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Heidelberg, Germany

Shu A.,Colorado Center for Lunar Dust and Atmospheric Studies | Shu A.,University of Colorado at Boulder | Shu A.,Laboratory for Atmospheric and Space Physics | Collette A.,Colorado Center for Lunar Dust and Atmospheric Studies | And 24 more authors.
Review of Scientific Instruments | Year: 2012

A hypervelocity dust accelerator for studying micrometeorite impacts has been constructed at the Colorado Center for Lunar Dust and Atmospheric Studies (CCLDAS) at the University of Colorado. Based on the Max-Planck-Institüt für Kernphysik (MPI-K) accelerator, this accelerator is capable of emitting single particles of a specific mass and velocity selected by the user. The accelerator consists of a 3 MV Pelletron generator with a dust source, four image charge pickup detectors, and two interchangeable target chambers: a large high-vacuum test bed and an ultra-high vacuum impact study chamber. The large test bed is a 1.2 m diameter, 1.5 m long cylindrical vacuum chamber capable of pressures as low as 10-7 torr while the ultra-high vacuum chamber is a 0.75 m diameter, 1.1 m long chamber capable of pressures as low as 10 -10 torr. Using iron dust of up to 2 microns in diameter, final velocities have been measured up to 52 km/s. The spread of the dust particles and the effect of electrostatic focusing have been measured using a long exposure CCD and a quartz target. Furthermore, a new technique of particle selection is being developed using real time digital filtering techniques. Signals are digitized and then cross-correlated with a shaped filter, resulting in a suppressed noise floor. Improvements over the MPI-K design, which include a higher operating voltage and digital filtering for detection, increase the available parameter space of dust emitted by the accelerator. The CCLDAS dust facility is a user facility open to the scientific community to assist with instrument calibrations and experiments. © 2012 American Institute of Physics. Source


Bunyatyan A.,MPI fur Kernphysik | Bunyatyan A.,Yerevan Physics Institute
Proceedings - 38th International Symposium on Multiparticle Dynamics, ISMD 2008 | Year: 2012

Small-angle detectors at the LHC give access to a broad physics programme within and beyond the Standard Model. We present here some studies of forward physics processes related to underling event, multi-parton interactions and low-x QCD dynamics. Source


Bonnivard V.,French National Center for Scientific Research | Combet C.,French National Center for Scientific Research | Daniel M.,University of Liverpool | Funk S.,Friedrich - Alexander - University, Erlangen - Nuremberg | And 10 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2015

Dwarf spheroidal (dSph) galaxies are prime targets for present and future Γ-ray telescopes hunting for indirect signals of particle darkmatter. The interpretation of the data requires careful assessment of their dark matter content in order to derive robust constraints on candidate relic particles. Here, we use an optimized spherical Jeans analysis to reconstruct the 'astrophysical factor' for both annihilating and decaying dark matter in 21 known dSphs. Improvements with respect to previous works are: (i) the use of more flexible luminosity and anisotropy profiles to minimize biases, (ii) the use of weak priors tailored on extensive sets of contamination-free mock data to improve the confidence intervals, (iii) systematic cross-checks of binned and unbinned analyses on mock and real data, and (iv) the use of mock data including stellar contamination to test the impact on reconstructed signals. Our analysis provides updated values for the dark matter content of 8 'classical' and 13 'ultrafaint' dSphs, with the quoted uncertainties directly linked to the sample size; themore flexible parametrizationwe use results in changes compared to previous calculations. This translates into our ranking of potentiallybrightest and most robust targets-namely Ursa Minor, Draco, Sculptor-and of the more promising, but uncertain targets-namely Ursa Major 2, Coma-for annihilating dark matter. Our analysis of Segue 1 is extremely sensitive to whether we include or exclude a few marginal member stars, making this target one of the most uncertain. Our analysis illustrates challenges that will need to be addressed when inferring the dark matter content of new 'ultrafaint' satellites that are beginning to be discovered in southern sky surveys. © 2015 The Authors. Source


Mocker A.,University of Stuttgart | Mocker A.,University of Colorado at Boulder | Grun E.,MPI fur Kernphysik | Grun E.,University of Colorado at Boulder | And 5 more authors.
Journal of Applied Physics | Year: 2012

In-situ measurements, the direct interception and analysis of dust particles by spacecraft-based instrumentation, provide insights into the dynamical, physical and chemical properties of cosmic dust. The most sensitive detection methods for dust particles in space are based on impact ionization. Laser ionization is used for the test, development, and calibration of impact ionization instruments and to complement laboratory based particle impact experiments. A typical setup uses a 355 nm Nd-YAG laser with a pulse length of about 5 ns. It is necessary to investigate the properties of both processes with respect to their comparability. A study was performed to find out to what extent laser ionization can be used to simulate impact ionization. The findings show that laser ionization and impact ionization show similarities, which can be used to test the functionality of dust impact detectors, especially time-of-flight instruments. Our paper provides information on what extent these similarities hold and where their limits are. © 2012 American Institute of Physics. Source


Hsu H.-W.,MPI fur Kernphysik | Hsu H.-W.,University of Heidelberg | Kempf S.,MPI fur Kernphysik | Kempf S.,TU Braunschweig | And 9 more authors.
AIP Conference Proceedings | Year: 2010

The stream particles are nanometer-size dust particles ejected from the jovian and the saturnian systems with velocities greater than 100kms -1. Due to their small size, stream particles are more sensitive to the electromagnetic force than to gravity. It has been shown by the simulations that the stream - particle dynamics in interplanetary space should be dominated by the interplanetary magnetic field (IMF) [15]. Based on the measurements by the dust detector on board the Cassini spacecraft, we found that the detection patterns of the stream particles are well correlated with the IMF structures. As the spacecraft crosses the compression regions of the Co - rotation Interaction Regions (CIRs), not only the directionality of the impacts changes with the field direction, but also the impact signal and rate vary with an increase of field strength. By understanding the interaction of stream particles and the solar wind, the data provide important insight to the formation environments of the stream particles and is an unique opportunity to study the dust-moon-magnetosphere system of Jupiter and Saturn. © 2010 American Institute of Physics. Source

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