1. First complete test measurements of the AGATA Core _ Pulser Assembly. AGATA Core Pulser, Segments Bulk Capacitances (First measurements of the Pulser Core / Segment Ratio) Real transfer function measurements of the AGATA Pulser_Core and Segments preamplifiers Core recovery from saturation ( with SHD_C ON / OFF ) Pulser dynamic range and intrinsic pulser energy resolution for core & segments Conclusion, hints to improve the characteristic. G. Pascovici on behalf of preamplifier & detector teams Cologne, March 16, 2006

2. CSPs for the first AGATA_Detector Core Tests Specs IKP-Cologne (a) (FET_BF862) IKP-Cologne (b) (FET_IF1320) IKP-Cologne (Miniball - FET_IF1320) Sensitivity ( mV / MeV ) ~ 100 mV/MeV ( differential ) ~ 100 mV/MeV ( differential ) ~ 175 mV/MeV ( single ended ) Resolution (Cd= 0pF; cold FET) ~ 600 eV Slope ( + eV/ pF) [Cd] < 10 eV / pF ( cold FET ) < 10 eV / pF ( cold FET ) < 10 eV / pF ( cold FET ) Rise time *) (Cd= 0pF); *[Amplit.] < 12 ns ( warm FET) ~ 15 ns ( cold FET) ~ 15 ns ( cold FET) Slope ( + ns/ pF) [Cd] ~ 0.25 ns ( ~ 23 ns / 45 pF ) ~ 0.25 ns ( ~ 26.5 ns / 45 pF ) ~ 0.3 ns ( ~ 25 ns / 33 pF ) U(out) @ [100 Ohm] / Power [mW] ~ 2.0V*/ ~ 290 mW (LM-6171; *AD-8057) ~ 2.0V*/~ 290 mW (AD-8057; LMV-6723) ~ 4.5V*/~ 450 mW ( + /- 12V) (LM - 6172) Saturation of the 1st stage @ equiv. ~ 90 MeV (@ ~20 mW_ jFET) equiv. ~100 MeV (@ ~60mW_ jFET) equiv. ~100 MeV (@ ~60mW_ jFET) Open Loop Gain> 80,000~ 20,000

3. One-wire test pulse for all segments From an idea available in literature A.Pullia, presented at AGATA week, GSI, Feb.2005 also: “Test of a new low-noise preamplifier with the MARS segmented detector and extraction of physical data from the noise measurements” presented at EDAQ meeting, Padova, Sept. 19-20, 2002

4. Advantage - Disadvantage Pulser Resolution in Core ( < 1.5 keV @ tr ~ 30-35 ns ) Rectangular Exponential - Signal & Pulser same P/Z adj. - DC level - good DC level at low count. rates Signal & Pulser different P/Z * Pulser return ground signal 0 to 40 mA

5. Pulser block diagram Rectangular or Exponential form Attenuation 0 to 40 dB

6. Pulser @ GND_1 (!) Core & Segments @GND_0 Problems:  twisted Core Signal_ GND ? - Segments return GND ?! - GND one_both ends ?!  thermal shunt limitations  pulser wirering, return GND (very important  up to 40 mA !)  Connector problems: - only MicroMatch(20)? - formerly also MDR-26?  we badly need a test Cryostat ! (  HP-Ge Detector thermal stress) - GND_0 Cold part - GND_1 Warm Part Triple Cryostat Wirering_Grounding D1D2D3 CBCB CBCB CSCS CFCF RFRF CFCF CFCF RFRF RFRF CDCD CSCS C VACUUM x36 x3x36 1.8 Ω cold part 6x TRIPLE CORE + PULSER 6x TRIPLE SEGMENTS Ro [GND0 GND1] Al GND_1 ~8cm GND0GND0 GND_0 GND_1 MDR(26) PTFE~8cm ~12-15cm MDR(26) GND_1 ~8cm MicroMatch (20) MicroMatch (18) MicroMatch (20) LN2 - DEWAR Al CTT Feed through

7. - Superposition of individual, time dependent, Core_Return_GND_Signals  Strong crosstalk due to BLR effect if the R( GND_0  GND_1) Cluster of three detector – and the related GND_ing problem Common Core_GND (cold_warm?) Individual GND_0 (cold) Resistance between GND_0  GND_1

8. Very Fast Pulser (TEK type PG-502; tr ~ 1ns) Pulser rise time t r ~ 1ns / 50 Ohm Core / Segment fastest transfer function Overshoots ~ 20-40 % (but adjusted on bench for NO overshoot !)

