2,218 research outputs found
First observation of Cherenkov rings with a large area CsI-TGEM-based RICH prototype
We have built a RICH detector prototype consisting of a liquid C6F14 radiator
and six triple Thick Gaseous Electron Multipliers (TGEMs), each of them having
an active area of 10x10 cm2. One triple TGEM has been placed behind the liquid
radiator in order to detect the beam particles, whereas the other five have
been positioned around the central one at a distance to collect the Cherenkov
photons. The upstream electrode of each of the TGEM stacks has been coated with
a 0.4 micron thick CsI layer.
In this paper, we will present the results from a series of laboratory tests
with this prototype carried out using UV light, 6 keV photons from 55Fe and
electrons from 90Sr as well as recent results of tests with a beam of charged
pions where for the first time Cherenkov Ring images have been successfully
recorded with TGEM photodetectors. The achieved results prove the feasibility
of building a large area Cherenkov detector consisting of a matrix of TGEMs.Comment: Presented at the International Conference NDIP-11, Lyon,July201
Evaluating potential artifacts of tethering techniques to estimate predation on sea urchins
Measuring the strength of trophic interactions in marine systems has been central to our understanding of community structuring. Sea urchin tethering has been the method of choice to evaluate rates of predation in marine benthic ecosystems. As standardly practiced, this method involves piercing the urchin test, potentially introducing significant methodological artifacts that may influence survival or detection by predators. Here we assess possible artifacts of tethering comparing invasive (pierced) and non-invasive tethering techniques using the sea urchin Paracentrotus lividus. Specifically we looked at how degree of confinement and high water temperature (first order artifacts), and predator guild and size of the prey (second order artifacts) affect the survival and/or detectability of pierced urchins. Our results show that first order artifacts only arise when pierced sea urchins are placed in sheltered bays with confined waters, especially when water temperature reaches extremely high levels. Prey detectability did not increase in pierced sea urchins for the most common predators. Also, test piercing did not alter the preferences of predators for given prey sizes. We conclude that the standard tethering technique is a robust method to test relative rates of sea urchin predation. However, local conditions could increase mortality of the tethered urchin in sheltered bays or in very high temperature regimes. Under these conditions adequate pierced controls (within predator exclusions) need to be included in assays to evaluate artifactual sources of mortality
VHMPID: a new detector for the ALICE experiment at LHC
This article presents the basic idea of VHMPID, an upgrade detector for the
ALICE experiment at LHC, CERN. The main goal of this detector is to extend the
particle identification capabilities of ALICE to give more insight into the
evolution of the hot and dense matter created in Pb-Pb collisions. Starting
from the physics motivations and working principles the challenges and current
status of development is detailed.Comment: 4 pages, 6 figures. To be published in EPJ Web of Conference
Development and first tests of GEM-like detectors with resistive electrodes
We have developed and tested several prototypes of GEM-like detectors with electrodes coated with resistive layers or completely made of resistive materials. These detectors can operate stably at gains close to 105. The resistive layers limit the energy of discharges appearing at higher gains thus making the detectors very robust. We demonstrated that the cathodes of some of these detectors could be coated by CsI or SbCs layers to enhance the detection efficiency for the UV and visible photons. We also discovered that such detectors can operate stably in the cascade mode and high overall gains () are reachable. Applications in several areas, for example in RICH or in noble liquid TPCs are therefore possible. The first results from the detection of UV photons at room and cryogenic temperatures will be given
The Development of Sealed UV Sensitive Gaseous Detectors and their Applications
We have developed commercial prototypes of sealed gaseous detectors combined
with CsI photocathodes and/or filled with photosensitive vapors. The rirst
results of application of these devices for the detection of flames in daylight
conditions and for the detection of scintillation lights from noble liquids
will be presented. The main conclusion from our studies is that for some
applications the sealed UV sensitive gaseous detectors have superior
performance (higher practical quantum efficiency and better signal to noise
ratio) than existing commercial UV sensitive detectors. Additionally, they are
much cheaper.Comment: Presented at the Pisa Meeting "Frontier Detectors for Frontier
Physics", May 200
Development of innovative micropattern gaseous detectors with resistive electrodes and first results of their applications
The paper summarizes our latest progress in the development of newly
introduced micro pattern gaseous detectors with resistive electrodes. These
resistive electrodes protect the detector and the front-end electronics in case
of occasional discharges and thus make the detectors very robust and reliable
in operation. As an example, we describe in greater detail a new recently
developed GEM-like detector, fully spark-protected with electrodes made of
resistive kapton. We discovered that all resistive layers used in these studies
(including kapton), that are coated with photosensitive layers, such as CsI,
can be used as efficient photo cathodes for detectors operating in a pulse
counting mode. We describe the first applications of such detectors combined
with CsI or SbCs photo cathodes for the detection of UV photons at room and
cryogenic temperatures.Comment: Presented at the 11 Vienna Conference on Instrumentation, February,
200
Semicosimplicial DGLAs in deformation theory
We identify Cech cocycles in nonabelian (formal) group cohomology with
Maurer-Cartan elements in a suitable L-infinity algebra. Applications to
deformation theory are described.Comment: Largely rewritten. Abstract modified. 15 pages, Latex, uses xy-pi
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