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Advanced FEE solutions for large arrays of semiconductor detectors. Signal formation for energy, time and position measurements Segmented detectors; - advanced FEE for Ge Detectors Briefly, some specific issues and cases:

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Signal formation for energy time and position measurements

Advanced FEE solutions for large arrays

of semiconductor detectors

  • Signal formation for energy, time and position

  • measurements

  • Segmented detectors; - advanced FEE for Ge Detectors

  • Briefly, some specific issues and cases:

  • ◦ 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


Signal formation for energy time and position measurements

  • a) Signal formation for energy, time and position

  • measurements,

  • (we’ll limit our attention to capacitive & segmented detectors)

  • b) Related issues in segmented detectors

  • - dynamic range

  • - high counting rates

  • - induced signals & crosstalk - pros vs. conts

  • c) 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

  • LYCCA & TASISpec - FEE for DSSSD

G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012

Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest


A typical structure of a segmented tapered and encapsulated hp ge detector

A typical structure of a segmented, tapered and encapsulated, HP-GeDetector

[- HV] (GND)

+ HV

(~ kV/cm)

Rp

Ci

(-)

Central contact

(Core)

(- e ~ mm)

Exterior contacts

(N Segments)

(+)

- Qi

N = 6; 12; 18; 28; 36

  • Standard n-type

  • Intrinsic HP-Ge (P-I-N)

  • Closed end

  • Coaxial structure

  • Io ~ < 100 [pA]

  • Cdet ~ 30 - 45 pF

  • Collection time ~ 30 - 1000 ns


Signal formation for energy time and position measurements

FFEFEE

[HP-Ge + CSP] +Analog Nuclear Electronics Spectroscopic Chain is used in order to extract the: E, t, position (r, azimuth)

Fast pipeline ADC [DGF]

FEE

Fast Pipe line ADC [DGF]

Analog E+T Filter Amplifier Chain

Collected charge pulses (+ &-)

Qd - delta

t

UCSP – exponential

Pile-up of pulses

t

Digital

Filters

(Fast, Slow)

UFA ~ Gaussian

t

Baseline restorer


Signal formation for energy time and position measurements

[HP-Ge + CSP] +Digital Nuclear Electronics Spectroscopic Chain is used in order to extract the: E, t, position (r, azimuth)

Fast pipeline ADC + PSA

FEE

Fast pipeline ADC & [DGF]

Digital Filters [for Trigger, Timing, Energy, Position]

Collected charge pulses (+ &-)

Qd - delta

t

UCSP – exponential

Pile-up of pulses

t

Digital

Filters

(Fast, Slow)

UFA ~ Gaussian

t

Baseline restorer


Detector signal collection

+

Rp

-

Detector

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

  • a voltage or a current pulse

Z(ω)

  • Final objectives:

  • amplitude measurement(E)

  • time measurement (t)

  • position(radius, azimuth)

Electronic Circuit

Which kind of electronic circuit ; Z(ω)?


Detector signal collection1

Z(ω)

Rp

+

-

Electronic Circuit

Detector

Detector Signal Collection

ifZ(ω) is high,

  • charge is kept on capacitor nodes and a voltage builds up (until capacitor is discharged)

  • Advantages:

  • Disadvantages:

if Z(ω) is low,

  • charge flows as a current through the

    impedance in a short time.

  • Advantages:

  • Disadvantages:

  • limited signal pile up (easy BLR)

  • limited channel-to-channel crosstalk

  • low sensitivity to EMI

  • good time and position resolution

  • excellent energy resolution

  • friendly pulse shape analysis position

  • channel-to-channel crosstalk

  • pile up above 40 k c.p.s.

  • larger sensitivity to EMI

  • signal/noise ratio to low worse resolution


Charge sensitive preamplifier

Charge Sensitive Preamplifier

  • Active Integrator(Charge Sensitive Preamplifier -CSP)

  • Input impedance very high ( i.e. ~ no signal current flows into amplifier),

  • Cf/Rffeedback capacitor /resistor between output and input,

  • very large equivalent input dynamic capacitance,

  • sensitivityor~(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)

Ci ~ “dynamic” input capacitance

tr~ 30-1000ns)

- Qi

Step function

R f

o

Invert ing

-

Ao

  • Ci ~ 10 - 20,000 pF

  • ( up to 100,000)

“GND”

Non- Inv.

