pixel readout electronics - from hep to imaging to hep… status, requirements, new ideas m....
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Pixel Readout Electronics -Pixel Readout Electronics -from HEP to imaging to HEP…from HEP to imaging to HEP…
Status, requirements, new ideasStatus, requirements, new ideas
M. Campbell, R. Ballabriga, E. Heijne, X. Llopart, M. Campbell, R. Ballabriga, E. Heijne, X. Llopart,
L. Tlustos, W. Wong L. Tlustos, W. Wong
CERNCERN
Geneva, SwitzerlandGeneva, Switzerland
EUDET Annual Meeting 2007, ParisEUDET Annual Meeting 2007, Paris
OutlineOutline
BackgroundBackground TimepixTimepix
Description of circuit Demonstration with Si
Medipix3 Medipix3 Description of circuit First results
Medipix2 to Timepix to Medipix3 to … GasSiPix?Medipix2 to Timepix to Medipix3 to … GasSiPix? Requirements and possibilitiesRequirements and possibilities Summary and conclusionsSummary and conclusions
BackgroundBackground
Pixel readout developments at CERN started with LAA and Pixel readout developments at CERN started with LAA and then RD19 Collaboration – LHC R detector and Dthen RD19 Collaboration – LHC R detector and D
Work in RD19 was used directly by Omega, WA97 and NA57 Work in RD19 was used directly by Omega, WA97 and NA57 and indirectly by Delphiand indirectly by Delphi
Alice, Altas and CMS use pixel vertex detectors based on Alice, Altas and CMS use pixel vertex detectors based on hybrid pixels. (LHCb has a RICH detector using the hybrid hybrid pixels. (LHCb has a RICH detector using the hybrid pixels too) pixels too)
The Medipix1 imaging chip was a direct spin off of RD19 The Medipix1 imaging chip was a direct spin off of RD19 chipschips
The Medipix2 imaging chip was a separate development The Medipix2 imaging chip was a separate development using the same CMOS technology (0.25using the same CMOS technology (0.25m) as Alice, Altas m) as Alice, Altas and CMSand CMS
The Timepix chip (imaging and time tagging) comes directly The Timepix chip (imaging and time tagging) comes directly from Medipix2from Medipix2
Michael Campbell
From Medipix2 to TimepixFrom Medipix2 to Timepix
A novel approach for the readout of a TPC at the A novel approach for the readout of a TPC at the future linear collider is to use a CMOS pixel detector future linear collider is to use a CMOS pixel detector combined with some kind of gas gain gridcombined with some kind of gas gain grid
Using a Using a nakednaked photon counting chip Medipix2 photon counting chip Medipix2 coupled to GEMs or Micromegas demonstrated the coupled to GEMs or Micromegas demonstrated the feasibility of such approach feasibility of such approach
6 mm
2 mm
2mm
1 mm
e-
σpos
σcluster-size
14 mm
6 mm
2 mm
2mm
1 mm
e-
σpos
σcluster-size
14 mm
14.08mm
14.0
8mm
GEMMicromegas
50um
From Medipix2 to Timepix (contd)From Medipix2 to Timepix (contd)
These experiments These experiments ((by NIKHEF/Saclay, Freiburg 2004/2005 )by NIKHEF/Saclay, Freiburg 2004/2005 ) demonstrated that single electrons could be detected using a demonstrated that single electrons could be detected using a nakednaked Medipix2 chip Medipix2 chip 2D2D
Did not provide information on the arrival time of the electron in Did not provide information on the arrival time of the electron in the sensitive gas volume the sensitive gas volume 3D (position + time) !!!3D (position + time) !!!
To further exploit this approach the Medipix2 has been redesigned To further exploit this approach the Medipix2 has been redesigned to incorporate a time stamp with a tunable resolution of 100 to to incorporate a time stamp with a tunable resolution of 100 to 10ns.10ns.
