1. Status report Detector team
Dirk Weißhaar
IKP Köln
Acceptance test of three symmetric AGATA-detectors
- energy resolution with standard analogue electronics
- cross-talk with digital coincidence electronics (XIA)
In-beam test: position resolution for Doppler correction
- analysis is ongoing

5. Questions:
Fold dependent shift of add-back energies
Negative and positive outliers (>0.5keV) of
add-back energies

6. Core signal is AC-coupled to segments via bulk capacity CsegX !
Split charge model HV
Split charge
Cseg1
Cseg2 Cc
Core
Seg1
Seg2 GΩ
Core signal is AC-coupled to segments via bulk capacity CsegX !
Segment I sees Qind=Qcore*CsegI/(Cc+ΣCsegX)

7. Standard Cc
of AGATA

8. For AGATA-detector bulk capacity of segments is ~1.3pF
→ 1.3pF/1246pF = 0.105% → shift 1.3MeV is ~1.4keV
Notice:
MINIBALL detector tested with Cc=5000pF should result in a shift of 0.15%.
But measurement showed a shift of 0.54% (Cc=1200pf →0.59%).

9. V1=Q1/Cf - Q2*C21/Cf2 Cross-talk, A. Pullia, Legnaro 2002 Cf C21
Seg1
Seg2 Cf
pre1
pre2
C21 Q2 Q1
V1=Q1/Cf - Q2*C21/Cf2
Cf=1pF → C21=1fF yields to
0.1% crosstalk
Eγ=E1+E2, a=C21/Cf, b=C12/Cf
Emeasured=Eγ – aEγ - (b-a) E1
shift
tilt
Always Emeasured ≤ Eγ

10. AGATA cold preamplifier
16mm

11. Crosstalk
E1 → E2

12. Measurement of the tilt by unfolding 2-fold spectra
in spectra Eγseg1> Eγseg2 and Eγseg2 >Eγseg1

13. Position of cold preamps for nearest neighbours event

16. Nevertheless: cross-talk <10-3
Conclusion for cross-talk
Split charge model solves
the fold dependent energy shift of the add-back spectra.
Preamplifier cross–talk yields a negative shift and a tilt
for the add-back energies.
No systematics has been found for the outliers in the add-back
spectra for the three detectors
(same cryostat, same cold and warm preamplifiers)
Model for positive outliers?
Nevertheless: cross-talk <10-3

18. ~ 15% of core peak intensity

21. The ‘bow’-effect only occurs in
nearest neighbour add-back of front segments
The ‘bow’-effect not occurs in any other 2-fold combination
(also between not neighbouring front segments !)