Transcript Слайд 1 - Demokritos

4-th International Workshop on Very Large Volume
Neutrino Telescopes for the Mediterranean Sea
LIGHT TRANSMISSION MEASUREMENTS WITH
LAMS in the MEDITERRENIAN SEA
Vladimir Zhukov
on behalf of the KM3NeT collaboration
VLVnT 09 – Vladimir Zhukov
Introduction
One of the important tasks of particle physics and astrophysics in
coming years is the detection of high energy cosmic neutrinos. In order
to build a deep under water Cherenkov neutrino telescope the
knowledge of the water optical characteristics is mandatory.
Monitoring of the water optical properties
Choice of the telescope site
Input parameters for
Monte Carlo and
reconstructions
VLVnT 09 – Vladimir Zhukov
Introduction
Optical parameters
In case of very clear Mediterranean water the optical base of the
instrument should be long enough (10 and more meters) in order to
minimize the errors of measurements. Since the KM3NeT is an open
geometry experiment we are using non-collimated light beam to
measure the
transmission length Lβ = 1/β,
β is the transmission coefficient.
The quantity Lβ can be derived by the relation
I(λ,R) = [I0(λ)/4πR2]exp[- R/Lβ(λ)] ,
where R is the path of light.
VLVnT 09 – Vladimir Zhukov
Introduction
Optical parameters
Measure intensity at two known distances RS and RL (indexes S and L
mean “short” and “long”) the transmission length Lß can be derived by
the ratio of intensities
IS / IL = (RL/ RS )2 exp [(RL – RS)/Lβ ]
In this case we don’t care for knowledge of I0 and internal optical
parameters of the instrument.
NESTOR collaboration has built a transmissometer with optical base of
changeable length LAMS = Long Arm Marine Spectrophotometer
Transparency of water have been investigated. Measurements have been
performed in Ionian Sea in site near Pylos (April and October 2008, and
May 2009) and in sites near Capo Passero (May 2009).
VLVnT 09 – Vladimir Zhukov
Construction of the LAMS
LAMS Mechanical Structure
10 m, 15 m, 17 m and 22 m
Light source
VITROVEX
glass sphere
VITROVEX
glass sphere
Ti- frame
Pressure
meter
•Long rigid Ti-frame
•Two VITROVEX glass spheres
with light source and photodetector inside
Photo
detector
VLVnT 09 – Vladimir Zhukov
Construction of the LAMS
Light Source
• LED matrix, 8 groups of LEDs,  8 Wavlengths
• Wavelength range 375nm – 520nm.
• Each LED group turned on sequentially for 10s.
• Between groups 2s off, and 14s off between rounds.
• Autonomous, controlled by microcontroller.
λm(nm)
Photo-detector
376 386 400 425 445 463 502 520
Number of LEDs
15
15
FWHM (nm)
13
14
7
4
4
7
8
15
14 17
18
27
31
32
• Two plane HAMAMATSU S6337-01 photodiodes,
large sensitive area of 324 mm2 .
•
•
•
•
DAQ has two different channels.
Photocurrent converted to voltage & digitized.
Data taking rate ~70 Hz.
Data stored on SD memory card
VLVnT 09 – Vladimir Zhukov
Construction of the LAMS
LAMS Lab test 1/R2-law
The relation between photodiode signal and distance from
light source to detector is obtained in the tests in air.
The attenuation of intensity due to geometrical spreading of
light beam follows the 1/R2 law perfectly.
VLVnT 09 – Vladimir Zhukov
LAMS deployments MAY 2009
NEMO
(Near Capo Passero)
NESTOR
(Near Pylos
In May 2009 the system was deployed in sites
• Site 1 near Capo Passero (36 11.019’N / 16 06.017’E), depth 3350 m
• Site 2 near Capo Passero (36 11.910’N / 15 45.922’E), depth 3600 m
• Site near Pylos 4.5D(36O 31.336’ N / 21O 25.635’ E), depth 4300 m
VLVnT 09 – Vladimir Zhukov
LAMS deployments
Measurements were taken continuously during
deployment with the system stationary at specific depths
and during motion.
