119408500
Observations of Electromagnetically Coupled Dust in the Jovian Magnetosphere
We report on dust measurements obtained during the seventh orbit of the Galileo spacecraft about Jupiter. The most prominent features observed are highly time variable dust streams recorded throughout the Jovian system. The impact rate varied by more than an order of magnitude with a 5 and 10 hour periodicity, which shows a correlation with Galileo's position relative to the Jovian magnetic field. This behavior can be qualitatively explained by strong coupling of nanometer-sized dust to the Jovian magnetic field. In addition to the 5 and 10 h periodicities, a longer period which is compatible with Io's orbital period is evident in the dust impact rate. This feature indicates that Io most likely is the source of the dust streams. During a close (3,095 km altitude) flyby at Ganymede on 5 April 1997 an enhanced rate of dust impacts has been observed, which suggests that Ganymede is a source of ejecta particles. Within a distance of about 25 RJ(Jupiter radius, RJ= 71,492 km) from Jupiter impacts of micrometer-sized particles have been recorded which could be particles on bound orbits about Jupiter.
119344064
Dust Measurements in the Outer Solar System
Dust measurements in the outer solar system are reviewed. Only the plasma wave instrument on board Voyagers 1 and 2 recorded impacts in the Edgeworth-Kuiper belt (EKB). Pioneers 10 and 11 measured a constant dust flux of 10-micron-sized particles out to 20 AU. Dust detectors on board Ulysses and Galileo uniquely identified micron-sized interstellar grains passing through the planetary system. Impacts of interstellar dust grains onto big EKB objects generate at least about a ton per second of micron-sized secondaries that are dispersed by Poynting-Robertson effect and Lorentz force. We conclude that impacts of interstellar particles are also responsible for the loss of dust grains at the inner edge of the EKB. While new dust measurements in the EKB are in an early planning stage, several missions (Cassini and STARDUST) are en route to analyze interstellar dust in much more detail.
7572210
A dust cloud of Ganymede maintained by hypervelocity impacts of interplanetary micrometeoroids
Abstract A dust cloud of Ganymede has been detected by in situ measurements with the dust detector onboard the Galileo spacecraft. The dust grains have been sensed at altitudes below five Ganymede radii (Ganymede radius =2635 km ). Our analysis identifies the particles in the dust cloud surrounding Ganymede by their impact direction, impact velocity, and mass distribution and implies that they have been kicked up by hypervelocity impacts of micrometeoroids onto the satellite's surface. We calculate the radial density profile of the particles ejected from the satellite by interplanetary dust grains. We assume the yields, mass and velocity distributions of the ejecta obtained from laboratory impact experiments onto icy targets and consider the dynamics of the ejected grains in ballistic and escaping trajectories near Ganymede. The spatial dust density profile calculated with interplanetary particles as impactors is consistent with the profile derived from the Galileo measurements. The contribution of interstellar grains as projectiles is negligible. Dust measurements in the vicinities of satellites by spacecraft detectors are suggested as a beneficial tool to obtain more knowledge about the satellite surfaces, as well as dusty planetary rings maintained by satellites through the impact ejecta mechanism.
13912153
Analysis of the sensor characteristics of the Galileo dust detector with collimated Jovian dust stream particles
Abstract The Dust Detector System onboard Galileo records dust impacts in the Jupiter system. Impact events are classified into four quality classes. Class 3, our highest quality class, has always been noise-free and, therefore, contains only true dust impacts. Depending on the noise environment, Class 2 are dust impacts or noise. Within 20RJ from Jupiter (Jupiter radius, RJ = 71,492 km) Class 2 shows clear indications for contamination by noise. We analyse the dust data from Galileos prime Jupiter mission (1996 and 1997), separate dust impacts from noise events and derive a complete denoised set of Galileo dust data (Classes 2 and 3). Collimated streams of nanometer-sized dust particles which have been detected throughout the Jovian system (Grun et al., 1998, J. Geophys. Res., 103, 20,011–20,022) are used to analyse the sensitive area and the field of view of the dust detector itself. The sensitive area for stream particles which trigger Class 3 events is 110±37 cm2. This is almost a factor of ten smaller than the total sensitive area for Class 2 impacts (1000 cm2). Correspondingly, the field of view of the detector for Class 3 stream particles is reduced from 140 to 96°. The magnetometer boom and other instruments on board Galileo cause a significant shadowing of the field of view of the dust sensor. Our analysis is supplementary to ground calibrations of the dust instrument because the low masses and high speeds of the stream particles could not be achieved in the laboratory. Our new results have important consequences for the analysis of dust in the Jupiter system.
209521249
Search for long-lived, heavy particles in final states with a muon and multi-track displaced vertex in proton-proton collisions at √s=7 TeV with the ATLAS detector
Many extensions of the Standard Model posit the existence of heavy particles with long lifetimes. In this Letter, results are presented of a search for events containing one or more such particles, which decay at a significant distance from their production point, using a final state containing charged hadrons and an associated muon. This analysis uses a data sample of proton-proton collisions at root s = 7 TeV corresponding to an integrated luminosity of 4.4 fb(-1) collected in 2011 by the ATLAS detector operating at the Large Hadron Collider. Results are interpreted in the context of R-parity violating supersymmetric scenarios. No events in the signal region are observed and limits are set on the production cross section for pair production of supersymmetric particles, multiplied by the square of the branching fraction for a neutralino to decay to charged hadrons and a muon, based on the scenario where both of the produced supersymmetric particles give rise to neutralinos that decay in this way. However, since the search strategy is based on triggering on and reconstructing the decay products of individual long-lived particles, irrespective of the rest of the event, these limits can easily be reinterpreted in scenarios with different numbers of long-lived particles per event. The limits are presented as a function of neutralino lifetime, and for a range of squark and neutralino masses.
122134670
TCT characterization of different semiconductor materials for particle detection
The development of digital semiconductor based X-ray detectors necessitates a detailed understanding of the applied sensor material. Under this premise a broad-band transient current technique (TCT) setup has been developed and used to characterize different semiconductors. The measurements are based on the generation of electrical charges within the sensor material and the subsequent time-resolved analysis of the charge carrier movement. From the recorded current pulses the charge collection efficiency, the charge carrier mobility and the electric field profile have been extracted. The examined materials are silicon p in n diodes, ohmic and Schottky contacted CdTe detectors, CdZnTe (CZT) crystals with Schottky contacts as well as two single-crystal CVD-diamonds.
113671167
Test Results of the first 3D-IC Prototype Chip Developed in the Framework of HL-SLHC/ATLAS Hybrid Pixel Upgrade
To face new challenges brought by the upgrades of the Large Hadron Collider at CERN and of ATLAS pixels detector, for which high spatial resolution, very good signal to noise ratio and high radiation hardness are needed, 3D Integrated Technologies are investigated. Commercial offers of such technologies are only very few and the 3D designer's choice is as a consequence strongly constrained. We present here the test results of the first 3D prototype chip developed in the GlobalFoundries 130 nm chips processed by the Tezzaron Company, submitted within the 3D-IC consortium for which a reliable qualification program was developed. Reliability and influence on the integrated devices behavior of Bond Interface (BI) and Through Silicon Via (TSV) connections, both needed for the 3D integration process, has also been addressed by the tests.