+

jFET

GND

Charge Sensitive Stage

(it is a converter not an amplifier)


Pole zero cancellation technique

Pole - Zero cancellation technique

Rf . Cf ~ 1 ms

Cf~ 1pF (0.5pF-1.5pF), Rf ~ 1GOhm

Rd . Cd ~ 50 µs

simpledifferentiation

without

Rpz

Rpz~ 20 k Ohm

Baseline shifts

if (RfCf)= (Rpz .Cd) and

RdCd ~ 50 µs

differentiation with P/Z adj.

 no baseline shifts

with

Rpz

Cd~ 47 nF, Rd~1.1 kOhm

Baseline restored


Pole zero cancellation technique1

Pole - Zero cancellation technique

Rf . Cf ~ 1 ms

Cf~ 1pF (0.5pF-1.5pF), Rf ~ 1GOhm

Rd . Cd ~ 50 µs

simpledifferentiation

without

Rpz

Rpz~ 20 k Ohm

Baseline shifts

if (RfCf)= (Rpz .Cd) and

RdCd ~ 50 µs

differentiation with P/Z adj.

 no baseline shifts

with

Rpz

Cd~ 47 nF, Rd~1.1 kOhm

Baseline restored


Pole zero cancellation technique2

Pole - Zero cancellation technique

Rf . Cf ~ 1 ms

Cf~ 1pF (0.5pF-1.5pF), Rf ~ 1GOhm

CSP

Rd . Cd ~ 50 µs

simpledifferentiation

without

Rpz

R pz ~ 21 k Ohm

Baseline shifts

if (RfCf)= (Rpz .Cd) and

RdCd ~ 50 µs - clean

differentiation with P/Z adj.

 no baseline shifts

with

Rpz

Cd ~ 47 nF, Rd ~1.1 kOhm

Baseline restored


Signal formation for energy time and position measurements

  • This is only the ‘hard core’ of the CSP stage

  • (ChargeSensitivePreamplifier) 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


Signal formation for energy time and position measurements

Block diagram of a standard CSP

(discrete components and integrated solution…

- what they have in common )

(alternatives)

(alternatives)

(+)

Optionally with

cold jFET

(-)

Warm part

(outside cryostat)

Cold part

(cryostat)

(alternatives)

G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012

Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest


Signal formation for energy time and position measurements

Block diagram of a standard CSP

(discrete components and integrated solution…

- what they have in common )

(alternatives)

(alternatives)

(+)

Optionally with

cold jFET

(-)

Warm part

(outside cryostat)

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)

(alternatives)

G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012

Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest


Signal formation for energy time and position measurements

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

Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest


Signal formation for energy time and position measurements

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 /fnoise ~ Cd2


Signal formation for energy time and position measurements

  • 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 )

DC – unipolar (-)

Saturation (+Vc)

δFilter

A(q) ~ - Qi/ Cf

Δf+

( forbidden

region )

Linear

range

DC - bipolar

DC coupled channel

Δf-

Saturation (-Vc)

DC – unipolar (+)

-Vc

(- Rail)

G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012

Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest

δFilter


Signal formation for energy time and position measurements

  • 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

A(q) ~ - Qi/ Cf

Δf+

( forbidden

region )

AC -Unipolar

(negative)

Linear

range

AC -Unipolar

(positive)

BL shift

Δf-

AC coupled channel

Saturation (-Vc)

-Vc

(- Rail)

G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012

Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest


Signal formation for energy time and position measurements

  • 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 ( Rfsmaller )

      • 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


Signal formation for energy time and position measurements

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


Signal formation for energy time and position measurements

  • a) Custom designed vs. Commercial FEE ?

  • b) 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


Signal formation for energy time and position measurements

- the dominant pole

compensation technique

GDC~30,000

Zo~ 66 Ohm

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


Signal formation for energy time and position measurements

“ A Large Ion Collider Experiment, ALICE-TPC -TDR”, ISBN 92-9083-153-3, (1999), CERN


Signal formation for energy time and position measurements

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


Signal formation for energy time and position measurements

Best performance: Majorana dedicated FEE

(PTFE~0.4mm; Cu~0.2mm;C~0.6pF; R ~2GΩAmorphous 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

Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest


Signal formation for energy time and position measurements

Dual Gain Core Structure

Ch1 (fast reset)-Pulser @ ~19 MeV

Ch2 (linear mode)

Ch 1 ~200 mV / MeV

C-Ch1

/C-Ch1

INH1

SDHN1

Pole /Zero Adj.

