IFIC - Instituto de Física Corpuscular (CSIC - UV) VALENCIA, SPAIN

IFICIFIC - - Instituto de Física Corpuscular Instituto de Física Corpuscular (CSIC - UV)(CSIC - UV)

VALENCIA, SPAIN

On behalf of the ANTARESANTARES collaboration

WATER ABSORPTION LENGTH WATER ABSORPTION LENGTH MEASUREMENT WITH THE ANTARES MEASUREMENT WITH THE ANTARES

OPTICAL BEACON SYSTEMOPTICAL BEACON SYSTEM

WATER ABSORPTION LENGTH WATER ABSORPTION LENGTH MEASUREMENT WITH THE ANTARES MEASUREMENT WITH THE ANTARES

OPTICAL BEACON SYSTEMOPTICAL BEACON SYSTEMHAROLD HAROLD

YEPESYEPES

Inte

rnati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes

13 – 15 October 2009, Athens, 13 – 15 October 2009, Athens, GreeceGreece

1.1. THE ANTARES NEUTRINO THE ANTARES NEUTRINO TELESCOPETELESCOPE

2.2. THE ANTARES OPTICAL THE ANTARES OPTICAL BEACON SYSTEMBEACON SYSTEM

3.3. EXPERIMENTAL EXPERIMENTAL PROCEDUREPROCEDURE

4.4. PROPAGATION OF PROPAGATION OF PHOTONS AND MC PHOTONS AND MC

SIMULATIONSSIMULATIONS

5.5. PRELIMINARY RESULTSPRELIMINARY RESULTS

6.6. CONCLUSIONSCONCLUSIONS

OUTLINEOUTLINEOUTLINEOUTLINEIn

tern

ati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes


1.2 TeV Muon crossing the detector (SIMULATION)

CPPM, Marseille DSM/IRFU/CEA, Saclay APC, Paris LPC, Clermont-Ferrand IPHC (IReS), Strasbourg Univ. de H.-A., Mulhouse IFREMER, Toulon/Brest C.O.M. Marseille LAM, Marseille GeoAzur Villefranche

IFIC, Valencia UPV, Valencia UPC, Barcelona

NIKHEF (Amsterdam) KVI (Groningen) NIOZ Texel

University of Erlangen Bamberg Observatory

ISS, Bucarest

ITEP, Moscow Moscow State

Univ

THE ANTARES NEUTRINO TELESCOPETHE ANTARES NEUTRINO TELESCOPETHE ANTARES NEUTRINO TELESCOPETHE ANTARES NEUTRINO TELESCOPEIn

tern

ati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes


University/INFN of Bari University/INFN of

Bologna University/INFN of

Catania LNS – Catania

University/INFN of Pisa University/INFN of Rome

University/INFN of Genova

7 COUNTRIES7 COUNTRIES28 INSTITUTES28 INSTITUTES

~ 150 SCIENTISTS AND ~ 150 SCIENTISTS AND ENGINEERSENGINEERS

3

Neutrinos can interact with the surrounding of Neutrinos can interact with the surrounding of the detector.the detector.Neutrinos can interact with the surrounding of Neutrinos can interact with the surrounding of the detector.the detector.

THE ANTARES NEUTRINO TELESCOPE THE ANTARES NEUTRINO TELESCOPE THE ANTARES NEUTRINO TELESCOPE THE ANTARES NEUTRINO TELESCOPE In

tern

ati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes


Two kinds of background at the ANTARES site:

Physical Background : Cosmic Rays interactions (atmospheric and ).

Optical Background: Bioluminescence and 40K decay (sea environment).

Two kinds of background at the ANTARES site:

Physical Background : Cosmic Rays interactions (atmospheric and ).

Optical Background: Bioluminescence and 40K decay (sea environment).

42°

Seabed

Interaction

Cherenkov light from µ

PMT array

N XW

p

atm

p

Main detection Main detection channel:channel:

interaction interaction giving an ultra-giving an ultra-relativistic relativistic inducing inducing Cherenkov light in Cherenkov light in a cone (a cone (ee and and tt can also be can also be detected)detected).

