First complete test measurements of the AGATA Core

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

CSPs for the first AGATA_Detector Core Tests Specs Sensitivity ( m. V / Me. V) Resolution (Cd= 0 p. F; cold FET) Slope ( + e. V/ p. F) [Cd] Rise time *) (Cd= 0 p. F); *[Amplit. ] Slope ( + ns/ p. F) [Cd] U(out) @ [100 Ohm] / Power [m. W] IKP-Cologne (a) (FET_BF 862) (b) (FET_IF 1320) (Miniball - FET_IF 1320) ~ 100 m. V/Me. V ( differential ) ~ 175 m. V/Me. V ( single ended ) ~ 600 e. V < 10 e. V / p. F (cold FET) < 10 e. V / p. F < 12 ns ( warm FET) (cold FET) ~ 15 ns ( cold FET) ~ 0. 25 ns ( ~ 23 ns / 45 p. F ) ~ 0. 25 ns ~ 0. 3 ns ( ~ 26. 5 ns / 45 p. F ) ( ~ 25 ns / 33 p. F ) ~ 2. 0 V*/ ~290 m. W ~ 2. 0 V*/~ 290 m. W ~ 4. 5 V*/~ 450 m. W (LM-6171; *AD-8057) (AD-8057; LMV-6723) ( + /- 12 V) (LM-6172) Saturation of equiv. ~ 90 Me. V equiv. ~100 Me. V the 1 st stage @ (@ ~20 m. W_ j. FET) (@ ~60 m. W_ j. FET) Open Loop Gain > 80, 000 ~ 20, 000

One-wire test pulse for all segments 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 From an idea available in literature

Pulser Resolution in Core ( < 1. 5 ke. V @ tr ~ 30 -35 ns ) Pulser • PTFE Coaxial Cable (0. 9 mm) * Pulser return ground signal 0 to 40 m. A Advantage Rectangular Exponential - - Signal & Pulser same P/Z adj. - good DC level at low count. rates Disadvantage - DC level Signal & Pulser different P/Z

Pulser block diagram Rectangular or Exponential form Attenuation 0 to 40 d. B

Triple Cryostat Wirering_Grounding Ro [GND 0 <-> GND 1] LN 2 - DEWAR - GND_0 Cold part - GND_1 Warm Part Al Al CB CD CS D 1 CB G N D 0 D 2 D 3 • Pulser @ GND_1 (!) • Core & Segments @GND_0 GND_1 CC CF CF RF RF CS CF RF VACUUM 1. 8Ω ~12 -15 cm Problems: GND_0 cold part ~12 -15 cm § twisted Core Signal_GND? - Segments return GND ? ! - GND one_both ends ? ! § thermal shunt limitations § pulser wirering, return GND CTT Feed through x 36 ~8 cm Micro. Match (20) x 36 GND_1 6 x TRIPLE SEGMENTS Micro. Match (18) ~8 cm GND_1 Micro. Match (18) ~8 cm MDR(26) (very important up to 40 m. A !) Micro. Match (20) CORE + PULSER 6 x TRIPLE SEGMENTS MDR(26) ~8 cm x 3 GND_1 PTFE MDR(26) ~8 cm GND_1 § Connector problems: - only Micro. Match(20)? - formerly also MDR-26? § we badly need a test Cryostat ! ( HP-Ge Detector thermal stress)

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 - Superposition of individual , time dependent, Core_Return_GND_Signals Strong crosstalk due to BLR effect if the R( GND_0 GND_1)

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

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

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

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

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, 50 107, 00 100, 50 115, 00 114, 60 119, 00 110, 00 113, 50 120, 00 97, 00 123, 00 104, 50 120, 50 109, 00 102, 00 109, 00 113, 30 105, 00 111, 00 102, 00 100, 00 103, 40 109, 00 113, 00 112, 00 111, 00 108, 00 114, 00 106, 00 111, 50 107, 50 117, 00 106, 00 87, 50 97, 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 !)

