Tackling the search for
Lepton Flavor Violation
with GHz waveform digitizing
using the DRS chip
Stefan Ritt
Paul Scherrer Institute, Switzerland
Agenda
MEG Experiment searching
for me g down to 10-13
DRS1
DRS2
DRS3
Feb. 26th, 2008
Fermilab
2
Motivation
Why should we search for m  e g ?
The Standard Model
Fermions (Matter)
u
c
Bosons
t
charm
top
photon
d
s
b
g
down
strange
bottom
ne
nm
nt
Leptons
muon
neutrino
tau
neutrino
e
m
t
electron
muon
tau
I
II
III
Feb. 26th, 2008
Fermilab
gluon
W
W boson
Z
Z boson
Force carriers
Quarks
up
electron
neutrino
Generation
g
Higgs*
boson
*) Yet to be confirmed
4
The success of the SM
• The SM has been proven to be extremely successful since 1970’s
• Simplicity (6 quarks explain >40 mesons and baryons)
• Explains all interactions in current accelerator particle physics
• Predicted many particles (most prominent W, Z )
• Limitations of the SM
• Currently contains 19 (+10) free parameters such as particle
(neutrino) masses
• Does not explain cosmological observation
such as Dark Matter and Matter/Antimatter
Asymmetry
Today’s goal is to look for
physics beyond the standard
model
Feb. 26th, 2008
Fermilab
CDF
5
Beyond the SM
Find New Physics
Beyond the SM
High Energy Frontier
High Precision Frontier
• Produce heavy new particles directly
• Heavy particles need large colliders
• Complex detectors
• Look for small deviations from SM
(g-2)m , CKM unitarity
• Look for forbidden decays
• Requires high precision at low energy
Feb. 26th, 2008
Fermilab
6
The Muon
Seth Neddermeyer
• Discovery: 1936 in cosmic radiation
ne
• Mass: 105 MeV/c2
• Mean lifetime: 2.2 ms
m   e n en m
W-
Carl Anderson
≈ 100%
m-
m   e n en m g
m   e g
e-
nm
0.014
< 10-11
led to Lepton Flavor Conservation
as “accidental” symmetry
Feb. 26th, 2008
Fermilab
7
LFV and Neutrino Oscillations
Neutrino Oscillations  Neutrino mass 
m  e g possible even in the SM
g
W-
m-
nm
ne
e-
 LFV in the charged sector is
forbidden in the Standard Model
n mixing
mn4
BR( m  e g )  4  10-60
SM
mW
-
Feb. 26th, 2008
-
Fermilab
8
LFV in SUSY
• While LFV is forbidden in SM, it is possible in SUSY
g
Wmn4
BR( m  e g )  4  10-60
SM
mW
-
m-
nm
e-
ne
-
mm2~~e
g
m~
m-
e~
~ 0
4
e-
me2m  100 GeV 
-5
tan2  ≈ 10-12
BR( m  e g )  10


2
SUSY
m  mSUSY 
Current experimental limit: BR(m  e g) < 10-11
Feb. 26th, 2008
Fermilab
9
History of LFV searches
cosmic m
• Long history dating back to 1947!
10-1
• Best present limits:
m→eg
mA → eA
m → eee
10-2
• 1.2 x 10-11 (MEGA)
10-3
• mTi → eTi < 7 x
10-4
10-13
(SINDRUM II)
• m → eee < 1 x 10-12 (SINDRUM II)
• MEG Experiment aims at 10-13
• Improvements linked to advance
in technology
10-5
stopped p
10-6
10-7
m beams
10-6
stopped m
10-9
10-10
10-11
SUSY SU(5)
BR(m  e g) = 10-13

mTi  eTi = 4x10-16

BR(m  eee) = 6x10-16
Feb. 26th, 2008
10-12
10-13
MEG
10-14
10-15
1940
Fermilab
1950
1960
1970
1980
1990
2000
2010
10
Current SUSY predictions
ft(M)=2.4 m>0 Ml=50GeV
1)
current limit
MEG goal
tan 
“Supersymmetric parameterspace
accessible by LHC”
1)
2)
J. Hisano et al., Phys. Lett. B391 (1997) 341
MEGA collaboration, hep-ex/9905013
Feb. 26th, 2008
W. Buchmueller, DESY, priv. comm.
Fermilab
11
Experimental Method
How to detect m  e g ?
