tools for discovery
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Tools for Discovery
Digital Pulse Processing WorkshopSeptember 22nd 2010, GSI
Carlo Tintori
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Outline
• Description of the hardware of the waveform digitizers
• Use of the digitizers for physics applications
• Comparison between the traditional analog acquisition chains and the new fully digital approach
• DPP algorithms:• Pulse triggering
• Zero suppression
• Pulse Height Analysis
• Charge Integration
• Gamma-Neutron discrimination
• Time measurement
• Multi Channel Scaler
• Overview on the CAEN Digitizer family
• Experimental setup description and practical demonstrations
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• The principle of operation of a waveform digitizer is the same as the digital oscilloscope: when the trigger occurs, a certain number of samples (acquisition window) is saved into one memory buffer
• However, there are important differences:– no dead-time between triggers (Multi Event Memory)– multi-board synchronization for system scalability– high bandwidth data readout links– on-line data processing (FPGA or DSP)
PRE POST TRIGGER
ACQUISITION WINDOW
Sampling Clock
TRIGGER
Time
TIME STAMPS[0]
S[n-1]
S[1]S[2]S[3]
Memory Buffer
Digitizers vs Oscilloscopes
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ADC
FIXED GAINAMPLIFIER
+
DAC
FPGA(AMC)
SRAMMEMORY
DAUGTHER BOARDS
FPGA(VME)
LOCAL BUS
PLL
CONET
CLK-IN
INT. OSCILL.
MOTHER BOARD
TRG-IN
SYNC-IN
TRG-OUT
GLOBAL TRG
SYNC
SELF TRG
I/Os
CLK-OUT
SAMPLING CLOCK
DAC MONITOR
ANALOGINPUTs
VME/USB
n CHANNELS
Block Diagram
• Mother-daughter board configuration:
• The mother board defines the form-factor; it contains one FPGA for the readout interfaces and the services (power supplies, clocks, I/Os, etc…)
• The daughter board defines the type of digitizer; it contains the input amplifiers, the ADCs, the FPGA for the data processing and the memories
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PLL
FPGA
Opt. Link
LOCAL BUS
DC-DC
ADC
FPGA
Memory
Lin. Reg.
DC-DC
I/OsCLK in-out
VME
TRG in-outDAC out
Board Layout
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Multi-board synchronization (I)
• Clock distribution
• External Clock In/Out (differential LVDS)
• Clock Distribution: • Daisy Chain: Clock-Out to Clock-In chain (the first board can act as a
clock master)• Fan-Out: one clock source + 1 to N fan-out
• High performance and low jitter PLL for clock synthesis• Frequency multiplication: necessary when the sampling clock frequency
is high• Jitter cleaning: the PLL can reduce the jitter coming from the external
clock source
• Programmable clock phase adjust to compensate the cable delay
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• Trigger and Sync Distribution• External Trigger In/Out plus 16 PIOs(*) for individual trigger
propagation
• Trigger Time Stamp synchronous with the ADC sampling clock
• External Sync input to start-stop the acquisition synchronously and/or to keep the time stamp alignment between boards
• External Trigger and Sync must be synchronous with the sampling clock, otherwise the re-synchronization causes a one clock period jitter between the boards
• The trigger in-out daisy chain can be used to distribute both trigger and sync synchronously with the sampling clock
• In any case, when the trigger represents also a precise time reference, it is necessary to digitize it using one channel
• The trigger latency can be compensated by means of the pre-trigger size (memory look back)
(*) VME boards only
Multi-board synchronization (II)
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• Trigger types:• External Trigger (same as the ‘Ext Trigger’ in the scopes)• Software Trigger (same as the ‘Auto Trigger’ in the scopes)• Self-Trigger (same as the ‘Normal Trigger’ in the scopes)
