First complete test measurements of the AGATA Core _ Pulser Assembly

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 600 eV 600 eV
Slope ( eV/ pF) Cd lt 10 eV / pF (cold FET) lt 10 eV / pF (cold FET) lt 10 eV / pF (cold FET)
Rise time ) (Cd 0pF) Amplit. lt 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) _at_ 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 _at_ equiv. 90 MeV (_at_ 20 mW_ jFET) equiv. 100 MeV (_at_ 60mW_ jFET) equiv. 100 MeV (_at_ 60mW_ jFET)
Open Loop Gain gt 80,000 20,000 20,000
3
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
4
Pulser Resolution in Core ( lt 1.5 keV _at_ tr
30-35 ns )
Advantage - Disadvantage

Pulser return ground signal 0 to 40 mA

Rectangular
- Signal Pulser same P/Z adj.
- DC level
Exponential

• good DC level
• at low count. rates

Signal Pulser different P/Z


5
Pulser block diagram
Rectangular or Exponential form
Attenuation 0 to 40 dB
6
Triple Cryostat Wirering_Grounding

- GND_0 Cold part - GND_1 Warm Part
Ro GND0 lt-gt GND1
LN2 - DEWAR
Al
Al
D1
D2
D3
CB
CB
GND0

• Pulser _at_ GND_1 (!)
• Core Segments _at_GND_0

GND_1
CD
CC
CS
CF
CF
CF
CS
RF
RF
RF
VACUUM

• 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
1.8?
12-15cm
12-15cm
CTT Feed through
x36
x3
x36
8cm
8cm
MicroMatch (20)
MicroMatch (20)
MicroMatch (20)
GND_1
6x TRIPLE
CORE PULSER
6x TRIPLE
SEGMENTS
SEGMENTS
MicroMatch (18)
MicroMatch (18)
MicroMatch (18)
PTFE
8cm
8cm
8cm
GND_1
MDR(26)
MDR(26)
MDR(26)
GND_1
GND_1
7

• 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)

8
Very Fast Pulser (TEK type PG-502 tr 1ns)

• Pulser rise time
• tr 1ns / 50 Ohm

• Core / Segment fastest
• transfer function
• Overshoots 20-40
• (but adjusted on bench
• for NO overshoot !)

9
FAST PULSER ( tr 10, 50 ns )
core
core
segment
segment
Pulser tr 50 ns
Pulser tr 10 ns

• tr segments 25 ns _at_ 15-20 pF
• tr core 29 ns _at_ 45 pF
• we have to understand the equivalent
• transfer function of the pulser signals
• for core and segments !

• Both core and segments preamplifiers
• bench adjusted for fastest transfer
• function with no ringing for pulser signals
• with tr gt 10 ns and/or for core_pulser
• tr gt 65 ns

10
High Precision Slow Pulser Pulser PB-4 ( tr
100 250 ns)
Triple with Det. twisted core.
Triple with Det. twisted core
core
core
segment
segment
Pulser tr 100 ns
Pulser tr 100 ns
Pulser tr 250 ns
No twisted core
No twisted core
core
core
segment
segment
Pulser tr 100 ns
Pulser tr 250 ns
Pulser tr 100 ns
11
Pulser Core /Segments Ratio
Uncorrected for individual Gain
R (40-75)
Gain corrected
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)
120,50 107,00 100,50 115,00 114,60 119,00
110,00 113,50 120,00 97,00 123,00 104,50
120,50 109,00 102,00 109,00 113,30 105,00
111,00 111,00 102,00 100,00 103,40 109,00
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 lt /- 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 itll bring additional
technological problems !)
13
Recovery from core saturation versus SHDW command

• Recovery time in
• lt 2 us after INH.
• Saturation _at_
• 100MeV (equivalent
• gamma)

SHD_C OFF
SHD_C ON

• Maximum Dead Time
• SHD_C OFF 45 µs
• SHD_C ON 12.8 µs

SHD_C ON
SHD_C ON
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 lt 2
• resolution lt 1

see also A.Pullia, F.Zocca
17
Saturated Pulses Linear Amplitude-Time
converter

• VIP signals
• ( 30 100 MeV)
• linearity lt 2
• resolution lt 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
a(2)
a(1)

• Core baseline deterioration at very large
  signals
• versus pulser mode of operation
• a) exponential ( decay time 100µs)
• a(1) _at_ 15 MeV
• a(2) _at_ 90 MeV
• b) rectangular _at_ 90 MeV

b)
19
Core Rise Time versus I(D), C(v)
Core Rise Time / I(Drain)
Core Rise Time / C(v) ()
Rise Time ns
Rise Time ns
C(v) pF
I (Drain) mA
() Pulser PB-4 (BNC) _at_ 50ns rise time
20
Segment Ringing versus Core Bandwidth (a)

• Fast core rise time range
• Core_Pulser constant tr 30ns
• Core rise time range tr 30-60 ns

tr 32 ns
tr 38 ns
tr 46 ns
tr 60.5 ns
21
Segment Ringing versus Core Bandwidth (b)

• Slow core rise time range
• PB4_Pulser (tr 50 ns)
• Core rise time tr 60-100 ns

tr 62 ns
tr 72 ns
Tr 32ns
tr 98 ns
tr 76.5 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. 57
• i.e. core return ground signal)

23
Rise Time versus Amplitude

• LM 6171 data sheets
• ( /- 12V )
• tr 28 ns _at_ 50 mV
• 24 ns _at_ 1000 mV
• (terminated _at_ R100 Ohm)
• Alternatives
• AD8057 (Volt. Feedback)
• ( /- 6V only ) lt 1.5 ns
• LMH6723 (Current Feedback)
• ( /- 6V only ) lt 1.5 ns

LM6171
( I quiescent 3 mA )
AD8057
( I quiescent 6 mA )
24
Intrinsic Pulser Resolution ( lt 1keV _at_ tr 30
ns )
122 keV
57
Co
Pulser

• Intrinsic Core_Pulser
• resolution measured
• at different segments
• lt 900 eV !
• Equivalent energy range
• in segments
• 10 keV- 3 MeV !

136 keV
X- Pb
25
Intrinsec Pulser Resolution ( lt 1keV _at_ tr
30 ns )
57
Co
Pulser (Rectangular) (equiv. 3.3MeV)

• Highest Pulser
• Amplitude in segments
• 3.3 MeV (equivalent
• gamma)
• ( in Core saturated _at_
• 100 MeV respectively)

60
Co
26
Pulser Resolution in Core ( lt 1.5 keV _at_ tr
30 ns )

• Intrinsic Core resolution in
• AGATA Triple Cryostat (01)
• with NO Pulser 1.3 keV
• with Pulser ON 1.5 keV

122 keV
1173 keV
1173 keV
1332keV
Pulser ()
Pulser (-)
1332keV
Pulser ()

• Pulser Mode
• Pulser Exponential
• Pulseform
• (decay time 100µs)
• () normal
• (-) supressed 201

136 keV
X_Pb
27
Structure of Core Resolutionin Coincidence with
Segments Rings
1 2 3 4 5 6
Peak Position (1332,...) keV .285 keV .166 keV .353 keV .535 keV .543 keV .495 keV
Resolution FWHM ( keV ) 2.37 2.38 2.27 2.22 2.24 2.34
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 gt 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

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Conclusions

• Test demonstrated that a pulser with a very good
  energy resolution (lt 1keV _at_ segments , lt 1.5keV _at_
• core) with a rather good very long time
  stability and fast rise time (lt 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
31
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