Decay topology m  e g
meg
52.8 MeV
N
g
m
52.8 MeV
180º
10
20
30
40
50
60
Eg[MeV]
N
e
52.8 MeV
m
•
•
•
→ e g signal very clean
Eg = Ee = 52.8 MeV
qge = 180º
e and g in time
52.8 MeV
10
Feb. 26th, 2008
Fermilab
20
30
40
50
60
Ee[MeV]
13
“Accidental” Background
meg
g
Background
g
g
n
m  e nn
m
m
n
e
Annihilation
in flight
180º
e
e
n
m
m  e nn
n
m
•
•
•
→ e g signal very clean
Eg = Ee = 52.8 MeV
qge = 180º
e and g in time
Feb. 26th, 2008
Good energy resolution
Good spatial resolution
Excellent timing resolution
Good pile-up rejection
Fermilab
14
Previous Experiments
Exp./
Lab
Author
Year
Ee/Ee
%FWHM
Eg /Eg
%FWHM
teg
(ns)
qeg
(mrad)
Inst. Stop
rate (s-1)
Duty
cycle
(%)
Result
SIN
(PSI)
A. Van der
Schaaf
1977
8.7
9.3
1.4
-
(4..6) x 105
100
< 1.0  10-9
TRIUMF
P.
Depommier
1977
10
8.7
6.7
-
2 x 105
100
< 3.6  10-9
LANL
W.W.
Kinnison
1979
8.8
8
1.9
37
2.4 x 105
6.4
< 1.7  10-10
Crystal
Box
R.D. Bolton
1986
8
8
1.3
87
4 x 105
(6..9)
< 4.9  10-11
MEGA
M.L. Brooks
1999
1.2
4.5
1.6
17
2.5 x 108
(6..7)
< 1.2  10-11
?
?
?
?
?
?
~ 10-13
MEG
How can we achieve a quantum step in detector technology?
Feb. 26th, 2008
Fermilab
15
Collaboration
~70 People (40 FTEs) from five countries
Feb. 26th, 2008
Fermilab
16
Paul Scherrer Institute
Proton Accelerator
Swiss Light Source
Feb. 26th, 2008
Fermilab
17
PSI Proton Accelerator
Feb. 26th, 2008
Fermilab
18
MEG beam line
Rm ~ 1.1x108 m+/s at experiment
e+
m+
s ~ 10.9 mm
m+
Feb. 26th, 2008
Fermilab
19
Liquid Xenon Calorimeter
• Calorimeter: Measure g Energy, Position
and Time through scintillation light only
• Liquid Xenon has high Z and homogeneity
Refrigerator
• Extremely high purity necessary:
1 ppm H20 absorbs 90% of light
• Currently largest LXe detector in the
world: Lots of pioneering work necessary
Feb. 26th, 2008
Fermilab
Signals
Cooling pipe
• ~900 l (3t) Xenon with 848 PMTs
(quartz window, immersed)
• Cryogenics required: -120°C … -108°
H.V.
Vacuum
g
Liq. Xe
for thermal insulation
Al Honeycomb
window
m
PMT
Plasticfiller
1.5m
20
• Use GEANT to
carefully study
detector
• Optimize
placement of PMTs
according to MC
results
Feb. 26th, 2008
Fermilab
21
The complete MEG detector
Liq. Xe Scintillation
Detector
Liq. Xe Scintillation
Detector
Thin Superconducting Coil
g
Stopping Target
Muon Beam
e+
g
Timing Counter
e+
Drift Chamber
Drift Chamber
1m
Feb. 26th, 2008
Fermilab
22
Current resolution estimates
Exp./
Lab
Author
Year
Ee/Ee
%FWH
M
Eg /Eg
%FWHM
teg
(ns)
qeg
(mrad)
Inst. Stop
rate (s-1)
Duty
cycle
(%)
Result
SIN
(PSI)
A. Van der
Schaaf
1977
8.7
9.3
1.4
-
(4..6) x 105
100
< 1.0  10-9
TRIUMF
P.