• The trigger can be common to all the channels in a board (like in the scopes) or individual
• Self trigger: just a digital comparator (voltage threshold) or advanced triggers based on algorithms implemented in the FPGAs (input pulse recognition)
• Programmable Acquisition Window and Pre/Post Trigger Size
• Dead-Timeless Multi Event Acquisition (memory paging)
• VME digitizers can use the digital I/Os to send and receive the individual self-triggers to an external logic unit (like the V1495) to make coincidences, multiplicity, neighbour trigging, etc…
• Individual trigger propagation and coincidence is used for segmented germanium detectors, silicon strip detectors, wire chambers, PET, etc…
Triggers and acquisition
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• Analog Bandwidth <= Sampling rate / 2
• LSB = Dynamic Range / 2Nbit
• Quantization noise: = LSB / 12 = ~ 0.3 LSB
• SNR = 20 log (S/N); THD = 20 log (S/D); SINAD = 20 log (S / (N+D))
• Effective Number of bits: ENOB = (SINAD – 1.76dB) / 6.02
• Oversampling: Fovs = 4 Nadd * Fs N’bit = Nbit + NAdd
• Sampling clock jitter: SNRJITTER = -20 log (2 FANALOG TJITTER)
• Other sources of noise: DNL, INL
Fundamentals of A/D conversion
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• Traditionally, the acquisition chains for radiation detectors are made out of mainly analog circuits; the A to D conversion is performed at the very end of the chain
• Nowadays, the availability of very fast and high precision flash ADCs permits to design acquisition systems in which the A to D conversion occurs as close as possible to the detector
• In theory, this is an ideal acquisition system (information lossless)
• The data throughput is extremely high: it is no possible to transfer row data to the computers and make the analysis off-line!
• On-line digital data processing in needed to extract only the information of interest (Zero Suppression & Digital Pulse Processing)
Digitizers for Physics Applications
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Traditional chain: example 1charge sensitive preamplifiers
DECAY TIMERISE TIME
TIME Q = ENERGY
PEAK AMPLITUDE = ENERGY
ZERO CROSSING
This delay doesn’t depend on the pulse amplitude
DETECTOR
PREAMPLIFIER
SHAPING AMPLIFIER
TIMING AMPLIFIER
CFD
CFD OUTPUT
DETECTOR
Charge SensitivePreamplifier
SHAPINGAMPLIFIER
ENERGY
POSITION,IDENTIF.
TIMING
COUNTINGSHAPING TIME,GAIN THRESHOLDS
PEAK SENSING ADC
DISCRIMINATOR
TDC
SCALER
LOGICUNIT
Trigger, Coincidence
Fast Out
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TIME Q = ENERGY
ZERO CROSSING
DETECTOR
CFD
GATE
DELAYED SIGNALCHARGE
INTEGRATION
• The QDC is not self-triggering; need a gate generator
• need delay lines to compensate the delay of the gate logic
TransimpedancePreamplifier
(optional)
SPLITTER
DETECTOR
ENERGY
POSITION,IDENTIF.
TIMING
COUNTINGTHRESHOLDS
DISCRIMINATOR
TDC
SCALER
LOGICUNIT
Gate
QDCDelayLine
Traditional chain: example 2trans-impedance (current sensitive)
preamplifier
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• One single board can do the job of several analog modules
• Full information preserved
• Reduction in size, cabling, power consumption and cost per channel
• High reliability and reproducibility
• Flexibility (different digital algorithms can be designed and loaded at any time into the same hardware)DETECTOR
ENERGY
SHAPE
TIMING
COUNTINGDPPIN
SAMPLESA/D INTERF
DIGITIZER COMPUTER
VERY HIGH DATA THROUGHPUT
Benefits of the digital approach
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• Example with Mod720: • 1 sample = 12 bit = 1.5 byte• 1 channel = 1.5 byte @ 250MHz = 375 MB/s• 1 VME board = 8 channels = 3 GB/s !!!
• Continuous acquisition not possible!
