Advanced FEE solutions for large arrays
of semiconductor detectors
Signal formation for energy, time and position
measurements
o Segmented detectors; - advanced FEE for Ge Detectors
o Briefly, some specific issues and cases:
o
◦ MINIBALL & AGATA (& GRETINA)  FEE for gamma rays
(CERN-Isolde & EU Tracking Array -LNL; GSI; Ganil)
◦ LYCCA & TASISpec

FEE for particles
(GSI -Calorimeter & Superheavy Element Spectroscopy)
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
a) Signal formation for energy, time and position
measurements,
(we’ll limit our attention to capacitive & segmented detectors)
b) Related issues in segmented detectors
c)
- dynamic range
- high counting rates
- induced signals & crosstalk - pros vs. conts
AGATA & MINIBALL – advanced FEE solutions
- Dual Gain CSP - for the central contact
- ToT method ( - combined dynamic range  ~100 dB, up to 170 MeV)
- Transfer function, Induced signals, Crosstalk
- Applications: - Impurities concentration measurement;
- Cosmic ray direct measurement up to 170MeV equiv. gamma
d) LYCCA
&
TASISpec - FEE for DSSSD
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
2
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
A typical structure of a segmented,
tapered and encapsulated, HP-Ge Detector
Parameter
Ge
Dielectric
16
Electronhole pair E
2.96
[eV]
Mobility
e / hole(+)
3,900 /
1,900
@ o 300 K
e / hole(+)
[cm2 /V.s]
Vd=μE
40,000 /
50,000
@ o80 K
[- HV] (GND)
+ HV
(~ kV/cm)
Rp
Ci
(-)
Central contact
(- e  ~ mm)
(Core)
(+)
•
•
•
•
•
- Qi
Standard n-type
Intrinsic HP-Ge (P-I-N)
Closed end
Coaxial structure
Io ~ < 100 [pA]
Exterior contacts
(N Segments)
N = 6; 12; 18; 28; 36
• Cdet ~ 30 - 45 pF
• Collection time ~ 30 - 1000 ns
[HP-Ge + CSP] +
Analog
Fast pipeline ADC [DGF]
Nuclear Electronics
Spectroscopic Chain is used
in order to extract the:
FEE
FFEFEE
E, t, position (r, azimuth)
Fast Pipe line ADC [DGF]
Analog E+T Filter Amplifier Chain
Collected charge pulses (+ & -)
Qd
- delta
UCSP – exponential
t
Pile-up of pulses
t
UFA ~ Gaussian
Digital
Filters
(Fast, Slow)
Baseline restorer
t
[HP-Ge + CSP] +
Digital
Fast pipeline ADC + PSA
Nuclear Electronics
Spectroscopic Chain is used
in order to extract the:
FEE
E, t, position (r, azimuth)
Fast pipeline ADC & [DGF]
Digital Filters [for Trigger, Timing, Energy, Position]
Collected charge pulses (+ & -)
Qd
- delta
UCSP – exponential
t
Pile-up of pulses
t
UFA ~ Gaussian
Digital
Filters
(Fast, Slow)
Baseline restorer
t
Detector Signal Collection
• a gamma ray crossing the Ge
detector generates electron-hole pairs
• charges are collected on electrode
plates (as a capacitor) building up
+
Rp
-
Z(ω)
a voltage or a current pulse
Final objectives:
Electronic Circuit
Detector
• amplitude measurement
(E)
• time measurement
(t)
• position
Which kind of electronic circuit ; Z(ω) ?
(radius, azimuth)
+
-
Rp
Detector
Z(ω)
Electronic Circuit
if Z(ω) is high,
• charge is kept on capacitor nodes
and a voltage builds up (until
capacitor is discharged)
• Advantages:
• excellent energy resolution
• friendly pulse shape analysis  position
• Disadvantages:
• channel-to-channel crosstalk
• pile up above 40 k c.p.s.
• larger sensitivity to EMI
Detector
Signal
Collection
if Z(ω) is low,
• charge flows as a current through the
impedance in a short time.
• Advantages:
•
•
•
•
limited signal pile up (easy BLR)
limited channel-to-channel crosstalk
low sensitivity to EMI
good time and position resolution
• Disadvantages:
• signal/noise ratio to low  worse resolution
Charge Sensitive Preamplifier
Active Integrator (Charge Sensitive Preamplifier -CSP)
• Input impedance very high ( i.e. ~ no signal current flows into amplifier),
• Cf /Rf feedback capacitor /resistor between output and input,
• very large equivalent input dynamic capacitance,
• sensitivity or ~ (conversion factor) A(q) ~ - Qi / Cf
• large open loop gain Ao ~ 10,000 - 150,000
• clean transfer function (no over-shoots, no under-shoots, no ringing)
(Rf.Cf ~ 1ms)
tr ~ 30-1000ns)
- Qi
Step function
Rf
Invert ing
-
“GND”
GND
Non- Inv.
+
Ao
jFET
Charge Sensitive Stage
(it is a converter not an amplifier)
Ci ~ “dynamic” input capacitance
o
Ci ~ 10 - 20,000 pF
( up to 100,000)
Pole - Zero cancellation technique
Rf . Cf ~ 1 ms
Cf ~ 1pF (0.5pF-1.5pF), Rf ~ 1GOhm
without
Rpz
Rpz~ 20 k Ohm
Cd~ 47 nF, Rd~1.1 kOhm
Rd . Cd ~ 50 µs
simple differentiation
Baseline shifts
with
Rpz
if (Rf Cf ) = (Rpz .Cd) and
Rd Cd ~ 50 µs
differentiation with P/Z adj.
 no baseline shifts
Baseline restored
Pole - Zero cancellation technique
Rf . Cf ~ 1 ms
Cf ~ 1pF (0.5pF-1.5pF), Rf ~ 1GOhm
without
Rpz
Rpz~ 20 k Ohm
Cd~ 47 nF, Rd~1.1 kOhm
Rd . Cd ~ 50 µs
simple differentiation
Baseline shifts
with
Rpz
if (Rf Cf ) = (Rpz .Cd) and
Rd Cd ~ 50 µs
differentiation with P/Z adj.
 no baseline shifts
Baseline restored
Pole - Zero cancellation technique
Rf . Cf ~ 1 ms
Cf ~ 1pF (0.5pF-1.5pF), Rf ~ 1GOhm
CSP
without
R pz ~ 21 k Ohm
Rpz
Rd . Cd ~ 50 µs
simple differentiation
Baseline shifts
Cd ~ 47 nF, Rd ~1.1 kOhm
with
Rpz
if (Rf Cf ) = (Rpz .Cd) and
Rd Cd ~ 50 µs - clean
differentiation with P/Z adj.
 no baseline shifts
Baseline restored
This is only the ‘hard core’ of the CSP stage
(Charge Sensitive Preamplifier) but the FEE
must provide additional features:


