| 1. |
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| 2. |
- Alfvén, Hannes
(author)
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Paradigm transition in cosmic plasma physics
- 1982
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In: Physica scripta. T. - : IOP Publishing. - 0281-1847. ; T2, s. 10-19
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Journal article (peer-reviewed)abstract
- In situ measurements in the magnetospheres together with general advancement in plasma physics are now necessitating introduction of a number of effects that have been recently discovered or earlier neglected. Examples are:Electric double layers (like in the lower magnetosphere);Thin current layer (like in the magnetopause) giving space a cellular structure;Current produced filaments (e.g., in prominences, solar corona and interstellar clouds).Further it is important to use the electric current (particle) description and to study the whole circuit in which the current flows.The pinch effect cannot be neglected as is now usually done.The critical velocity phenomenon is essential, for example for the band structure of solar system.Theory of dusty plasmas is important. The result is a change in so many theories in cosmic plasma physics that it is appropriate to speak of an introduction of a new paradigm. This should be based on empirical knowledge from magnetospheric and laboratory investigations. Its application to astrophysics in general, including cosmology, will necessarily lead to a revision of, e.g., the present theories of the formation of stars, planets and satellites. It is doubtful whether the big bang cosmology will survive.
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| 3. |
- Alfvén, Hannes
(author)
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Plasma universe
- 1987
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In: Physica scripta. T. - : IOP Publishing. - 0281-1847. ; T18, s. 20-28
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Journal article (peer-reviewed)abstract
- Traditionally the views on our cosmic environment have been based on observations in the visual octave of the electromagnetic spectrum, during the last half-century supplemented by infrared and radio observations.Space research has opened the full spectrum. Of special importance are the x-ray-γ-ray regions, in which a number of unexpected phenomena have been discovered. Radiations in these regions are likely to originate mainly from magnetised cosmic plasmas. Such a medium may also emit synchrotron radiation which is observable in the radio region.If we try to base a model of the universe on the plasma phenomena mentioned we find that the plasma universe is drastically different from the traditional visual universe.Information about the plasma universe can also be obtained by extrapolation of laboratory experiments and magnetospheric in situ measurements of plasmas. This approach is possible because it is likely that the basic properties of plasmas are the same everywhere.In order to test the usefulness of the plasma universe model we apply it to cosmogony. Such an approach seems to be rather successful. For example, the complicated structure of the Saturnian C ring can be accounted for. It is possible to reconstruct certain phenomena 4-5 billions years ago with an accuracy of better than 1%.
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| 4. |
- Anderson, D, et al.
(author)
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Analysis of profile effects on high Q subignited Tokamak fusion plasmas
- 1998
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In: PHYSICA SCRIPTA. - : ROYAL SWEDISH ACAD SCIENCES. - 0281-1847. ; 58:3, s. 256-261
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Journal article (other academic/artistic)abstract
- An analysis is made of the maximum power multiplication factor Q, achievble in subignited Tokamak fusion plasmas where the burn is sustained by feedback controlled auxiliary heating. Using a 1-D model equation for the plasma temperature, simple analytical
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| 5. |
- Anderson, D., et al.
(author)
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Exact Schrödinger Solitons in Optical Fibers in the Presence of Space Dependent Damping or Amplification
- 1999
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In: Physica scripta. T. - 0281-1847. ; 82, s. 42-43
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Journal article (peer-reviewed)abstract
- It is shown that the nonlinear Schrödinger equation describing pulse propagation in optical fibers in the presence of a properly space-tailored damping or amplification is exactly integrable. A simple transformation of variables is given which transforms the inhomogeneous nonlinear Schrödinger equation into the standard form with constant coefficients, thus generating new explicit bright and dark soliton solutions in the cases of anomalous and normal dispersion, respectively.
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| 6. |
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| 7. |
- Asp, Elina, et al.
(author)
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Localising Effects of a Peaked Diamagnetic Frequency on Drift Modes in Rotating Tokamak Plasmas
- 2002
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In: Physica scripta. T. - 0281-1847. ; T98:-, s. 151-154
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Journal article (peer-reviewed)abstract
- In this paper we investigate the effects of a diamagnetic frequency peaking and velocity shear on a two-dimensional drift mode structure. Previous study made by Horton et al. showed that a strong diamagnetic frequency peaking can trap the wave energy both radially and along the magnetic field lines. We show that the localising effect of the diamagnetic frequency peaking can be suppressed by a strong velocity shear in the edge plasma. The same phenomenon is present in the bulk plasma, but due to the velocity shear not being as pronounced there, the effect is nominal.