Recovery from core saturation versus SHDW command • Recovery time in < 2 us after INH. • Saturation @ ~ 100 Me. V (equivalent SHD_C OFF SHD_C ON gamma) Maximum “Dead Time” • SHD_C OFF ~ 45 µs • SHD_C ON ~ 12. 8 µs SHD_C ON

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

Core_Pulser Programmable Attenuation • Coarse Attenuation in four steps of 10 d. B (0; 10; 20; 30; 40 ) Attn 40 d. B Attn 20 d. B

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

“Saturated” Pulses Linear Amplitude-Time converter • “VIP“ signals (~ 30 – 100 Me. V) • 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

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

Core Rise Time versus I(D), C(v) Core Rise Time / I(Drain) Rise Time [ns] Core Rise Time / C(v) (*) I (Drain) [m. A] C(v) [p. F] (*) Pulser PB-4 (BNC) @ 50 ns rise time

Segment Ringing versus Core Bandwidth (a) tr ~ 32 ns tr ~ 46 ns Fast core rise time range • Core_Pulser constant tr ~30 ns • Core rise time range tr: 30 -60 ns tr ~ 38 ns tr ~ 60. 5 ns

Segment Ringing versus Core Bandwidth (b) Slow core rise time range • PB 4_Pulser (tr ~ 50 ns) • Core rise time tr: 60 -100 ns tr ~ 62 ns tr ~ 72 ns Tr~ 32 ns tr ~ 76. 5 ns tr ~ 98 ns

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)

Rise Time versus Amplitude • LM 6171 data sheets ( +/- 12 V ) • tr ~ 28 ns @ 50 m. V 24 ns @ 1000 m. V LM 6171 ( I quiescent ~ 3 m. A ) (terminated @ R=100 Ohm) Alternatives : • AD 8057 (Volt. Feedback) ( +/- 6 V only ) • AD 8057 < 1. 5 ns LMH 6723 (Current Feedback) ( +/- 6 V only ) < 1. 5 ns ( I quiescent ~ 6 m. A )

Intrinsic Pulser Resolution ( < 1 ke. V @ tr ~30 ns ) 122 ke. V 57 Co Pulser X- Pb 136 ke. V • Intrinsic Core_Pulser resolution measured at different segments < 900 e. V ! • Equivalent energy range in segments: ~ 10 ke. V- 3 Me. V !

Intrinsec Pulser Resolution 57 Co ( < 1 ke. V @ tr ~30 ns ) Pulser (Rectangular) (equiv. ~3. 3 Me. V) 60 Co • Highest Pulser Amplitude in segments ~ 3. 3 Me. V (equivalent gamma) ( in Core saturated @ ~100 Me. V respectively)

Pulser Resolution in Core ( < 1. 5 ke. V @ tr ~30 ns ) 122 ke. V Pulser (-) Intrinsic Core resolution in AGATA Triple Cryostat (01) X_Pb 1173 ke. V Pulser (-) 136 ke. V 1173 ke. V Pulser (+) 136 ke. V X_Pb • with NO Pulser 1. 3 ke. V • with Pulser ON 1. 5 ke. V 1332 ke. V Pulser (+) Pulser Mode • Pulser Exponential Pulseform (decay time 100µs) (+) normal (-) supressed 20: 1

Structure of Core Resolution in Coincidence with Segments Rings 1 2 3 4 5 6 . 285 ke. V . 166 ke. V . 353 ke. V . 535 ke. V . 543 ke. V . 495 ke. V 2. 37 2. 38 2. 27 2. 22 2. 24 2. 34 Peak Position (1332, . . . ) ke. V Resolution FWHM ( ke. V ) Nigel Warr, “AGATA core resolution with gate on segment

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 !

Conclusions • Test demonstrated that a pulser with a very good energy resolution (< 1 ke. V @ segments , < 1. 5 ke. V @ 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)

A. Pullia, AGATA week, Nov. 2005

A. Pullia, AGATA week, Nov. 2005

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

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

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