| 1. |
- Ögren, Magnus, 1977-, et al.
(author)
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Super-shell structure in harmonically trapped fermionic gases and its semi-classical interpretation
- 2006
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In: Physica Scripta. - : Royal Swedish Academy of Sciences. - 0031-8949 .- 1402-4896. ; :T125, s. 37-40
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Journal article (peer-reviewed)abstract
- It was recently shown in self-consistent Hartree–Fock calculations that a harmonically trapped dilute gas of fermionic atoms with a repulsive two-body interaction exhibits a pronounced super-shell structure: the shell fillings due to the spherical harmonic trapping potential are modulated by a beat mode. This changes the 'magic numbers' occurring between the beat nodes by half a period. The length and amplitude of the beating mode depends on the strength of the interaction. We give a qualitative interpretation of the beat structure in terms of a semi-classical trace formula that uniformly describes the symmetry breaking U(3) → SO(3) in a three-dimensional harmonic oscillator potential perturbed by an anharmonic term ∝ r 4 with arbitrary strength. We show that at low Fermi energies (or particle numbers), the beating gross-shell structure of this system is dominated solely by the twofold degenerate circular and (diametrically) pendulating orbits.
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| 2. |
- Mårtensson-Pendrill, Ann-Marie, 1952
(author)
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The Manhattan Project - a part of physics history
- 2006
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In: Physics Education. - 0031-9120. ; 41:6, s. 493-501
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Journal article (peer-reviewed)abstract
- Current physics textbooks tend to exclude military applications, but it is explained here how a study of the Manhattan project—the devastatingly successful attempt to develop an atomic bomb—can show students how the lives and work of physicists are shaped by events in society. Much of the original source material is available in books and on the internet (and referenced here), which allows students to discover the views of the scientists for themselves.
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| 3. |
- Rubio, Berta, et al.
(author)
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NuSTAR
- 2006
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In: International Journal of Phytoremediation. - : Informa UK Limited. - 1522-6514 .- 1549-7879. ; 16:1, s. 9-14
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Journal article (peer-reviewed)abstract
- Our knowledge of the properties of atomic nuclei rests mainly on the study of nuclear reactions and radioactive decays. The latter is extremely valuable and often provides the first information on newly synthesized nuclei, but the former has the great advantage of its flexibility. It allows us to vary the degrees-of-freedom in the nucleus that are important such as the excitation energy, the angular momentum, or the rotational frequency (spin) of the final products. By selecting a suitable combination of projectile target and beam energy, we can obtain a variety of results ranging from the reaction products to the character of the states that are populated. © 2006, Taylor & Francis Group, LLC.
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| 4. |
- Fritioff, T., et al.
(author)
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Purification of radioactive neutron-rich argon beams using an ion source in charge breeding mode
- 2006
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In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576 .- 0167-5087. ; 556:1, s. 31-37
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Journal article (peer-reviewed)abstract
- Measurements of nuclear properties of some neutron-rich asymmetric fission isotopes at an ISOL laboratory present a severe problem when a plasma ion source is used as the primary ion-source. The problem is associated with intense multi-charged symmetric fission contaminants that cannot be mass-separated from asymmetric fission products. In this work we demonstrate how this problem can be overcome on-line by using an electron cyclotron resonance ion source (ECRIS) as a charge-breeding secondary ion-source. Mixed Ar+/Kr2+/Xe3+ radioactive beams from an plasma ion-source were injected into the PHOENIX ECRIS that currently is installed at the ISOLDE facility at CERN in order to improve the ratio of Ar to the background contaminants of Kr and Xe. The signal to noise ratio was improved by more than two orders of magnitude after charge-breeding and mass-separation of the Ar8+, Ar9+ beams. The information on the decay of the Ar-48 nucleus obtained in these tests is useful for a better understanding of the origin of the Ca-48/Ca-46 meteorite isotopic anomaly. Potential applications of the method are discussed.
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| 5. |
- Gustafson, Johan, et al.
(author)
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Oxygen-induced step bunching and faceting of Rh(553): Experiment and ab initio calculations
- 2006
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In: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121 .- 1550-235X. ; 74:3
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Journal article (peer-reviewed)abstract
- Using a combined experimental and theoretical approach, we show that the initial oxidation of a Rh(553) surface, a surface vicinal to (111), undergoes step bunching when exposed to oxygen, forming lower-index facets. At a pressure of about 10(-6) mbar and a temperature of 380 degrees C this leads to (331) facets with one-dimensional oxide chains along the steps, coexisting with (111) facets. Further increase of the pressure and temperature results in (111) facets only, covered by an O-Rh-O surface oxide. Our density functional theory calculations provide an atomistic understanding of the observed behavior.
