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L. Greiner 1SLAC Instrumentation – May 22, 2013
STAR HFTSTAR HFT
LBNLLeo Greiner, Eric Anderssen, Giacomo Contin,Thorsten Stezelberger, Joe Silber, Xiangming
Sun, Michal Szelezniak, Chinh Vu, Howard Wieman
UT at AustinJerry Hoffman, Jo Schambach
IPHC StrasburgMarc Winter CMOS group
A novel MAPS based vertex detector for the STAR experiment at RHIC
2SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTTalk Outline
• STAR vertex detector upgrades at RHIC.• Pixel detector requirements, design and characteristics.• Overview of detector design.• Detector development and construction flow path. Novel
sensors and mechanics.• Detector assembly, integration and installation for
engineering run.• Summary and plans.
The primary focus of this talk is technical and on instrumentation.
3SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTVertex Detector Motivation
Direct topological reconstruction of Charm
Detect charm decays with small c, including D0 K
Method: Resolve displaced vertices (100-150 microns)
200 GeV Au-Au collisions
4SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTPXL in STAR Inner Detector Upgrades
TPC – Time Projection Chamber(main tracking detector in STAR)
HFT – Heavy Flavor Tracker SSD – Silicon Strip Detector
r = 22 cm IST – Inner Silicon Tracker
r = 14 cm PXL – Pixel Detector
r = 2.5, 8 cm
We track inward from the TPC with graded resolution:
TPC SSD IST PXL~1mm ~300µm ~250µm vertex<30µm
5SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTPXL Detector Requirements and Design Choices
• -1 ≤ Eta ≤ 1, full Phi coverage (TPC coverage)• ≤ 30 µm DCA pointing resolution required for 750 MeV/c kaon
– Two or more layers with a separation of > 5 cm.– Pixel size of ≤ 30 µm– Radiation length as low as possible but should be ≤ 0.5% / layer (including
support structure). The goal is 0.37% / layer (limits MCS)• Integration time of < 200 μs (limit pile-up, occupancy of ~250 hits/inner sensor)• Sensor efficiency ≥ 99% with accidental rate ≤ 10-4.• Survive radiation environment.
• Air cooling• Thinned silicon sensors (50 μm thickness)• MAPS (Monolithic Active Pixel Sensor) pixel technology
– Sensor power dissipation ~170 mW/cm2
– Sensor integration time <200 μs (L=8×1027)• Quick detector installation or replacement (1 day)
Req
uire
men
tsD
esig
n C
hoic
es
6SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTPXL Detector Design
Mechanical support with kinematic mounts (insertion side)
Insertion from one side2 layers5 sectors / half (10 sectors total)4 ladders/sector
Aluminum conductor Ladder Flex Cable
Ladder with 10 MAPS sensors (~ 2×2 cm each)
carbon fiber sector tubes (~ 200 µm thick)
20 cm
7SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFT
2 m (42 AWG TP)11 m (24 AWG TP)
100 m (fiber optic)
Highly parallel system
4 ladders per sector 1 Mass Termination Board (MTB) per sector 1 sector per RDO board 10 RDO boards in the PXL system
RDO motherboard w/ Xilinx Virtex-6 FPGA
RDO PC with fiber link to RDO board
Mass Termination Board (signal buffering) + latch-up protected power
PXL Detector Basic Unit (RDO)
Clk, config, data, powerClk, config, data
PXL built events
Trigger, Slow control,Configuration,etc.
