A few words on tracking A few words on tracking and background suppression and background suppression E.Farnea INFN Sezione di Padova
Efficiency behaviour ... Efficiency behaviour ... With an off-center source, the photopeak efficiency is higher than with a centered source! Simulated data: A180 configuration, β =0, 1 MeV photons, M γ =1, tracking performed with mgt
... And geometrical considerations - 1 ... And geometrical considerations - 1 θ z γ The efficiency increase can be explained by geometrical considerations, such as the larger solid angle covered by the detectors and their larger effective thickness
... And geometrical considerations - 2 ... And geometrical considerations - 2 The P/T ratio is pretty insensitive to the geometrical effects and seem to confirm that the efficiency variation are indeed due to the geometry rather than to the tracking algorithm
... And geometrical considerations - 3 ... And geometrical considerations - 3 The P/T ratio is pretty insensitive to the precision with which the source position is measured!!! Simulated data: A180 configuration, β =0, 1 MeV photons, M γ =1, tracking performed with mgt. Unknown source position: mgt assumes a centered source instead of the off-center one.
Tracking efficiency Tracking efficiency β =0 β =20% Centered source P/T=82.3% P/T=81.9% Tr. Eff. = 92.3% Tr. Eff. = 88.0% Off-center source P/T=82.8% P/T=82.7% (1m from centre) Tr. Eff. = 77.5% Tr. Eff. = 77.7% The tracking algorithm implemented in mgt is surprisingly insensitive to the knowledge of the source position!
Conclusions: Conclusions: 1. No background suppression based on the mgt tracking algorithm is possible 2. The other algorithms should be checked 3. Eventually, the algorithms should be optimized on the basis of background suppression rather than efficiency and P/T ratio
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