Speaker
Description
Summary
A proposal for a system to capture signals in the Optical
Module of an Underwater Neutrino Telescope is described.
An underwater neutrino telescope detects the muons
produced by the interaction of neutrinos with the nuclei of
matter along the path through the Earth.
These, emerging from the bottom of the sea and passing
through sea water, produce light due to the Cherenkov
effect.
The detection of the tracks allows the direction and energy
of the primary neutrinos to be reconstructed.
The detector sensors are large area (>8”)photomultipliers
(PMT) in pressure resistant borosilicate glass spheres called
Optical Modules (OM).
These also contain the high voltage power supply device,
the front-end electronics and the required data transfer and
communication unit.
There is a large number of OMs, about 6000, and the power
they require is a key element when considering the
feasibility of such a detector.
In the experimantal conditions the power transfer is limited,
the electronics power consumption must be limited to not
more than a few kW in the whole detector, that is
less than 200-300 mW in the OM.
Power is transferred to the whole telescope at a great
distance from the shore by means of an electro-optic cable
and is limited by cable capacity.
Anything which is commercially available and satisfies the
technical and power consumption requirements will be
adopted in the OM.
Not included in this forecast are: the Switched Capacitor
Array Analogue Memory to capture the signal (LIRA), the
module which triggers and classifies the signals, the
T&SPC, the synchronous frequency multiplier (PLL), the
Control system, the DC/DC conversion system that supplies
power starting from the single one that enters from
the connector.
The front-end electronics, therefore, have to have low
power consumption.
The aim of the Catania Microelectronics group is to design a
full custom VLSI ASIC containing as many circuital blocks as
possible in order to reduce the total cost of the electronics,
utilizing commercial devices for the other blocks.
In the following the blocks which are present in the chip will
be described in more detail.
In particular, a device to capture the electric signals of the
PMT must perform suitably.
These signals have a very wide dynamic range and a lot of
care has to be devoted to the design of the device with the
aim of its being able to respond to the need to acquire all
the PMT signals adequately.
An accurate analysis of the signal shapes and careful design
of the front-end architecture must guarantee the efficiency
and precision of the electronics in capturing the signals in
very low power conditions.
The design of the Smart Autotriggering Sampler (SAS) chip is
the final result.
It is introduced in this presentation together with the
simulation results.
A proposal for a system to capture signals in the Optical
Module of a Underwater Neutrino Telescope has been
described.
It pays great attention to the problem of power
consumption with relation to precision.
All considerations regarding the signals and their acquisition
are made starting from the most general hypothesis
possible, so that they will be valid for any Underwater
Cherenkov Neutrino Telescope.