The depth was determined by means of the wire length
and verified by pressure meter data.
The length of LAMS was changed on the deck of ship by
adding or removing additional parts of the frame.
R = 10 m, 15 m, 17 m and 22 m were used
VLVnT 09 – Vladimir Zhukov
Data analysis
• A mean value of the intensity is calculated for all
distances between the source and the photo-detector.
• A fit to the mean values with exponential relation
I(λ,R) = [I0(λ)/4πR2]exp[- R/Lβ(λ)]
provides the transmission length Lβ = 1/β,
β is the transmission coefficient.
R is the distance between light source and detector
VLVnT 09 – Vladimir Zhukov
Results
Measurements of the Pylos 4.5D and Capo Passero 1 Sites
Site near Pylos
(36o 31.336’ N / 21o 25.635’ E)
Site 1 near Capo Passero
(36 11.019’N / 16 06.017’E)
Data from May 2009
VLVnT 09 – Vladimir Zhukov
Results
Measurements of the Pylos 4.5D and Capo Passero 2 Sites
Site near Pylos
(36o 31.336’ N / 21o 25.635’ E)
Site 2 near Capo Passero
(36 11.910’N / 15 45.922’E )
Data from May 2009
VLVnT 09 – Vladimir Zhukov
Results
Transmission length at similar depths per Site
Depth (m)
3100, Capo Passero 1
3000, Capo Passero 2
3100
3000,
Pylos 4.5D
Site 1 near Capo Passero
(36 11.019’N, 16 06.017’E)
Depth: 3100m (seabed: 3350m)
Site 2 near Capo Passero
(36 11.910’N, 15 45.922’E)
Depth: 3000m (seabed: 3600m)
Site near Pylos
(36o 31.336’N, 21o 25.635’E)
Depth: 3000m (seabed: 4300m)
Data from May 2009
VLVnT 09 – Vladimir Zhukov
Results
Transmission length at deepest depth per Site
Depth (m)
3100, Capo Passero 1
3400, Capo Passero 2
4100, Pylos 4.5D
After all this depths
the telescope is located
Site 1 near Capo Passero
(36 11.019’N, 16 06.017’E)
Depth: 3100m (seabed: 3350m)
Site 2 near Capo Passero
(36 11.910’N, 15 45.922’E)
Depth: 3400m (seabed: 3600m)
Site near Pylos
(36o 31.336’N, 21o 25.635’E)
Depth: 4100m (seabed: 4300m)
Data from May 2009
VLVnT 09 – Vladimir Zhukov
Results
Transmission lengths from LAMS May 2009 deployments
Depth (m)
Wavelength (nm)
2000
2500
3000
3100
4100
Transmission length (m) at site Capo Passero 1
375.7
18.5
18.8
18.3
385.7
22.0
22.4
21.8
400.3
26.3
26.5
25.6
425.0
32.7
32.6
30.8
445.4
38.3
37.2
35.0
462.6
41.9
40.3
37.6
501.6
27.0
26.4
25.2
519.5
20.6
20.2
19.7
Wavelength (nm)
3400
Transmission length (m) at site Capo Passero 2
375.7
16.5
17.0
18.2
17.4
385.7
19.4
20.1
21.8
20.7
400.3
22.6
23.4
25.7
24.3
425.0
27.3
28.8
32.2
30.8
445.4
30.9
32.4
36.5
35.7
462.6
34.3
36.2
41.4
39.9
501.6
23.6
24.4
26.0
25.7
519.5
18.3
18.8
19.9
19.7
Wavelength (nm)
Transmission length (m) at site Pylos 4.5D
375.7
19.5
20.2
20.4
20.4
19.7
385.7
22.9
24.1
24.4
24.4
23.6
400.3
26.8
28.3
28.8
28.8
27.6
425.0
32.8
34.3
35.7
36.1
34.1
445.4
36.5
39.1
40.5
41.1
39.2
462.6
40.2
43.6
45.1
45.6
44.1
501.6
26.3
27.1
27.7
