1,991 research outputs found

    From single point of measurement to distributed sensing in long-term glacier monitoring

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    Glacial environment monitoring is a key task in understanding natural phenomena related to global warming. For the last 30 years, Automatic Weather Stations (AWSs) have been spreading among the meteorological and geophysical community, and are on the way to become a de facto standard to perform long-lasting unattended data acquisitions in single localized points of interest. Sensor Networks (SNs), on the other hand, promise the possibility to perform measurements with a higher spatial density and lower cost. Designing and developing a SN for glacial environment face particular challenges for embedded electronics and sensor systems, which is why SNs are still under research and development in this eld. This paper surveys the AWSs and SNs for glacial monitoring applications and compares their characteristics

    Deploying a Communicating Automatic Weather Station on an Alpine Glacier

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    The cost and effort of installing and maintaining an automatic weather station (AWS) on a glacier may be mitigated by the possibility of gathering sensor data in near real-time, and of controlling and programming the station remotely. In this paper we report our experience with upgrading an existing AWS, operating over an Italian glacier, from a mere datalogger into a networked sensing station. Design choices, energy constraints and power-aware programming of the station determined by harsh environment are discussed. Deployment operations and results are described. The upgraded AWS provides low-power connectivity from a remote location and is able to serve as a base station for a wireless sensor network working in the glacier

    Longitudinal phase-space manipulation with beam-driven plasma wakefields

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    The development of compact accelerator facilities providing high-brightness beams is one of the most challenging tasks in field of next-generation compact and cost affordable particle accelerators, to be used in many fields for industrial, medical and research applications. The ability to shape the beam longitudinal phase-space, in particular, plays a key role to achieve high-peak brightness. Here we present a new approach that allows to tune the longitudinal phase-space of a high-brightness beam by means of a plasma wakefields. The electron beam passing through the plasma drives large wakefields that are used to manipulate the time-energy correlation of particles along the beam itself. We experimentally demonstrate that such solution is highly tunable by simply adjusting the density of the plasma and can be used to imprint or remove any correlation onto the beam. This is a fundamental requirement when dealing with largely time-energy correlated beams coming from future plasma accelerators

    Evidence for long-term Gamma-ray and X-ray variability from the unidentified TeV source HESS J0632+057

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    HESS J0632+057 is one of only two unidentified very-high-energy gamma-ray sources which appear to be point-like within experimental resolution. It is possibly associated with the massive Be star MWC 148 and has been suggested to resemble known TeV binary systems like LS I +61 303 or LS 5039. HESS J0632+057 was observed by VERITAS for 31 hours in 2006, 2008 and 2009. During these observations, no significant signal in gamma rays with energies above 1 TeV was detected from the direction of HESS J0632+057. A flux upper limit corresponding to 1.1% of the flux of the Crab Nebula has been derived from the VERITAS data. The non-detection by VERITAS excludes with a probability of 99.993% that HESS J0632+057 is a steady gamma-ray emitter. Contemporaneous X-ray observations with Swift XRT reveal a factor of 1.8+-0.4 higher flux in the 1-10 keV range than earlier X-ray observations of HESS J0632+057. The variability in the gamma-ray and X-ray fluxes supports interpretation of the ob ject as a gamma-ray emitting binary.Comment: 8 pages, 3 figures, Accepted for publication in The Astrophysical Journa
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