Depommier
1977
10
8.7
6.7
-
2 x 105
100
< 3.6  10-9
LANL
W.W.
Kinnison
1979
8.8
8
1.9
37
2.4 x 105
6.4
< 1.7  10-10
Crystal
Box
R.D. Bolton
1986
8
8
1.3
87
4 x 105
(6..9)
< 4.9  10-11
MEGA
M.L. Brooks 1999
1.2
4.5
1.6
17
2.5 x 108
(6..7)
< 1.2  10-11
MEG
2008
0.8
4.3
0.18
18
3 x 107
100
~ 10-13
Feb. 26th, 2008
Fermilab
23
MEG Current Status
• Goal: Produce “significant” result before LHC
• R & D phase took longer than anticipated
http://meg.psi.ch
• Detector has been completed by the
end of 2007
• Expected sensitivity in 2008: 2 x 10-12
(current limit: 1 x 10-11)
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
Feb. 26th, 2008
R&D
Set-up
Engineering
Data
Taking
Fermilab
24
Pile-up in the DC system
• Pile-up can severely degrade the experiment performance ( MEGA
Experiment) !
• Traditional electronics cannot detect pile-up
TDC
Discriminator
Measure Time
hits
Amplifier
Need full
waveform digitization
> 100 MHz to reject pile-up
Moving average baseline
Feb. 26th, 2008
Fermilab
25
Beam induced background
108 m/s produce 108 e+/s produce 108 g/s
Cable ducts
for Drift Chamber
Feb. 26th, 2008
Fermilab
26
Pile-up in the LXe calorimeter
n
PMT
sum
0.511 MeV
meg
radiative
muon
decay
50
51.5 MeV
51
52
(menn)2 + g
g
m
e
e
m
Feb. 26th, 2008
E[MeV]
~100ns
t
• g’s hitting different parts of LXe can be
separated if > 2 PMTs apart (15 cm)
• Timely separated g’s need waveform
digitizing > 300 MHz
• If waveform digitizing gives timing
<100ps, no TDCs are needed
Fermilab
27
Requirements summary
• Need 500 MHz 12 bit digitization for Drift Chamber system
• Need 2 GHz 12 bit digitization for Xenon Calorimeter + Timing
Counters
• Need 3000 Channels
• At affordable price
Solution: Develop own
“Switched Capacitor Array” Chip
Feb. 26th, 2008
Fermilab
28
The Domino Principle
0.2-2 ns
Inverter “Domino” ring chain
IN
Waveform
stored
Clock
Shift Register
Out
FADC
33 MHz
“Time stretcher” GHz  MHz
Keep Domino wave running in a circular fashion and
stop by trigger  Domino Ring Sampler (DRS)
Feb. 26th, 2008
Fermilab
29
Switched Capacitor Array
• Cons
t
t
t
t
t
• No continuous acquisition
• No precise timing
• External (commercial) FADC needed
• Pros
• High speed (~5 GHz) high resolution (~12 bit equiv.)
