1. RlRl A R fb C fb C ac +Bias A R fb C fb A R bf C fb v0v0 v1v1 v2v2 V 0,out V 1,out V 2,out A simple detector model to describe crosstalk in segmented detectors Bart Bruyneel, IKP Köln 2006 AGATA: C ac = 1000pF C fb = 1.2pF A (Core) = 80000 A (Seg) = 10000 (R l = R fb = 1G  )

2. Small signal equivalent scheme Z 00 i0i0 Z 22 i2i2 Z 11 i1i1 Z 02 Z 01 Z 12 v1v1 v2v2 v0v0 Seg–to –ground impedances Z ii Seg–to –Seg capacities: Z i,j = (sC ij ) -1 ; i≠j Currents to electrodes: Potentials at electrodes: Small crosstalk if: are small compared to

3. Segment-to-ground impedance Z ii and Core-to-gound impedance Z 00 Z 00 i0i0 Z 22 i2i2 Z 11 i1i1 Z 02 Z 01 Z 12 A R fb C fb vivi V i,out AC fb V 0,out R fb A A ViVi i Miller Equivalent Z ii ~ (sAC fb ) -1 AC fb V 0,out R fb A A V0V0 i0i0 C ac C ac ~ 1nF AC fb ~ 10nF Z 00 ~ (sC ac ) -1 Impedance In reality A R fb C fb V 0,out C ac v0v0 Segments Core

4. Summary RlRl +Bias v0v0 v1v1 v2v2 AC fb V 0,out R fb A A ViVi i AC fb V 0,out R fb A V0V0 i0i0 C ac A Core-to-SegSegment-to-Segment Segment-to-Core Since C ac << AC fb, Core-to-Segment crosstalk dominates

5. C 0-X4 = 1.19 pF C 0-X5 = 1.16 pF C 0-X6 = 0.98 pF C 0-X1 = 0.943 pF C 0-X2 = 0.666 pF C 0-X3 = 0.980 pF Agata measured capacities: Core and Segment crosstalk Core normalization Seg. normaliz. Observed shift in segments

6. Segment sum shifts in 2-folds vs. hit pattern Theory Segment 1 Segment 2 Experiment Segment 1 Segment 2 Column averages Seg 1 Relative shifts theory Exp. D3: problem “Ring 2” Ring to neighbor C ac 1000pF 800pF 600pF

7. Core shifts in singles (experimental) Relative shifts Segment Number

8. Most important crosstalk: from core to segment on the 0.16% level in reality, 0.10% explained by the model Segment to core crosstalk: ~ 0.03% level observed 10 times bigger than predicted Conclusion