Studies of correlated events in the CBM STS silicon microstrip sensors

V. Pugatch, J. Heuser, P. Larionov, M. Pugach, I. Sorokin, C. Sturm
Physically correlated signals in adjacent strips of a microstrip detector appear due to charge sharing. A significant fraction of tracks is reconstructed from two-and threestrip cluster events where analogue read-out improves the position resolution. Non-physically correlated signals originated by cross-talk, pick-up or common mode fluctuations may also occur in read-out channels. Measurements of charge sharing between adjacent strips of the CBM05 and CBM06 prototype silicon sensors designed
more » ... the CBM Silicon Tracking System were performed at KINR [1]. In a two-dimensional (E i x E i+1 ) energy distribution of physically correlated events loci from an alpha-particle source were clearly observed in adjacent strips i and (i+1) (Fig. 1 ). ADC units (strip i) 0 20 40 60 80 100 120 ADC units (strip i+1) 0 20 40 60 80 100 120 0 20 40 60 80 100 120 140 160 U = 147 V expTime = 11 min nEvents = 29339 Figure 1: Two-dimensional (E i x E i+1 ) energy distribution in adjacent strips i and (i+1) obtained with alpha-particles. Detailed studies revealed also non-physical correlated events populating loci from the very low amplitudes along the straight lines and reaching the positions of the alpha particle contribution. Among possible explanations we considered a cross-talk with the channels (i-1) and (i+2) located in close vicinity to the ones under the test. Correlated event studies were carried out recently with n-XYTER readout electronics at GSI. Examples of data obtained are shown in Fig. 2 . In the upper panel physically correlated events at the pside triggered by MIP β-particles from 90 Sr are observed along the expected line (most probable value) with a sum of amplitudes around 140 ADC counts. The simulated noise distribution is shown in the middle part of Fig. 2 . The events populating the loci alongside the straight lines originating from the (0.0 × 0.0) coordinate are apparently correlated non-physical events (see lower Fig. 2) . These signals simultaneously appearing at adjacent strips i and (i+1) *
doi:10.15120/gr-2015-1-mu-nqm-cbm-30 fatcat:kmrapr2wkzdxdgrddphuz3matm