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Sökning: swepub > Larsson Anders > Kungliga Tekniska Högskolan

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21.
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22.
  • Midya, Surajit, et al. (författare)
  • Understanding Pantograph Arcing in Electrified Railways - Influence of Various Parameters
  • 2008
  • Ingår i: IEEE International Symposium on Electromagnetic Compatibility Detroit, MI, AUG 18-22, 2008. - NEW YORK : IEEE. ; , s. 592-597
  • Konferensbidrag (refereegranskat)abstract
    • The most common and yet unavoidable EMC problems with electrified railways are due to pantograph arcing. This distorts the waveform of the supply voltage and current, can generates transients during the zero crossings of the current and can cause interference with the traction power and signalling system. Pantograph arcing is a complex phenomenon and depends on speed of the train, current, presence of inductance etc. In a sliding contact like pantograph and contact wire, the am root moves across both electrodes because of the relative motion between them. In this paper, we will present an experimental analyses of the are root movement and influence of different parameters on it using a laboratory setup.
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23.
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24.
  • Möller, Cecilia, et al. (författare)
  • Experimental Studies of the Influence of a Resonance Cavity in an Axial Vircator
  • 2010
  • Ingår i: IEEE Transactions on Plasma Science. - 0093-3813 .- 1939-9375. ; 38:6, s. 1318-1324
  • Tidskriftsartikel (refereegranskat)abstract
    • Experiments on an axial virtual-cathode oscillator (vircator) with a resonance cavity enclosing the virtual cathode are reported. The vircator is driven by a repetitive Marx generator operating in a single-shot mode. To be able to separate different radiation mechanisms, the design of the vircator allows adjustment of the cavity depth as well as the way microwave radiation is extracted. The microwave radiation is measured with a pair of free-field B-dot sensors. The maximum field strengths were registered when the bandwidth was very narrow.
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25.
  • Möller, Cecilia, et al. (författare)
  • Magnetic field measurement system for HPM research
  • 2009
  • Ingår i: Proc. of Radiovetenskap och kommunikation (RVK08). ; , s. 86-93
  • Konferensbidrag (refereegranskat)abstract
    • One method to characterize the radiated microwave field from a high-power microwave (HPM) source is to measure the radiated high-level electromagnetic field in several locations at a high sampling rate registering the frequency time dependence, thus being able to determine the radiated pattern and mode. A complete free-field measurement system for measuring the magnetic field component in high-level electromagnetic fields has been developed at FOI. The system consists of a B-dot sensor and a balun, both designed and constructed at FOI. The B-dot sensor is designed as two cylindrical loop sensors with differential output. The balun is a microstrip design etched on a dual sided PTFE circuit board. Complete systems have been calibrated at SP Technical Research Institute of Sweden. A method to analyze the data from the free-field systems has been developed.
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26.
  • Möller, Cecilia, et al. (författare)
  • Numerical Simulation of the TE11 Mode in a Coaxial Vircator
  • 2007
  • Ingår i: IEEJ Transactions on Fundamentals and Materials. - 0385-4205. ; 127:11, s. 687-689
  • Tidskriftsartikel (refereegranskat)abstract
    • Studies of the concept of direct excitation of the TE11 mode in a coaxial vircator using three-dimensional particle-in-cell simulations is presented. The excitation of the TE11 mode is made possible by sectioning the emitting surface of the cathode, thus creating two interacting virtual cathodes. It is shown that the two virtual cathodes formed oscillate in push-pull mode as previously has been described for a planar geometry.  
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27.
  • Möller, Cecilia, et al. (författare)
  • Proof of Principle Experiments on Direct Generation of the TE11 Mode in a Coaxial Vircator
  • 2010
  • Ingår i: IEEE Transactions on Plasma Science. - 0093-3813 .- 1939-9375. ; 38:1, s. 26-31
  • Tidskriftsartikel (refereegranskat)abstract
    • Experiments on a coaxial vircator with a sectioned emitter are reported. The emitting area is sectioned to form two opposing emitters in order to favor growth of the TE11 mode and inhibit growth of the TM01 mode that is usually excited in a coaxial vircator. Experiments are performed using a compact 320-J 400-kV Marx generator and a compact coaxial vircator built in a standard 8 '' vacuum tube. The radiated magnetic-field strength is measured by means of four free-field (B-dot) probes, and experiments show that sectioning the emitter does, in fact, lead to generation of the TE11 mode.
