G. Riccobene, INFN-LNS Pylos - Km3Net General Meeting April 2007 G. Riccobene Acoustic positioning system for NEMO phase II

G. Riccobene, INFN-LNS Pylos - Km3Net General Meeting April Overview Acoustic positioning system is mandatory for the detector The frequency range of intereset for acoustic positioning is kHz The freqeuncy range of interest for acoustic neutrino detection is f<80 kHz Hydrophones are large bandwidth sensors  We can use the same sensors for both goals All data to shore  data rate fully sustainable with NEMO-like electronics The array must be calibrated in amplitude and time (OK for the NEMO- like DAQ system)

G. Riccobene, INFN-LNS Pylos - Km3Net General Meeting April 2007 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 1µPa Tonals: very narrowband signals, usually characterised as amplitude in dB re 1µPa and frequency. turbolence tides shipping sea surface Urik Knudsen

G. Riccobene, INFN-LNS Pylos - Km3Net General Meeting April 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

G. Riccobene, INFN-LNS Pylos - Km3Net General Meeting April Acoustic positioning Long Baseline (NEMO Phase 1) Beacon On Junction Box 350 m Mini Tower with 4 floors 8 acoustic receivers and a monitoring station Battery Beacon Battery Beacon On Tower Distances between beacons were calculated with ROV and GPS e.o. cable 350 m e.o. cable

G. Riccobene, INFN-LNS Pylos - Km3Net General Meeting April BEACON TOWER BASE BEACON SYNCHRONIZATION MEASUREMENTS Acoustic positioning: Measurement Principle Hydrophone Times are syncrhonized The monitoring station is still on the sea-bed Resolution ~15 cm Times are syncrhonized The monitoring station is still on the sea-bed Resolution ~15 cm

G. Riccobene, INFN-LNS Pylos - Km3Net General Meeting April 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

G. Riccobene, INFN-LNS Pylos - Km3Net General Meeting April 2007 Measured distance in laboratory = m Mean value = m Calculation of distance beetween H0-H1 on Floor 2 (each point is averaged in 5 minutes) Performances of the system

G. Riccobene, INFN-LNS Pylos - Km3Net General Meeting April 2007 G. Riccobene, CM LNS, 18 December 2008 NEMO - Phase 29 Acoustics in NEMO Phase 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  Optical and acoustic data in the same data stream with the same timing  Interdisciplinary  Environment and Detector acoustic monitoring 10 m 2 PMTs, 1 hydrophone

G. Riccobene, INFN-LNS Pylos - Km3Net General Meeting April 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

G. Riccobene, INFN-LNS Pylos - Km3Net General Meeting April The Acoustic Board The Acou-board consists of a DAQ section and a power supply section Signal from preamp 5 V power supply FCM interface cable: data, clock reset ADC Crystal CS-5381 Max input 2 V RMS Preamp power

G. Riccobene, INFN-LNS Pylos - Km3Net General Meeting April Tests : noise floor (AcouBoard and FCM) pts FFT no average 0 dB = 2 V RMS

G. Riccobene, INFN-LNS Pylos - Km3Net General Meeting April Hydrophone and Preamplifier

G. Riccobene, INFN-LNS Pylos - Km3Net General Meeting April Preamplificatori e idrofono TOP VIEWFRONT VIEWPIN-OUT A : NC B : IN – C : IN + 1 : COM 2 : – OUT 3 : NC 4 : + OUT 5 : + V Gain32dB Single Ended Z IN 100MΩ/40pF Z OUT 50Ω I OUT 30mA Band4Hz÷150kHz Equivalent Noise1 nV/√Hz (f=25kHz, C=2nF) Distorsion1% (V IN =20mV) V IN-MAX 50mVptp V OUT-MAX 4Vptp Single Ended V ALIM 4÷6 V (80mA)

G. Riccobene, INFN-LNS Pylos - Km3Net General Meeting April Test with the whole chain: noise floor pts FFT no average 0 dB = 2 V RMS

G. Riccobene, INFN-LNS Pylos - Km3Net General Meeting April 2007 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 Trigger Signal (time known) Time of trigger known ( accuracy < ns ) Latency Measuremnet = 170 us ± 100 ns For all boards sinus

G. Riccobene, INFN-LNS Pylos - Km3Net General Meeting April 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 pattern But 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

G. Riccobene, INFN-LNS Pylos - Km3Net General Meeting April 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

G. Riccobene, INFN-LNS Pylos - Km3Net General Meeting April 2007 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

G. Riccobene, INFN-LNS Pylos - Km3Net General Meeting April 2007 Typical Hydrophone Response

G. Riccobene, INFN-LNS Pylos - Km3Net General Meeting April “Acoustic” Data transmission Chain ShoreSea INFN ACSA Beacon ACSA

G. Riccobene, INFN-LNS Pylos - Km3Net General Meeting April Beacon ACSA Characteristics Frequency: 32 kHz +/- 500 Hz (f may be different for different beacons) Pulse duration: 5 ms +/- 200 µs Source level: 180 dB Repetition rate: programmable TSSC sequence. Approximate rate: 1 Hz Ultra stable clock embedded – Drift & jitter < Consumption: Inrush current : <220mA Run mode current : <220mA Pulse current : <220mA Maximum depth: 3600 m, External power supply option activated. Size: Diameter: < 10 cm – Length : < 50 cm.

G. Riccobene, INFN-LNS Pylos - Km3Net General Meeting April 2007 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/ log (SS +1) re μPa 2 /Hz

G. Riccobene, INFN-LNS Pylos - Km3Net General Meeting April 2007 Simulation beacon signal over Sea Noise Beacon signal over background  SS= 5 16 th floor Correlation of acquired signal with the original beacon signal Tower base beacon Other beacons (TSSC)

G. Riccobene, INFN-LNS Pylos - Km3Net General Meeting April 2007 Common work with CPPM and Valencia Free Flooded Rings (SX30) Resonance Frequency (kHz)30 Transmit Voltage Response, TVR (dB Ref. 1 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 Cable1N2 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.

G. Riccobene, INFN-LNS Pylos - Km3Net General Meeting April 2007 Search for ceteacens