a P/Z cancellation (moderate and high counting rate)
a local drive stage (to be able to drive even an unfriendly

detector wiring !)
(opt.) an additional amplifier (but with Gmax.~ 5)
(N.B. a “free advice”: … never install an additional gain
in front of the ADC ! -namely, after the transmission cable !)

a cable driver (either single ended –coax. cable or
differential output - twisted pair cable)
Any free advice is very suspicious ( anonymous quote )
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
Block diagram of a standard CSP
(discrete components and integrated solution…
- what they have in common )
(alternatives)
(alternatives)
(+)
Optionally with
cold jFET
Cold part
(cryostat)
(-)
Warm part
(outside cryostat)
(alternatives)
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
Block diagram of a standard CSP
(discrete components and integrated solution…
- what they have in common )
(alternatives)
(alternatives)
(+)
Optionally with
cold jFET
Cold part
•(cryostat)
tr  25 ns
(-)
( 1 - 200 ) ns
• tf  50 μs ( 10 - 100 ) μs
• CSP- ‘gain’  50 mV / MeV (Ge)
(10-500 mV / MeV)
Warm part
(outside cryostat)
(alternatives)
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
tr ~ 30-40 ns Ch.1 @ 800 mV
- no over & under_shoot
IF1320 (IF1331)
(5V; 10mA)&
1pF; 1 GΩ
also
GRETINA
Eurysis
warm
•
•
Warm & cold jFET
DGF-4C(Rev.C)
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
15
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
AGATA
τopt~ 3-6 µs
J.-F. Loude, Energy Resolution in Nuclear
Spectroscopy, PHE 2000-22, Univ. of Lausanne
• the equivalent noise
charges Qn assumes
a minimum when the
current and voltage
contributions are equal
• current noise ~ (RC)
• voltage noise ~ 1/(RC)
~ Cd 2
• 1 / f noise ~ Cd 2
Dynamic range issue
(DC - coupled)
Factors contributing to saturation:
- Conversion factor – ( step amplitude / energy unit [mV/MeV] );
- Counting rate [c. p. s.] and fall time;
- The allowed Rail-to-Rail area [LV-PS]  {(+Vc - Vc ) – 2xΔf -2δFilt.}
+Vc
(+ Rail )
Saturation (+Vc)
DC – unipolar (-)
δFilter
A(q) ~ - Qi / Cf
Δf+
( forbidden
region )
DC - bipolar
Linear
range
DC coupled channel
Δf-Vc
(- Rail)
Saturation (-Vc)
δFilter
DC – unipolar (+)
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
Dynamic range issue
(AC - coupled)
Factors contributing to saturation:
- Conversion factor – ( step amplitude / energy unit [mV/MeV] );
- Counting rate [c. p. s.] and fall time;
- The allowed Rail-to-Rail area [LV-PS]  {(+Vc - Vc ) – 2xΔf -2δFilt.}
+Vc
(+ Rail )
Saturation (+Vc)
δFilt
Δf+
( forbidden
region )
AC -Unipolar
(negative)
Linear
range
AC -Unipolar
(positive)
BL shift
Δf-Vc
(- Rail)
A(q) ~ - Qi / Cf
AC coupled channel
Saturation (-Vc)
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
What to do to avoid saturation? Conts (“price”)
• to reduce the “gain”