9. FAST PULSER ( t r ~ 10, 50 ns ) Pulser t r ~ 50 nsPulser t r ~ 10 ns t r segments ~ 25 ns @ ~15-20 pF t r core ~ 29 ns @ ~ 45 pF we have to understand the equivalent “transfer function” of the pulser signals for core and segments ! core segment core segment Both core and segments preamplifiers bench adjusted for fastest transfer function with no ringing for pulser signals with t r > 10 ns and/or for core_pulser t r > 65 ns

10. High Precision Slow Pulser Pulser PB-4 ( t r ~ 100; 250 ns) Pulser tr ~ 100 ns Pulser tr ~ 250 ns Triple with Det. & twisted core.Triple with Det. & twisted core No twisted core core segment

11. Uncorrected for individual Gain Gain corrected Pulser Core /Segments Ratio R ~ (40-75)

12. Distribution of the real Segment Preamplifiers Gain (cold + warm) Gain Gr (A) Gain Gr (B) Gain Gr (C) Gain Gr (D) Gain Gr (E) Gain Gr (F) 120,50107,00100,50115,00114,60119,00 110,00113,50120,0097,00123,00104,50 120,50109,00102,00109,00113,30105,00 111,00 102,00100,00103,40109,00 113,00112,00111,00108,00114,00106,00 111,50107,50117,00106,0087,5097,20 N.B. a) but with a distribution of the warm preamplifier gain of < +/- 2 % ! b) to reduce the influence of feedback capacitor a new design of cold part is mandatory ( … silica substrate could be a very good candidate but it’ll bring additional technological problems !)

13. Recovery from core saturation versus SHDW command Recovery time in < 2 us after INH. Saturation @ ~ 100MeV ( equivalent gamma) SHD_C OFF SHD_C ON Maximum “Dead Time” SHD_C OFF ~ 45 µs SHD_C ON ~ 12.8 µs

14. Amplitude to Time Converter Core “Saturated “ Pulses Active Reset _”Saturated “ Core - ‘Amplitude to Time Converter’ for saturated core pulses and - Non saturated Segment pulses

15. Core_Pulser Programmable Attenuation Coarse Attenuation in four steps of 10 dB (0; 10; 20; 30; 40 ) Attn 40 dB Attn 20 dB

16. Linear Amplitude to Time conversion of the “saturated” reset pulses “ VIP“ signals (~ 12 – 25 MeV) linearity < 2% resolution < 1%* * see also A.Pullia, F.Zocca

17. “Saturated” Pulses Linear Amplitude-Time converter “VIP“ signals (~ 30 – 100 MeV) linearity < 2% resolution < 1% F. Zocca, A new low-noise preamplifier for gamma ray sensors with smart device for large signal management. Laurea Degree Thesis, Univ. of Milan, 2004

18. Core baseline deterioration at very large signals versus pulser mode of operation: a) exponential ( decay time 100µs) –a (1) @ ~ 15 MeV; –a (2) @ ~90 MeV b) rectangular @ ~ 90 MeV a (2) a (1) b)

19. Core Rise Time versus I( D ), C( v ) C(v) [pF] Rise Time [ns] Core Rise Time / C(v) (*) Rise Time [ns] Core Rise Time / I(Drain) (*) Pulser PB-4 (BNC) @ 50ns rise time I (Drain) [mA]

20. Segment Ringing versus Core Bandwidth (a) Fast core rise time range Core_Pulser constant t r ~ 30 ns Core rise time range t r: 30-60 ns t r ~ 32 ns t r ~ 38 ns t r ~ 46 nst r ~ 60.5 ns

21. Segment Ringing versus Core Bandwidth (b) Slow core rise time range PB4_Pulser ( t r ~ 50 ns ) Core rise time t r: 60-100 ns t r ~ 62 ns t r ~ 76.5 ns Tr~ 32ns t r ~ 72 ns t r ~ 98 ns