Main detection Main detection channel:channel:

interaction interaction giving an ultra-giving an ultra-relativistic relativistic inducing inducing Cherenkov light in Cherenkov light in a cone (a cone (ee and and tt can also be can also be detected)detected).

4

3D array of ~900 PMT.

12 detection lines.

25 storeys / line.

3 PMTs / storey (detection units).

40 km off Toulon coast (France).

THE ANTARES NEUTRINO TELESCOPETHE ANTARES NEUTRINO TELESCOPETHE ANTARES NEUTRINO TELESCOPETHE ANTARES NEUTRINO TELESCOPEIn

tern

ati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes


~60 m

100 m

14.5 m

Link cables

2500 m depth

Junction box

45°

Storey

5

THE ANTARES OPTICAL BEACON SYSTEMTHE ANTARES OPTICAL BEACON SYSTEMTHE ANTARES OPTICAL BEACON SYSTEMTHE ANTARES OPTICAL BEACON SYSTEMIn

tern

ati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes

13 – 15 October 2009, Athens, Greece13 – 15 October 2009, Athens, Greece

F2

F9

F15

F21

LED and LASER fast and controlled sources of pulsed light with a well-known emission time.

The main goal is to perform an in-situ timing calibrationtiming calibration, moreover they can be used to study water water optical propertiesoptical properties.

60 m

300

m60 m

300

mLEDLED Beacon: Beacon:

Floors 2, 9, 15, 21

LASERLASER Beacon: Beacon:

Lines 7, 8

6

The LED BeaconThe LED BeaconThe LED BeaconThe LED Beacon

Inte

rnati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes


Energy per pulse at maximum (DC level, 24 V) ~ 150 pJ (wavelength 472 nm).

Internal PMT Hamamatsu H6780-03 (rise time ~ 0.8 ns) to know the emission time of the light pulse.

A variable capacitor to synchronise (~200 ps) the emission time of the 36 LEDs.

THE ANTARES OPTICAL BEACON SYSTEMTHE ANTARES OPTICAL BEACON SYSTEMTHE ANTARES OPTICAL BEACON SYSTEMTHE ANTARES OPTICAL BEACON SYSTEM

7

Inte

rnati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes


Energy per pulse ~ 1.0 J (wavelength 532 nm).

Variable light intensity (crystal liquid attenuator system).

Internal fast photodiode to know the time emission of the light pulse.

The LASER BeaconThe LASER BeaconThe LASER BeaconThe LASER Beacon

THE ANTARES OPTICAL BEACON SYSTEMTHE ANTARES OPTICAL BEACON SYSTEMTHE ANTARES OPTICAL BEACON SYSTEMTHE ANTARES OPTICAL BEACON SYSTEM

8

One single LED of the top group of the lowest LED Beacon in the

line (F2) flashes

Measure amount of light collected by OMs of the upper storeys in

the same line

Isotropic source of photons, the photon field measured by a PMT at a distance R is:Plot the charge (Q) collected as a

function of the distance (R)

Skip all points at R < Rmin to avoid the electronic dead time effects

Skip all points at R > Rmax to avoid fake signals due to

noise fluctuations

F2

Inte

rnati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes


EXPERIMENTAL PROCEDUREEXPERIMENTAL PROCEDUREEXPERIMENTAL PROCEDUREEXPERIMENTAL PROCEDURE

L

R

eR

AII

20 4L

Rpe

pe eR

QQ

20

9

Rmax

Rmin

¡ PRELIMINARY!

TIME DISTRIBUTION FOR SELECTED HITSTIME DISTRIBUTION FOR SELECTED HITSTIME DISTRIBUTION FOR SELECTED HITSTIME DISTRIBUTION FOR SELECTED HITS

Inte

rnati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes



Determine the peak Gaussian fit

Choose fixed time window [Tmin,Tmax] and select the hits in this time window.