• Example2 (triggered acquisition):• Record length = 512 samples (~ 2 s) = 768 bytes per channel• Trigger Rate = 10 KHz• 1 VME board = ~ 61 MB/s
• Readout Bandwidth of CAEN digitizers:• VME with MBLT: 60 MB/s• VME with 2eSST: 150 MB/s• Optical Link: 70 MB/s• USB 2.0: 30 MB/s
Readout Bandwidth
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Digital Pulse detection (self-triggering)
• A good trigger is the basis for both the DPP and the Zero Suppression
• The aim of the self-trigger is to identify the good pulses and trigger the acquisition on channel by channel basis
• Pulse identification can be difficult because of the noise, baseline fluctuation, pile-up, fast repetition, etc…
• Trigger algorithms based on a fixed voltage threshold are not suitable for most physics applications
• It is necessary to apply digital filters able to reject the noise, cancel the baseline and to do shape and timing analysis
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DPP algorithms for triggering
TimeTrigger
Missed Pulse
Threshold
Bad Trigger
TimeTrigger
ThresholdInput Signal
TimingFilter
• Timing filter RC-(CR)N:• High frequency noise rejection (RC filter mean)• Baseline restoration (CR or CR2 filter 1st or 2nd derivative) to
reduce the pile-up and low frequency noise effects• Bipolar signal Zero crossing time-stamp (digital CFD)
• Constraints on the Time Over Threshold and/or Zero Crossing can be added to improve the noise rejection
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DPP for the Zero Suppression
• Data reduction algorithms can be developed to reduce the data throughput:– Full event suppression: one event (acquisition window) is discarded if no pulse is detected inside the window– Zero Length Encoding: only the parts exceeding the threshold (plus a certain number of samples before and after) are saved.
suppressed suppressed suppressed
ZLE threshold
Look BackWindow
Look AheadWindow
Region ofInterest
SAMPLEST T TSAMPLES SAMPLES
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DPP for the Pulse Height Analysis (DPP-TF)
• Digital implementation of the shaping amplifier + peak sensing ADC (Multi-Channel Analyzer)
• Implemented in the 14 bit, 100MSps digitizers (mod. 724)
• Use of trapezoidal filters to shape the long tail exponential pulses
• Pile-up rejection, Baseline restoration, ballistic deficit correction
• High counting rate, very low dead time
• Energy and timing information can be combined
• Best suited for high resolution spectroscopy (especially Germanium detectors)
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DPP-TF Block Diagram
DECIMATOR
RC-(CR)N
N = 1,2
COMP
TRAPEZOIDALFILTER
TRG & TIMING FILTER
COMP
ARMED
ZERO
TRIGGER
BASELINEMEAN
a b N
k m M
D
D = 1,2,4,8
Nsbl
Thr
SUB
INPUT
TIME STAMP
ENERGY
ftd Nspk
CLK
PEAKMEAN
COUNTER
b = RiseTime
Nsbl = Baseline Mean
Nspk = Peak meanftd = Flat Top Delay (ballistic deficit)
m = Flat Top
Thr = TRG Threshold
a = Low Pass mean
zero crossing
M = Time Constant (PZ cancellation)K = Shaping Time
TRAPEZOIDTIMINGFILTER
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DPP-TF / Analog Chain set-ups
N1470High
VoltageN968
ShapingAmplifier
N957Peak
Sensing ADC
DT572414bit @ 100MSpsDigitizer + DPP-TF
Energy
Energy
Time
Ge / SiC.S. PRE
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DPP-TF vs Analog Chain
• PROs– All in one board– Stability and reproducibility– Flexibility (FPGA based algorithms)– Counting rate (low dead-time)– Ballistic deficit correction– Timing information– Wide Dynamic Range– Channel density– Synchronization and coincidences in multiple channel systems– Total Cost per Channel
• CONs – Parameters set-up (need good software interface)– Getting started more difficult
Energy Resolution? Better or worse depending on the conditions
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DPP-TF: Test Results
FWHM @ 1.33 MeV: 2.2 KeV
• Germanium Detectors at LNL (Legnaro - Italy) in Nov-08 and Feb-09, at GSI (Germany) on May-09, at INFN-MI on Jan-10, in Japan on Feb-10, at Duke University (USA) on Jul-10; resolution = 2.2 KeV @ 1.33 MeV (60Co)
• Silicon Strip (SSSSD and DSSSD) and CsI detectors in Sweden at Lund and Uppsala (ion beam test)
• NaI detectors in CAEN (see demo)
• PET in U.S.A.