22. Segment Overshoot versus Core Rise Time Unexpected dependence between core rise time (not only pulser rise time) and segments overshoot (to understand that see also cableling details on pag. 5–7 i.e. core return ground signal)

23. Rise Time versus Amplitude LM 6171 data sheets ( +/- 12V ) t r ~ 28 ns @ 50 mV 24 ns @ 1000 mV (terminated @ R=100 Ohm) Alternatives : AD8057 (Volt. Feedback) ( +/- 6V only ) < 1.5 ns LMH6723 (Current Feedback) ( +/- 6V only ) < 1.5 ns LM6171 AD8057 ( I quiescent ~ 3 mA ) ( I quiescent ~ 6 mA )

24. Intrinsic Pulser Resolution ( < 1keV @ t r ~30 ns ) 122 keV 136 keV Pulser X- Pb Intrinsic Core_Pulser resolution measured at different segments < 900 eV ! Equivalent energy range in segments: ~ 10 keV- 3 MeV ! 57 Co

25. Intrinsec Pulser Resolution ( < 1keV @ t r ~30 ns ) Co 60 57 Co Pulser (Rectangular) (equiv. ~3.3MeV) Highest Pulser Amplitude in segments ~ 3.3 MeV (equivalent gamma) ( in Core saturated @ ~100 MeV respectively)

26. Pulser Resolution in Core ( < 1.5 keV @ tr ~30 ns ) 1173 keV 1332keV Pulser (+) 122 keV 136 keV X_Pb Pulser Mode Pulser Exponential Pulseform (decay time 100µs) (+) normal (-) supressed 20:1 Pulser (-) X_Pb Pulser (-) 122 keV 136 keV 1173 keV Pulser (+) 1332keV Intrinsic Core resolution in AGATA Triple Cryostat (01) with NO Pulser 1.3 keV with Pulser ON 1.5 keV

27. Structure of Core Resolution in Coincidence with Segments Rings 1 23456 Peak Position (1332,...) keV.285 keV.166 keV.353 keV.535 keV.543 keV.495 keV Resolution FWHM ( keV ) 2.372.382.272.222.242.34 Nigel Warr, “AGATA core resolution with gate on segment

28. Cryostat Wirering_Cableling Segments: - two detectors self made “flat band” cable, one individual Cu(Be) wires - one GND_0 / detector, no twisted cable Core: - twisted cable for D and FB signals at GND_0 (in the case of only one detector), - if all three detectors at common GND then large crosstalk (due to the superposition of Return_GND(i) signals) - Core return GND on the segments cold motherboard! Pulser: - Pulser coaxial PTFE, 0.9 mm external diameter with individual GND_1 Warm Core_CSP: - common GND for Pulser & CSP > most probable has to be changed ?! - on board separation between A_GND and D_GND, but only one GND to the F_ADCs (as decided by Infrastructure Group, Feb. 2005) - differential outputs, with the same polarity as Segments, as well as the INH_C and SHD_C signals functionality identical to the INH_A(B) and SHD_A(B), respectively. Triple Cryostat Wirering: - has to be decided, as soon as possible !

29. Conclusions Test demonstrated that a pulser with a very good energy resolution (< 1keV @ segments, < 1.5keV @ core) with a rather good very long time stability and fast rise time (< 35 ns) can be obtained, Further developments of core_pulser assembly is mandatory (to reduce the core CSP noise with pulser, to optimize pulser rise time if “in situ” transfer function measurements are foreseen), Solution to improve the wirering in the triple cryostat have been presented by A.Pullia at the AGATA week, Strasbourg, Nov. 2005 (next two slides), (milestones for the above mentioned tasks has to be decided)

30. A.Pullia, AGATA week, Nov. 2005

32. Position of cold preamps for nearest neighbours event D. Weisshaar et al. AGATA Week, GSI, Feb. 2005

33. Crosstalk Core versus Segment Open Loop Gain B. Bruyneel – PhD Thesis, IKP-Cologne, 2006

34. Crosstalk Segments versus Core_Open Loop Gain B. Bruyneel – PhD Thesis, IKP-Cologne, 2006