G. Riccobene Acoustic positioning system for NEMO phase II - PowerPoint Presentation

Slide1

G. Riccobene

Acoustic positioning system for NEMO phase II

Slide2

2

Overview

Acoustic positioning system is mandatory for the detector

The frequency range of intereset for acoustic positioning is

10-40

kHz

The freqeuncy range of interest for acoustic neutrino detection is f<80 kHzHydrophones are large bandwidth sensors  We can use the same sensors for both goalsAll data to shore  data rate fully sustainable with NEMO-like electronicsThe array must be calibrated in amplitude and time (OK for the NEMO-like DAQ system)

Slide3

Ambient noise definition and spectra

Ambient noise is generally made up of three constituent types:

wideband continuous noise, tonals and impulsive noise

Impulsive noise:

transient, wide bandwidth and short duration. It is best characterised by quoting the peak amplitude and repetition rate.

Continuous wideband noise:

normally characterised as a spectrum level (in a 1 Hz bandwidth) intensity in dB relative to a reference level of 1µPaTonals: very narrowband signals, usually characterised as amplitude in dB re 1µPa and frequency. turbolence

tides

shipping

sea surface

Urik

Knudsen

Slide4

4

Acoustic positioning in NEMO-Phase 1

In

NEMO Phase

1 a commercial acoustic positioning system was used (ACSA

).

Acoustic poisitionig board with DSP onboard: acoustic signal analysis underwater  detection time sent to shore to recover hydrophone position.

GPS Time packet

Signal detection time

Acoustic

positioning PC

Acoustic

positioning board

200 kHz digitization

Beacon Long Base Line

15 m

300 m

Beacon

Slide5

5

Acoustic positioning Long Baseline (NEMO Phase 1)

Beacon

Beacon

Beacon

On Junction Box

350 m

350 m

350 m

Mini Tower with 4 floors

8 acoustic receivers

and a monitoring station

Battery

Battery

Beacon

Battery

Beacon

On Tower

Distances between beacons were calculated with ROV and GPS

e.o. cable

350 m

e.o. cable

Slide6

6

BEACON

TOWER BASE

BEACON

BEACON

BEACON

SYNCHRONIZATION

MEASUREMENTS

Acoustic positioning: Measurement Principle

Hydrophone

Times are syncrhonized

The monitoring station is still on the sea-bed

Resolution ~15 cm

Slide7

7

ACSA TSSC Patent

Delay time from monitoring station time

time

Beacon TSSC code

A custom code based on TDOA recovers hydrophone position

Sound velocity profile recoverd from CTD

Slide8

Measured distance in laboratory

= 14.25 m

Mean value

= 14.24 m

Calculation of distance beetween H0-H1 on Floor 2

(each point is averaged in 5 minutes)

Performances of the system

Slide9

G. Riccobene, CM LNS, 18 December 2008

NEMO - Phase 2

9

Acoustics in NEMO Phase 2

750 m

40 m

NEMO Phase II: Installation and operation of a “full scale” tower in Capo Passero Site

16 floors, 64 Optical Modules, 750 m total height

Same electronics and DAQ and DAT as NEMO Phase I:

All detectors data synchronised and phased (about 1 nsec)

32 hydrophones used mainly for Acoustic Positioning and also for Acoustic Physics/Biology

Reduce costs and improve reliability of the tower acoustic positioning system

O(1km) long antenna for feasibility studies on acoustic detection

O

ptical and acoustic data in the same data stream with the same timing

Interdisciplinary

Environment and Detector acoustic monitoring

10 m

2 PMTs, 1 hydrophone

Slide10

10

NEMO Phase II – “Acoustic” Electronics Chain

ADC

Floor Conrtol Module

Adds GPS Time

Send data to shore

On-Shore

Floor Conrtol Module

Data Parsing

Acoustic

Physics / Biology

Acoustic

Positioning

Acoustic

Data Server

Hydros +

preamps

OMs

“All data to shore” philosophy data payload: 2 Hydros = 1 OM, fully sustainable

optical

fiber

New design: we use the FCM offshore to time stamp the acoustic data

A “phased and syncronised” acoustic array

Slide11

11

The Acoustic Board

The Acou-board consists of a DAQ section and a power supply section

S

ignal from preamp

5 V power supply

FCM interface cable: data, clock reset

ADC Crystal

CS-5381

Max input 2 V

RMS

Preamp power

Slide12

12

Tests : noise

floor (AcouBoard and FCM)32000 pts FFT no average

0 dB = 2 V RMS

Slide13

13

Hydrophone and Preamplifier

Slide14

14

Preamplificatori e idrofono

TOP VIEW

FRONT VIEW

PIN-OUT

A :

NC

B : IN –

C : IN +

1 :

COM

2 :

– OUT

3 :

NC

4 : + OUT

5 :