• Homeland security application using CsI
• BGO detector at ENEA ‘Centro Ricerche Casaccia’ (Rome)
228Th with DSSSD
60Co with Ge
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DPP for Segmented and Strip Detectors
• Same algorithms implemented in the DPP-TF (trapezoidal filters)
• Being implemented in the 14 bit, 100MSps digitizers (mod. V1724)
• Neighbour channels trigger logic: it must be possible to propagate the local trigger of any channel to any other channel, either within the board or from board to board
• Use of the GPIO[15:0] connected to a V1495 (general purpose programmable trigger unit)
• Triggered channel save an event made of Time Stamp, Energy and a short piece of Waveform (the rising edge, typically a few tens of samples)
• The memory buffers are used to pack many small events in order to increase the readout efficiency
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Neighbour triggers: example of application
• Drift of charge carriers induces a signal on adjacent electrodes
• The horizontal position can be calculated as a function of the induced charges
• The amplitude of the signal in the adjacent strips can be lower than the trigger threshold need neighbour triggers
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DPP for the Charge Integration(DPP_CI)
• Digital implementation of the QDC + discriminator and gate generator
• Implemented in the 12 bit, high speed digitizers ( Mod. 720(*) )
• Self-gating integration; no delay line to fit the pulse within the gate
• Automatic pedestal subtraction
• Extremely high dynamic range
• Dead-timeless acquisition (no conversion time)
• Energy and timing information can be combined
• Typically used for PMT or SiPM/MPPC readout and for gamma-neutron discrimination in scintillating detectors
(*) Implementation in the Mod751 is being studied
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DPP-CI Block Diagram
INPUT
a = Low Pass mean
b = RiseTimeThr = TRG Threshold
W = Gate width
Nsbl = Baseline mean
TIMING FILTER
GATE
DELAYED INPUT
D = Delay (Pre-Gate) COMP
DELAY
TRG & TIMING FILTER
TRIGGER
BASELINEMEAN
a b
Nsbl
Thr
SUB
INPUT
TIME STAMP
CHARGE
W
CLK COUNTER
ACCUMULATOR(INTEGRATOR)
DMONOSTABLE
GATE
QLSB = TS * VLSB / 50 = 40 fC (Mod 720)
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DPP-CI / Analog Chain set-ups
N1470High
Voltage
DT572012bit @ 250MSpsDigitizer + DPP-CI
Charge
Charge
Time
NaI(Tl)
PMT
Dual TimerN93B
DelayN108A
QDCV792N
CFDN842
TDC V1190 Time
SplitterA315
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DPP-CI vs Analog Chain• PROs
– All in one board– Stability and reproducibility Flexibility – (FPGA based algorithms)– Self-Independent-Retroactive-Adaptive Gate– No conversion time (dead-timeless acquisition)– Baseline restoration– Accept positive, negative and bipolar signals– Extremely wide Dynamic Range– Coincidences between couples of channels– Total Cost per Channel
• CONs – Parameters set-up (need good software interface)– Getting started more difficult– Channel density
Energy Resolution? Better or worse depending on the conditions
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DPP-CI: Test Results
DPP-CI Analog QDC
Energy (MeV) Res (%) Res (%)
0.481 (137Cs Compton edge)
9.41 1.18 12.80 0.70
0.662 (137Cs Photopeak) 7.01 0.04 8.17 0.04
1.33 (60Co Photopeak) 5.67 0.03 6.66 0.18
1.17 (60Co Photopeak) 5.46 0.02 5.89 0.13
2.51 (60Co Sum peak) 3.82 0.11 4.10 0.24Resolution = FWHM * 100 / Mean
NaI detector and PMT directly connected to the QDC or digitizer
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DPP-CI: Other Tests
• Tested with SiPM/MPPC detectors at Univerità dell’Insubria (Como – Italy) and in CAEN (2009/2010):– Dark Counting Rate– LED pulser– Readout of a 3x3mm Lyso Crystal + Gamma source– Readout of a scintillator tile for beta particles
•0.5 ph
•1.5 ph
•2.5 ph
•Th
resho
ld scan
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DPP for -n Discrimination
