ciro bigongiari. schematic view 17/05/2011ciro bigongiari 2 photon path optical beacon optical...
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Ciro Bigongiari 3
History
Calibob was derived from KM3 code It was written in f90 language It was recoded in f77 transforming all
structures in common blocks (No need of f90 compiler)
On the assumption that the simulated light sources are nearly monochromatic all the dependencies on the wavelength were removed La, Ls, β(θ) and n didn’t depend on λ
Recently reintroduced the dependence on λ of La, Ls and n trying to improve the Data-MC agreement17/05/2011
Ciro Bigongiari 4
LED Spectrum
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From AVAGO CB30 Datasheet
Peak wavelength 470 nm
Sigma 15nm
Slightly asymmetric Values confirmed by measurements in Valencia labANTARES LED
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Code structure (I)
Three step package: GEN, HIT, CAL GEN
Simulates photon emission and photon propagation through sea water up to a maximum distance (350 m)
No absorption simulated at this stage Photon position, direction, transit time and
wavelength on 34 spherical shells (10 m step) centred on the light source are recorded
Some more histograms and ntuples saved for debugging purposes
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Code structure (II)
Three step package: GEN, HIT, CAL HIT
Simulates absorption by weighting photons Weight = exp(-PhotonPath/AbsorptionLength)
Simulates photon detection by an optical module at different position/direction w.r.t. to the optical beacon
Stores detection probability tables CAL
Reads in detector geometry Loops over OB flashes and optical modules Stores hits in ASCII format
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Optical Beacons
Light emission from point-like light sources Angular distribution of emitted photons
Uniform Cleaved LED Laser + Glass Rod
Time distribution of emitted photons Gaussian LED pulse
Wavelength distribution of emitted photons Gaussian LED spectrum
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Optical Modules
Photon detection by optical modules is simulated exactly in the same way as in KM3 Angular acceptance Glass transmission Gel transmission Photo-conversion efficiency
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9
Sea Water (I)
Absorption: Absorption is simulated by weighting
photons The absorption length is calculated
rescaling the Smith&Baker parameterization
17/05/2011Ciro Bigongiari
)ker(/)ker(* ReRe ffa SmithBaSmithBaLL
WARNING: in this way LA can be larger than SmithBaker(λ) which should be an upper limit (pure water).
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Sea Water (II)
Scattering: The scattering length is calculated rescaling
the Kopelevich parametrization with Vs = Vl = 0.1
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)(/)(* ReRe fsfs KopelevichKopelevichLL
3.07.13.4 )550
(**3120.0)550
(**3400.1)550
(*0017.0)(
nmV
nmV
nmKopelevich LS
The values of VS and VL presently used are different from the ones used in KM3 which are outside the allowed region (Mobley )
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Sea Water (III)
Refraction Index: The refraction index is a function of photon
wavelength and water temperature, pressure and salinity. We fixed
T = 13.1 ºC P = 220 bar S = 38.44 %0
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32 )1
(*)1
(*1
*)(
DCBAnPhase )(*1)()( '
Phase
PhaseGroup n
nn
A = 1.3201 B = 16.2561 C = -4382.0 D = 1.1455e6
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Sea Water (IV)
Volume Scattering Function: β = β(θ,λ) is a function of scattering angle and photon
wavelength The dependence on λ has not be considered so far
β = β(θ) Usually we use the so-called PARTIC model
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)(*)1()(*)( Petzoldw
WARNING: Petzold’s measurements were performed at 514 nm
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Summary & Outlook
Reintroduced absorption length, scattering length and refraction index dependence on wavelength
No big improvement found. To be investigated further
Dependence of volume scattering function still to be implemented.
Continue comparison with KM3
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Water Models
There are some recently developed water models with a reasonably low number of parameters. For example Kopelevich’s Haltrin’s Morel’s Zege – Katsev – Prikcach
Should we try a more recent water model ? Can they be used for very deep waters ?
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Smith&Baker ?
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…………………………In the visible part of the spectrum, recent studies from Sogandares and Fry (1997) and Pope and Fry (1997), based on different measuring techniques, provided very precise measurements of pure water absorption from 380 to 700 nm. The results obtained by these authors emphasized that Smith and Baker (1981) formulation strongly overestimated the actual aw(λ) in particularly below 490 nm. At 380 nm Pope and Fry (1997) values are about 2 times lower.Such differences between Smith and Baker (1981) and Pope and Fry (1997) formulations have been attributed to biases in the former measurements induced by organic impurities absorption and scattering effects. Moreover, Pope and Fry (1997) confirmed the existence of seventh and eighth harmonics of the OH stretch at 449 and 401 nm and the presence of the absorption minimum at 420 nm as previously observed by Sogandares and Fry (1997). The data by Pope and Fry (1997) are currently considered as the reference value and are widely used in bio-optical modeling and remote sensing applications in the visible………(Vantrepotte&Mélin2006).