TTminmin = T= Tpeakpeak – 3 – 3..

TTmaxmax = T= Tpeakpeak + 1000 ns. + 1000 ns.

Calculate their overall charge Qtot.

Qnoise

Tmax

Tmin

Qsignal

10

Inte

rnati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes



Substract the noise Substract the noise contribution contribution

(Q(Qsignalsignal = Q = Qtot tot - Q- Qnoisenoise))

Fit a constant in the

[-1000, -50] ns range:

Background Level (B)

Qnoise = B*(Tmin - Tmax)

NOISE CONTRIBUTION FOR SELECTED HITSNOISE CONTRIBUTION FOR SELECTED HITSNOISE CONTRIBUTION FOR SELECTED HITSNOISE CONTRIBUTION FOR SELECTED HITS

NOISE LEVEL

11

Some hits get lost due to the Some hits get lost due to the electronic dead time from the electronic dead time from the readout of the two electronic readout of the two electronic cards (ARSs) of the PMT.cards (ARSs) of the PMT.

Inte

rnati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes



Electronics dead time effects Electronics dead time effects related to related to RRminmin to fit.to fit.

Consider only the region Consider only the region where the probability to get where the probability to get more than one photoelectron more than one photoelectron is negligible (i.e. < 1 %):is negligible (i.e. < 1 %):

flashes

hits

N

N

15.0

%1)1(

hitsNP

CHARGE LOSSESCHARGE LOSSESCHARGE LOSSESCHARGE LOSSES

12

PMTs don’t have the same efficiency (PMTs don’t have the same efficiency (PMTPMT):):

Assume that the QAssume that the Qnoisenoise ~ ~ PMTPMT..

Normalize PMTs signal charge to their own noise Normalize PMTs signal charge to their own noise charge:charge:

Inte

rnati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes



PMT RELATIVE EFFICIENCY CORRECTIONPMT RELATIVE EFFICIENCY CORRECTIONPMT RELATIVE EFFICIENCY CORRECTIONPMT RELATIVE EFFICIENCY CORRECTION

13

noise

signalsignal Q

QQ

CORRECTED BY EFFICIENCY

Inte

rnati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes



At large distances the signal can At large distances the signal can be confused with noise be confused with noise fluctuations.fluctuations.

Consider only points with:Consider only points with:

The maximum distance The maximum distance RRmaxmax to fit to fit

is related with the noise is related with the noise fluctuations at higher distances.fluctuations at higher distances.

NOISE

3noisetot

signaltot

Q

Q

NOISE FLUCTUATIONSNOISE FLUCTUATIONSNOISE FLUCTUATIONSNOISE FLUCTUATIONS

14

Inte

rnati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes


PROPAGATION OF PHOTONS IN DEEP SEA PROPAGATION OF PHOTONS IN DEEP SEA WATERWATER


effscatabs

effatt

111

cos1scateff

scat

Attenuation Length

Effective Attenuation Length

Absorption length Scattering Length

Collimated beam

15

Scattering phase

function ()

Isotropic source

Scattering angle Scattering angle

distributiondistributionMolecular scattering (Rayleigh) Isotropic

Particle scattering (Mie)

Strong forward peaked

Inte

rnati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes




Scattering phase function Morel and Loisel approach

Average cosine of global distribution

)()1()()( *** MieRay

Mie cos)1(cos

Probability of molecular scattering

(Rayleigh)

Molecular scattering

(isotropic)

<cos<cos>=0>=0

Particle scattering (Petzold’s values)

(strong forward peaked)

<cos<cos>=0.924>=0.924

16

Inte

rnati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes


MC SIMULATIONSMC SIMULATIONSMC SIMULATIONSMC SIMULATIONS

CALIBOB

Special simulation code for timing calibration with Optical Beacons.

MAIN FEATURES

Width of the light pulse.

Light absorption in water simulated.

Light scattering in water simulated.

PMT response simulated (KM3 parametrisation for 10’’ Hamamatsu PMTs).