• High channel density (12 channels on 5x5 mm2)
• Low power (10 mW / channel)
• Low cost (< 100$ / channel incl. VME board)
Feb. 26th, 2008
Fermilab
30
Folded Layout
Linear inverter chain causes non-linearity
Feb. 26th, 2008
Fermilab
31
“Tail Biting”
speed
enable
1
2
3
4
1
2
3
4
Feb. 26th, 2008
Fermilab
32
Sample readout
DRS1
Tiny signal
20 pF
0.2 pF
I
DRS2
~kT
Temperature
Dependence
DRS3
Feb. 26th, 2008
Fermilab
33
DRS3
DENABLE
DWRITE
DSPEED
DMODE
• Sampling speed
10 MHz … 5 GHz
• Readout speed
33 MHz, multiplexed
or in parallel
• 50 prototypes received
in July ‘06
MUX
WRITE SHIFT REGISTER
• 12 ch. each 1024 bins,
6 ch. 2048, …, 1 ch. 12288
IN0+
IN0IN1+
IN1IN2+
IN2IN3+
IN3IN4+
IN4IN5+
IN5IN6+
IN6IN7+
IN7IN8+
IN8IN9+
IN9IN10+
IN10IN11+
IN11-
DOMINO WAVE CIRCUIT
WSRCLK
SRIN
WSROUT
SRLOAD
RSRLOAD
RSRCLK
RSRRST
ENABLE
• Fabricated in 0.25 mm
1P5M MMC process
(UMC), 5 x 5 mm2,
radiation hard
DTAP A0 A1 A2 A3
DGND DVDD
CHANNEL 0
MUXOUT /
OUT0
CHANNEL 1
OUT1
CHANNEL 2
OUT2
CHANNEL 3
OUT3
CHANNEL 4
OUT4
CHANNEL 5
OUT5
CHANNEL 6
OUT6
CHANNEL 7
OUT7
CHANNEL 8
OUT8
CHANNEL 9
OUT9
CHANNEL 10
OUT10
CHANNEL 11
OUT11
BIAS
ROFS
STOP SHIFT REGISTER
SSROUT
READ SHIFT REGISTER
RSROUT
AGND AVDD
Feb. 26th, 2008
Fermilab
34
VME Board
USB adapter
board
32 channels input
40 MHz
12 bit
FADC
General purpose VPC board built at PSI
Feb. 26th, 2008
Fermilab
35
Bandwidth + Linearity
Readout chain shows excellent linearity from 0.1V … 1.1V @ 33 MHz readout
Analog Bandwidth is currently limited by high resistance of on-chip signal bus, will
be increased significantly with DRS4
2
2
1
0
1
-1
AMPLITUE [dB]
NONLINEARITY [mV]
ROFS = 0.95 V
BIAS = 0.70 V
0
0.5 mV max.
-1
-2
-3
-4
-5
-6
450 MHz (-3dB)
-7
-8
-9
-2
0
0.2
Feb. 26th, 2008
0.4
0.6
0.8
ANALOG OUTPUT [V]
1
-10
1.2
Fermilab
1
10
100
FREQUENCY [MHz]
36
Signal-to-noise ratio
0.52
SNR:
Crosstalk from trigger signal
ANALOG OUTPUT [V]
“Fixed pattern” offset error of 5 mV RMS
can be reduced to 0.35 mV by offset
correction in FPGA
0.51
0.5
0.49
1 V linear range / 0.35 mV = 69 dB (11.5 bits)
0.48
200
200
180
180
140
120
100
80
80
40
20
20
Feb. 26th, 2008
0.51
0
0.48
0.52
Fermilab
1000
100
40
0.5
OUTPUT VOLTAGE [V]
800
120
60
0.49
400
600
BIN NUMBER
140
60
0
0.48
200
160
OCCURENCE
Offset
Correction
160
OCCURENCE
0
0.49
0.5
OUTPUT VOLTAGE [V]
0.51
0.52
37
12 bit resolution
1
0.9
WAVEFORM [V]
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
20
40
60
80
100 120
TIME [ns]
140 160 180 200
<8 bits effective resolution
11.5 bits effective resolution
Feb. 26th, 2008
Fermilab
38
Sampling speed
6
• Unstabilized jitter: ~70ps / turn
30°C
5
• Temperature coefficient: 500ps / ºC
50°C
3
f
SAMP
[GHz]
4
2
1
0
0
0.5
1
1.5
DSPEED [V]
2
2.5
~200 psec
PLL
Vspeed
Reference
Clock (1-4 MHz)
R. Paoletti, N. Turini, R. Pegna, MAGIC collaboration
Feb. 26th, 2008
Fermilab
39
How far can we go?