• Digital implementation of the E/E or Rise Time discriminator (both are Pulse Shape Analysis)
• Digital E/E: double gate charge integration (same as DPP-CI but with two gates); applied to fast output (typ. organic liquid scintillators)
• Digital Rise Time discrimination: T in the Zero Crossing of two CFDs at 25% and 75%; applied to integrated output (either from C.S. preamp or digital integrator)
• PSA used to discard unwanted events (typ. gammas); good events saved including waveform, energy and time stamp
• Dead-timeless acquisition (no conversion time)
• Algorithms tested at Duke University on July 2010 (off-line). FPGA implementation in progress.
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-n Discrimination Block Diagram (I)
SHORT GATE
LONG GATE
Algorithms tested off-line
Firmware being implemented
DELAY
BASELINE
BLns
TRGthr
SUBINPUT
TIME STAMP
Q-FAST
CLKTIME
COUNTER
GATE1
ACCUMULATOR(INTEGRATOR)
COMPTRIGGER
BLthr GateWidth1
WAVEFORM
PULSE SHAPEDISCRIMINATOR
GATE2
EV
EN
T B
UIL
DE
R
PSDthr
Q-SLOW
PreTrigger
GateWidth2
OUTDATA
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-n Discrimination Block Diagram (II)
T
Algorithms tested off-line
Firmware not planned
DELAY
BASELINE
BLns
TRGthr
SUBINPUT
TIME STAMPCLK
TIME COUNTER
COMP
T1
BLthr
WAVEFORM
PULSE SHAPEDISCRIMINATOR
PreTrigger
CFD DELAY
25% ATTEN
75% ATTEN
SUB
SUB
ZC
ZC
EV
EN
T B
UIL
DE
R
T2
OUTDATA
PSDthr
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-n Discrimination: preliminary results (I)
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-n Discrimination: preliminary results (II)
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-n Discrimination: preliminary results (III)
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-n Discrimination: preliminary results (IV)
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DPP for Time Measurements
• Digital implementation of the TDC + CFD
• DPP-TF and DPP-CI give time stamps with the resolution of the sampling period (10 ns and 4 ns, = Ts/12); no interpolation for better timing information
• Digital algorithms to implement Constant Fraction Discriminators or Timing Filters (RC-CRN)
• Extremely high dynamic range
• Dead-timeless acquisition (no conversion time); can manage long bursts of pulses (theoretical unlimited double pulse resolution)
• Interpolation between a set of samples can increase the resolution well beyond the sampling period (up to picoseconds)
• Big dependence of the resolution from the rise-time and amplitude of the pulses (V/ T)
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Digital algorithms for Timing Analysis
• Positive/negative pulses digitally transformed into bipolar pulses
• The Zero Crossing doesn’t depend on the pulse amplitude
• Timing filters: RCN or Digital CFD
• Optional RC filter (mean filter) to reduce the HF noise
• ZC interpolations:
• Linear (2 points)
• Cubic (4 points)
• Best fit line or curve (4 or more points) S1
S2
S3
S4S4 = ZC time stampResolution = Ts / 12
High Resolution ZC aftermath. Interpolation
TimeINPUT
Timing Filter
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INPUT
CR2 Filter:2nd derivative
CR Filter:1st derivative
Digital CFD
e-t/T
-(1/T) e-t/T
(1/T2) e-t/T
K e-t/TK = f(D, F)
D = CFD delay
F = CFD Fraction
Digital CFD and Timing Filters
NOTE: the higher ZC slope and the lower tail, the better filter
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ZC timing errors• The timing resolution is affected by three main
sources of noise:– Electronic noise in the analog signal (not
considered here)– Quantization error Eq– Interpolation error Ei
• Both simulations and experimental test demonstrate that there are two different regions:
• When Rise Time > 5*Ts the pulse edge can be well approximated to a straight line, hence Ei is negligible. The resolution is proportional to the rise time and to the number of bits of the ADC.