Gain fluctuations simulated.

TTS of PMTs simulated.

WHAT ARE WE MEASURING?

L

Rpe

pe eR

QQ

20

17

L Convolution of optical properties.

MC Tools to clarify what parameter is.

MC TOOLS SIMULATION

Inte

rnati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes



• L depends strongly on the scattering and time integration gate for selected hits.

Tmax ↓ L → att Tmax ↑ L → abs

MC PRODUCTIONWater model: abs = 60 m fixed = 0.17, 0.05scat = 30, 40, 50, 60, 70 m

L

Rpe

pe eR

QQ

20

abs = 60 m

abs = 60 m

18

Inte

rnati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes



• For all the scat – η couples considered:

att < L < abs

• Depending on scattering:

abs – L ≈ 5 - 10 m

( ↓ + scat ↑) L → abs

( ↑ + scat ↓) L → att

MC PRODUCTION:

Tmax = 1000 ns fixed.

abs = 60 m fixed

η = 0.17, 0.15, 0.12, 0.10, 0.05

LL10001000 IS A LOWER LIMIT FOR IS A LOWER LIMIT FOR

THE THE absabs

19

abs = 60 m

att

sca

Inte

rnati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes


PRELIMINARY RESULTSPRELIMINARY RESULTSPRELIMINARY RESULTSPRELIMINARY RESULTS

20

SYSTEMATIC EFFECTS ARE NOT YET FULLY UNDERSTOOD

SOME FIT EXAMPLES

Rmax

Rmin

¡PRELIMINARY!

Rmax

Rmin

¡PRELIMINARY!

Preliminary results indicate abs ~ 60 m or greater in agreement with MC muon track reconstruction.

Take more special RUNs to check the reproducibility of the results.

Still more work on systematics.

Inte

rnati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes


One different wavelength on each face.

Three LEDs per face pointing up-wards.

To assure redundance and to check systematics.

Flashing at 300 Hz

Voltage at 23 Volts

Rise Time ~ 2.5 ns

FWHM ~ 5 ns

LED CB 30 (470 nm)

FUTURE PLANSFUTURE PLANS

[nm][nm] 385385 400400 440440 470470 505505 518518

21


Inte

rnati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes


PROVIDED BY MANUFACTURERPROVIDED BY MANUFACTURER MEASURED AT IFICMEASURED AT IFIC

LEDLED FWHM (nm)FWHM (nm) Mean (nm)Mean (nm) FWHM (nm)FWHM (nm) Mean (nm)Mean (nm)

VAOL-5GUV8T4VAOL-5GUV8T4 55 385385 1111 383383

HUVL400-520BHUVL400-520B 2020 400400 1212 399399

Ultrabright PinkUltrabright Pink -- 440440 2222 445445

HLMP-CB30-K000HLMP-CB30-K000 3535 470470 3030 455455

HLMP-CE36-WZ000HLMP-CE36-WZ000 3030 505505 3737 493493

SLA-580ECT3FSLA-580ECT3F 3535 518518 5050 537537

LED HLMP-CB30-K000

FWHM

Mean

442 477 [nm]

LED VAOL-5GUV8T4

FWHM

Mean

365 405 [nm]

22


Inte

rnati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes


CONCLUSIONSCONCLUSIONSCONCLUSIONSCONCLUSIONS• The ANTARES Optical Beacon system has been designed for timing calibration, but it can be also used to study of water optical properties.

• An experimental procedure to measure the absorption length has been developed based on the exponential fit to the collected charge by the PMTs and the arrival time distributions.

• MC simulations confirm the difficulty to disentangle the optical parameters from the measured value. The higher the integration gate when measuring L, the closer L is to the absorption length.

• Systematics effects still not fully understood but work is in progress.

• First measurements indicate that L ~ 57 m < abs. More data RUNs needed to check this result.

• A modified version of the Optical Beacon to measure the absorption length at different wavelengths will be ready soon for integration and deployment on the ANTARES detector.

