Results 1 - 9 of 9
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[en] Using a unique database of end-user local energy data and the recently developed Autoregressive Distributed Lag (ARDL) bounds testing approach to cointegration, we estimate the long-run elasticities of the Namibian energy demand function at both aggregated level and by type of energy (electricity, petrol and diesel) for the period 1980-2002. Our main results show that energy consumption responds positively to changes in GDP and negatively to changes in energy price and air temperature. The differences in price elasticities across fuels uncovered by this study have significant implications for energy taxation by Namibian policy makers. We do not find any significant cross-price elasticities between different fuel types. (author)
[en] A phenomenological model for double charged pion production is presented, aimed to exact N* electromagnetic form factors from measured observables (differential cross-sections, asymmetries). The preliminary results of CLAS data analysis on double charged pion production by virtual photons are discussed, focusing on high lying N* electromagnetic excitation and signals from possible ''missing'' baryon states
[en] Statistical properties of plasma turbulence are investigated by means of two-dimensional Vlasov simulations. In particular, a classical technique called signed measure is used to characterize the scaling behavior and the topology of sign-oscillating structures in simulations of the hybrid Vlasov-Maxwell model. Exploring different turbulence regimes, varying both the plasma β and the level of fluctuations, it is observed that Vlasov turbulence manifests two ranges with different exponents, the transition being observed near the ion skin depth. These results, which may have applications to both laboratory and astrophysical systems, further confirm the singular nature of small scale fluctuations in a plasma, mainly classified as intermittent, narrow, and intense current sheets
[en] Using a unique database of end-user local energy data and the recently developed Autoregressive Distributed Lag (ARDL) bounds testing approach to cointegration, we estimate the long-run elasticities of the Namibian energy demand function at both aggregated level and by type of energy (electricity, petrol and diesel) for the period 1980-2002. Our main results show that energy consumption responds positively to changes in GDP and negatively to changes in energy price and air temperature. The differences in price elasticities across fuels uncovered by this study have significant implications for energy taxation by Namibian policy makers. We do not find any significant cross-price elasticities between different fuel types
[en] A new DEPFET detector-amplifier structure with strongly non-linear characteristics is presented. It will be used as basic element of an X-ray pixel detector at the new XFEL free electron laser radiation source to be constructed in Hamburg, Germany, providing at the same time single X-ray photon detection and high dynamic range even when operated at readout frequency up to 5 MHz. This is possible due to the new detector concept that adds to the excellent DEPFET properties - combined function of detector amplifier and data storage, full sensitivity over whole bulk, non-destructive readout, low serial noise and absence of reset noise - the new features of very large charge handling capability and signal compression. Concept and design will be presented and properties demonstrated by extended computer simulations.
[en] In this paper, we propose a novel architecture to implement the current readout of DePFET Active Pixel Sensor (APS) matrices to be used in experiments at the European X-ray Free Electron Laser (XFEL). The circuit performs a fast trapezoidal filtering of the DePFET signal with a very simple architecture based on a Flip Capacitor Filter solution. We discuss the possible available trade-offs between noise and speed performances based on three different timing strategies that can be used to readout the DePFET matrix. Simulation results are shown for a first design of the circuit and expected noise performances are discussed in the last part of the paper.
[en] The 64 channel ASTEROID ASIC has been developed to readout DEPFET Macro-Pixel Arrays operated in source follower mode. In particular ASTEROID will be coupled with the DEPFET Macro-Pixel sensors designed for the X-ray astronomy application BepiColombo. This is a satellite-based mission that requires a detector system with high speed readout, high energy resolution and radiation hardness properties. In the source follower operating mode of the DEPFETs, the front-end electronics is AC-coupled. This allows easy coping with non homogeneity of the pixel matrix and an easy compensation of threshold voltage shifts of the DEPFET devices due to radiation damage. In order to achieve the low noise value required at short processing time, ASTEROID implements a trapezoidal weighting function. This is the time-limited optimum filter for white series noise, which is dominant at the foreseen readout speed. The ASIC is realized in the 0.35μm3.3V AMS CMOS technology. The outputs of the 64 analog channels are multiplexed to one serial output with a speed up to 20 MHz. Thanks to the new multiplexer architecture adopted, ASTEROID is the only ASIC that allows window-mode readout of the pixel matrices, i.e. that allows to address selectively arbitrary sub-areas of the pixel array or even to readout different sub-areas at different speeds. In order to fully operate the 64 channels in parallel, the ASIC contains a digital section that generates the timing signals for the analog circuits. This digital section is based on SEU-immune dual port memory cells. ASTEROID has been tested for the first time with a demonstrator 64x64 macro-pixel Matrix of the size of 3.2x3.2cm2. The energy resolution measured on the Mn-kα peak of 55Fe is of 124 eV with a pixel processing time of 4.8μs at -800C. This excellent result, never achieved before with source follower DEPFET at this readout speed, perfectly matches the requirements of BepiColombo Mission.
[en] Solar Active Region NOAA 11158 has hosted a number of strong flares, including one X2.2 event. The complexity of current density and current helicity are studied through cancellation analysis of their sign-singular measure, which features power-law scaling. Spectral analysis is also performed, revealing the presence of two separate scaling ranges with different spectral index. The time evolution of parameters is discussed. Sudden changes of the cancellation exponents at the time of large flares and the presence of correlation with Extreme-Ultra-Violet and X-ray flux suggest that eruption of large flares can be linked to the small-scale properties of the current structures
[en] The new DSSC (DEPFET sensor with signal compression) detector system is being developed in order to fulfil the requirements of the future XFEL in Hamburg. The instrument will be able to record X-ray images with a maximum frame rate of 5 MHz and to achieve a high dynamic range. The system is based on a silicon pixel sensor with a new designed non-linear-DEPFET as a central amplifier structure. The detector chip is bump-bonded to mixed signal readout ASICs that provide full parallel readout and temporary data storage. The signals coming from the detector are processed by an analog filter, immediately digitized by 8-ENOB ADCs and locally stored in a custom designed memory. The ASICs are designed in 130 nm CMOS technology. During the time gap of 99 ms of the XFEL machine, the digital data are sent off the focal plane to a DAQ electronics that acts as an interface to the back-end of the whole instrument. The pixel sensor has been designed so as to combine high energy resolution at low signal charge with high dynamic range. This has been motivated by the desire to be able to be sensitive to single low energy photons and, at the same time, to measure at other positions of the detector signals corresponding to up to 104 photons of 1 keV. In order to fit this dynamic range into a reasonable output signal swing, achieving at the same time single photon resolution, a strongly non-linear characteristic is required. The new proposed DEPFET provides the required dynamic range compression at the sensor level, considerably facilitating the task of the electronics. At the same time the DEPFET charge handling capacitance is enormously increased with respect to standard DEPFETs. The sensor matrix will comprise 1024x1024 pixels of hexagonal shape with a side-length of 136μm. The simultaneous implementation of the 5 MHz frame rate, of the single low-energy photon resolution and of the high dynamic range goes beyond all the existing instruments and requires the development of new concepts and technologies.