Resolution ( Cf larger )
• to fix the base line asymmetric if DC coupled (expand: F ~ 2),
but for AC ? (expand only: F ~ 1.5)!
• to reduce the fall time  Resolution ( Rf smaller )
(OK only for high counting rate limitation)
• to reduce the fall time, how ?
• passively (smaller tf)  Resolution ( Rf smaller )
• linear active fast reset
• in the 2. stage
 ToT 2.nd stage ( <10 -3)
(GP et al, AGATA- FEE solution)
• in the first stage 
ToT 1.st stage ( <10 -3 ??)
(not yet tested for high spectroscopy)
(G. De Geronimo et al, FEE for imaging detectors solution
A. Pullia, F. Zocca, Proposal for HP-Ge detectors)
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
Potential solutions for active reset
@ 1st
stage
a) & b)
 for sequential reset
c) through g)  for continuous reset
G. De Geronimo, P. O’Connor, V. Radeka, B.Yu; FEE for imaging detectors, BNL-67700
a)
b)
Custom designed vs. Commercial FEE ?
Discrete components vs. ASIC FEE ?
(Application Specific Integrated Circuits)
- Pros vs. Cons (price, performance, size, quantity, price/performance
ratio, R&D and production time, maintenance
manpower … but generally, it is more a
project management problem ! )
- personally, I am trying to avoid generalization !
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
GDC ~ 30,000
Zo ~ 66 Ohm
- the dominant pole
compensation technique
NINO, an ultra-fast, low-power,
front-end amplifier discriminator
for the Time-Of-Flight detector
in ALICE experiment
F. Anghinolfi et al, ALICE Collab.
ANALOGUE CIRCUITS TECHNIQUES, April , 2002; F. ANGHINOLFI ; CERN
“ A Large Ion Collider Experiment, ALICE-TPC -TDR”, ISBN 92-9083-153-3, (1999), CERN
1. Charge Sensitive Preamplifier
( Low Noise, Fast, Single & Dual Gain
~ 100 dB extended range with ToT )
2. Programmable Spectroscopic Pulser
(as a tool for self-calibrating)
3. Updated frequency compensations
to reduce the crosstalk between
participants (-from adverse cryostat wiring
and up to - electronic crosstalk in the trans. line)
C. Chaplin, Modern Times (1936)
crosstalk between participants
 transfer function issue
GSI-2012
8 Clusters (Hole 11.5cm, beam line 11cm)
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
24
Best performance: Majorana dedicated FEE
(PTFE~0.4mm; Cu~0.2mm;C~0.6pF; R ~2GΩ Amorphous Ge
(Mini Systems) ~ 55 eV (FWHM) @ ~ 50 µs (FWHM)
BAT17
diode
(GERDA)
BF862
(2V; 10mA)
1pF; 1 GΩ
Test Pulser ?
-yes-not & how ?
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
25
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
Dual Gain Core Structure
Ch1 (fast reset)-Pulser @ ~19 MeV
Ch2 (linear mode)
Ch 1 ~200 mV / MeV
Pole /Zero Adj.
Fast Reset
(Ch1)
Segments (linear mode)
36_fold segmented
HP-Ge detector + cold jFET
Ch1 ( tr ~ 25.5 ns)
Common
Charge
Sensitive
Loop
+
Pulser
+
Wiring
Differential
Buffer
(Ch1)
C-Ch1
/C-Ch1
INH1
SDHN1
Ch 2 ~ 50mV / MeV
Pole /Zero Adj.
Fast Reset
(Ch2)
Programmable
Spectroscopic
Pulser
Differential
Buffer
(Ch2)
C-Ch2
/C-Ch2
INH2
SDHN2
one
MDR
10m
cable
Pulser CNTRL
Ch2 ( tr ~ 27.0 ns)
2keV -170 MeV @ +/- 12V
in two modes & four sub-ranges
of operations: a) Amplitude and b) TOT
26
Segment CSP  Negative Output
AGATA CSPs – the versions
with large open loop gain
( INFN-Milan – IKP-Cologne )
Segment
Non-Inverting
DC coupled
P/Z cancellation
Cv
R1
R1
Core CSP  Positive Output
R1
Core
Inverting
Cv
* (Cv) stability adj.
AC coupled
why large Ao > 100,000 ?
