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O Signal formation for energy, time and position measurements o Segmented detectors; - advanced FEE for Ge Detectors o Briefly, some specific issues and.

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Presentation on theme: "O Signal formation for energy, time and position measurements o Segmented detectors; - advanced FEE for Ge Detectors o Briefly, some specific issues and."— Presentation transcript:

1 o Signal formation for energy, time and position measurements o Segmented detectors; - advanced FEE for Ge Detectors o 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 Advanced FEE solutions for large arrays of semiconductor detectors

2 2 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 d) 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

3 A typical structure of a segmented, tapered and encapsulated, HP-Ge Detector Central contact (Core) Exterior contacts ( N Segments ) Standard n-type Intrinsic HP-Ge (P-I-N) Closed end Coaxial structure I o ~ < 100 [pA] (-) (+) + HV [- HV]  (GND) Ci C det ~ pF Collection time ~ ns (- e  ~ mm) ParameterGe Dielectric16 Electron- hole pair E 2.96 [eV] Mobility e / hole(+) 3,900 / o 300 K e / hole(+) [cm 2 /V.s] V d =μE 40,000 / o 80 K N = 6; 12; 18; 28; 36 - Q i (~ kV/cm) Rp

4 Q d - delta U CSP – exponential U FA ~ Gaussian t t t Pile-up of pulses Baseline restorer Collected charge pulses ( + & - ) Digital Filters (Fast, Slow) Fast Pipe line ADC [DGF] FFEFEE Fast pipeline ADC [DGF] Analog E+T Filter Amplifier Chain FEE [ HP-Ge + CSP ] + Analog Nuclear Electronics Spectroscopic Chain is used in order to extract the: E, t, position (r, azimuth)

5 t t t Pile-up of pulses Baseline restorer Digital Filters (Fast, Slow) Fast pipeline ADC + PSA Fast pipeline ADC & [ DGF ] Collected charge pulses ( + & - ) U CSP – exponential U FA ~ Gaussian Q d - delta Digital Filters [ for Trigger, Timing, Energy, Position] FEE [ HP-Ge + CSP ] + Digital Nuclear Electronics Spectroscopic Chain is used in order to extract the: E, t, position (r, azimuth)

6 Detector Signal Collection + - Detector Rp 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 Final objectives: amplitude measurement (E) time measurement (t) position (radius, azimuth) Electronic Circuit Z (ω) Which kind of electronic circuit ; Z(ω) ?

7 Z ( ω) + - Detector Electronic Circuit Rp if Z(ω) is high, charge is kept on capacitor nodes and a voltage builds up (until capacitor is discharged) Advantages: Disadvantages: Detector Signal Collection 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 signal/noise ratio to low  worse 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

8 Charge Sensitive Preamplifier Active Integrator (Charge Sensitive Preamplifier -CSP) Input impedance very high ( i.e. ~ no signal current flows into amplifier), C f /R f feedback capacitor /resistor between output and input, very large equivalent input dynamic capacitance, sensitivity or ~ (conversion factor) A (q) ~ - Q i / C f large open loop gain A o ~ 10, ,000 clean transfer function (no over-shoots, no under-shoots, no ringing) C i ~ “dynamic” input capacitance R f Step function  C i ~ ,000 pF ( up to 100,000) - Invert ing - Q i GND (R f. C f ~ 1ms ) t r ~ ns) jFET + Ao Ao Charge Sensitive Stage (it is a converter not an amplifier) “GND” Non- Inv. o

9 Pole - Zero cancellation technique R f. C f ~ 1 ms R d. C d ~ 50 µs simple differentiation if ( R f C f ) = ( R pz.C d ) and R d C d ~ 50 µs differentiation with P/Z adj.  no baseline shifts Baseline shifts Baseline restored C f ~ 1pF (0.5pF-1.5pF), R f ~ 1GOhm Cd~ 47 nF, Rd~1.1 kOhm Rpz~ 20 k Ohm without R pz with R pz

10 Pole - Zero cancellation technique R f. C f ~ 1 ms R d. C d ~ 50 µs simple differentiation if ( R f C f ) = ( R pz.C d ) and R d C d ~ 50 µs differentiation with P/Z adj.  no baseline shifts Baseline shifts Baseline restored C f ~ 1pF (0.5pF-1.5pF), R f ~ 1GOhm Cd~ 47 nF, Rd~1.1 kOhm Rpz~ 20 k Ohm without R pz with R pz

