HFT PIXEL Detector

Director’s review

11-13 May-2009

Wieman

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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

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HFT inner tracker for STARto Extract D mesons from heavy ion collisons

invariant mass

reduced combinatoric background with a precision vertex detector

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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

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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

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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)

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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

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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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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

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Sensor Development Status

S0 S1 S15

N Hits N Hits

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A/D A/D… A/D A/D A/D A/D

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Memory with M states storage and serial transmission

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(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 Andrea.Brogna@IReS.in2p3.fr 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.

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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

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vertex projection from two points

212

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rr

rrxv

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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

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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:

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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

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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)

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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

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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

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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

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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

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wind tunnel, rapid prototype parts from model

air flow controlparts built with3D printer

parts built with SLA, stereolithography apparatus

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Ladder vibration induced by cooling air

30m

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20m

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system resolution limitall errors

desired vibration target

required air velocity18 mph

0 2 4 6 8 10 120

2

4

6

8

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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

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no reinforcement at the end

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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

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prototype design being built

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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

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Sector structures

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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

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conclusion

• significant progress– detector chip

development– silicon readout and

testing– mechanical design,

analysis, prototyping and testing

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