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28.
  • Novac, Bucur M., et al. (författare)
  • A 10-GW pulsed power supply for HPM sources
  • 2006
  • Ingår i: IEEE TRANS PLASMA SCI. ; , s. 1814-1821
  • Konferensbidrag (refereegranskat)abstract
    • A research activity involving the detailed consideration of novel high-voltage transformers for pulsed-power applications has recently begun at Loughborough University. Although the main goal is the demonstration of a compact and lightweight unit employing magnetic insulation under vacuum conditions, the initial stage of the work is directed toward the development of a conventional air-cored transformer as a main component in a compact power supply for high power microwave sources. In cooperation with the Swedish Defence Research Agency (FOI), the power supply has been tested with a microwave source of the vircator type. The power generator for the system uses a 70-kJ/25-kV capacitor bank and an exploding wire array to generate a 150-kV voltage pulse in the primary circuit of a transformer. A pressurized SF6 spark gap in the secondary circuit sharpens the high-voltage output so that pulses approaching 500 kV and with a rise time well below 100 ns are generated on a 20-Omega high-power resistors With the peak power in excess of 10 GW. Experimental results are presented from final testing of the system, where a reflex triode vircator replaces the 20-Omega resistor. Measurements of the microwave emission using free-field sensors are presented, and comments are made with the microwave emission from the same vircator when powered by a Marx generator at FOI.
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29.
  • Soderberg, Emma, et al. (författare)
  • Suppression of higher order transverse and oxide modes in 1.3-mu m InGaAsVCSELs by an inverted surface relief
  • 2007
  • Ingår i: IEEE Photonics Technology Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1041-1135 .- 1941-0174. ; 19:08-maj, s. 327-329
  • Tidskriftsartikel (refereegranskat)abstract
    • It is shown, by a systematic variation of design parameters, that the use of an inverted surface relief is very effective for suppressing higher order transverse modes in oxide confined 1.3-mu m InGaAs vertical-cavity surface-emitting lasers (VCSELs). Single-mode emission is achieved for a large variety of oxide aperture and surface relief diameters, with optimum designs, having a surface relief with a diameter half of that of the oxide aperture, producing 1.1-1.3 mW of single-mode power. It is also shown that the anti-phase layer employed to enable the use of an inverted surface relief is effective for suppressing oxide modes that otherwise appear in oxide confined VCSELs with a large detuning between the gain peak and the cavity resonance.
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30.
  • Söderberg, Emma, et al. (författare)
  • High-temperature dynamics, high-speed modulation, and transmission experiments using 1.3-mu m InGaAs single-mode VCSELs
  • 2007
  • Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 25:9, s. 2791-2798
  • Tidskriftsartikel (refereegranskat)abstract
    • High-temperature dynamics, including small and large signal modulation response, of 1.28-ftm GaAs-based vertical-cavity surface-emitting lasers (VCSELs) with highly strained InGaAs quantum wells have been investigated. The VCSELs are oxide-confined with a relatively large oxide aperture for high output power and have a surface relief for fundamental mode operation. An inverted surface relief is used to improve manufacturability and to suppress oxide modes that otherwise appear in VCSELs with a large detuning, between the cavity resonance and the gain peak. The size dependence of the modulation bandwidth and bandwidth limitations are. investigated. A VCSEL with an optimum combination of oxide aperture and surface relief diameters produces clear open eyes with an extinction ratio of > 6 dB at OC-48 and 10-GbE bit rates from 25 degrees C to 85 degrees C under constant drive conditions. The same VCSEL is also shown to be capable of eiror-free transmission (BER < 10(-9)) over 9 km of standard single-mode fiber under the same conditions.
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