Speaker
Description
Summary
The NEMO underwater neutrino telescope uses large area
photomultipliers (PMTs) inside optical modules (OMs) to
detect the Cherenkov light emitted by the muons generated by
neutrinos in the seawater. The PMTs are put in a 17” glass
sphere capable to stand more than 350 Atm external pressures.
The signals at the output of the PMT must be suitably coded
and sent on-shore. The OM contains the PMT and its base
board, the front-end electronics, the data pack and transfer
electronics, the slow control interface and a set of
environmental sensors.
The work described in this paper is aimed at the
development of a low-power front-end for the OMs of the
NEMO submarine neutrino detector. A mini-tower
equipped with 16 OMs (NEMO-Phase1 MiniTower) has been
successfully deployed in December 2006 in front of the
Catania harbour as a first prototype. The technological solutions
adopted provided results in agreement with expectations. In
the meantime, we have developed a solution which can fulfil
all requirements of a km3-scale detector, in particular for what
concerns power consumption, PMTs aging and signal
dynamics. The final version of the presented front-end
electronics will be employed in one of the 16 floors NEMOPhase2
Tower to be deployed at the end of 2008.
This solution is based on the use of an Application
Specific Integrated Circuit (ASIC) for the fast sampling of the
PMT signal, which is performed according to its shape
classification made by another unit. Two other units, one ADC
and a Field Programmable Gate Array (FPGA), provide digital
encoding of the voltage sampled signals, the packing of the
data and its transfer towards the shore station.
An electronic board containing the PMT interface and the
mentioned units constitutes the OM front-end. By means of
the FPGA, this board receives the slow control signals and
transmits the measurements of environmental parameters such
as temperature and humidity, together with the data.
A proposal for a system to capture signals from Optical
Modules of an underwater neutrino telescope has been
described, with focus on power consumption and dynamics
considerations. All considerations regarding the signals and
their acquisition are discussed, starting from the most general
hypothesis possible, so that they will be valid for any
underwater Cherenkov neutrino telescope.
The development of the demonstration board to evaluate
the advantages of the proposed architecture fitting the
specifications of power dissipation, multi input dynamics,
signal reconstruction, establishes the basis for the definitive
design of the final front end board using the SAS chip. As
soon as the chip will be available, the whole front-end will be
tested together with the PMT.
