Download Diapositiva 1

R&D towards the acoustic positioning
system of KM3NeT
M. Ardid, M. Bou-Cabo, F. Camarena, V. Espinosa, G. Larosa,
C.D. Llorens, and J.A. Martínez-Mora (IGIC –UPV),
representing the KM3NeT consortium
VLVNT’09 – Athens - October 2009
Introduction
• In undersea neutrino telescopes, sea currents result on drifts of
the top of the detection units and Optical Modules (OMs) by
several meters
• However, muon track reconstruction is based on:
– precise arrival time of Cherenkov photons to the OMs(< 2 ns)
– Monitor the OM position with the corresponding resolution (< 40 cm)
• An acoustic triangulation system is needed for monitoring the OM
positions, so as to provide the tracking precision and angular
resolution required for astronomical neutrino source searches.
• We present our effort in R&D towards this system for KM3NeT
– Activities, solutions proposed, prototype systems and tests
– We have focused in the transceiver design
Specifications for the system
• Difficulties of the system:
– Deep water, large volume, number of elements, integration in the
telescope.
– Combined in a system with reasonable cost and complexity
• Large uncertainty in the description of the detector:
– mechanics, optical modules, distances between elements, etc.?
• General specifications:
–
–
–
–
Acoustic range > 1 km
Cost: of the order of 1% of the total cost
Reliable
Redundancy
Solution proposed
• Acoustic transducer:
– We have selected the commercial available SX30 Free Flooded Ring
from Sensortech, Canada, since it fulfils all the requirements:
•
•
•
•
It can operate as emmiter and receiver with good efficiencies (20-40 kHz)
It can stand high power signals
It can stand high pressures
It can be affordable in the large number of units required by KM3NeT
• Electronics
– Worth to do R&D in the electronics to::
• Fulfil the special requirements of the system: low-power consumption,
configurable from shore, etc.
• Optimise to the transducer chosen
• Reduce costs
Acoustic transducer: Specifications
• Info from the supplier
Tests to transducers: Transmit Voltage Response
Generator
Signal
PC
Acoustic
Board
TRIGGER
Power Supply
5V
Recorded
Board
Osciloscope
Preamplifier
EMITTER
10 cm
ITC 1042 10 cm
RECEIVER
10 cm
Reson
FFR
Tests to transducers: Transmit Voltage Response
• Small variations with respect to the supplier calibration
130
TVR (dB re 1uPa/V @ 1m)
128
126
124
hydro SX30-788
hydro SX30-530
122
hydro SX30-566
hydro SX30-774
120
16
20
24
28
32
36
Frequency [kHz]
40
44
Calibration from the supplier
Tests to transducers: Received Voltage Response
Recorded
Board
PC
TRIGGER
Acoustic
Board
Generator
Signal
Preamplifier
RECEIVER
EMITTER
10 cm
ITC 1042 10 cm
10 cm
Reson
FFR
Power Supply
5V
Tests to transducers: Received Voltage Response
• Larger variations observed: possible effect of the preamplifier used
• Need deeper investigation
-180
Calibration from the supplier
RVR (dB re 1V/uPa @ 1m)
-182
-184
-186
-188
hydro SX30-FFR788
-190
hydro SX30-FFR530
hydro SX30-FFR566
-192
hydro SX30-FFR774
-194
16
20
24
28
32
36
Frequency [kHz]
40
44
Tests to transducers: Transmiting Directivity
• We will check in the following months
Calibration from the supplier
Tests to transducers: Pressure dependence
• Tests performed at the large hyperbaric tank at IFREMER-Brest
– Small variations with pressure
Electronics: Requirements
• To handle emission and reception
– Protect reception from high tension
• All-data-to-shore approach
– Increase reliability, easier tuning, and versatility
• Configurable from shore
– Communication using Slow Control (RS232)
• Low power consumption
– Less than 1 W at 5 V
– Store energy to have very high electric power in short time
Electronics: solution proposed
• Design of the 1st electronic board:
– Blue: Communication and control
– Red: Emission part
• Digital feeding + transducer response
– Green: Reception part
• Limiter to protect from emission
• Analogic, see G. Riccobene’s talk for
ADC and rest of the electronic chain
Performance of the first electronic board
• Low consumption
– Less than 1 W at 5 V
• Easy configuration and control by RS232
– Possible to handle arbitrary signals for emission, but could be improved
• Fast synchronisation using a TTL signal
– A few ms delay for emission, stability better than 1 ms
• High power for emission
– Transducer feeded with 300 Vpp, but probably not enough for KM3NeT
• Low intrinsic noise
• Good matching between the electronics and the transducer and
response according to the design
Almost ready a 2nd version of the electronic board, which overcomes the
limitations observed and improves performance.
Tests before the end of the year.
Tests to electronics + transducers: Signals emmitted
• Arbitrary signal emission not implemented in
the first version of the board.
• Some examples of tone bursts at 30 kHz are
shown.
• 2nd version of the board, possible to use
arbitrary signals easily. Take advantage of
signal processing techniques.
5 cycles
10 cycles
1 cycle
100 cycles
Fluctuations in received amplitude
due to reflections in the tank
Tests to board + transducers: Receiving response and
transmitting power
-170
Transmitting Power
(dB re 1uPa @ 1m)
Receiving Voltage Response
(dB re 1V/uPa)
175
-175
-180
174
173
172
-185
171
-190
16
20
24
28
32
36
Frequency [kHz]
40
44
170
16
20
24
28
32
36
Frequency [kHz]
40
44
Tests to board + transducers: Intrinsic noise
• Measurement done in the anechoic chamber
• Singular frequencies appear, most probable due to
electromagnetic contamination of our lab
• Need confirmation in a cleaner environment
• For the rest, noise below 120 dB (~ ≤Sea State 1)
Preliminary
Tests to board + transducers: Whole process (echo)
• Whole performance of the
system can be studied in a pool
looking at echoes.
• Measurements from last week:
– Analyses are going on to study
the stability in amplitude and
time.
Wall echoes
Floor echo
Amplitude limited
during emission
Red :with reflector
Blue: w/o reflector
Tests to board + transducers: Summary
• We have designed and tested a system that can be used in the
acoustic positioning system fulfilling most of the requirements:
– Low cost, Low power, stability, etc.
– We have acquired an important know-how
• Improvements are needed in some aspects:
– Transmitting power (or sensitivity) is not enough:
• We are in the 0-10 dB Signal-to-Noise ratio.
• 2nd Electronic Board will provide about 185 dB ref 1 mPa at 1 m
– Arbitrary signals for emission very helpful for KM3:
• Possible in the 2nd version
• More checks needed in some aspects:
– Intrinsic noise, stability.
2nd Electronic board
• More accurate arbitrary signal: using a more powerful
microcontroller and the PWM technique
• Power up the signal more than four times: using an H-Bridge
• Capacity of acquiring and processing the received signal in the
board
Conclusions
• We have the know-how and are in the way to have a solution for the
transceivers of the acoustic positioning system of KM3NeT
• In principle, t is compatible with the different options for the receiver
hydros:
– Good sensitive hydrophones that can be used in acoustic detection of
neutrinos or bioacoustic monitoring
– Acoustic modules: piezos glued inside the glass spheres
– And of course with the free flooded ring transducers.