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| 8. |
- Asp, Elina, et al.
(author)
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Ship-Wave Eigenmodes of Drift Type in Rotating Tokamak Plasmas
- 2000
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In: Physica scripta. T. - 0281-1847. ; 62:2-3, s. 169-176
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Journal article (peer-reviewed)abstract
- Ship waves of drift type in rotating plasma of axisymmetric, large aspect-ratio tokamaks with concentric, circular magnetic surfaces are investigated. Plasma rotation is driven by an electrostatic radial electric field and the waves under consideration may be excited by plasma flow past some static obstacle. The analysis performed is based on rigorously derived eigenmode equations coupled in poloidal mode numbers through toroidal effects. The existence of two qualitatively different types of ship wave eigenmodes is demonstrated. Namely (i) global modes that have a structure of quasimodes localised in both radial and poloidal directions and correspond to the bounded states in a potential well which are marginally stable and (ii) propagating modes that experience shear convective damping. The dispersion relations for both types of eigenmodes are obtained both in the weak and the strong coupling approximation.We find the analytical solutions of the dispersion relations and the regions of their existence which are defined, mainly, by the value and direction of the poloidal rotation velocity. An accumulation point for global ship eigenmodes is determined. For propagating ship waves the real and the imaginary parts of the poloidal wavenumber are found. It is shown that the imaginary part always corresponds to convective damping of these waves
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| 9. |
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| 10. |
- Beckman, O., et al.
(author)
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Susceptibility Measurements and Magnetic Ordering of Hexagonal FeGe
- 1972
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In: Physica scripta. T. - : IOP Publishing. - 0281-1847 .- 0031-8949 .- 1402-4896. ; 6:2-3, s. 151-157
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Journal article (peer-reviewed)abstract
- The spin structure of the metallic hexagonal B 35 phase of FeGe has been studied by means of susceptibility and magnetization measurements. Below the Neel temperature TN = 411 K hexagonal FeGe is a uniaxial antiferromagnet with the spins parallel to the c-axis. In each c-plane all spins are ferromagnetically coupled with an exchange constant J0 ≈ 22 meV. The antiferromagnetic exchange constant between nearest neighbour and next nearest neighbour c-planes are J1 = -3.5 meV and J2 = -0.9 meV resp. in the molecular field model. Susceptibility and spin flop experiments indicate that the spins tilt away from the c-axis below 30 K. We suggest that the spins then form a double cone structure with a cone halfangle of 20° at 4.2 K. In the double cone the c-plane components have a turn angle in the vicinity of 180° between nearest neighbour planes, which implies absence of long range order. The result is in good agreement with Fermi surface calculations by Sundström (Physica Scripta, following paper), which show the existence of several spin density wave vectors between Q = 0.89 π/c and Q = 1.3 π/c calipering different parts of the Fermi surface in a direction parallel to the c-axis.
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| 11. |
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| 12. |
- Bentell, J., et al.
(author)
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Characterisation of n-InP/n-GaAs Wafer Fused Heterojunctions
- 1999
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In: Physica scripta. T. - 0281-1847. ; 79, s. 206-208
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Journal article (peer-reviewed)abstract
- We have investigated the properties of wafer-fused Si-doped isotype hetero-junctions between GaAs and InP. Current/voltage measurements were conducted to study the influence of the doping concentrations on each side of the interface on the electrical conductivity. An almost ohmic behavior with a very low series resistance was obtained for the highest examined doping level on the GaAs side, whereas the doping concentration on the InP side was found to be of little significance. Fusion at different temperatures showed that the conductivity degrades significantly below 500°C, although mechanically stable junctions were obtained also at temperatures as low as 305°C. Secondary ion mass spectroscopy measurements showed no redistribution of Si, but indicated the presence of small amounts of C and Fe impurities at the interface.
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| 13. |
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| 14. |
- Bergström, Lars
(author)
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Cosmology and the dark matter frontier
- 2013
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In: Physica scripta. T. - : Institute of Physics (IOP). - 0281-1847. ; T158:Art.nr., s. UNSP 014014-
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Journal article (peer-reviewed)abstract
- A brief overview is given about some issues in current astroparticle physics, focusing on the dark matter (DM) problem, where the connection to Large Hadron Collider (LHC) physics is particularly strong . New data from the Planck satellite has made the evidence in favour of the existence of DM even stronger. The favourite, though not the only, candidates for cosmological DM, weakly interacting massive particles, are being probed by a variety of experiments—direct detection through scattering in terrestrial detectors, indirect detection by observing products of annihilation of DM in the Galaxy and finally searches at accelerators such as the LHC. The field is in the interesting situation that all of these search methods are reaching sensitivities where signals of DM may plausibly soon be found, and a vast array of models will be probed in the next few years. Of course, expectations for a positive signature are high, which calls for caution regarding ‘false alarms’. Some of the presently puzzling and partly conflicting pieces of evidence for DM detection are discussed as well as expectations for the future.
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| 15. |
- Bersani, Andrea, et al.
(author)
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The PANDA detector at FAIR
- 2012
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In: Physica scripta. T. - : Institute of Physics Publishing (IOPP). - 0281-1847. ; T150, s. 014006-
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Journal article (peer-reviewed)abstract
- The PANDA detector will be installed at FAIR to enterprise a long-term, wide-spectrum physics program in the strong interaction framework. The detector will be installed at the HESR accumulation ring, which will provide an anti-proton beam of unprecedented luminosity and momentum definition. The beam will interact with an internal target. The detector has been designed to allow a 4π coverage around the interaction region. Due to the relatively high energy of the beam, up to 15 GeV, PANDA will feature two magnetic spectrometers: the target spectrometer (TS), with a superconducting solenoid and covering the interaction region, and a forward spectrometer (FS), with a normal-conducting dipole and covering the small angles region. Since the physics program is wide and the requirements on the various subsystems are different, the detector has been designed to be as flexible as possible. The complete detector will be described in detail, both from the viewpoint of the proposed techniques and from the viewpoint of the expected performances. An overview of the status of various components of the detector will be presented, too.
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| 16. |
- Bijnens, Johan, et al.
(author)
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Eta decays at and beyond p(4) in Chiral Perturbation Theory
- 2002
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In: PHYSICA SCRIPTA. - 0031-8949 .- 1402-4896. ; 99, s. 34-44
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Conference paper (peer-reviewed)abstract
- An overview is given of Chiral Perturbation Theory and various applications to eta decays. In particular. the main decay eta --> 3pi is discussed at the one-loop level, and estimates of the higher order corrections are given. The importance of p(6) and higher order effects in double Dalitz and eta --> pi(0)gammagamma decays is pointed out. In all these cases the need for new experimental results is stressed.
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| 17. |
- Bingham, R, et al.
(author)
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Coronal heating by dissipating current sheets
- 2004
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In: Physica scripta. T. - Bristol : Institute of Physics (IOP). - 0281-1847. ; T107, s. 247-249
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Journal article (peer-reviewed)abstract
- It is shown that the lower-hybrid turbulence produced by the lower-hybrid-drift wave instability at current sheets can heat electrons and ions in the solar corona. The waves heat the plasma particles by collisionless Landau damping. The waves resonate with electrons moving in the direction of the magnetic field, while they resonate with ions moving in the perpendicular direction.
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| 18. |
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| 19. |
- Blomquist, T, et al.
(author)
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Conductance of a ballistic electron billiard in a magnetic field : does the semiclassical approach apply?
- 2001
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In: Physica scripta. T. - 0281-1847. ; T90, s. 37-40
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Journal article (peer-reviewed)abstract
- We utilize a semi-classical approach to calculate conductance and weak localization corrections in a triangular billiard in non-zero magnetic field. Results of the calculations and comparison to numerical quantum mechanical simulations suggest that applicability of the standard semiclassical method for description of the geometry-specific features in the conductance of such systems is not obvious as the unitarity of the semiclassical scattering matrix is violated as well as the symmetry of the conductance/reflectance with respect to the magnetic field and the direction of the current is not satisfied. The reason for this is given. Our findings raise the question to what extend one can rely on numerous predictions for statistical properties of the conductance oscillations of ballistic cavities including the WL lineshapes and fractal conductance which were essentially based on the standard SC approach.
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| 20. |
- Bowallius, Olof, et al.
(author)
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Scanning Capacitance Microscopy for Two-Dimensional Doping Profiling in Si- and InP-Based Device Structures
- 1999
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In: Physica Scripta T. - 0281-1847. ; 79, s. 163-166
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Journal article (peer-reviewed)abstract
- We report on the application of cross-sectional Scanning Capacitance Microscopy (SCM) for studying two-dimensional doping variations in Si and InP device structures. Different sample preparation methods were evaluated and the response of the SCM signal from various test structures, including epitaxially grown layers with n- and p-doping concentrations ranging from 5 × 1014 to 2 × 1019 cm-3, were examined under different imaging conditions. The technique was further evaluated by imaging a Si bipolar transistor structure and an InP-based buried heterostructure diode laser. We conclude that valuable information can be gained also from complex device structures.
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| 21. |
- Bracco, A, et al.
(author)
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Search for the GDR built on superdeformed nuclei
- 2000
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In: PHYSICA SCRIPTA. - : ROYAL SWEDISH ACAD SCIENCES. - 0281-1847. ; T88, s. 182-188
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Journal article (peer-reviewed)abstract
- An experiment aiming at finding evidence for gamma-decay of the giant dipole resonance built on superdeformed nuclear states has been made using the EUROBALL gamma-detector array coupled to the large BaF2 detectors of the HECTOR system. The reaction Pd-11
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| 22. |
- Brage, Tomas, et al.
(author)
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Core polarization effects on oscillator strengths in neutral zinc
- 1992
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In: Physica Scripta. Topical Issues. - : IOP Publishing. - 0281-1847. ; 45:1, s. 43-48
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Journal article (peer-reviewed)abstract
- The effect of core polarization on the oscillator strength for the resonance transition in neutral zinc is investigated using the multiconfiguration Hartree Fock approach. The use of model potentials and corrections to the dipole operator is compared to a method, where the core polarization is represented by including configuration state functions, with one hole in the 3d core subshell in the CI-expansion. The latter, which is labeled explicit CI, gives results in good agreement with experiment. The reason for deviations in earlier calculations is discussed, together with the validity of the comparison of length and velocity forms of oscillator strengths, as a test of accuracy. The dependence of the model potential results on the choice of cut-off radius is investigated.
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| 23. |
- Brage, Tomas, et al.
(author)
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Experimental and theoretical study of core-excited states of Mg II
- 1991
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In: Physica Scripta. Topical Issues. - : IOP Publishing. - 0281-1847. ; 44:4, s. 336-342
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Journal article (peer-reviewed)abstract
- The 2p(5)3s3p, 3p2, 3s4s, 3s3d, and 3s4f core-excited configurations of Mg II have been studied experimentally by beam-foil spectroscopy and theoretically by multiconfiguration Hartree-Fock calculations with Breit-Pauli relativistic corrections. The previously established energy levels belonging to the former four configurations have been reexamined leading to significant corrections of the 3p2 4D and 3s4s 4P levels. Many previously unidentified spectral lines have now been assigned allowing a confident set of energy levels of the nearly degenerate 3p2, 3s4s, and 3s3d configurations to be established. in addition, the higher lying 3s4f states have been studied allowing the assignment of the prominent, but unidentified line at 3480 angstrom to the 3s4f 4G11/2 --> 3s3d 4F9/2 transition, and the establishment of some 3s3d states which primarily decay by autoionization.
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| 24. |
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| 25. |
- BROSTROM, L, et al.
(author)
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MEASUREMENTS OF ISOTOPE SHIFT IN EU-II
- 1995
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In: PHYSICA SCRIPTA. - : ROYAL SWEDISH ACAD SCIENCES. - 0281-1847. ; 51:3, s. 330-333
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Journal article (other academic/artistic)abstract
- The isotope shift between singly-charged Eu-151 and Eu-153 in the 4f(7)(S-8 degrees)6s S-9 degrees(4) - 4f(7)(S-8 degrees)6p(1/2) J = 4 transition at 4129 Angstrom has been measured using fast ion beam-laser technique. This Eu line has attracted interest
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