Existing STAR infrastructure
8SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTDetector Characteristics
Pointing resolution (12 19 GeV/pc) mLayers Layer 1 at 2.5 cm radius
Layer 2 at 8 cm radiusPixel size 20.7 m X 20.7 m Hit resolution 6 mPosition stability 6 m rms (20 m envelope)Radiation length per layer X/X0 = 0.37%Number of pixels 356 MIntegration time (affects pileup) 185.6 s
Radiation environment 20 to 90 kRad / year2*1011 to 1012 1MeV n eq/cm2
Rapid detector replacement ~ 1 day
356 M pixels on ~0.16 m2 of Silicon
L. Greiner 9SLAC Instrumentation – May 22, 2013
STAR HFT
2 2
GEANT: Realistic detector geometry + Standard STAR trackingincluding the pixel pileup hits at RHIC-II luminosity
Hand Calculation: Multiple Coulomb Scattering + Detector hit resolutionPXL telescope limit: Two PIXEL layers only, hit resolution only
Mean pT
30 m
Expected DCA resolution performance
10SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTPXL Detector Production Path (post CD – 2/3)
Sensor development
Readout development
Mechanical development
Cable development
Pre-production prototype
UltProbe tests
Infrastructure development
Ult sensorprototype
10 sensorCu+kapton pre-prod
Eng run Sector
prototype
Final Ladder readout
Final individual readout
Update mech for
size
Prod readout
production sensors
ProdProbe tests
10 sensorAl+kapton
prod
prod Sector
Eng run detector
prod detector
May 2013
Dec 2013
Culmination of >9 years of development
11SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTPXL Detector Highlights• The HFT upgrade to STAR received DOE CD-2/3 approval in
September 2011 and became a construction project.• We installed a 3 sector engineering run detector into the STAR
experiment on May 8, 2013. • The production detector is scheduled to be installed in December of
2013.
I will give a brief overview of the PXL detector design details, components and assembly in the following areas:
• Sensors• Ladders• Sectors• Detector Half• Insertion mechanics• RDO System• Engineering run
12SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFT
• Sensors
13SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFT
• Standard commercial CMOS technology
• Room temperature operation• Sensor and signal processing are
integrated in the same silicon wafer• Signal is created in the low-doped
epitaxial layer (typically ~10-15 μm) → MIP signal is limited to <1000 electrons
• Charge collection is mainly through thermal diffusion (~100 ns), reflective boundaries at p-well and substrate.
• High resistivity epi for larger depleted region → more efficient charge collection, radiation tolerance.
• 100% fill-factor • Fast readout• Proven thinning to 50 micron
MAPS pixel cross-section (not to scale)
Monolithic Active Pixel Sensors
14SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTSensor generation and RDO attributes
Pixel
Sensors CDS
ADC Data
sparsification
readout
to DAQ
analogsignals
Complementary detector readout
MimoSTAR sensors 4 ms integration time
PXL final sensors (Ultimate) < 200 μs integration time
analog
digital digital signals
Disc.
CDS
Phase-1 sensors 640 μs integration time
Sensor and RDO Development Path
9 year program with IPHC – Strasbourg, France
3 generation program with highly coupled sensor and readout development
1
2
3
15SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTPixel signal extraction and operation
GND
VDD
select
outputoutputin equilibrium
time
pote
ntia
l on
the
char
ge c
olle
ctin
g no
de
chargecollection
chargecollectingdiode
Capacitor Storage for Correlated Double Sampling (CDS)
~ 100s ms
Discriminator
Zero suppression and memory
LVDS outputs 160 MHz
1 2 3
(Sample 1 – Sample 2) > threshold => hit(Sample 2 – Sample 3) < threshold => no hit
CDS
Simplified description
O
Self-biasedconfiguration
16SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTPXL detector Ult -1/2 Sensor• Reticle size (~ 4 cm²)
• Pixel pitch 20.7 μm • 928 x 960 array ~890 k pixels
• Power dissipation ~170 mW/cm² @ 3.3V• Short integration time 185.6 μs• In pixel CDS• Discriminators at the end of each column
(each row processed in parallel)• 2 LVDS data outputs @ 160 MHz• Zero suppression and run length encoding on
rows with up to 9 hits/row.• Ping-pong memory for frame readout (~1500
hits deep)• 4 sub-arrays to help with process variation• JTAG configuration of many internal
parameters.• Individual discriminator disable, etc.• Built in automated testing routines for sensor
probe testing and characterization.• High Res Si option – significantly increases
S/N and radiation tolerance.
Developed by IPHC, Strasbourg France
17SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTUltimate 1 efficiency vs. fake hit rate
Tested for STAR Operating conditions
Developed and tested by IPHC Marc WinterCMOS GroupIPHC, Strasbourg, France
18SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFT
• Building sensors into ladders
19SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFT
• Probe card with readout electronics – derived from individual sensor test card
• Analog and digital sensor readout• Full speed readout at 160 MHz• Full sensor characterization at full speed
– Test results used for initial settings in ladder testing and PXL detector configuration
• 2nd generation for production testing– only digital readout pins loaded
Yield modeling makes probe testing critical to the goal of assembling functional 10 sensor ladders.We test thinned and diced 50 µm thick sensors (curved). This is hard.
