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HFT PIXEL Detector
Director’s review
11-13 May-2009
Wieman
1
PIXEL Work• Eric Anderssen• Mario Cepeda• Leo Greiner• Tom Johnson• Howard Matis• Hans Georg Ritter• Thorsten Stezelberger• Xiangming Sun• Michal Szelezniak • Jim Thomas• Chi Vu
ARES Corporation:Darrell BultmanSteve NeyRalph RickettsErik Swensen
2
HFT inner tracker for STARto Extract D mesons from heavy ion collisons
invariant mass
reduced combinatoric background with a precision vertex detector
3
special requirements:•low pt•high track density•must be extra thin with•excellent position resolution
HFT precision inner tracker for STAR
• Inner tracking layers– SSD
– IST
– PIXELS
• PIXELS – LBL project• PIXELS new technology
– Ultra low X0, 50 m Silicon
– monolithic silicon pixel chips
– air cooling
– rapid replacement, multiple detector copies
– pre spatially calibrated
4
One of two half cylinders
20 cm
coverage +-1
total 40 ladders
Inner layer2.5 cm radius
Outer layer8 cm radius
PIXELS
Topics
• Features of the PIXEL detector• Development of active pixel silicon detector
chips• Progress on read out and testing• Mechanical design, analysis, prototyping and
testing
5
6
Some pixel features and specificationsPointing resolution (13 22GeV/pc) m
Layers Layer 1 at 2.5 cm radiusLayer 2 at 8 cm radius
Pixel size 18.4 m X 18.4 m
Hit resolution 10 m rms
Position stability 6 m (20 m envelope)
Radiation thickness per layer
X/X0 = 0.37%
Number of pixels 436 M
Integration time (affects pileup) 0.2 ms
Radiation tolerance 300 kRad
Rapid detector replacement
< 8 Hours
criticalanddifficult
more than a factor of 2 better than other vertex detectors (ATLAS, ALICE and PHENIX)
7
Monolithic Active Pixel Sensors
• Standard commercial CMOS technology • Only NMOS transistors inside the pixels• 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 → cluster size is about ~10 pixels (20-30 μm pitch)• 100% fill-factor • Fast readout• Proven thinning to 50 micron
MAPS pixel cross-section (not to scale)
Detector chips developed by Marc Winter’s group at IPHC in Strasbourg, France
8
HFT PIXEL MAPS120 GeV π- beam test at CERN
Efficiency and Fake hit rate for Mimosa-16. 25um pixels at 20º C. This is the sensor design that is the basis for the HFT Phase-1 Pixel sensors.
Efficiency and Fake hit rate for Mimosa-22. This sensor has the same design as the final HFT Pixel sensor. This sensor has been tested to 150k rad and maintained 99.5% efficiency with < 10-4 fake hit rate.
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9
Sensor development program
Mimostar–2 30 µm pixel, 128 x 128 array3 layer telescope tested in STARMimostar–330 µm pixel, 320 x 640 array½ size chip – production
demonstrationPhase–130 µm pixel, 640 x 640 arraydigital outputfull size chip - currently being tested at LBNLFinal (Ultimate)18.4 µm pixel, 1024 x 1088 array≤ 200 µs integration timezero suppression2 digital outputs (hit addresses
only)
Sensor
Will be used in engineering run
(full system)
Gen
1
1
2
3Final pixel detector
CHIPS designed by IPHCand tested at LBNL
10
Sensor Development Status
S0 S1 S15
N Hits N Hits
-
Co
lum
n -
0
Co
lum
n -
63
Co
lum
n -
0
Co
lum
n -
63
Co
lum
n -
63
Co
lum
n -
0
A/D A/D… A/D A/D A/D A/D
…
…
…
…
…
…
…
…
S0 S1 S16
Memory with M states storage and serial transmission
Co
lum
n -
0
Co
lum
n -
63
Co
lum
n -
0
Co
lum
n -
63
Co
lum
n -
63
Co
lum
n -
0
A/D A/D… A/D A/D A/D A/D
…
…
…
…
…
…
…
…
(N states)
Priority Look-Aheadalgorithm
Selection of 9 states among 17x 9 states for each row
(N states)
Priority Look-Aheadalgorithm
(N states)
Priority Look-Aheadalgorithm
Memory 1
Memory 2
core of the zero suppression
Phase 1 [email protected] 523/11/2007
iPHC
Preliminary floor-plan
Ex. FRDO = 160 MHz Discriminator frequency = 1 MHz In pixel frequency = 16 MHz Integration time = 640 µs
Integration time = 160 / FRDO x 640
640 Discriminators
Pixel array 640x640
MUX41 LVDS FRDO
FRDO / 160
FRDO / 10(16 CK)
401 401 401 401
MUX41 LVDS MUX 41 LVDS MUX 41 LVDS
401 401 401 401 401 401 401 401 401 401 401 401 FRDO / 4
Shift Row Reg 640bits
Pixel sequencer+
Buffer tree
Simple digital pattern generator for data transfer test purpose
Disable discriminator Register
Selectable analog outputs ~ 200 µm for Pads + Electronics
Pads
Phase-1 SUZE – Zero suppression(prototype successfully tested 04/2008)
+
The overall design is in progress. IHPC has produced a smaller prototype of the final STAR pixel sensor named Mimosa-26. It is currently under test in Strasbourg. Expected delivery of the final sensor prototype is early 2010.