 frequency compensation, slope & crosstalk
from
Active
Reset
27
Fast Reset as tool to implement the “TOT” method
Core Active Reset
OFF
one of the segments
Core -recovery from saturation (but base line …)
Fast Reset
circuitry
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
28
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
Fast Reset as tool to implement the “TOT” method
Core Active Reset – OFF
one of the segments
Core -recovery from saturation
Active Reset – ON
Fast Reset
circuitry
ToT
Normal analog spectroscopy
one of the segments
-
very fast recovery from TOT mode of operation
fast comparator LT1719 (+/- 6V)
factory adj. threshold + zero crossing
> 220 MeV
LV-CMOS (opt)
@ +/-15V
LVDS by default
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
29
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
Fast Reset as tool to implement the “TOT” method
Core Active Reset – OFF
one of the segments
Core -recovery from saturation
Active Reset – ON
Fast Reset
circuitry
ToT
Normal analog spectroscopy
one of the segments
INH-C
-
very fast recovery from TOT mode of operation
fast comparator LT1719 (+/- 6V)
factory adj. threshold + zero crossing
> 220 MeV
LV-CMOS (opt)
@ +/-15V
LVDS by default
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
30
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
see Francesca Zocca PhD Thesis, INFN, Milan
A. Pullia at al, Extending the dynamic range of nuclear pulse spectrometers,
Rev. Sci. Instr. 79, 036105 (2008)
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
31
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
Comparison between “reset” mode (ToT) vs. “pulse-height” mode (ADC)
A. Pullia at al, Extending the dynamic range of nuclear pulse spectrometers,
32
Rev. Sci. Instr. 79, 036105 (2008)
Due to
FADC; G=3
range  !
X-talk !
with CMOS
 10 MeV
33
AGATA Dual-Core LVDS transmission of digital signals:
- INH-C1 and INH-C2 (Out) and Pulser Trigger (In) signals
AGATA Dual Core crosstalk test measurements
Ch2 (analog signal) vs. LVDS-INH-C1 (bellow & above threshold)
Core amplitude just below the INH threshold
Core amplitude just above the INH threshold
Ch1 @ INH_Threshold - (~ 4mV)
Ch1 @ INH_Threshold + (~ 4mV)
Ch2 @ INH_Threshold
Ch2 @ INH_Threshold + (- 1mV)
LV_CMOS
Vp-Vp (~ 1mV)
LV_CMOS
INH_Ch1/-/
tr ~ 1.65 ns
INH_Ch1/+/
tf ~ 2.45 ns
INH_Ch1/+/
INH_Ch1/-/
(1) Core_Ch1, (2) Core_Ch2, (3) INH_Ch1(LVDS/-/, (4) INH_Ch1(LVDS/+/)
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
34
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
If we have developed a FEE solution with:
• Dual gain for the central contact (Core);
• ToT for both Core channels and all Segments;
• Saturation of the CSP at 170 MeV @ +/-12V …
( and ~ 220 MeV @ +/- 15V )
… then why not to perform a direct spectroscopic
measurement up to 170 MeV equivalent gammas ?
… were to find them ? … in cosmic rays!
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
To extend the comparison between
active “reset” mode (ToT) vs.
“pulse-height” mode (ADC) well
above 100 MeV measuring directly
cosmic rays (i.e. equivalent with interaction of gamma rays above 100 MeV)
Interaction of muons with matter
• Low energy correction:
excitation and ionization ‘density effect’
• High energy corrections:
bremsstrahlung, pair production
and photo-nuclear interaction
MUON STOPPING POWER AND RANGE TABLES