Fast Reset

(Ch1)

Differential

Buffer

(Ch1)

Segments (linear mode)

Common

Charge

Sensitive

Loop

+

Pulser

+

Wiring

Ch 2 ~ 50mV / MeV

one

MDR

10m

cable

36_fold segmented

HP-Ge detector + cold jFET

C-Ch2

/C-Ch2

INH2

SDHN2

Pole /Zero Adj.

Fast Reset

(Ch2)

Differential

Buffer

(Ch2)

Ch1 ( tr ~ 25.5 ns)

Programmable

Spectroscopic

Pulser

Pulser CNTRL

Ch2 ( tr ~ 27.0 ns)

2keV -170 MeV @ +/- 12V

in two modes & four sub-ranges

of operations: a) Amplitude and b) TOT


Signal formation for energy time and position measurements

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

from

Active

Reset

Cv

* (Cv) stability adj.

whylarge Ao > 100,000 ?

 frequency compensation, slope & crosstalk

AC coupled


Signal formation for energy time and position measurements

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

Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest


Signal formation for energy time and position measurements

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

  • LV-CMOS (opt)

  • LVDS by default

> 220 MeV

@ +/-15V

G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012

Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest


Signal formation for energy time and position measurements

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

  • LV-CMOS (opt)

  • LVDS by default

> 220 MeV

@ +/-15V

G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012

Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest


Signal formation for energy time and position measurements

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

Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest


Signal formation for energy time and position measurements

Comparison between “reset” mode (ToT) vs. “pulse-height” mode (ADC)

A. Pullia at al, Extending the dynamic range of nuclear pulse spectrometers,

Rev. Sci. Instr. 79, 036105 (2008)


Signal formation for energy time and position measurements

Due to

FADC; G=3

range  !

X-talk !

with CMOS

 10 MeV


Signal formation for energy time and position measurements

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

Vp-Vp(~ 1mV)

[email protected]_Threshold + (- 1mV)

LV_CMOS

LV_CMOS

INH_Ch1/+/

INH_Ch1/-/

tr ~ 1.65 ns

INH_Ch1/+/

tf ~ 2.45 ns

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

Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest


Signal formation for energy time and position measurements

  • 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


Signal formation for energy time and position measurements

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 inter-

action 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


Signal formation for energy time and position measurements

Two set-up have been used:

LeCroy Oscilloscope with only Core

signals: Ch1; Ch2, INH-Ch1; INH-Ch2

from Core Diff-to-Single Converter Box

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


Signal formation for energy time and position measurements

Experimental results for cosmic ray measurement

Calibrated energy sum of all

segments vs. both low & high-gain core signals (both in ToT

mode of operation)

Calibrated energy sum of all

segments vs. both low &

high-gain core signals

(linear & ToT )

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%)

David Schneiders, Cosmic radiation analysis by a segmented HPGe detector,

IKP-Cologne, Bachelor thesis, 03.11.2011


Signal formation for energy time and position measurements

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


Signal formation for energy time and position measurements

Transfer Function & Crosstalk

Transfer function

- calculation (Frequency domain, Laplace transf., time domain)

- measurement  spectroscopic pulser

- applications:

- bulk capacities measurement

- crosstalk measurements and

corrections


Signal formation for energy time and position measurements

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


Signal formation for energy time and position measurements

δq(t)

G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012

Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest


Signal formation for energy time and position measurements

AGATA

HP-Ge Detector

Front-End Electronics

Cold partWarm part

AGATA – 3D Dummy detector

Cold partWarm part

G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012

Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest


Signal formation for energy time and position measurements

AGATA

HP-Ge Detector

Front-End Electronics

Cold partWarm part

Cold partWarm part

G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012

Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest


Signal formation for energy time and position measurements

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


Signal formation for energy time and position measurements

  • 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


Signal formation for energy time and position measurements

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

Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest


Signal formation for energy time and position measurements

The use of PSP for self-calibrating

ParameterPotential Use / Applications

  • Pulse amplitudeEnergy, Calibration, Stability

  • Pulse FormTransferFunction in time

    (rise time, fall time, structure)domain, ringing (PSA)

