Calibration of Under Water Neutrino Telescope ANTARES

Calibration of Under Water Neutrino Telescope ANTARES

Garabed HALLADJIANOctober 15th, 2008

GDR Neutrino, CPPM, Marseille

15/10/2008 GDR Neutrino - G. Halladjian 2

Presentation plan

• Introduction• Time calibration

– Dark room calibration– In situ calibration

• Efficiency control• Acoustic positioning system• Conclusion


Introduction

Good neutrino astronomy=

Good angular resolution neutrino telescope


Introduction

Good neutrino astronomy=

Good angular resolution neutrino telescope=

Good calibration


Detection principle

neutrino

muon

interaction

Cherenkov light

earth

water

3D OMnetwork

neutrino


Detection principle

neutrino

muon

interaction

Cherenkov light

earth

water

3D OMnetwork

1.Time2.Positions3.Charge


ANTARES ν-telescope

2475m

450m

70m

12 lines25 stories

3 OM


Storey components

Hydrophone:acoustic positioning

Optical Module:10”

Hamamatsu PMT

in 17” glass sphere

(TTS 1.3 ns)photon

detectionLocal Control Module

(in Ti cylinder):Front-end ASIC,

DAQ/SC, DWDM, Clock, tilt/compass, power distribution…

Optical Beaconwith blue LEDs:timing calibration


Angular resolution

Angular resolution better than 0.3° above a few TeV, limited by:

• Light scattering + chromatic dispersion in sea water: σ ~ 1.0 ns

• TTS in photomultipliers: σ ~ 1.3 ns

• Electronics + time calibration: σ < 0.5 ns

• OM position reconstruction: σ < 10 cm (↔ σ < 0.5 ns)

dominated by reconstruction

rec− true

rec− dominated

by kinematics


Time calibration

• Internal clock calibration system

• Optical Beacons• K40 decay• Internal Optical

Module LEDs• …


Local Control ModulesLCM clock boards

Link Cables200-500 m fibre

START STOPTDC

STARTSTOPGPS E/O/E

TXRX

Main Electro-Optical Cable 40 km

from shore to Junction BoxSingle bidirectional fibre

(1534 nm / 1549 nm)

Junction Box116 passive splitter

String Control ModuleBIDI modules

O/E and E/O convertersby sectors (5 storeys)

On-shore Station

Clock distribution


Transit time measuring of principal EO cable

In situ measurementsof clock delay


σ ~ 9 ps Line 4, storey 16 Line 12, storey 8σ ~ 11 ps

Clock phase in situmeasurements

Individual relative delay measuring of clock for each storey


OM time calibration

Dark room calibration In situ calibration


Optical fibers

t0

t1t2

t3

Optical Splitter

Laser 532 nm

Attenuator

Filter

Dark room calibration

Apparatus check !


OMs calibration in dark room

t (ns)


OMs calibration in dark room

t (ns)


Optical beacon

Optical Beaconwith blue LEDs:timing calibration

• 36 LEDs• λ = 470 nm• Rise time ~ 1.9 ns• FWHN ~ 5 ns


Led OpticalBeacon:

32 blue LEDssynchronisedflash < 0.5 ns

Timing resolution of electronics

<0.5ns

Time difference between signalsfrom 2 OMs in a storey

Time in OMs relative to reference PMT in OB

MILOM

15 m

Intense light flash:PMT TTS

contributionis negligible

Optical beacon


Line 1 time calibrationwith MILOM LED beacon

MILOM

~70 m

~150 m = 0.7 ns

= 2.6 ns

t [ns]

"horizontal"

"diagonal"

larger distance

• less intensity

• light scattering

All timing measurements in good agreement with expectations

Line 1


Light attenuation measuredby optical LED beacons


Light attenuation measuredby optical LED beacons


Optical

fibresLaser

On shorelaser

system

In seaLED beacon

system

LED beacon

RMS 0.74ns

RMS 0.60ns

Time calibration


In situ calibration with K40

40K40Ca

e-

Cherenkovphotons

Gaussian peak on coincidence plot

Peak time offset : Cross check of time calibration

Integral under peak = rate of correlated

coincidences

High precision (~5%) monitoring of OM efficiencies

MC prediction =13 ± 4 Hz


Coincidence on 2 storeys

2 pairs of coincidences in adjacent storeys

±20 ns in same storey


Calibration with down-goingmuons

2 pairs of coincidences in adjacent storeys±100 ns between storey

Preliminary


Relative positioning of detector

Z(m)

r(m)

Example forSea currentV = 25 cm/srmax = 22 m


AutonomousTransponder

TransmitterReceiver

5 + 1 Receiver / line

Acoustic positioning system


Acoustic positioning system

• Frequency = 40 – 60 kHz• Accuracy < 10 cm• Acoustic cycle: Successive emission of

each BSS in each second• Simultaneous measure of acoustic

propagation times between each transmitter and all hydrophones

• 3D position determination of each hydrophone using all RxTxRx distances of acoustic cycle (global positioning each 2 minutes)


Acoustic components

After current correction

Transmitter / Receiver

Pressure sensor

Celerimeter

CCTD

Receiver

Current velocityPressureE. ConductivityTemperature


Sound Velocity

00 0171.0, zztVtzV


Acoustic measurementsof fixed distances


L2→L3 L3→L2 average

5 mm





5 mm

+

+

=

=





5 mm


Hydrophone : Ligne 4 étage 25

Emission RxTx ligne 5Emission transpondeur

Acoustic measurementsof hydrophone distances


Acoustic triangulationof hydrophones




Radial displacement



Storey 1Storey 8

Storey 14Storey 20Storey 25

Radial displacement



Radial displacement

Radial displacement


BSS absolute positions

• BSS position are measured by the boat• Boat position are measured by satellites

DGPS

LF LBL (σx σy ~ 1m)


Before triangulation



7 m


BSS position uncertainty












BSS absolute positions

Distances between BSSs (acoustic distances) decrease the uncertainty on BSS positions.

DGPS

HF



Before triangulation After triangulation



Before triangulation After triangulation



7 m


After triangulation

7 m


Angular Error due to BSS

σ (horizontal) = 0.13 degree

σ (vertical) = 0.02 degree


Conclusion

• ANTARES is complete and working very well• Detector calibration is permanently controlled in

situ• Calibration performance agree with expectation:

– Time uncertainty < 0.5 ns– Position uncertainty < 10 cm

• ANTARES should reach its excellent angular resolution ~ 0.3o

Documents

Calibration of Under Water Neutrino Telescope ANTARES