Assembling sensors into ladders – Probe Testing
20SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTAssembling sensors into ladders – Probe Testing• Vacuum chuck for testing 20 thin
sensors (50 µm)– Thin sensors are sensitive to chuck
surface imperfections– Need a special probe pin design and
to work in clean environment• Testing up to 18 sensors per batch
– Optimized for sensor handling in 9-sensor carrier boxes
• Manual alignment (18 sensors ~ 1 hr)– Testing time is ~ 15 minutes per
sensor (3 supply voltages)
Thr
esho
ld D
AC
cou
nts (
x5)
Column number
LabW
indo
ws
GU
I
Dis
crim
inat
or T
hres
hold
21SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTPXL Sensor selection• Automated interface to a database (18 config + 68 result parameters)• Sensors are binned according to performance
Example of wafer maps for Ultimate-2 wafers with DRIE processing (ion etching)
~65% - 70% yield
22SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTAssembling sensors into ladders – Hybrid Cable• The cable is needed to deliver power and ground and provide signal routing to and from
the sensors on the ladder with minimal radiation length.• Production aluminum conductor flex cables are being fabricated in the CERN PCB shop.
(difficult to produce, only one real vendor)
Hybrid Copper / Aluminum conductor flex cable design concept
Low mass region calculated X/X0 for Al conductor = 0.079 %Low mass region calculated X/X0 for Cu conductor = 0.232 %
• 20 differential signal pairs• JTAG, 2 temp diodes, CLK, START• VDD, VDA, GND - ~1.8 A / ladder
Layout (in copper)
23SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTAssembling sensors into ladders – Assembly
• We use precision vacuum chuck fixtures to position sensors and assemble ladders.
• Sensors are positioned with butted edges. Acrylic adhesive mechanically decouples sensors from the cable and prevents CTE difference based damage.
• Weights taken at all assembly steps to track material and as QA.
Reference pins for cable/sensor alignment
24SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTAssembling sensors into ladders – Assembly
• Hybrid cable with carbon fiber stiffener plate on back in position to glue on sensors.
• The cable reference holes are used for all aspects of assembly of ladders and sectors.
25SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTAssembling sensors into ladders – Assembly
Early optimizationTesting results (ladder with 2 bad sensors)
Assembled ladder on FR-4 handling piece
Sensor noise performance only minimally degraded with all sensors running
26SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFT
• Ladders to sectors
27SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTLadders to sectors
28SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTLadders to sectors
Sector in optical metrology machine
• Sensor positions on sector are measured and related to tooling balls.
• After touch probe measurements, sectors are tested electrically for damage from metrology.
Radiation Length of active area
NOTE: Does not include sector tube side walls
30SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTsectors to detector half
Sectors are mounted in dovetail slots on detector half.Metrology is done to relate sector balls to each other and to kinematic mounts.
31SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFT
• PXL detector mechanics
32SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTPXL detector – insertion mechanics
• Unusual mechanical approach.• Cantilevered and insertable (1 day)• Pre-surveyed and mechanically stable to a level that preserves the survey.• Detector inserts and initiates a clamshell closing around beam pipe, and is
locked into position on kinematic mounts.• Cooling vibration and displacement stability, thermal stability, humidity stability.
33SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTPXL insertion mechanics
Interaction point view of the PXL insertion rails and kinematic mount points
Carbon fiber rails
Kinematic mounts
34SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTPXL insertion mechanics
PXL detector half with complete insertion mechanism
35SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFT
• RDO electronics
36SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTRead-out Electronics1. The detector is 10 parallel sector chains.2. Each sector is configured and delivers data to the RDO boards
continuously into a data pipeline.3. The receipt of a trigger opens an event buffer for 1 frame of data.