  • Pulse C/S amplitude ratio  Crosstalk input data

    (Detector Bulk Capacities)(Detector characterization)

  • Pulse FormTOT Method (PSA)

  • Repetition Rate (c.p.s.) Dead Time(Efficiency)

    (periodical or random distribution)

  • Time alignment  Correlated time spectra (DAQ)

  • Segments calibration Low energy and very high energy

    calibration

  • Detector characterization  Impurity concentration, passivation

    (Detector characterization)

G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012

Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest


Signal formation for energy time and position measurements

  • +/- 1ppm

  • 16 bit +/- 1bit

  • fast R-R driver

CSP

return GND

  • Analog Switches:

  • -t on / t off ,

  • -Qi,

  • -dynamic

  • range (+/- 5V)

  • Op Amp:

  • -~ R to R

  • -bandwidth

  • Coarse attenuation

  • (4x 10 dB) (zo~150Ohm)

  • transmission line

  • to S_ jFET and

  • its return GND!

G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012

Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest


Signal formation for energy time and position measurements

AGATA

HP-Ge Detector

Front-End Electronics

Cold partWarm part

Cold partWarm part

G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012

Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest


Pulser ratio core segments

Pulser Ratio Core / Segments

Uncorrected for individual segment gain

Corrected for each individual segment gain


Core and segment crosstalk

Agata

measured capacities:

C0-X6 = 0.98 pF

C0-X5 = 1.16 pF

C0-X4 = 1.19 pF

C0-X3 = 0.980 pF

C0-X2 = 0.666 pF

Segment normalization

C0-X1 = 0.943 pF

Core normalization

Observed shift in segments

Core and Segment crosstalk


Signal formation for energy time and position measurements

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


Signal formation for energy time and position measurements

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


Signal formation for energy time and position measurements

  • simple planar capacitor

  • 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”

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.

G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012

Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest


Signal formation for energy time and position measurements

Electrical model of 36-fold segmented detector

Current [pA]

Core

electrode

Bias [V]

G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012

Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest


Signal formation for energy time and position measurements

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


Signal formation for energy time and position measurements

[10 10 /cm 3 ]

Crystal Height [mm]

Pulser peak position for different voltages of det. C006


Signal formation for energy time and position measurements

Energy vs. Applied Voltage

Detector Capacity vs. Applied Voltage

  • 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)

  • 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


Signal formation for energy time and position measurements

Crosstalk and signal induction in segmented detectors

  • Segmented detector show mutual capacitive coupling of the: - segments & -core 

  • crosstalk and worsening the energy resolution

  • 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

  • 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. Rieglerdeveloped an extended formalism to allows calculation of induced signals for a larger number of detectors with general materials by time dependent weighting fields


Signal formation for energy time and position measurements

  • 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


Signal formation for energy time and position measurements

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’


Signal formation for energy time and position measurements

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


Signal formation for energy time and position measurements

Miniball (HeKo) PSC 823 PSC-2008 AGATA like Miniball

(Eurysis /Ortec propr. prod.) (differential out.) 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)


Signal formation for energy time and position measurements

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


Signal formation for energy time and position measurements

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

Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest


Miniball charge sensitive preamplifier specifications

MINIBALLCharge Sensitive Preamplifier Specifications

  • By design optimized

  • Transfer Function

  • (no over/under-shoots)

  • Crosstalk requirements

  • < 10-3core-segment

G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012

Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest


Signal formation for energy time and position measurements

A. Wendt et al – Der LYCCA-Demonstrator, HK 36.60, DPG, Bonn, 2010

G. Pascovici,Institute of Nuclear Physics, Univ. of Cologne


Signal formation for energy time and position measurements

LYCCA-0

Set-up for DSSSD + CsI

TASISpec (TASCA)

A new detector Set-up for

Superheavy Element Spectroscopy


Signal formation for energy time and position measurements

G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012

Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest


Signal formation for energy time and position measurements

~1.25 sq.cm

G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012

Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest


Signal formation for energy time and position measurements

G. Pascovici , Carpathian Summer School of Physics, Sinaia 2012

Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest


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