- 10 MeV|100 TeV
D. E. GROOM, N. V. MOKHOV, and S. STRIGANOV
David Schneiders, Cosmic radiation analysis by a segmented HPGe detector,
IKP-Cologne, Bachelor thesis, 03.11.2011
Two set-up have been used:
a) LeCroy Oscilloscope with only Core
signals: Ch1; Ch2, INH-Ch1; INH-Ch2
from Core Diff-to-Single Converter Box
b) 10x DGF-4C-(Rev.E) standard DAQ
- complete 36x segments and
4x core signals from Diff-to-Single
Converter Boxes (segments & core)
David Schneiders, Cosmic radiation analysis by a segmented HPGe detector,
IKP-Cologne, Bachelor thesis, 03.11.2011
Experimental results for cosmic ray measurement
Determination of the High Gain
Core Inhibit width directly from
the trace while the low gain core
operates still in linear mode up
to ~22 MeV ( deviation ~0.5%)
Calibrated energy sum of all
segments vs. both low &
high-gain core signals
(linear & ToT )
Calibrated energy sum of all
segments vs. both low & highgain core signals (both in ToT
mode of operation)
David Schneiders, Cosmic radiation analysis by a segmented HPGe detector,
IKP-Cologne, Bachelor thesis, 03.11.2011
Combined spectroscopy
up to ~170 MeV
Direct measurement of cosmic rays with
a HP-Ge AGATA detector, encapsulated
and 36 fold segmented
• Averaged calibrated segments sum +++
• Averaged calibrated Low gain Core
xxx
• Scaled pulser calibration (int. & ext.) ----
R.Breier et al., Applied Radiation and Isotopes, 68, 1231-1235,
2010
David Schneiders, Cosmic radiation analysis by a segmented HPGe detector,
IKP-Cologne, Bachelor thesis, 03.11.2011
Transfer Function & Crosstalk
Transfer function
- calculation (Frequency domain, Laplace transf., time domain)
- measurement  spectroscopic pulser
- applications:
- bulk capacities measurement
- crosstalk measurements and
corrections
In standard way the pulser input signal is injected
AC (1pF) in the gate electrode of the jFET
δq(t)
1pF
50 Ω The AC coupled Pulser classical approach !
Detector
δq(t)
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
AGATA
HP-Ge Detector
Front-End Electronics
Cold part Warm part
AGATA – 3D Dummy detector
Cold part Warm part
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
43
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
AGATA
HP-Ge Detector
Front-End Electronics
Cold part Warm part
Cold part Warm part
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
44
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
Rewritten as a Laplace
transform of an exp.
decaying function
with
If τ1 is sufficiently small, the exponential
function can be “δ(t)“ and than the
transfer function becomes:
Simple current
dividing rule
Miller part
Cold resistance
equivalent input impedance of the preamplifier
•
to be able to measure the transfer function,
we need to build and incorporate also a clean pulser with
spectroscopic properties and rectangular pulse form …
!
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
Incorporated Programmable Spectroscopic Pulser (PSP)
• why is needed?  self-calibration purposes
• brief description
• Specifications, measurements and application:
- Transfer function;
- Charge distribution;
- Impurities concentration measurements
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
48
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
The use of PSP for self-calibrating
Parameter
•
•
Pulse amplitude
Pulse Form
Potential Use / Applications