Inte

rnati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes


BACKUP SLIDESBACKUP SLIDESBACKUP SLIDESBACKUP SLIDES

Bioluminescence Median rate from 03/06 – until 05/08

F2

F9

F15

F21

LINE

γ

40K

40Ca

e- ( decay)

Inte

rnati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes


OPTICAL BACKGROUND IN THE ANTARES OPTICAL BACKGROUND IN THE ANTARES SITESITE

OPTICAL BACKGROUND IN THE ANTARES OPTICAL BACKGROUND IN THE ANTARES SITESITEMuon:

2 ms crossing the detector.

Bioluminescence:

Continuous background ~ 30 kHz over 10” PMT and 0.3 p.e threshold. Sudden bursts ~ MHz.

40K Decay:

Continuous background ~ 30 kHz over 10” PMT and 0.3 p.e threshold.

Inte

rnati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes



WATER MODELS

Two water models available:

Medsea.

Partic.

Both models use Kopelevich’s parameterization of scattering length, but with different parameters, and the same parameterization of absorption length.

The two models differ also for the parameterization of scattering angle:

Medsea Two Henyey-Greenstein phase functions .

Partic Rayleigh scattering + water particle diffusions.

The number n of hits collected on the OM follow the The number n of hits collected on the OM follow the Poissonian statistics:Poissonian statistics:

The probability to get more than one hit in the same The probability to get more than one hit in the same flash is:flash is:

To avoid charge losses, consider only the region To avoid charge losses, consider only the region where this probability is negligible (i.e < 1 %):where this probability is negligible (i.e < 1 %):

!)(

n

enP

n

flashes

hits

N

N

eenP

eenP

PPnP

1)1(

!1!01)1(

)1()0(1)1(10

15.0

01.01

%1)1(

ee

nP

Inte

rnati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes


MAIN PARAMETERS IN DATA ANALYSISMAIN PARAMETERS IN DATA ANALYSISMAIN PARAMETERS IN DATA ANALYSISMAIN PARAMETERS IN DATA ANALYSIS

The number of signal hits at closest The number of signal hits at closest useful distance Ruseful distance Rminmin is is

This number decreases quickly as the This number decreases quickly as the distance R growsdistance R grows

Increase the number ofIncrease the number of flashes N flashes Nflashesflashes

Limited by the maximum DAQ rate of Limited by the maximum DAQ rate of 300 Hz300 Hz

L

RRMin

MinHitsHits

Min

eR

RRNRN

**)()(

2

1500015.0*10*)( 5 FMinHits NRN

50060240120 HitsNmLmRmRMin

Rmin FOR HIGH INTENSITY RUNS (Tmax = 1000 ns)

Rmin is not the sameRmin is not the same for high intensity RUNs. For for high intensity RUNs. For = 0.20, Rmin changes = 0.20, Rmin changes (1 floor aprox -> 15 m)(1 floor aprox -> 15 m)..

Rmin ~ 145 m

¡ VERY PRELIMINARY !

Rmax ~ 300 m

Inte

rnati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes


RESULTSRESULTSRESULTSRESULTS

Rmin ~ 130 m Rmax ~ 300 m

¡ VERY PRELIMINARY!

¡ VERY PRELIMINARY !

Inte

rnati

onal W

ork

shop o

n V

ery

Larg

e V

olu

me N

eutr

ino

Tele

scopes


RESULTSRESULTSRESULTSRESULTS

Wavelength (nm) 10 V 17 V 23 V Δλ

385 383 383 383 0

400 400 399 399 1

440 447 446 445 2

470 461 458 455 6

505 507 497 493 14

518 541 540 537 4

LED – 505 nm

Effect of the Voltage on the wavelength

LED – 385 nm

IFIC - Instituto de Física Corpuscular (CSIC - UV) VALENCIA, SPAIN

Documents

Transcript of IFIC - Instituto de Física Corpuscular (CSIC - UV) VALENCIA, SPAIN