| 1. |
- Erni, W., et al.
(författare)
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Technical design report for the PANDA (AntiProton Annihilations at Darmstadt) Straw Tube Tracker
- 2013
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Ingår i: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 49:2
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Tidskriftsartikel (refereegranskat)abstract
- This document describes the technical layout and the expected performance of the Straw Tube Tracker (STT), the main tracking detector of the PANDA target spectrometer. The STT encloses a Micro-Vertex-Detector (MVD) for the inner tracking and is followed in beam direction by a set of GEM stations. The tasks of the STT are the measurement of the particle momentum from the reconstructed trajectory and the measurement of the specific energy loss for a particle identification. Dedicated simulations with full analysis studies of certain proton-antiproton reactions, identified as being benchmark tests for the whole PANDA scientific program, have been performed to test the STT layout and performance. The results are presented, and the time lines to construct the STT are described.
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| 2. |
- Dupont, E., et al.
(författare)
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A phonon scattering assisted injection and extraction based terahertz quantum cascade laser
- 2012
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Ingår i: Applied Physics Reviews. - : AIP Publishing. - 1931-9401. ; 111:7
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Tidskriftsartikel (refereegranskat)abstract
- A lasing scheme for terahertz quantum cascade lasers, based on consecutive phonon-photon-phonon emissions per module, is proposed and experimentally demonstrated. The charge transport of the proposed structure is modeled using a rate equation formalism. An optimization code based on a genetic algorithm was developed to find a four-well design in the GaAs/Al0.25Ga0.75As material system that maximizes the product of population inversion and oscillator strength at 150 K. The fabricated devices using Au double-metal waveguides show lasing at 3.2 THz up to 138 K. The electrical characteristics display no sign of differential resistance drop at lasing threshold, which, in conjunction with the low optical power of the device, suggest-thanks to the rate equation model-a slow depopulation rate of the lower lasing state, a hypothesis confirmed by non-equilibrium Green's function calculations. [http://dx.doi.org/10.1063/1.3702571]
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| 3. |
- Razavipour, S. G., et al.
(författare)
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An indirectly pumped terahertz quantum cascade laser with low injection coupling strength operating above 150 K
- 2013
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 113:20
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Tidskriftsartikel (refereegranskat)abstract
- We designed and demonstrated a terahertz quantum cascade laser based on indirect pump injection to the upper lasing state and phonon scattering extraction from the lower lasing state. By employing a rate equation formalism and a genetic algorithm, an optimized active region design with four-well GaAs/Al0.25Ga0.75As cascade module was obtained and epitaxially grown. A figure of merit which is defined as the ratio of modal gain versus injection current was maximized at 150 K. A fabricated device with a Au metal-metal waveguide and a top n(+) GaAs contact layer lased at 2.4 THz up to 128.5 K, while another one without the top n(+) GaAs lased up to 152.5 K (1.3 (h) over bar omega/k(B)). The experimental results have been analyzed with rate equation and nonequilibrium Green's function models. A high population inversion is achieved at high temperature using a small oscillator strength of 0.28, while its combination with the low injection coupling strength of 0.85 meV results in a low current. The carefully engineered wavefunctions enhance the quantum efficiency of the device and therefore improve the output optical power even with an unusually low injection coupling strength. (C) 2013 AIP Publishing LLC.
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| 4. |
- Zozoulenko, Igor, et al.
(författare)
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Magnetoconductance of a few-electron open quantum dot
- 2000
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Ingår i: Physica. E, Low-Dimensional systems and nanostructures. - 1386-9477 .- 1873-1759. ; 6:1, s. 409-413
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Tidskriftsartikel (refereegranskat)abstract
- Magnetoconductance of a small open lateral dot is studied both theoretically and experimentally for the conditions when the dot contains down to approximately 15 electrons. We confirm the existence of a new regime for open dots in which the transport through the structure occurs through individual eigenstates of the corresponding closed dot. In particular, at low magnetic fields the characteristic features in the conductance are related to the underlying eigenspectrum shells. When the number of modes in the leads is reduced more detailed structures within the shells due to single eigenlevels becomes discernible. At higher fields Landau level condensation is evident as well as the crossing of levels collapsing to the different Landau levels.
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