(2 actual frames with address selection performed to give one compete frame based on the time the trigger is received)
4. The data is formed into an event and shipped to the DAQ receiver PCs.
Full PXL RDO fits into 1 crate
37SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTEngineering Run
Left detector half being inserted
Right detector half being inserted
38SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTEngineering Run
PXL eng detector inserted, cabled and working in 1 day access
39SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTEngineering Run
• PXL system working with 3 sectors
• Integrated with STAR trigger, DAQ, slow controls, online event pool.
• Doing data quality checks and tweeking firmware and software.
Hit display for PXL engineering run detector.
More to come…
40SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTSummary
• The PXL detector simulations and prototyping indicate that we should be able to achieve a very high resolution and low radiation length vertex detector.
• The STAR PXL detector will be the first MAPS based vertex detector used at a collider accelerator experiment.
• We have produced and inserted a three sector prototype detector on May 8.
• Construction on the production detector is beginning. The first batch of 25 wafers of sensors has arrived and been sent for thinning.
• The final PXL detector along with the rest of the HFT upgrades will be installed for the December 2013 run.
41SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFT
• Extra slides
42SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTHFT PXL status – fabrication and tooling
43SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTMechanical Development
Silicon power: tested at 170 mW/cm2 (~ power of sunlight) 350 W total in the ladder region (Si + drivers)
computational fluid dynamics
Air-flow based cooling system for PXL to minimize material budget.
Detector mockup to study cooling efficiency
ladder region
44SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFT
Power ~340 W Airflow 10.1 m/s
Thermal camera image of sector 1 (composite image):
Mechanical Development
unsuported endmid-sectionfixed endSolid – inner layerOpen – outer layer
340 W with ambient air = 26.8 C
NTC thermistors(averaged at same “Z” position)
• Measurement results agree with simulations and meets calculated stability envelope tolerance.
• Air flow-induced vibrations (≤ 10 m/s) are within required stability window.
45SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFT
Driver section ~ 6 cm
Sensor section ~20 cm
Kapton cables with copper traces forming heaters allow us to dissipate the expected amount of power in the detector
6 NTC thermistors on each ladder
Sector 1 was equipped with 10 thinned dummy silicon chips per ladder with Pt heaters vapor deposited on top of the silicon and wire bonded to heater power.
Power ~340 W Airflow 10.1 m/s
Thermal camera image of sector 1 (composite image):
Mechanical Development
46SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTAlternate Technologies Considered
• Hybrid– X0 large (1.2%)– Pixel Size large (50 m x 450 m)– Specialized manufacturing - not readily available
• CCDs– Limited radiation tolerance– Slow frame rate, pileup issues– Specialized manufacturing
• DEPFET– Specialized manufacturing– very aggressive unproven technology
MAPS sensors are the technology selected
47SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTFast, column-parallel architecture
VREF1 PWR_ON
MOSCAP
RESET
VREF2 VDD
PWR_ON
VR1VR2
READ
CALIB
ISF
PIXEL
COLUMN CIRCUITRY
OFFSET COMPENSATED COMPARATOR
(COLUMN LEVEL CDS)
SOURCEFOLLOWER
latch
Q
Q_
READ
READ
+
+
+
+
+ +
-
- -
-
LATCH
CALIB
READ
PWR_ON
RESET
READ
CALIB
LATCH
CDS at column level (reduces Fixed Pattern Noise belowtemporal noise)
122 , inrefCsfrefCALIB VVVVVV
)( 122
122
2
ininsfref
inrefsfin
sfCinREAD
VVVV
VVVV
VVVV
VREAD,CALIB
VCVin1,2
12122
2_ 1 offRREADoffREADS VVVAV
AAV
READSoffoffRCALIBout VVVVVAAV _21112
1212 RRREADCALIBout VVVVAAV
VS_READ
A1 Voff1
A2, Voff2
Developed in IPHC - DAPNIA collaboration
L. Greiner 48SLAC Instrumentation – May 22, 2013
STAR HFTLadder 3 (separated VDA and VDD)
Results consistent with previous ladders (L1, L2)
- Faulty sensors and/or fine-wire cable issues (under investigation)
(slight improvement?)
(From previous IPHC-LBL phone meetings)
49SLAC Instrumentation – May 22, 2013L. Greiner
STAR HFTMimosa-26 in HR