+ V

Gain

32dB Single Ended

Z

IN

100M

Ω

/40pF

Z

OUT

50

Ω

I

OUT

30mA

Band

4Hz÷150kHz

Equivalent Noise

1 nV/√Hz (f=25kHz, C=2nF)

Distorsion

1% (V

IN

=20mV)

V

IN-MAX

50mVptp

V

OUT-MAX

4Vptp Single Ended

V

ALIM

4÷6 V (80mA)

Slide15

15

Test with the whole chain: noise floor

32000 pts FFT no average

0 dB = 2 V RMS

Slide16

Measurement of the latency

FMC on-shore

FMC

off-shore

Insert time in data

Optical link

Acoustic Data

acquisition board

Signal

generator

Acoustic

Board

(sampling)

preamp

preamp

Trigger

Signal

(time

known)

Time of trigger known

( accuracy

< ns

)

Latency Measuremnet =

170 us

±

100

ns

For all boards

sinus

Slide17

17

Hydrophone Amplitude Calibrations at High Pressure

Commercial Hydrophones

are typically factory calibrated:



piston test at 250 Hz, water pool test above 5 kHz (due to reflections)

 directionality patternBut for many hydrophones sensitivity change as a function of pressure (about 10 dB less at 3500 m)NEMO and an italian company (SMID) have developed low cost hydrophones for 4000 m depth, with no change of calibration as a function of depth.NATO has developed for / with NEMO a standard procedure for calibration under pressure

0.1 bar / 30 kHz ping

300 bar / 30 kHz ping

Hydros for NEMO Phase 2 (SMID) don’t show change of sensitivity at 3500 m after several cycles).

Sensitivity (now poor) can be improved

Slide18

18

NURC Acoustic calibration facilities

Calibration Tank

Tank dimensions: 4.6m long, 3.6m wide, 2.7m deep

Crane: Wall mounted, 500kg capacity

Rotators:

2 units, 50kg and 500kg capacity, 0.1 degree resolution Instruments: PC with National Instrument PXI 6115 DAQ card & GPIB HP 33120a signal generator interfaced through GPIB bus Stanford Research Systems DG 535 delay generator Stanford Research Systems SRS 560 pre-amplifier Instruments Inc L2 power amplifier

Slide19

NURC Tests

Set-up for high pressure tests

Relative Hydrophone sensitivity

variation with hydrostatic

pressure at 20kHz

Hydrophone placed in pressure vessel filled with oil & immersed in a calibration tank

• A projector (ITC1042) is placed at approximately 1m from the pressure vessel• Pressure is increased to 400 bar and allowed to settle for 30 minutes.• Hydrophone signal is acquired at 400, 300 and 50 bar.Calibration curves (32 hydros) in water tank

Slide20

Typical Hydrophone Response

Slide21

21

“Acoustic” Data transmission Chain

Shore

Sea

INFN

ACSA

Beacon

ACSA

Slide22

22

Beacon

ACSA CharacteristicsFrequency:

32 kHz +/- 500 Hz (f may be different for different beacons

)

Pulse

duration: 5 ms +/- 200 µsSource level: 180 dBRepetition rate: programmable TSSC sequence. Approximate rate: 1 HzUltra stable clock embedded – Drift & jitter < 5.10-8

Consumption

:

Inrush

current

 : <220mA

Run

mode current : <220mA Pulse

current : <220mAMaximum depth: 3600 m,

External

power supply option activated.

Size

: Diameter: < 10 cm – Length : < 50 cm.

Slide23

Simulation of the

positioning system

Base tower Beacon

1

st

floor hydro

Base tower Beacon

1

st

floor hydro

Lateral Beacon

1

st

floor hydro

Lateral Beacon

16

st

floor hydro

Beacon signal at source

32 kHz

Knudsen's relation:

SPD (f

Hz

, SS)

≈ 94,5 – 10 log f

5/3

+ 30 log (SS +1) re μPa

2

/Hz

Slide24

Simulation beacon signal

over

Sea Noise

Beacon signal over background

SS= 5

16

th

floor

Correlation of acquired signal with

t

he original beacon signal

Tower base beacon

Other beacons (TSSC)

Slide25

Common work with CPPM and Valencia

Free

Flooded Rings

(SX30)

Resonance Frequency

(kHz)

30Transmit Voltage Response, TVR

(dB Ref. 1 µPa/Volt @ 1

metre

)

133

Receive Voltage Response, OCV

(dB Ref. 1 volt/ µPa.)

-183

Useable Frequency Range

(kHz)

20-40

Beam Pattern

           Radial

           Axial

Omni

Toroidal (60°)

Efficiency

(% min)

50

Input Power

(2% duty Cycle)

300W

Operating Depth

(Metres)

Unlimited

Cable

1N2

Install a couple of recieving/transmitting hydrophones on 1 floor:

The pulse emission time is triggered by the FCM



pulse emission time and pulse reception time on other hydrophones are known with a precision better than 1 usec.

Slide26

Search for ceteacens