• Maximal sampling speed with current technologies
• DRS4: 5.5 GHz in favor of linearity and flexibility
• 0.250 mm technology maximum: 8 GHz
• 0.130 mm technology maximum: 15 GHz
• Timing in O(10ps) region is tough
• Sampling has to be close to source (cable effect)
• TDCs can work in this region (vernier method), but what about
discriminator?
• Probably only possible with analog sampling
first
electrons
noise
Feb. 26th, 2008
threshold level
timing jitter
Fermilab
40
Timing Reference
domino wave
signal
8 inputs
20 MHz
Reference clock
Reference
clock
PMT hit
shift register
Domino stops after
trigger latency
MUX
• Calibrate inter-cell t’s for each chip
• 200 ps uncertainty using PLL
• 25 ps uncertainty for timing relative to edge
Feb. 26th, 2008
Fermilab
41
What timing can be obtained?
• Detailed studies by G. Varner1) for
LAB3 chip
• Bin-by-bin calibration using a
500 MHz sine wave
• Accuracy after calibration: 20 ps
1ns
1)
G. Varner et al., Nucl.Instrum.Meth. A583, 447 (2007)
Feb. 26th, 2008
Fermilab
42
On-chip PLL
loop filter
Simulation:
DRS4
PLL
Vspeed
Reference
Clock
fclk = fsamp / 2048
Feb. 26th, 2008
• On-chip PLL should show smaller phase jitter
• If <100ps, no clock calibration required
Fermilab
43
Comparison with other chips
MATACQ
D. Breton
LABRADOR
G. Varner
DRS3
Bandwidth (-3db)
300 MHz
> 1000 MHz
450 MHz
Sampling frequency
1 or 2 GHz
10 MHz … 3.5 GHz
10 MHz … 5 GHz
Full scale range
±0.5 V
+0.4 …2.1 V
+0.1 … 1.1V
Effective #bits
12 bit
10 bit
12 bit
Sample points
1 x 2520
9 x 256
12 x 1024
Channel per board
4
N/A
32
Digitization
5 MHz
N/A
33 MHz
Readout dead time
650 ms
150 ms
3 ms – 370 ms
Integral nonlinearity ± 0.1 %
± 0.1 %
± 0.05%
Radiation hard
No
No
Yes (chip)
Board
V1729 (CAEN)
-
planned (CAEN)
Feb. 26th, 2008
Fermilab
44
Waveform Analysis
What can we learn from acquired waveforms?
On-line waveform display
S848
PMTs
“virtual oscilloscope”
template
fit
click
pedestal
histo
Feb. 26th, 2008
Fermilab
46
QT Algorithm
t
original
waveform
Region for
pedestal
evaluation
integration area
•
Inspired by H1 Fast Track Trigger (A. Schnöning,
Desy & ETH)
•
Difference of Samples (= 1st derivation)
•
Hit region defined when DOS is above threshold
•
Integration of original signal in hit region
•
Pedestal evaluated in region before hit
•
Time interpolated using maximum value and two
neighbor values in LUT  1ns resolution for
10ns sampling time
smoothed and
differentiated
(Difference Of
Samples)
Threshold in DOS
Feb. 26th, 2008
Fermilab
47
Pulse shape discrimination
a
g
-(t - t 0 ) /τ s
-(t - t 0 )/τ d 
 -(t - t 0 ) /τi
V(t)  A e
 Be
 Ce
θ(t - t 0 )  [...]θ.. - t 0 - t r )


Leading edge
Feb. 26th, 2008
Decay time
Fermilab
AC-coupling
Reflections
48
t-distribution
ta = 21 ns