11 Pole - Zero cancellation technique R f. C f ~ 1 ms R d. C d ~ 50 µs simple differentiation if ( R f C f ) = ( R pz.C d ) and R d C d ~ 50 µs - clean differentiation with P/Z adj.  no baseline shifts Baseline shifts Baseline restored C f ~ 1pF (0.5pF-1.5pF), R f ~ 1GOhm C d ~ 47 nF, R d ~1.1 kOhm R pz ~ 21 k Ohm without R pz with R pz CSP

12 This is only the ‘hard core’ of the CSP stage (C harge S ensitive P reamplifier ) 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 G max. ~ 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

13 Block diagram of a standard CSP ( discrete components and integrated solution… - what they have in common ) Cold part (cryostat) Warm part (outside cryostat) (alternatives) Optionally with cold jFET G. Pascovici, Carpathian Summer School of Physics, Sinaia 2012 Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest (+) (-)

14 Block diagram of a standard CSP ( discrete components and integrated solution… - what they have in common ) Cold part (cryostat) Warm part (outside cryostat) (alternatives) Optionally with cold jFET G. Pascovici, Carpathian Summer School of Physics, Sinaia 2012 Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest (+) (-) t r  25 ns ( ) ns t f  50 μs ( ) μs CSP- ‘gain’  50 mV / MeV (Ge) ( mV / MeV)

15 15 IF1320 (IF1331) (5V; 10mA)& 1pF; 1 GΩ t r ~ ns 800 mV - no over & under_shoot 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 also GRETINA Eurysis

16 the equivalent noise charges Q n assumes a minimum when the current and voltage contributions are equal current noise ~ (RC) voltage noise ~ 1/(RC) ~ C d 2 1 / f noise ~ C d 2 J.-F. Loude, Energy Resolution in Nuclear Spectroscopy, PHE , Univ. of Lausanne AGATA τ opt ~ 3-6 µs

17 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 ]  { ( + V c - V c ) – 2xΔ f -2δ Filt. } Saturation (+Vc) Saturation (-Vc) +V c (+ Rail ) -V c (- Rail) Linear range Δ f- Δ f+ ( forbidden region ) G. Pascovici, Carpathian Summer School of Physics, Sinaia 2012 Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest DC coupled channel DC – unipolar (+) DC - bipolar A (q) ~ - Q i / C f DC – unipolar (-) δ Filter

18 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 ]  { ( + V c - V c ) – 2xΔ f -2δ Filt. } Saturation (+Vc) Saturation (-Vc) +V c (+ Rail ) -V c (- Rail) Linear range A (q) ~ - Q i / C f Δ f- Δ f+ ( forbidden region ) G. Pascovici, Carpathian Summer School of Physics, Sinaia 2012 Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest AC coupled channel AC -Unipolar (positive) BL shift δ Filt AC -Unipolar (negative)

19 What to do to avoid saturation? Conts (“price”) to reduce the “gain”  Resolution ( C f 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 ( R f smaller ) (OK only for high counting rate limitation) to reduce the fall time, how ? passively (smaller t f )  Resolution ( R f 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

20 G. De Geronimo, P. O’Connor, V. Radeka, B.Yu; FEE for imaging detectors, BNL a) & b)  for sequential reset c) through g)  for continuous reset Potential solutions for active 1 st stage

21 G. Pascovici, Carpathian Summer School of Physics, Sinaia 2012 Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest 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 !

22 ANALOGUE CIRCUITS TECHNIQUES, April, 2002; F. ANGHINOLFI ; CERN - 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. G DC ~ 30,000 Z o ~ 66 Ohm

23 “ A Large Ion Collider Experiment, ALICE-TPC -TDR”, ISBN , (1999), CERN

24 24 C. Chaplin, Modern Times (1936) crosstalk between participants  transfer function issue 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) 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 GSI-2012

25 25 Best performance: Majorana dedicated FEE (PTFE~0.4mm; Cu~0.2mm;C~0.6pF; R ~2GΩ Amorphous Ge (Mini Systems) ~ 55 eV ~ 50 µs (FWHM) BF862 (2V; 10mA) 1pF; 1 GΩ BAT17 diode (GERDA) 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