Requirements:Requirements: Keep Timepix as similar as possible to Medipix2 in order to benefit from large
prior effort in R/O hardware and software Avoid major changes in pixel and/or readout logic – risk of chip failure due to
poor mixed mode modeling Eliminate 2nd threshold Add possibility of programming pixel by pixel arrival time or TOT information
This modification was supported by the JRA2/EUDET This modification was supported by the JRA2/EUDET Collaboration (www.eudet.org)Collaboration (www.eudet.org)
Timepix SchematicTimepix Schematic
Preamp
Disc
THR14 bitsShift
Register
Input
Ctest
Testbit
Test Input
Mask
4 bits thr Adj
Mux
Mux
Clk_Read
Previous Pixel
Next Pixel
Conf
8 bits configuration
Polarity
Analog Digital
Clk_Count
Timepix Synchronization
Logic
Clk_Countb
P0
P1
Shutter
Ovf Control
Clk_Read
Shutter_int
Michael Campbell
Timepix chip architectureTimepix chip architecture
IO
Logic
LVDS
In
LVDS
Out32-bit CMOS Output
256-bit Fast Shift Register35
84-b
it P
ixel
Col
umn
-035
84-b
it P
ixel
Col
umn
-0
Bandgap + 13 DACs
1612
0 m
14111 m
3584
-bit
Pix
el C
olum
n-1
3584
-bit
Pix
el C
olum
n-1
3584
-bit
Pix
el C
olum
n-2
5535
84-b
it P
ixel
Col
umn
-255
1408
0 m
(pix
el a
rray
)
Chip architecture almost identical to Chip architecture almost identical to Mpix2MXR20Mpix2MXR20
M0=M1=1 and Shutter ON -> FClock used as Ref_Clk
256x256 55µm square pixels256x256 55µm square pixels Analog Power -> 440mWAnalog Power -> 440mW Digital Power (Ref_Clk=50MHz) -> 220mWDigital Power (Ref_Clk=50MHz) -> 220mW Serial readout (@100MHz) -> 9.17 msSerial readout (@100MHz) -> 9.17 ms Parallel readout (@100MHz) -> 287 µs Parallel readout (@100MHz) -> 287 µs > 36M Transistors> 36M Transistors
Timepix Layout statusTimepix Layout status
11 22 44
55
66
33
55μm
55μm
Mpix2MXR20 layoutMpix2MXR20 layout Timepix layoutTimepix layout
11 22 44
55
66
55μm
55μm
DemonstrationDemonstration
6th June 2007.. [email protected]
Limitations of TimepixLimitations of Timepix
Charge below threshold in shared events is Charge below threshold in shared events is lost in all modeslost in all modes
Charge measurement near to threshold in Charge measurement near to threshold in TOT is impreciseTOT is imprecise
Arrival time/TOT measurement range is Arrival time/TOT measurement range is limited by counter depthlimited by counter depth
Chip is neither triggerable nor data drivenChip is neither triggerable nor data driven There is no FAST-OR There is no FAST-OR
55
The winner takes all
• Charge processed is summed in every 4 pixel cluster on an event-by-event basis
• The incoming quantum is assigned as a single hit
Medipix3 – charge summing conceptMedipix3 – charge summing concept
gm
gm
Vfbk
PolarityBitGainMode
ThAdjustBitChSummingMode
Test Input
Input Pad
TestBit
B_TH<0:3>B_TH<4>
TH1
clustercommoncontrollogic
+Arbitration
circuitry
15 bits Shift
RegisterSR1
MUX
Previous Pixel SR1
Next Pixel SR1
ModeContRWDisablePixelCom
AdjustTHHModeCS_Cluster4
ANALOG DIGITAL
Cf
Ctest
To adjacent pixels (A, B, D)x3
From adjacent pixels (F, H, I)
x2
From adjacent pixels (A, B, D)
To adjacent pixels (F, H, I)
A B CD E FG H I
BLOCK DIAGRAM PIXEL E
Disc
DiscTH2
15 bits Shift
RegisterSR2
MUX
Previous Pixel SR2
Next Pixel SR2
x1
x3
Medipix3 – pixel block diagramMedipix3 – pixel block diagram
17 October 2006 Michael Campbell
2
1 3
4
5
6 7
DIGITAL CIRCUITRY
4. Control logic (124)
5. 2x15bit counters / shift registers (480)
6. Configuration latches (152)
7. Arbitration circuits (100)
Total digital 856
ANALOG CIRCUITRY
1. Preamplifier (24)
2. Shaper (134)
3. Discriminators and Threshold Adjustment Circuits (72)
Total analog 230
55
55
Front End Operating Front End Operating ModeMode
Single Pixel Single Pixel ModeMode
Charge Charge Summing ModeSumming Mode
CSA Gain (CCSA Gain (CFF)) 11.4mV/Ke- (C11.4mV/Ke- (CFF=14fF)=14fF)
CSA-Shaper Gain CSA-Shaper Gain 65nA/Ke- (High Gain Mode), 30nA/Ke- 65nA/Ke- (High Gain Mode), 30nA/Ke- (Low Gain Mode) (Low Gain Mode)
Non linearityNon linearity <5% 9Ke- (High Gain Mode) , <2% <5% 9Ke- (High Gain Mode) , <2% 22Ke- (Low Gain Mode)22Ke- (Low Gain Mode)
Peaking TimePeaking Time ~~100ns100ns
Return to baselineReturn to baseline <1<1s for 4Ke- (nominal conditions), s for 4Ke- (nominal conditions), <300ns (tuning R<300ns (tuning RFF))
Electronic noiseElectronic noise 72e72e-- r.m.s. r.m.s. 144e144e-- r.m.s. r.m.s.