tg = 34 ns
a
Waveforms can
be clearly
distinguished
g
Feb. 26th, 2008
Fermilab
49
Coherent noise
Si Vi (t)
All PMTs
Pedestal
Charge
average
integration
• Found some coherent low frequency (~MHz) noise
• Energy resolution dramatically improved by properly
subtracting the sinusoidal background
• Usage of “dead” channels for baseline estimation
Feb. 26th, 2008
Fermilab
50
Pileup recognition
T 8ns
T 50ns
original
T 10ns
T 100ns
derivative
E1
E1  E 2
t = 15ns
E1
E2
MC simulation
T 15ns
Rule of thumb: Pileup can be detected if T ~ rise-time of signals
Feb. 26th, 2008
Fermilab
51
Crosstalk elimination
Crosstalk removal by subtracting empty channel
subtract
Hit
Feb. 26th, 2008
Hit
Fermilab
52
Spurious Noise Problem
• Found “sometimes” a high frequency
“ring” on all channels
• 40 MHz, ~20 mV, 1kHz repetition
• Finally identified the liquid xenon
pump as the source
• This noise can screw up timing
for rare events
• Without waveform digitizing, this
would have been very hard to
debug
Feb. 26th, 2008
Fermilab
53
Template Fit
• Determine “standard” PMT pulse by
averaging over many events  “Template”
p Experiment
500 MHz sampling
• Find hit in waveform
• Shift (“TDC”) and scale (“ADC”)
template to hit
• Minimize 2
• Compare fit with waveform
• Repeat if above threshold
• Store ADC & TDC values
Feb. 26th, 2008
Fermilab
54
High pass filtering
• Get rid of
baseline (low
frequency)
noise
• Improve
resolution
significantly
original
waveform
template fit
integration
area
Feb. 26th, 2008
Fermilab
after optimized high
pass FIR filter
55
Baseline Subtraction
Baseline
Subtraction
S
-
<thr
Feb. 26th, 2008
-
S
S
Latch
+
+
S
Latch
S
Latch
Latch
Latch
12 bit
Latch
100 MHz Clock
Baseline
subtracted
signal
LUT
12x12
Calibrated
and
linearized
signal
Baseline
Register
Fermilab
56
Constant Fraction Discr.
Delayed
signal
Inverted
signal
Sum
+
S
Latch
+
Latch
Latch
Latch
Latch
12 bit
Latch
Clock
<0
0
MULT
Feb. 26th, 2008
&
Fermilab
57
Data Reduction
• Zero suppression: hit if max. value > n
x s(baseline)
• Readout window: start / width in
respect to trigger
• Pile-up flag: Zero-crossings of first
derivation
• Re-binning 4:1, 8:1, 16:1
• ADC: Numerical integral of hit
over baseline
• TDC: Only simple threshold (usable to
recognize accidentals) and time-overthreshold
MEG: Applying to 94% of 100 Hz data
Keeping only 6 Hz of waveforms
Feb. 26th, 2008
0.5 ns bins
4 ns bins
TOT
Fermilab
58
Huffman encoding
15
signal
diff
Diff
Bin. Code
Huffman
-1
00
110
0
01
0
1
10
10
2
11
111
Diff
Bin. Code
Huffman
0
01
0
1
10
10
0
01
0
-1
00
110
1
10
10
0
01
0
0
01
0
-1
00
110
0
01
0
0
01
0
20
16
10
5
0
1
-5
-10
0
1
-1
2
0
0.6
0.2
10
1
110
0.2
11
111
1
0.4
0.2
S
0
Feb. 26th, 2008
Fermilab
59
Where to perform waveform analysis?