• When Rise Time < 5*Ts the approximation to a straight line is too rough and Ei is the dominant source of error. The resolution is still proportional to the number of bit but becomes inversely proportional to the rise time. Resolution improvement expected for cubic interpolation.
• The best resolution is for Rise Time = 5*Ts, regardless the type of digitizer
• The resolution is always proportional to the pulse amplitude (more precisely to the slope V/T)
SN
SN+1
TSAMPL
LSBADC
zero
Eq
Ei
ANALOG SIGNAL
LINEAR INTERPOLATION
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Sampling Clock phase effect (RT<5Ts) (I)
ERRA
CHA CHB
ERRB
DELAYA-B = N*TS
CHA CHB
ERRA ERRB
DELAYA-B = (N+0.5)*TS
DELAYAB = N * Ts: same clock phase for A and B same interpolation error ERRA ERRB Error cancellation in calculating TIMEAB
TIMEAB = (ZCA + ERRA) – (ZCB + ERRB) = ZCA– ZCB + (ERRA - ERRB )
DELAYAB = (N+0.5) * Ts:rotated clock phase for A and B different interpolation error ERRA ERRB No error cancellation. ERRA and ERRB are symmetric: twin peak distribution
When rise time < 5*Ts, the interpolation error has a big variation with the phase between the rising edge and the sampling clock.
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Sampling Clock phase effect (RT<5Ts) (II)
0
100
200
300
400
500
600
700
800
900
0 200 400 600 800 1000 1200 1400 1600
'histo_Mod724_dt10n.txt'
'histo_Mod724_dt15n.txt'
DELAY = N * Ts
DELAY = (N + 0.5) * Ts
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Sampling Clock phase effect (RT<5Ts) (III)
0.01
0.1
1
10
0.5 1 1.5 2 2.5
Std
_D
ev[
ns]
Delay in Ts
Mod1751: 10bit 1GSps
Mod1720: 12bit 250MSps
Mod1724: 14bit 100MSps
10bit – 1GSps
12bit – 250MSps
14bit – 100MSps
Vpp = 100mV
Rise Time = Ts
Emulation
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Sampling Clock phase effect (RT<5Ts) (IV)
Vpp = 100mV
Mod720: 12bit 250MSps
Emulation
0.01
0.1
1
10
3 4 5 6 7 8 9
Std
_D
ev[
ns]
Delay[ns]
RiseTime 5ns
RiseTime 10ns
RiseTime 15ns
RiseTime 20ns
RiseTime 30ns
5 ns10 ns15 ns20 ns30 ns
Rise Time
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Preliminary results: Mod724
DELAYAB = (N+0.5) * Ts (worst case)
50 mV
100 mV
200 mV
500 mV
(14 bit, 100 MS/s)
RiseTime (ns)
Std
Dev
(n
s)
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Preliminary results: Mod720
50mV
100mV
200mV
500mV
(12 bit, 250 MS/s)
DELAYAB = (N+0.5) * Ts (worst case)
RiseTime (ns)
Std
Dev
(n
s)
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Preliminary results: Mod751
50mV
100mV
200mV
500mV
(10 bit, 1 GS/s)
DELAYAB = (N+0.5) * Ts (worst case)
NOTE: the region with Rise Time < 5*Ts (5 ns) is missing in this plot
RiseTime (ns)
Std
Dev
(n
s)
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Mod724 vs Mod720 vs Mod751
10 bit, 1 GS/s
12 bit, 250 MS/s
14 bit, 100 MS/s
RiseTime (ns)
Std
Dev
(n
s)
Amplitude = 100 mV
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Mod751 @ 2 GS/sS
tdD
ev (
ns)
Amplitude (mV)
2 ps !