Analog power Analog power dissipationdissipation
16.216.2W (nominal conditions)W (nominal conditions)
Medipix3 prototype – electrical measurements Medipix3 prototype – electrical measurements summarysummary
The Timepix chip, although funded by EUDet, evolved from the The Timepix chip, although funded by EUDet, evolved from the successful Medipix2 developmentsuccessful Medipix2 development
The ready availability of chips and readout systems led to the initial The ready availability of chips and readout systems led to the initial experiments with gas and Medipix2 and sped up enormously the experiments with gas and Medipix2 and sped up enormously the exploitation of Timepix by the users exploitation of Timepix by the users
The future Medipix3 chip is being developed to mitigate charge sharing The future Medipix3 chip is being developed to mitigate charge sharing in single photon counting. But like its predecessor Medipix2 it should in single photon counting. But like its predecessor Medipix2 it should provide building blocks, experience or even entire readout systems provide building blocks, experience or even entire readout systems which could be reused for a future single event processing chip which could be reused for a future single event processing chip
Given the length and cost of such developments it would make sense Given the length and cost of such developments it would make sense to cluster users around a single ASIC development (technology to cluster users around a single ASIC development (technology oriented development) …oriented development) …
Summary of present statusSummary of present status
Requirements for a general purpose Requirements for a general purpose gas and semiconductor readout chipgas and semiconductor readout chip
Clean hit informationClean hit information Low and uniform thresholdLow and uniform threshold High spatial resolutionHigh spatial resolution Combined energy and arrival time informationCombined energy and arrival time information
GasSiPix - Front endGasSiPix - Front end
Medipix3 or GOSSIPO-2 likeMedipix3 or GOSSIPO-2 like Suitable for semiconductors and gas readout? Rise time 25ns? Noise 100 e- rms? Minimum threshold 750e-? Power <1W/cm2?
For gas detectors include spark protection and SiProt shieldingFor gas detectors include spark protection and SiProt shielding Which A:Si thickness? How many pC should it withstand?
Use precision time tag unit from Nikhef (GOSSIPO-2 V. Gromov) in pixel to Use precision time tag unit from Nikhef (GOSSIPO-2 V. Gromov) in pixel to measure arrival timemeasure arrival time
1-2ns precision for Vernier counter? 15-bit clock tick counter?
Use TOT for energy measurement and/or timewalk correction if charge summing Use TOT for energy measurement and/or timewalk correction if charge summing not includenot include
8-bit TOT precision?
*** Basic idea developed together with Ruud Kluit of NIKHEF ***
GasSiPix - ReadoutGasSiPix - Readout
Triggered or data initiated?Triggered or data initiated? If triggered how/when is a pixel reset Fast OR in any case?
Hit pixels only?Hit pixels only? Region of interest?Region of interest? Fast serial or parallel bus?Fast serial or parallel bus? 4 side buttable?4 side buttable? What level of rad tolerance needed (given area penalty)? What level of rad tolerance needed (given area penalty)?
Summary and Conclusions Summary and Conclusions
Medipix2 spawned TimepixMedipix2 spawned Timepix The synergy between imaging and HEP is The synergy between imaging and HEP is
evident (to me)evident (to me) Medipix3 is in full developmentMedipix3 is in full development GasSiPix is technically feasible (within limits)GasSiPix is technically feasible (within limits)
Collaboration with people with differing Collaboration with people with differing requirements requires compromises on all requirements requires compromises on all sides but the outcome can be rewarding for sides but the outcome can be rewarding for all.all.
AcknowledgementsAcknowledgements
Fellow members of the Medipix2 and Medipix3 Consortia Fellow members of the Medipix2 and Medipix3 Consortia
See: www.cern.ch/medipixSee: www.cern.ch/medipix
Stanislav Pospisil and co-workers at CTU, PragueStanislav Pospisil and co-workers at CTU, Prague