• Switching from ADC/TDC to ~GHz waveform digitization increases
amount of data by ~1000x
• Many algorithms suitable for on-board (FPGA) processing
• Charge integration and time estimation (“QT”)
• Zero-suppression, re-binning, Huffman encoding
• Basic pile-up recognition (zero-crossings of derivative)
• Algorithms for embedded CPUs or PC farms
• Inter-channel cross-talk removal
• Template fit (floating point)
DRS
Feb. 26th, 2008
FPGA
Front
End
PC
Fermilab
Off-line Analysis
60
DAQ System Principle
Liquid Xenon Calorimeter
Drift Chamber
Timing Counter
Active Splitter
VME
VME
Trigger
Event number
Event type
optical
link
(SIS3100)
Waveform
Digitizing
Trigger
Busy
Rack PC
Rack PC
Rack PC
Rack PC
Rack PC
Switch
Rack PC
Rack PC
Rack PC
Rack PC
Event Builder
Feb. 26th, 2008
Fermilab
61
Multi-threading model
Zero-copy
ring buffers
VME
Round-Robin
distribution
Calibration
Thread
Calibration
Thread
VME
Transfer
Thread
Collector
Thread
Calibration
Thread
Network
Calibration
Thread
Feb. 26th, 2008
Fermilab
62
Optimal rate with 4 calibration threads
Feb. 26th, 2008
Fermilab
63
DAQ System
• Use waveform digitization
(500 MHz/2 GHz) on all channels
• Waveform pre-analysis directly in
online cluster (zero suppression,
calibration) using multi-threading
• MIDAS DAQ Software
• Data reduction: 900 MB/s  5 MB/s
• Data amount: 100 TB/year
2000 channels
waveform digitizing
Feb. 26th, 2008
DAQ cluster
Fermilab
64
Advanced Topics
Reduced dead time, integrated triggering
“Residual charge” problem
R
After sampling a pulse, some residual
charge remains in the capacitors on the next
turn and can mimic wrong pulses
Solution: Clear before write
write
“Ghost pulse”
2% @ 2 GHz
Feb. 26th, 2008
Fermilab
clear
Implemented
in DRS4
66
ROI readout mode
delayed trigger
normal
stop
trigger stop after latency
Trigger
Delay
stop
33 MHz
e.g. 100 samples @ 33 MHz
 3 us dead time
(2.5 ns / sample @ 12 channels)
Feb. 26th, 2008
readout shift register
Patent pending!
Fermilab
67
Daisy-chaining of channels
Domino Wave Generation
1
Channel 0 – 1024 cells
1
0
Channel 1 – 1024 cells
0
1
Channel 2 – 1024 cells
1
0
0
Channel 3 – 1024 cells
0
1
Channel 4 – 1024 cells
1
0
0
Channel 5 – 1024 cells
0
1
Channel 6 – 1024 cells
1
0
0
Channel 7 – 1024 cells
0
DRS4 can be partitioned in: 8x1024, 4x2048, 2x4096, 1x8192 cells
Feb. 26th, 2008
Fermilab
68
Interleaved sampling
delays (200ps/8 = 25ps)
5 GSPS * 8 = 40 GSPS
G. Varner et al., Nucl.Instrum.Meth. A583, 447 (2007)
Feb. 26th, 2008
Fermilab
69
“Almost” Dead time free system
CMC1
16 channel
32 channel
VME board
MUX
CMC2
One board is active while other board is read out
Feb. 26th, 2008
Fermilab
70
DRS4 packaging
PIN CONFIGURATION
DGND
64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49
IN8+
1
IN8-
2
IN7+
IN7IN6+
48
47
A0
A1
3
46
A2
45
44
A3
OUT11
IN6-
4
5
6
43
IN5+
7
OUT10
OUT9
IN5-
8
IN4+
IN4-
9
PIN 1
DRS3
DRS3
TOP VIEW
(Not to Scale)
42
41
OUT8
40
OUT7
39
OUT6
OUT5
IN3-
12
38
37
IN2+
13