(rise time, fall time, structure)
•
•
•
•
•
•
Pulse C/S amplitude ratio 
(Detector Bulk Capacities)
Pulse Form
Repetition Rate (c.p.s.)


Energy, Calibration, Stability
Transfer Function in time
domain, ringing  (PSA)
Crosstalk input data
(Detector characterization)
TOT Method
Dead Time
 (PSA)

(Efficiency)
(periodical or random distribution)
Time alignment
Segments calibration


Detector characterization 
Correlated time spectra (DAQ)
Low energy and very high energy
calibration
Impurity concentration, passivation
(Detector characterization)
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
49
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
• +/- 1ppm
• 16 bit +/- 1bit
• fast R-R driver
CSP
return GND
• Analog Switches:
- t on / t off ,
+V13
+V13
+V13
6
+V13
D
GND_D
R30
-V13
GND_D
+V13
GND_D
-V13
- Qi ,
- dynamic
range (+/- 5V)
R31
8
6
D
D
D
D
3
1
R94
7
D
2
n
for
1
=
In
D
N
R107
Out
- ~ R to R
- bandwidth
• Coarse attenuation
(4x 10 dB) (zo~150 Ohm)
• transmission line
to S_ jFET and
its return GND!
Chopper
GND_D
Trigger
R81
GND_D
C59
GND_D
Mode
3
C53
3
GND_D
3
-V13
G
-V13
2
GND
GND_D
Shown
R80
6
1
=
In
D
N
G
I
2
4
for
Shown
V13
R79
4
V15
U13
n
I
V12
4
S
2
1
4
U11
V
V
8
1
R90
D
S
Vref
4
C94
3
7
2
6
D
D
V
8
C86
R75
C120
C101
• Op Amp:
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
50
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
AGATA
HP-Ge Detector
Front-End Electronics
Cold part Warm part
Cold part Warm part
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
51
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
Pulser Ratio Core / Segments
Uncorrected for individual segment gain
Corrected for each individual segment gain
Core and Segment crosstalk

v out 
1
sC fb

1

  C 01 C ac
C C
02
ac

 C 01 AC fb
1
 C12 AC fb
 C 02 AC fb 

 C12 AC fb  i

1

C0-X6 = 0.98 pF
C0-X5 = 1.16 pF

T
singles : i1  1 1 0

v out ,1   1  C 01 AC fb 1  C 01 C ac
Agata
measured capacities:
 C 02 C ac
C0-X4 = 1.19 pF