26 26 Pole /Zero Adj. Fast Reset (Ch2) Pole /Zero Adj. Fast Reset (Ch1) Differential Buffer (Ch1) Ch1 ( tr ~ 25.5 ns) Ch2 ( tr ~ 27.0 ns) Common Charge Sensitive Loop + Pulser + Wiring Differential Buffer (Ch2) Ch 1 ~200 mV / MeV Ch 2 ~ 50mV / MeV Programmable Spectroscopic Pulser Pulser CNTRL C-Ch1 /C-Ch1 INH1 SDHN1 C-Ch2 /C-Ch2 INH2 SDHN2 one MDR 10m cable Ch1 (fast ~19 MeV Ch2 (linear mode) Segments (linear mode) Dual Gain Core Structure 2keV /- 12V in two modes & four sub-ranges of operations: a) Amplitude and b) TOT 36_fold segmented HP-Ge detector + cold jFET

27 27 R1 Segment Non-Inverting Segment CSP  Negative Output Core Inverting AGATA CSPs – the versions with large open loop gain ( INFN-Milan – IKP-Cologne ) P/Z cancellation from Active Reset why large A o > 100,000 ?  frequency compensation, slope & crosstalk Cv * (Cv) stability adj. DC coupled AC coupled Core CSP  Positive Output

28 28 Fast Reset as tool to implement the “TOT” method Core Active Reset OFF Fast Reset circuitry Core -recovery from saturation (but base line …) one of the segments G. Pascovici, Carpathian Summer School of Physics, Sinaia 2012 Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest

29 29 Fast Reset as tool to implement the “TOT” method Core Active Reset – OFF Active Reset – ON - very fast recovery from TOT mode of operation - fast comparator LT1719 (+/- 6V) - factory adj. threshold + zero crossing - LV-CMOS (opt) - LVDS by default ToT Normal analog spectroscopy Fast Reset circuitry Core -recovery from saturation one of the segments G. Pascovici, Carpathian Summer School of Physics, Sinaia 2012 Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest > 220 +/-15V

30 30 Fast Reset as tool to implement the “TOT” method Core Active Reset – OFF Active Reset – ON ToT Normal analog spectroscopy Fast Reset circuitry Core -recovery from saturation 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 G. Pascovici, Carpathian Summer School of Physics, Sinaia 2012 Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest > 220 +/-15V

31 31 see Francesca Zocca PhD Thesis, INFN, Milan A. Pullia at al, Extending the dynamic range of nuclear pulse spectrometers, Rev. Sci. Instr. 79, (2008) G. Pascovici, Carpathian Summer School of Physics, Sinaia 2012 Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest

32 32 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, (2008)

33 33  10 MeV Due to FADC; G=3 range ! X-talk ! with CMOS

34 34 AGATA Dual Core crosstalk test measurements Ch2 (analog signal) vs. LVDS-INH-C1 (bellow & above threshold) INH_Threshold - (~ 4mV) INH_Threshold + (- 1mV) INH_Ch1/+/ INH_Ch1/-/ INH_Ch1/+/ LV_CMOS Core amplitude just below the INH thresholdCore amplitude just above the INH threshold t f ~ 2.45 ns t r ~ 1.65 ns INH_Threshold Vp-Vp (~ 1mV) INH_Threshold + (~ 4mV) LV_CMOS AGATA Dual-Core LVDS transmission of digital signals: - INH-C1 and INH-C2 (Out) and Pulser Trigger (In) signals (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

35 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 +/-12V … ( and ~ 220 +/- 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

36 Interaction of muons with matter Low energy correction: excitation and ionization ‘density effect’ High energy corrections: bremsstrahlung, pair production and photo-nuclear interaction 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) 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,

37 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,

38 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 & high- gain core signals (both in ToT mode of operation) David Schneiders, Cosmic radiation analysis by a segmented HPGe detector, IKP-Cologne, Bachelor thesis, Experimental results for cosmic ray measurement

