ific - instituto de física corpuscular (csic - uv) valencia, spain
DESCRIPTION
WATER ABSORPTION LENGTH MEASUREMENT WITH THE ANTARES OPTICAL BEACON SYSTEM. HAROLD YEPES. IFIC - Instituto de Física Corpuscular (CSIC - UV) VALENCIA, SPAIN On behalf of the ANTARES collaboration. International Workshop on Very Large Volume Neutrino Telescopes. - PowerPoint PPT PresentationTRANSCRIPT
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
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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
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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
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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
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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).
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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
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~60 m
100 m
14.5 m
Link cables
2500 m depth
Junction box
45°
Storey
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THE ANTARES OPTICAL BEACON SYSTEMTHE ANTARES OPTICAL BEACON SYSTEMTHE ANTARES OPTICAL BEACON SYSTEMTHE ANTARES OPTICAL BEACON SYSTEMIn
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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
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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
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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
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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
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EXPERIMENTAL PROCEDUREEXPERIMENTAL PROCEDUREEXPERIMENTAL PROCEDUREEXPERIMENTAL PROCEDURE
L
R
eR
AII
20 4L
Rpe
pe eR
20
9
Rmax
Rmin
¡ PRELIMINARY!
TIME DISTRIBUTION FOR SELECTED HITSTIME DISTRIBUTION FOR SELECTED HITSTIME DISTRIBUTION FOR SELECTED HITSTIME DISTRIBUTION FOR SELECTED HITS
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EXPERIMENTAL PROCEDUREEXPERIMENTAL PROCEDUREEXPERIMENTAL PROCEDUREEXPERIMENTAL PROCEDURE
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
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EXPERIMENTAL PROCEDUREEXPERIMENTAL PROCEDUREEXPERIMENTAL PROCEDUREEXPERIMENTAL PROCEDURE
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
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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.
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EXPERIMENTAL PROCEDUREEXPERIMENTAL PROCEDUREEXPERIMENTAL PROCEDUREEXPERIMENTAL PROCEDURE
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
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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:
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EXPERIMENTAL PROCEDUREEXPERIMENTAL PROCEDUREEXPERIMENTAL PROCEDUREEXPERIMENTAL PROCEDURE
PMT RELATIVE EFFICIENCY CORRECTIONPMT RELATIVE EFFICIENCY CORRECTIONPMT RELATIVE EFFICIENCY CORRECTIONPMT RELATIVE EFFICIENCY CORRECTION
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noise
signalsignal Q
CORRECTED BY EFFICIENCY
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EXPERIMENTAL PROCEDUREEXPERIMENTAL PROCEDUREEXPERIMENTAL PROCEDUREEXPERIMENTAL PROCEDURE
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
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PROPAGATION OF PHOTONS IN DEEP SEA PROPAGATION OF PHOTONS IN DEEP SEA WATERWATER
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
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Scattering phase
function ()
Isotropic source
Scattering angle Scattering angle
distributiondistributionMolecular scattering (Rayleigh) Isotropic
Particle scattering (Mie)
Strong forward peaked
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PROPAGATION OF PHOTONS IN DEEP SEA PROPAGATION OF PHOTONS IN DEEP SEA WATERWATER
PROPAGATION OF PHOTONS IN DEEP SEA PROPAGATION OF PHOTONS IN DEEP SEA WATERWATER
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
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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
20
17
L Convolution of optical properties.
MC Tools to clarify what parameter is.
MC TOOLS SIMULATION
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MC SIMULATIONSMC SIMULATIONSMC SIMULATIONSMC SIMULATIONS
• 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
20
abs = 60 m
abs = 60 m
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MC SIMULATIONSMC SIMULATIONSMC SIMULATIONSMC SIMULATIONS
• 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
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abs = 60 m
att
sca
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PRELIMINARY RESULTSPRELIMINARY RESULTSPRELIMINARY RESULTSPRELIMINARY RESULTS
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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.
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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
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PRELIMINARY RESULTSPRELIMINARY RESULTSPRELIMINARY RESULTSPRELIMINARY RESULTS
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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]
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PRELIMINARY RESULTSPRELIMINARY RESULTSPRELIMINARY RESULTSPRELIMINARY RESULTS
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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.
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BACKUP SLIDESBACKUP SLIDESBACKUP SLIDESBACKUP SLIDES
Bioluminescence Median rate from 03/06 – until 05/08
F2
F9
F15
F21
LINE
γ
40K
40Ca
e- ( decay)
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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.
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MC SIMULATIONSMC SIMULATIONSMC SIMULATIONSMC SIMULATIONS
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
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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
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RESULTSRESULTSRESULTSRESULTS
Rmin ~ 130 m Rmax ~ 300 m
¡ VERY PRELIMINARY!
¡ VERY PRELIMINARY !
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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