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Dynamic Range


The dynamic range of the SVT electronics is defined by the ratio of the integrated maximum ionizing to the integrated minimum ionizing signal. The maximum ionizing signal the SVT is interested in is a 100 MeV/c proton, which deposits around 30 times the minimum ionizing signal. The integrated minimum ionizing signal is about 24,000 electrons in 300 m of Silicon. This signal will spread out almost immediately after deposition (in the first 100 ns) due to Coulomb repulsion, though. The repulsion strength depends on the the size of the electron cloud and increases successively for higher ionizations. Coulomb repulsion at 30 times minimum ionizing spreads the cloud integrated for a single anode by a factor 2 which leads to a maximum signal on a single anode of at most 360,000 electrons. So the signal swing in the preamp has to accommodate a dynamic range of 15:1, if defined by maximum signal in electrons on one anode. If we assume that the 360,000 electrons form a Gaussian shaped signal, the maximum signal in one anode corresponds to 1500 mV. A -function minimum ionizing signal would deposit 160 mV. Thus, the dynamic range defined as maximum signal to minimum signal is 1500/160 = 10:1. If we compare the maximum signal to the noise level at the output we have to divide 1500 mV by (350 electrons160 mV/24,000 electrons) which yields a dynamic range of 600:1. Both numbers are listed in the PASA requirements.


The device has to accommodate the signal levels for maximum and minimum ionizing particles.

Claude Andre Pruneau
Thu Oct 12 17:29:54 EDT 1995