413 research outputs found
The GALATEA Test-Facility for High Purity Germanium Detectors
GALATEA is a test facility designed to investigate bulk and surface effects
in high purity germanium detectors. A vacuum tank houses an infrared screened
volume with a cooled detector inside. A system of three stages allows an almost
complete scan of the detector. The main feature of GALATEA is that there is no
material between source and detector. This allows the usage of alpha and beta
sources as well as of a laser beam to study surface effects. A 19-fold
segmented true-coaxial germanium detector was used for commissioning
Digital control of force microscope cantilevers using a field programmable gate array
This report describes a cantilever controller for magnetic resonance force
microscopy (MRFM) based on a field programmable gate array (FPGA), along with
the hardware and software used to integrate the controller into an experiment.
The controller is assembled from a low-cost commercially available software
defined radio (SDR) device and libraries of open-source software. The
controller includes a digital filter comprising two cascaded second-order
sections ("biquads"), which together can implement transfer functions for
optimal cantilever controllers. An appendix in this report shows how to
calculate filter coefficients for an optimal controller from measured
cantilever characteristics. The controller also includes an input multiplexer
and adder used in calibration protocols. Filter coefficients and multiplexer
settings can be set and adjusted by control software while an experiment is
running. The input is sampled at 64 MHz; the sampling frequency in the filters
can be divided down under software control to achieve a good match with filter
characterisics. Data reported here were sampled at 500 kHz, chosen for acoustic
cantilevers with resonant frequencies near 8 kHz. Inputs are digitized with 12
bits resolution, outputs with 14 bits. The experiment software is organized as
a client and server to make it easy to adapt the controller to different
experiments. The server encapusulates the details of controller hardware
organization, connection technology, filter architecture, and number
representation. The same server could be used in any experiment, while a
different client encodes the particulars of each experiment.Comment: submitted to Review of Scientific Instrument
The EEE Project
The new experiment ``Extreme Energy Events'' (EEE) to detect extensive air
showers through muon detection is starting in Italy. The use of particle
detectors based on Multigap Resistive Plate Chambers (MRPC) will allow to
determine with a very high accuracy the direction of the axis of cosmic ray
showers initiated by primaries of ultra-high energy, together with a high
temporal resolution. The installation of many of such 'telescopes' in numerous
High Schools scattered all over the Italian territory will also allow to
investigate coincidences between multiple primaries producing distant showers.
Here we present the experimental apparatus and its tasks.Comment: 4 pages, 29th ICRC 2005, Pune, Indi
Combined effects of compost and medicago sativa in recovery a PCB contaminated soil
The effectiveness of adding compost and the plant Medicago sativa in improving the quality of a soil historically contaminated by polychlorinated biphenyls (PCBs) was tested in greenhouse microcosms. Plant pots, containing soil samples from an area contaminated by PCBs, were treated with the compost and the plant, separately or together. Moreover, un-treated and un-planted microcosms were used as controls. At fixed times (1, 133 and 224 days), PCBs were analysed and the structure (cell abundance, phylogenetic characterization) and functioning (cell viability, dehydrogenase activity) of the natural microbial community were also measured. The results showed the effectiveness of the compost and plant in increasing the microbial activity, cell viability, and bacteria/fungi ratio, and in decreasing the amount of higher-chlorinated PCBs. Moreover, a higher number of ff-Proteobacteria, one of the main bacterial groups involved in the degradation of PCBs, was found in the compost and plant co-presence
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