28.1
27.1
519.5
19.7
20.3
20.3
20.7
20.1
VLVnT 09 – Vladimir Zhukov
Results
Transmission length ratio (at 463 nm – near the maximum transparency)
Lβ Pylos 4,5D Lβ Capo Pas.1 = 1.20
4100 m
(Lβ Pylos 4.5D
4100 m
3100 m
Lβ Capo Pas.1 )3 = 1.73
3100 m
Lβ Pylos 4,5D Lβ Capo Pas.2 = 1.14
4100 m
(Lβ Pylos 4,5D
4100 m
3400 m
Lβ Capo Pas.2 )3 = 1.50
3400 m
λ (nm)
375
385
400
425
445
463
502
520
Lβ P4.5/Lβ CP1
1.11
1.12
1.13
1.16
1.16
1.20
1.10
1.09
Lβ P4.5/Lβ CP2
1.17
1.18
1.19
1.17
1.15
1.14
1.09
1.05
Therefore the volume observed by one OM in the Pylos 4,5D site is
larger than in the Capo Passero site. This allows one to use a smaller
number of OMs for a detector built at the Pylos 4.5D site than for the
same detector built in Capo Passero site for the same sensitive
volume, or in other words for the same number of optical modules one
can achieve a larger sensitive volume at the Pylos site than at the Capo
Passero site.
VLVnT 09 – Vladimir Zhukov
Results
Comparison with attenuation
NESTOR 1992[1]
LAMS 2009
Attenuation of
pure water [2]
Pylos 4.5 D Site
Wavelength (nm)
VLVnT 09 – Vladimir Zhukov
Summary
The water transparency in the visible region of spectrum in the
various depths in the Pylos 4.5D and Capo Passero sites has
been investigated with Long Arm Marine Spectrophotometer.
It is established that the optical properties of both sites do not
differ considerably, but for all wavelengths and on all depths
water in the Pylos 4.5D site is a bit more transparent. The
maximum excess is 1.2 times, and is observed for 463 nm at a
depth of 3400 m.
VLVnT 09 – Vladimir Zhukov
BACKUP SLIDES
Results
Extraction of parameters Lsct and Labs
с
b
 cos  
  c   cos  b
с ab
a  cb
λ, nm,
C, m-1
*)
β, m-1 <cosθ>
**)
b, m-1
Lsct , m
a, m-1
Labs , m
425
0.031
0.028
0.70
0.004
233
0.027
37
445
0.028
0.024
0.72
0.006
180
0.022
45
463
0.026
0.022
0.74
0.005
200
0.021
48
Smith & Baker 1981 (clearest sea water)
λ (nm)
420
440
460
b (m-1)
0.0061
0.0049
0.0041
*) S.A.Khanaev et al. 1992
**)M.Jonasz and G.Fournier Light Scattering by Particles in Water, Elsevier 2007
Ocean Optics. Physical Optics of Ocean. Nauka, Moscow 1983 (in Russian)
VLVnT 09 – Vladimir Zhukov
References
S.A.Khanaev et al. Measurements of water transparency
South-West of Greece. 2nd NESTOR INTERNATIONAL
WORKSHOP. OCTOBER 19-21, 1992 in PYLOS-GREECE
R. Smith and K. Baker. Optical properties of the clearest
natural waters (200 – 800 nm) Appl.Opt. V20, N2, 1981
G.Riccobene et al. Deep sea water inherent optical
properties in The Southern Ionian Sea. arXiv: astroph/0603701 v1 25 Mar 2006
Ocean Optics. Physical Optics of Ocean. Nauka, Moscow,
1983, pp. 225, 226, 234 (in Russian, A.S Monin editor.
M.Jonasz and G.Fournier Light Scattering by Particles in
Water, Elsiver 2007
VLVnT 09 – Vladimir Zhukov