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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 3758-3761 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The spatial resolution of high-accuracy microchannel plate (MCP) detectors has reached the values, where the so-called detector walk (or image blurring) may start to limit any further improvements. Image blurring with gain is studied in detail for detectors incorporating angular-biased MCPs. It was found that the presence of the pore bias at the output MCP results in a variation of the charge footprint position for events with different gains. Events with higher gains are shifted in the direction of the pore bias and the absolute value of this shift is directly proportional to the absolute value of the detector gain. Variation of the detector modal gain from 7.5×106 to 2.5×107 resulted in a ∼100 μm image offset for a 13°-biased MCP positioned at a distance of 8.5 mm from the anode with an accelerating rear field of 75 V/mm. We also extended our previous study of another type of detector walk associated with fluctuations of the accelerating rear field. Image displacements as functions of the rear accelerating field for both 13°- and 19°-biased MCPs were measured and compared with the results of computer simulation based on our charge cloud propagation model presented earlier. A good agreement between the experimental and simulated data verifies the validity of the model for different MCPs. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Cyg X-l was observed to be in a 'high' state by the Uhuru satellite3 from December 1970 (its first observation of the source) to April 1971 and again during 1975 by the Ariel V (refs 4-6), and OSO-8 instruments7, as well as the Astronomical Netherlands Satellite8. Subsequent observations at many ...
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Space science reviews 78 (1996), S. 183-198 
    ISSN: 1572-9672
    Keywords: Local Interstellar Medium ; EUV emission ; Soft X-ray Background ; Local Bubble models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A summary of the lively discussions in working group 2 (WG2) on the origin and evolution of the LB is given below. The debate focussed mainly on the problem of how to pin down the physical properties of the LB. As a first step, we had to critically assess the observational constraints that are put on any model, predominantly from the SXR and EUV data. Next we were discussing models on the origin and evolution of the LB, which are able to explain the observations and which would allow to infer basic LB properties. A simple model, emphasizing the self-consistent dynamical and thermal evolution of a non-equilibrium plasma is presented. We also found, that picturing the LB as an isolated phenomenon is not supported by the data. Instead, the LB environment and its influence on the evolution of the LB have to be taken into consideration. Two different views are presented here. Either the LB and the Loop I superbubble are two physically separate phenomena, which are currently interacting, or star formation epochs in the Scorpius-Centaurus Association interacting with the molecular gas in the Aquila Rift and the interarm region around the Sun may have sculpted the configuration of interstellar matter within 200 parsecs, including the Local Bubble. However, so far observational constraints are insufficient to establish a canonical model of the evolution and the origin of the LB.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary On May 8, 1980, we conducted a 90 minute observation on hard X-ray emission (15-200 keV) from Her X-1, using a large area (∼ 1500 cm2), low background balloon borne X-ray telescope. The energy resolution of the telescope was ∼ 17% FWHM at 60 keV. Her X-1 was at binary phase 0.0725 and 2.7 ± 0.5 days after turn on in the 35 day cycle. Average pulsation light curves were obtained by sorting data into 25 equal bins, according to pulse arrival time, modulo the 1.24 sec pulsation period. The width of the main pulse is energy dependent and in the 45–75 keV region about 30% smaller than in the range from 15 to 30 keV. The data have been analyzed by taking the Her X-1 pulse minus background spectrum, where the pulse count rate is defined in a pulse phase interval around the pulse maximum of the 1.24 sec period. The background spectrum was intermittently obtained by a chopping collimator system. A spectral feature is present in emission at an energy of 49.5 (+ 1.5, -3) keV and a FWHM of 18 (+ 6, -3) keV and in absorption at an energy of 29.5 (+ 1.7, -1.5) keV and a FWHM of 17.0 (+ 2.6, -2.8) keV. The intensity of this line feature in emission is (1.8 ± 0.4) photons/cm sec. The line excess in emission over the continuum (with kT = 6.75 (+ 0.2, -0.4) keV) is ∼ 7σ.
    Type of Medium: Electronic Resource
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