypass routes are employed to increase the owspeed in loss-of-ow events for this design. It is shown thatthe 200 MWth accelerator-driven system with heat-exchangers inthe riser copes reasonably well with both a loss-of-ow accidentwith the beam on and an unprotected loss-of-heat-sink accident.For a total-loss-of-power (station blackout) and an immediatebeam-stop the core outlet temperature peaks at 680 K. After acombined loss-of-ow and loss-of-heat-sink accident the beamshould be shut off within 4 minutes to avoid exceeding the ASMElevel D of 977 K, and within 8 minutes to avoid fast creep.Assuming the same core inlet temperature, both the reactordesign with heat-exchanger in the risers and the downcomershave similar temperature evolutions after a total-loss-ofpoweraccident.

    A large accelerator-driven system of 800 MWth with a 17 mtall vessel may eventually become a standard size. For thishigher power ADS, the location of the heat-exchangers hasgreater impact on the natural convection capability. This isdue to that larger heatexchangers have more inuence on thedistance between the thermal centers during a lossof- owaccident. The design with heat-exchangers in the downcomers,the long-term vessel temperature peaks at 996 K during aloss-of-ow accident with the beam on. This does not pose athreat of creep rupture for the vessel. However, the locationof the heat-exchangers in the downcomers will probably requiresecondary coolant other than water, like for example oil (fortemperatures not higher than 673 K) or Pb/Bi coolant.

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    FULLTEXT01
  • 150.
    Carlsson, Kjell
    et al.
    KTH, Tidigare Institutioner (före 2005), Fysik.
    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 performance2000Ingår i: Journal of Microscopy, ISSN 0022-2720, E-ISSN 1365-2818, Vol. 199, s. 106-114Artikel i tidskrift (Refereegranskat)
    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.

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