RT = 1 ns - worst case
RT = 1 ns - best case
RT = 5 ns
The cubic interpolation can reduce the gap between best and worst case as well as increase the resolution for small signals!
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DPP for Pulse Counting (SCA)
• Digital implementation of the discriminator + scaler (Single-Channel Analyzer)
• Can be implemented in the high density digitizers (mod. 740)
• Pulse Triggering: baseline restoration, noise rejection, etc…
• Single or Multi-Channel Energy Windowing
COMPCR-RC
ThrL
INPUT
ACTIVITYCOUNTER
COMP
ThrH
ThrH
ThrL
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DPP readout modesWaveform mode• same operating mode of the standard firmware (except for the individual
pulse triggering). 1 event = record of samples (waveform). Typ. thousands of numbers.
• The memory buffer contains one acquisition window (1 trigger 1 buffer)
• Mainly used for debugging and parameters setting
• High data throughput low counting rate (typ. < 1KHz)
• The waveform mode allows the users to develop and test new DPP algorithms (off-line analysis)
List mode• 1 event = 1 or 2 numbers: Energy (Charge or Height) and/or Time Stamp
• The memory buffer contains many events (N triggers 1 buffer)
• Small event size high counting rate (1 MHz or more)
• Histograms, coincidences, etc… easily implemented off line
Mixed Mode• Energy and/or Time stamps saved together with a small piece of waveform for
post-analysis.
• 1 event = ~100 numbers. 1 buffer = N events.
• On-line pulse shape discrimination for event validation (discard unwanted events)
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Building new DPP algorithms
• The digitizer is a general purpose acquisition module; in most cases it requires a dedicated firmware or software to implement a specific application
• The first algorithm validation can be done using software signal emulators (mathlab, LabView, C/C++, etc…). Everything happens inside the computer
• Then it is then possible to verify the algorithms applying them to real data read from the digitizer in oscilloscope mode (DPP off-line)
• Once validated, the algorithm must be implemented in the FPGA (VHDL or Verilog) of the digitizer
• Finally, the algorithm can be tested on-line
• CAEN is open to collaborate with the customers at any level of the previous design flow
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CAEN Waveform Digitizers
• VME, NIM, PCI Express and Desktop• VME64X, Optical Link (CONET), USB 2.0,
PCI Express Interfaces available• Memory buffer: up to 10MB/ch (max. 1024
events)
• Multi-board synchronization and trigger distribution
• Programmable PLL for clock synthesis• Programmable digital I/Os• Analog output with majority or linear sum• FPGA firmware for Digital Pulse Processing
– Zero Suppression– Pulse Triggering– Trapezoidal Filters for energy calculation– Digital CFD for timing information– Digital Charge Integration– Pulse Shape Analysis– Coincidence– Possibility of customization
• Software Tools for Windows and Linux
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Digitizers Table
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Mod724: 14 bit, 100 MS/s
• Very high resolution and low noise digitizer
• DPP-TF for Pulse Height Analysis (Trapezoidal Filters)
• Replacement of the shaping amplifier + peak sensing ADC
• Three dynamic range options (500mVpp, 2.25Vpp and 10Vpp)
• Best suited for very accurate energy measurements
• Good timing resolution with slow signals (rise time >= 50 ns)
• Mid-Low speed signals (Typ: output of charge sensitive preamplifiers)
• Applications:
• Spectroscopy (MCA) with Ge, Si and other detectors
