2 research outputs found
Architecture and performance of the KM3NeT front-end firmware
The KM3NeT infrastructure consists of two deep-sea neutrino telescopes being
deployed in the Mediterranean Sea. The telescopes will detect extraterrestrial and atmospheric
neutrinos by means of the incident photons induced by the passage of relativistic charged particles
through the seawater as a consequence of a neutrino interaction. The telescopes are configured
in a three-dimensional grid of digital optical modules, each hosting 31 photomultipliers.
The photomultiplier signals produced by the incident Cherenkov photons are converted into
digital information consisting of the integrated pulse duration and the time at which it surpasses
a chosen threshold. The digitization is done by means of time to digital converters (TDCs)
embedded in the field programmable gate array of the central logic board. Subsequently, a state
machine formats the acquired data for its transmission to shore. We present the architecture and
performance of the front-end firmware consisting of the TDCs and the state machine
Deep-Sea Bioluminescence Blooms after Dense Water Formation at the Ocean Surface
<p>The deep ocean is the largest and least known ecosystem on Earth. It hosts numerous pelagic organisms, most of which are able to emit light. Here we present a unique data set consisting of a 2.5-year long record of light emission by deep-sea pelagic organisms, measured from December 2007 to June 2010 at the ANTARES underwater neutrino telescope in the deep NW Mediterranean Sea, jointly with synchronous hydrological records. This is the longest continuous time-series of deep-sea bioluminescence ever recorded. Our record reveals several weeks long, seasonal bioluminescence blooms with light intensity up to two orders of magnitude higher than background values, which correlate to changes in the properties of deep waters. Such changes are triggered by the winter cooling and evaporation experienced by the upper ocean layer in the Gulf of Lion that leads to the formation and subsequent sinking of dense water through a process known as "open-sea convection". It episodically renews the deep water of the study area and conveys fresh organic matter that fuels the deep ecosystems. Luminous bacteria most likely are the main contributors to the observed deep-sea bioluminescence blooms. Our observations demonstrate a consistent and rapid connection between deep open-sea convection and bathypelagic biological activity, as expressed by bioluminescence. In a setting where dense water formation events are likely to decline under global warming scenarios enhancing ocean stratification, in situ observatories become essential as environmental sentinels for the monitoring and understanding of deep-sea ecosystem shifts.</p>