36
OUT3
IN2IN1+
14
35
OUT2
OUT1
MUXOUT/
OUT0
15
34
16
33
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
OUT4
IN8+
IN8IN7+
IN7IN6+
IN6IN5+
IN5IN4+
IN4IN3+
IN3IN2+
IN2IN1+
IN1-
PIN 1
DRS4
DRS3
TOP VIEW
(Not to Scale)
AGND
AVDD
BIAS
SRIN
RSRLOAD
RSRCLK
RSROUT
RSRRST
SSRLOAD
SSROUT
WSRCLK
WSROUT
IN0IN0+
AVDD
AGND
IN3+
10
11
IN1-
DRS4
flip-chip
64-Lead QFN
DGND
DVDD
IN9IN9+
IN10IN10+
IN11IN11+
ROFS
DMODE
DENABLE
DWRITE
DSPEED
DTAP
DVDD
DGND
DSPEED
DTAP
DVDD
DMODE
DENABLE
DWRITE
IN11+
ROFS
IN10+
IN11-
IN10-
DVDD
IN9IN9+
DGND
64-Lead LQFP
A0
A1
A2
A3
OUT11
OUT10
OUT9
OUT8
OUT7
OUT6
OUT5
OUT4
OUT3
OUT2
OUT1
MUXOUT/
OUT0
5 mm
AGND
AVDD
BIAS
SRIN
RSRLOAD
RSRCLK
RSROUT
RSRRST
SSRLOAD
SSROUT
WSRCLK
WSROUT
IN0-
IN0+
AVDD
AGND
9 mm
18 mm
Feb. 26th, 2008
Fermilab
71
New generation of FADCs
• 8 simultaneous flash ADCs on one chip
• Require
differential
input
• DRS4 has been
redesigned with
differential
output
Feb. 26th, 2008
Fermilab
72
Trigger an DAQ on same board
DRS4
trigger
DRS
MUX
• DRS readout (5 GHz samples)
though same 8-channel
FADCs
analog front end
• FPGA can make local trigger
(or global one) and stop DRS
upon a trigger
FADC
12 bit
65 MHz
FPGA
global trigger bus
• Using a multiplexer, input signals can simultaneously digitized at 65
MHz and sampled in the DRS
LVDS
SRAM
• Multiplexer will be included in DRS4
No splitter (signal quality!), no dedicated trigger
boards, no dedicated scalers
Feb. 26th, 2008
Fermilab
73
“Redefinition of DAQ”
Because of the high channel density of the DRS system, it becomes affordable
to use waveform digitizing in experiments which today use ADC/TCDs
Conventional
New
AC coupling
Baseline subtraction
Const. Fract. Discriminator
DOS – Zero crossing
ADC
Numerical Integration
DRS
~GHz
FADC
~100
MHz
TDC
Disc.
Scaler
ADC
Scope
Feb. 26th, 2008
Bin interpolation (LUT)
TDC
Waveform Fitting
Scaler (250 MHz)
FPGA
Scaler (50 MHz)
CPU
Oscilloscope
Waveform sampling
400 $ / channel
100 $ / channel
Fermilab
74
Availability
• DRS4 will become available in larger quantities
in summer ’08
• Chip can be obtained from PSI on a “non-profit” basis
• Delivery “as-is”
• Reference design (schematics) from PSI
• Costs ~ 10-15$/channel
• Costs decrease if we find sell more…
• Full VME board can be purchased from CAEN
probably end of ’08 with firmware for
peak sensing ADC, QDC, …
• Struck, others, … ?
Feb. 26th, 2008
Fermilab
32-channel
65 MHz/12bit digitizer
“boosted” by
DRS4 chip to 5 GHz
75
Other experiments using DRS
BPM for XFEL@PSI
Magic Telescope, Canary Islands
8 chn.
with
PGA
PET scanners
MACE Telescope
India
Feb. 26th, 2008
Fermilab
76
Conclusions
• Switched Capacitor Array techniques has prospects to trigger a
quantum step in data acquisition
• The DRS chip has been designed with maximum flexibility and can
therefore be used in many applications
• Collaboration on a scientific basis is very welcome
Datasheets, publications:
http://midas.psi.ch/drs
Feb. 26th, 2008
Fermilab
77