T
C0-X3 = 0.980 pF
C0-X2 = 0.666 pF
Segment normalization

T
doubles : i2  1 x 1  x 

v out , 2   1  xC 01  (1  x )C 02  AC fb
x  C 01 C ac 1  x  C 02 C ac
C0-X1 = 0.943 pF

T
Core normalization
Segment sum  1  C01 Cac  C02 Cac
Observed shift in segments
3D Space charge reconstruction in highly segmented
HP-Ge detectors through CV measurements, using PSP
• The reconstruction of the three dimensional space charge distribution
inside highly segmented large volume HP-Ge Detector from
C-V measurement was investigated
• A computer program was developed to understand the impact of impurity
concentrations on the resulting capacities between core contact and
outer contact for HP-Ge detectors biased at different high voltages
 The code is intended as a tool for the reconstruction of the doping
profile within irregularly shaped detector crystals.
• The results are validated by comparison with the exact solution of a
true coaxial detector.
• Existing methods for space charge parameter extraction are shortly revised.
• The space charge reconstruction under cylindrical symmetry is derived.
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
Influence of the space
charge on the core
signal rise time
(in the coaxial part of
the AGATA detector )
The example indicates the need for
characterization of each individual
detector, including detailed investigation
of space charge distribution and the
exact geometry of the sensitive material
 simple planar capacitor
N(d) = [ND -NA ]
where ND ; NA donator, acceptor
concentration levels of the crystal
• The novel approach is a full 3D
reconstruction of the impurity
profile throughout the bulk of
the HP-Ge crystal.
• The technique should be applicable
for any detector geometry, not only
for planar detectors.
 from charge neutrality condition
of the device ( N(d) being the
remaining net charge at the boundary
of the depletion region) to the variations
in capacity with the bias voltage and
as function of the changing bias
voltage a scan through the depletion
depth of the sample is obtained only
the relationship between measured
bulk capacity and applied bias voltage
is sufficient to reconstruct the doping
profile
N.B. - one dimensional reconstruction 
planar approximation, where the space
charge depending only on “d”
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
Core
electrode
Current [pA]
Electrical model of 36-fold segmented detector
Bias [V]
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
Impurities concentration of last four rings of AGATA detector S002
B. Birkenbach at al, Determination of space charge distributions in highly segmented
large volume HP-Ge detectors from capacitance-voltage measurements
Nucl. Instr. Meth. A 640 (2011) 176-184
[10 10 /cm 3 ]
Crystal Height [mm]
Pulser peak position for different voltages of det. C006
59
Energy vs. Applied Voltage
Detector Capacity vs. Applied Voltage
o Variation of the Am (59.5keV) peak position with detector bias voltage (the error
bars indicate the FWHM of the energy peak – they do not represent an uncertainty)
o The core energy position is strongly varying with bias voltage, while segments
are nearly unaffected. The FWHM width is drastically growing due to the
increased detector capacity
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
Crosstalk and signal induction in segmented detectors
Segmented detector show mutual capacitive coupling of the: - segments & -core 
crosstalk and worsening the energy resolution
o The crosstalk has to be measured experimentally and to be corrected while due
to crosstalk effect the segment sum peak energy value (“add-back”) is reduced
o
The radiation leave a trail of ionization in the detector and the movement of
these charges in an electric field induces signals on the detector electrodes.