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| 6. |
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HIE-ISOLDE: the technical options
- 2006
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Editorial collection (peer-reviewed)abstract
- The ISOLDE facility at CERN has a long and successful tradition of continuous development and growthin order to meet the scientific requests from the user community. The current situation continues this habitand several projects to increase the scientific scope of the facility through technical developments are underway or envisaged within the medium-term future planning. These developments will result in a transformedfacility with the label HIE (High Intensity and Energy)-ISOLDE where the intensity, quality, and energy range of the secondary beams will be substantially improved. They are largely in line with the necessary technicaldevelopments towards the future EURISOL facility. This report summarizes these development projects.
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| 7. |
- Kylemark, Per, 1976, et al.
(author)
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Properties of pump-induced noise in fiber optic parametric amplifiers
- 2006
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In: Optics InfoBase Conference Papers. - Washington, D.C. : OSA. - 2162-2701.
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Conference paper (peer-reviewed)abstract
- We investigate the pump-induced noise in fiberoptic parametric amplifiers theoretically and experimentally, and find unique features with respect to wavelength dependence and noise statistics.
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| 8. |
- Enqvist, Andreas, 1981, et al.
(author)
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The Number Distribution and Factorial Moments of Neutrons and Gamma Photons Generated in a Multiplying Sample
- 2006
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In: JNMM, Journal of the Institute of Nuclear Materials Management. - 0893-6188. ; XXXV:1, s. 29 - 35
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Journal article (peer-reviewed)abstract
- An analytical derivation of the full probability distribution was demonstrated for the number of neutrons and gamma photons generated in a fissile sample with internal multiplication. The formulae for the probability distribution P(n) are derived in a recursive manner, and the results are compared with Monte Carlo calculations. We calculate the probability distribution up to values of n where P(n) becomes negligible. By introducing modified factorial moments of the number of neutrons and gamma photons generated in fission, the resulting probability distribution is formally equivalent with the expressions for factorial moments of the total number of neutrons and photons generated in the sample. These calculations are in very good agreement with Monte Carlo simulations. The results show that with increasing sample mass, the probability distributions change by acquiring a tail for higher n values.
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| 9. |
- Kitamura, Yasunori, et al.
(author)
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Calculation of the stochastic pulsed Rossi-alpha formula and its experimental verification
- 2006
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In: Progress in Nuclear Energy. - : Elsevier BV. - 0149-1970. ; 48:1, s. 37-50
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Journal article (peer-reviewed)abstract
- The Rossi-alpha formula for subcritical systems driven by a pulsed neutron source was derived with a solution technique that can effectively take different shape functions of the pulsed neutron source into account. The result of derivation showed that the present formula consists of the correlated and uncorrelated terms and an oscillating term whose period was identical to that of the pulsed neutron source.To investigate the validity of the pulsed Rossi-alpha formula and its applicability for the evaluation of the prompt neutron decay constant alpha from measurements, an experiment was performed at the Kyoto University Critical Assembly with a pulsed D-T neutron source. Although it seemed that fitting the present formula to the experimental curves was not practical because of an infinite-series expansion structure of the oscillating term, it was possible to extract only the correlated term, that explicitly includes the alpha value, by a simple data handling procedure. It was found that the measured alpha values agreed with those obtained by the pulsed neutron source method very well. This finding means that the pulsed Rossi-alpha method will be an attractive candidate for the monitoring method of the subcritical reactivity of future accelerator driven systems.
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| 10. |
- Grigoriev, Anton, et al.
(author)
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Electron transport in stretched monoatomic gold wires
- 2006
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In: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 97, s. 236807-
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Journal article (peer-reviewed)abstract
- The conductance of monoatomic gold wires containing 3-7 gold atoms has been obtained from ab initio calculations. The transmission is found to vary significantly depending on the wire stretching and the number of incorporated atoms. Such oscillations are determined by the electronic structure of the one-dimensional (1D) part of the wire between the contacts. Our results indicate that the conductivity of 1D wires can be suppressed without breaking the contact.
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