39 R.Breier et al., Applied Radiation and Isotopes, 68, , 2010 Averaged calibrated segments sum +++ Averaged calibrated Low gain Core xxx Scaled pulser calibration (int. & ext.) ---- Combined spectroscopy up to ~170 MeV Direct measurement of cosmic rays with a HP-Ge AGATA detector, encapsulated and 36 fold segmented David Schneiders, Cosmic radiation analysis by a segmented HPGe detector, IKP-Cologne, Bachelor thesis,

40 Transfer Function & Crosstalk Transfer function - calculation (Frequency domain, Laplace transf., time domain) - measurement  spectroscopic pulser - applications: - bulk capacities measurement - crosstalk measurements and corrections

41 Detector The AC coupled Pulser - classical approach ! In standard way the pulser input signal is injected AC (1pF) in the gate electrode of the jFET 1pF 50 Ω δ q (t)

42 G. Pascovici, Carpathian Summer School of Physics, Sinaia 2012 Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest δ q (t)

43 43 AGATA HP-Ge Detector Front-End Electronics AGATA – 3D Dummy detector G. Pascovici, Carpathian Summer School of Physics, Sinaia 2012 Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest Cold part Warm part

44 44 Cold part Warm part AGATA HP-Ge Detector Front-End Electronics G. Pascovici, Carpathian Summer School of Physics, Sinaia 2012 Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest

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46 Simple current dividing rule Rewritten as a Laplace transform of an exp. decaying function with If τ 1 is sufficiently small, the exponential function can be “δ(t)“ and than the transfer function becomes: equivalent input impedance of the preamplifier Miller part Cold resistance

47 G. Pascovici, Carpathian Summer School of Physics, Sinaia 2012 Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest 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 … !

48 48 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

49 49 Parameter Potential Use / Applications Pulse amplitude  Energy, Calibration, Stability Pulse Form  Transfer Function 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) The use of PSP for self-calibrating G. Pascovici, Carpathian Summer School of Physics, Sinaia 2012 Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest

50 50 Analog Switches: - t on / t off, - Q i, - dynamic range (+/- 5V) Op Amp: - ~ R to R - bandwidth Coarse attenuation (4x 10 dB) ( z o ~150 Ohm) transmission line to S_ jFET and its return GND! +/- 1ppm 16 bit +/- 1bit fast R-R driver return GND CSP G. Pascovici, Carpathian Summer School of Physics, Sinaia 2012 Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest

51 51 Cold part Warm part AGATA HP-Ge Detector Front-End Electronics G. Pascovici, Carpathian Summer School of Physics, Sinaia 2012 Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest

52 Uncorrected for individual segment gain Pulser Ratio Core / Segments Corrected for each individual segment gain

53 C 0-X4 = 1.19 pF C 0-X5 = 1.16 pF C 0-X6 = 0.98 pF C 0-X1 = pF C 0-X2 = pF C 0-X3 = pF Agata measured capacities : Core and Segment crosstalk Core normalization Segment normalization Observed shift in segments

54 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. 3D Space charge reconstruction in highly segmented HP-Ge detectors through CV measurements, using PSP G. Pascovici, Carpathian Summer School of Physics, Sinaia 2012 Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest

55 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

56  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) = [N D -N A ] where N D ; N A 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

57 Electrical model of 36-fold segmented detector Core electrode Current [pA] Bias [V] G. Pascovici, Carpathian Summer School of Physics, Sinaia 2012 Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest

58 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)

59 59 Pulser peak position for different voltages of det. C006 [10 10 /cm 3 ] Crystal Height [mm]

60 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 Energy vs. Applied Voltage Detector Capacity vs. Applied Voltage

61 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

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63 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

64 The segment sum energy for E γ = keV plotted for different segment multiplicities (‘fold’ – number of hit segments) Energy shift and ‘resolution’ vs. segment ‘fold’

65 The data points in this figure show peak energy shifts of the keV line of 60 Co 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

66 Miniball (HeKo) PSC 823 PSC-2008 AGATA like Miniball (Eurysis /Ortec propr. prod.) (differential out.) Technical Specifications - conversion factor ~ 200 mV/MeV (PSC-2008 opt. 100 mV/MeV) - open loop gain A o ~ 20,000 T he new series 2008 & single ended - reconfigurable as Inv. / Non Inv.); - A o ~ 100,000 - adjustments: - I drain ; - P/Z adj. ; - Offset adj. ; Bandwidth - differential outputs - adjustments: - I drain ; - 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) INH SHDN Either BF862 or IF1320