• In the case of a detector with ideal segmentation and ideal distributed
capacitors one can calculate the signal with an electrostatic approximation
using the so called “Ramo theorem” (HP-Ge Det.; MWPC; DSSSD).
• In the case of under-depleted DSSD; MRPC-detectors the time dependence
of the signal is not only given by the movement of the charges but also
by the time-dependent reaction of the detector materials. Using quasi-static
approximation of Maxwell’s equations –W. Riegler developed an extended
formalism to allows calculation of induced signals for a larger number of
detectors with general materials by time dependent weighting fields
Crosstalk correction is needed for AGATA
•
•
•
Crosstalk is present in any segmented detector
Crosstalk creates energy shifts proportional to fold
crosstalk can be corrected
without X-talk
with X-talk
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
The segment sum energy for
Eγ = 1332.5 keV plotted
for different segment
multiplicities (‘fold’ –
number of hit segments)
Energy shift and ‘resolution’ vs. segment ‘fold’
The data points in this figure show peak energy shifts of the 1332.5 keV line
of 60Co as a function of all possible twofold segment combinations.
A refined inspection of the peak position of the twofold events reveals a
regular pattern as a function of pair wise segment combinations
Miniball (HeKo)
PSC 823
(Eurysis /Ortec propr. prod.)
PSC-2008
(differential out.)
AGATA like Miniball
2011-2012
Either
BF862 or
IF1320
INH
SHDN
Technical Specifications
- conversion factor ~ 200 mV/MeV (PSC-2008 opt. 100 mV/MeV)
- open loop gain Ao ~ 20,000
The new series 2008 & 2012
- single ended - reconfigurable as Inv. / Non Inv.);
- Ao ~ 100,000
•- adjustments: - Idrain ; - P/Z adj. ; - Offset adj. ; Bandwidth
- differential outputs
- adjustments: - Idrain ; - P/Z adj. ; - Offset adj. ; Bandwidth
- INH-C & SDHN
- power supply: +/- 12V
(i.e. ToT mode of operation)
- rise time ~ 25 ns / 39 pF det. cap. (terminated)
Advanced solution for FEE:
- to extend the dynamic range and counting rate with a
combined dual gain and dual ToT method  100dB;
- transfer function tools ( from dummy to freq. comp.);
- programmable spectroscopic pulser;
- applications as:
- impurities concentration
- up to ~180 MeV equiv. gamma range
- crosstalk corrections
AGATA
Dual Gain Core
Final Specs.
• Summary active reset:
- active reset @ 2nd stage
- active reset @ 1st stage
with advantages vs. disadv.
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
69
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
Parameter
Sensitivity
( mV / MeV)
Resolution
IKP-Cologne
(Miniball – jFET IF1320)
~ 175
mV/MeV
( single ended )
(Cd= 0pF; cold FET)
~ 600 eV
Slope
< 10 eV / pF
( + eV/ pF) [Cd]
(cold FET)
Rise time
(Cd= 0pF);
~ 15 ns
( cold FET)
Slope
~ 0.3 ns
( + ns/ pF) [Cd]
( ~ 25 ns / 33 pF )
U(out) @ [50 Ohm] /
Power [mW]
~ 4.5V /~ 450 mW
( + /- 12V  Op.Amp.LM-6172)
Saturation of
equiv. ~100 MeV
the 1st stage @
(@ ~60mW_ jFET)
Open Loop Gain
~ 20,000
MINIBALL
Charge Sensitive
Preamplifier
Specifications
• By design optimized
Transfer Function
(no over/under-shoots)
• Crosstalk requirements
< 10 -3 core-segment
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
A. Wendt et al – Der LYCCA-Demonstrator, HK 36.60, DPG, Bonn, 2010
G. Pascovici, Institute of Nuclear Physics, Univ. of Cologne
LYCCA-0
Set-up for DSSSD + CsI
TASISpec (TASCA)
A new detector Set-up for
Superheavy Element Spectroscopy
74
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
75
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
~1.25 sq.cm
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
76
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest
G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012
Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest