12.07.2015 Views

Mohamad-Ziad Charif - Antares

Mohamad-Ziad Charif - Antares

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Figure 3.21: Diagram of how the HFLBL system works between two lines.method allows us to gain a precision of 5 cm on each hydrophone and eventuallyon the OMs of each floor. In addition to the HFLBL, the compass-tiltmeter systemfound on every floor is used to estimate the position the remaining stories and thisbe able to have a fit of each line and in the process getting the full geometry ofthe detector. The eventual precision on the position of the OMs in around 10 cm.This calibration is done every two minutes.Time CalibrationReconstruction of a muon track does not only depends on knowing precisely theposition of each OM, it also depends on knowing the time offset among the OMsas the timing is very critical.Time uncertainty comes from three sources.• The TTS (Transit Time Spread) which is equal to 1.3 ns.• Sea water effect on light propagation, and it is dependent on two effects.Light scattering and chromatic dispersion, the contribution of these two effectsis about 1.5 ns for photons traveling a distance of 40 m.• Time residual offset which is equal to 0.5 ns.The calibration is done by two different methods[92], onshore and in situ.53

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