• Any application using charge sensitive pre-amplifiers
• Low noise applications
• Neutrino and dark matter physics
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Mod720: 12 bit, 250 MS/s
• Best compromise between resolution and speed
• DPP-CI for Charge Integration
• Best suited for PMT and SiPM/MPPC readout
• Mid-High speed signals (Typ: output of PMT/SiPM)
• Good timing resolution with fast signals (rise time < 100 ns)
• Applications:
• Spectroscopy with NaI, CsI and other detectors (fast pre-ampli)
• Gamma Neutron discrimination
• Single Photon Counting
• PET
• Homeland Security
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Mod740: 12 bit, 65 MS/s• High channel density
• No DPP available (few FPGA resources)
• Best suited for high density systems
• Low speed signals (Typ: output of sensors, CCDs or shaping amplifiers)
• Applications:
• Sensors readout (temperature, pressure, CCD, etc…)
• Coincidence Matrix
• Imaging
• Single channel analyser
• Readout of Shaping Amplifiers
• TPC readout systems
• Any application with many channels
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Mod751/761: 10 bit, 1-2-4 GS/s
• Very high sampling rate
• 2 GS/s: half channels; 4GS/s: one fourth channels
• No DPP available (DPP-CI perhaps available in the future)
• Best suited for very high speed detectors (diamond? LaBr? …)
• High speed signals (Typ: output of wideband amplifiers)
• Applications:
• Diamond detectors
• RPC readout systems
• Time of flight
• Fast PMT readout
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Mod721/731: 8bit, 0.5-1 GS/s
• Precursor of the Mod751; today its low cost version
• No DPP available
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Mod742: 12bit, 5 GS/s
• Excellent combination of very high sampling rate, resolution and high density
• Based on the DRS chip (developed by S. Ritt at PSI)
• No DPP available (at least for the moment)
• Best suited for very high energy and timing resolution applications
• Very high speed / high dynamics signals
• Mixed fast and slow acquisition mode
• 50-100us Dead Time: not suitable for high counting rate
• Max. 1024 points: not suitable for long pulses
• Applications:
• Fast detector test benches
• Cherenkov Telescopes
• Ultra precise Pulse Shape discrimination
• Very high resolution TDC (5-10 ps)?
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DPP firmware table
Name Mod Status Detectors (typ.)
Notes
DPP-TF 724 Ready Hi res. Si, Ge Pulse Height analysis (Trapezoidal Filters)
DPP-CI 720 Ready PMT, SiPM Charge Integration (digital QDC)
DPP-NG 720 Q1 2011 Organic liquid -n Discrimination
DPP-SG 724 Q1 2011 Segmented/Strip DPP-TF for Segmented detectors
DPP-FCI 751 t.b.d. diamond Charge Integration with fast signals
DPP-PC 740 t.b.d. Plastic, strips Pulse Counting
DPP-TDC 751 761 742
t.b.d. High Res Timing
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Experimental Demo 1
N1470High
Voltage
EnergyNaI(Tl)
60Co
PMT
DT572414bit @ 100MS/s
Digitizer + DPP-TF
Charge SensitivePreamplifier for PMT
850V
USB
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Experimental Demo 2
N1470High
Voltage
ChargeLaBr3
60Co
PMT
DT572012bit @ 250MS/sDigitizer + DPP-CI
-650V
USB
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Experimental Demo 3
ChargeDT572012bit @ 250MS/sDigitizer + DPP-CI
USB
HIGH VOLTAGEBIAS GENERATOR
2 GHz, 0-50dBVARIABLE GAIN
WIDEBAND AMPLIFER
SiPM
SP5600
LEDPULSER
Trigger
USB
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Experimental Demo 4
N1470High
Voltage
WaveformDT575110bit @ 2GS/s
Digitizer
450V
USB
1.6 GHz – 52dBWideBand Amplifier
210Po
DPP off-line
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