Final (Ultimate) – full reticle final sensor1088 x 1024 pixels, 18.4 µm pitch, 150 MHz RDO clock, column level discriminators, zero suppression circuitry, 2 outputs for address data, <200 µs integration time.
11
LVDS Data Path Testing
•Significant test of system data path at up to 200 MHz with 3 streams of pseudo-random data•Xilinx Virtex-5 IODELAY element allows fine tuning of all individual input latching in 75 ps increments. Only system jitter affects data latching.•Measured BER (bit error rate) of <10-14 for 1 m 42 AWG and 6 m twisted pair data cables at 200 MHz and for 2.3 m 42 AWG at 160 MHz.
2 ns eye patternopening for 1 m 42 AWG cables at 200 MHz
Ladder mock-up with 1-to-4 LVDS fanout buffers
Mass termination board + LU monitoring
42 AWG wires
24 AWG wires
Virtex-5 based RDO system with RORC link to PC
http://rnc.lbl.gov/hft/hardware/docs/LVDS/LVDS_test_report_1.pdf
HFT PIXEL mechanical development
12
vertex projection from two points
212
21
22
rr
rrxv
0
6.13X
pc
Mevm
1rv m detector layer 1
detector layer 2
pointing resolution = (13 22GeV/pc) m
fromdetectorpositionerror
fromcoulombscattering
r2r1
true vertexperceived vertex
x
x
v
r2r1
true vertexperceived vertex
v
m
expectations for the HFT pixels
%37.00 X
first pixel layer
more than 3 timesbetter than anyoneelse
13
Mechanical Stability
• Movement from temperature changes• Movement from humidity changes• Deflection from gravity• Vibration movement from mounts in STAR• Movement induced by cooling air
– how much air is required– vibration and static displacement
Once the pixel positions are measured will they stay in the same place to within 20 µm? Issues that must be addressed:
14
Stability requirement drives design choices
• The detector ladders are thinned silicon, on a flex kapton/aluminum cable
• The large CTE difference between silicon and kapton is a potential source of thermal induced deformation even with modest 10-15 deg C temperature swings
• Two methods of control– ALICE style carbon composite
sector support beam with large moment of inertia
– Soft decoupling adhesive bonding ladder layers
15
FEA analysis of thermally induced deformation of sector beam
• FEA shell elements• Shear force load
from ladders • 20 deg temperature
rise• Soft adhesive
coupling• 200 micron carbon
composite beam• end cap
reinforcement• Maximum
deformation 9 microns (30 microns if no end cap)
16
FEA analysis - sector beam deformation – gravity load
• FEA shell analysis• 120 micron wall
thickness composite beam
• gravity load includes ladders
• maximum structure deformation 4 microns
• ladder deformation only 0.6 microns
17
Air cooling of silicon detectors – Computational Fluid Dynamics (CFD) analysis
air flow path – flows along both inside and outside surface of the sector
• Silicon power: 100 mW/cm2 (~ power of sunlight)
• 240 W total Si + drivers
18
Air cooling – CFD analysis• air flow velocity 9-10 m/s• maximum temperature rise above
ambient: 12 deg C• sector beam surface – important
component to cooling• dynamic pressure force 1.7 times
gravity
stream lines with velocity
silicon surface temperature
velocity contours
19
air velocity probetwo positions shown
capacitance vibration probetwo positions shown
carbon fiber sector beam
wind tunnel setup to test vibration and displacement
adjustablewall for airturn around
air in
air out
C:\Documents and Settings\Howard Wieman\My Documents\aps project\mechanical\PXL phase 1 sept 2008\sector ph1 wind tunnel.SLDASM
20
wind tunnel, rapid prototype parts from model
air flow controlparts built with3D printer
parts built with SLA, stereolithography apparatus
21
Ladder vibration induced by cooling air
30m
12
20m
12
system resolution limitall errors
desired vibration target
required air velocity18 mph
0 2 4 6 8 10 120
2
4
6
8
10
measured vibration with negative pressure modemeasured vibration with positive pressure mode
Ladder Vibration
air velocity (m/s)
vibr
atio
n R
MS
(m
icro
ns)
5.77
8.66
8
no reinforcement at the end
22
measured vibration (RMS) induced by 9 m/s air flow
13 µm14 µm
14 µm
4 µm 6 µm6 µm
8 µm
3 µm3 µm
2 µm
11 µm
4 µm
openend
reinforcedend
23
prototype design being built
24
Development of sector beam and ladder fabrication
• Eric Anderssen and Tom Johnson have been working on fabrication methods for:
– Sector Beam
– and Ladders
• Produced sample beams, 244 m thick, 7 ply, 21 gm
• expected ladder mass 7.5 gm
ladders
sector beam
25
Sector structures
26
ladder fabrication and tooling
27finalizing mechanical designs and developing rapid production methods
Full sized cooling tests
Thermal camera window not shown
> 300 CFPM air flow for verification of cooling capability
Cooling tests will begin as soon as prototype sectors completed
9 inch diameter tube mocks upISC
28
conclusion
• significant progress– detector chip
development– silicon readout and
testing– mechanical design,
analysis, prototyping and testing
29