67 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

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69 69 AGATA Dual Gain Core Final Specs. Summary active reset: - active 2 nd stage - active 1 st 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

70 By design optimized Transfer Function (no over/under-shoots) Crosstalk requirements < core-segment MINIBALL Charge Sensitive Preamplifier Specifications Parameter IKP-Cologne (Miniball – jFET IF1320) Sensitivity ( mV / MeV ) ~ 175 mV/MeV ( single ended ) Resolution (Cd= 0pF; cold FET) ~ 600 eV Slope ( + eV/ pF) [Cd] < 10 eV / pF ( cold FET ) Rise time (Cd= 0pF); ~ 15 ns ( cold FET) Slope ( + ns/ pF) [Cd] ~ 0.3 ns ( ~ 25 ns / 33 pF ) [50 Ohm] / Power [mW] ~ 4.5V /~ 450 mW ( + /- 12V  Op.Amp.LM ) Saturation of the 1st equiv. ~100 MeV ~60mW_ jFET) Open Loop Gain ~ 20,000 G. Pascovici, Carpathian Summer School of Physics, Sinaia 2012 Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest

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72 72 Front End Electronics for particles LYCCA's & TASCA’s DSSSD & Solar Cell Matrix LYCCA a core device for RISING HISPEC/DESPEC Objective is to uniquely identify event-by-event exotic nuclei by: mass A charge Z Flexible array of detector modules to measure: E, ∆E, Position, ToF (B) G. Pascovici, Carpathian Summer School of Physics, Sinaia 2012 Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest

73 G. Pascovici, Institute of Nuclear Physics, Univ. of Cologne A. Wendt et al – Der LYCCA-Demonstrator, HK 36.60, DPG, Bonn, 2010

74 74 TASISpec (TASCA) A new detector Set-up for Superheavy Element Spectroscopy LYCCA-0 Set-up for DSSSD + CsI

75 75 G. Pascovici, Carpathian Summer School of Physics, Sinaia 2012 Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest

76 76 ~1.25 sq.cm G. Pascovici, Carpathian Summer School of Physics, Sinaia 2012 Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest

77 G. Pascovici, Carpathian Summer School of Physics, Sinaia 2012 Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest

78 78 Sub - nanosecond CSP version A D 8351 t r ~ 200 gain 10dB (Vc ~ 3-5 V; 28 mA) alternative AD 8352 Ultrafast Voltage comparator family: ADCMP580 / ADCMP581 / ADCMP582 GaAs – HEMT *) (Q1, Q2) ultra-fast, narrow time output - fast rise time t r ~ 200ps !) energy output t f ~10 µs (no P/Z cancellation) high counting rates timing > ~1 Mcps dominant pole compensation included low power +/- 6V E; +/- 3V T) *) not implemented for LYCCA 8 GHz equivalent input rise time bandwidth < 40 ps typical output rise/fall 10 ps deterministic jitter (DJ) 200 fs random jitter (RJ) −2 V to +3 V input range with +5 V/−5 V supplies on-chip terminations at both inputs Resistor-programmable hysteresis Differential latch control Power supply rejection > 70 dB Silicon Germanium (SiGe) bipolar process G. Pascovici, Carpathian Summer School of Physics, Sinaia 2012 Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest

79 Pulse generator: - Tektronix PG502 modified (less than 700ps rise/fall time) - refurbish PG503 Scope: LeCroy 44Xs (400 Mhz, 2.5 GHz sampling) t r ~ 500 ps jFET, FET, HEMT selection a) jFET, FET BF861 (1,B,C); BF862; BF 889 b) GaAs-FETs (E-pHEMT) ATF-35143; ATF-55143; ATF c) I drain, V drain  to optimize the noise & bandwidth characteristics (10-15 mA, V, 20-30mW) G. Pascovici, Carpathian Summer School of Physics, Sinaia 2012 Institute of Nuclear Physics, Univ. of Cologne and NIPNE-HH, Bucharest

80 Advanced solution for FEE : - to extend the dynamic range with a combined dual gain and dual ToT method - transfer function tools ( from dummy to freq. comp.) - programmable spectroscopic pulser - applications as: - impurities concentration MeV equiv. gamma range - crosstalk corrections


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