physics motivation for a thin vertex detector

Howard Matis Pixel 2005 1

A High Resolution Vertex Tracker for the STAR Experiment using Active Pixel Sensors

andRecent work using APS Sensors

A High Resolution Vertex Tracker for the STAR Experiment using Active Pixel Sensors

andRecent work using APS Sensors

F. Bieser, R. Gareus, L. Greiner, J. King, J. Levesque, H.S. Matis, M. Oldenburg, H.G. Ritter, F. Retiere, A. Rose, K. Schweda, A. Shabetai, E. Sichtermann, J.H. Thomas, H. Wieman, Lawrence Berkeley National Laboratory

S. Kleinfelder, S. Li, University of California, Irvine

H. Bichsel, University of Washington

F. Bieser, R. Gareus, L. Greiner, J. King, J. Levesque, H.S. Matis, M. Oldenburg, H.G. Ritter, F. Retiere, A. Rose, K. Schweda, A. Shabetai, E. Sichtermann, J.H. Thomas, H. Wieman, Lawrence Berkeley National Laboratory

S. Kleinfelder, S. Li, University of California, Irvine

H. Bichsel, University of Washington


physics motivation for a thin vertex detectorphysics motivation for a thin vertex detector

Study initial properties of a nuclear collision

u, d, s quarks gain mass become thermalized Final state effects Measures later/cooler

times of the collision d, b quarks produced at

early time Intrinsic mass Measure of early

collision

Study initial properties of a nuclear collision

u, d, s quarks gain mass become thermalized Final state effects Measures later/cooler

times of the collision d, b quarks produced at

early time Intrinsic mass Measure of early

collision

deconfinement

Phase and Chiral transitions

u-, d-quarks and ‘bound-states’ gain mass

PART I - DETCTOR

Need to measure particles above 0.5 GeV/c High collision density - more than 2000 tracks

Measures secondary particles >100 µm from collision point

Need to measure particles above 0.5 GeV/c High collision density - more than 2000 tracks

Measures secondary particles >100 µm from collision point


detector requirementsdetector requirements

Study D0 measurement Multiple scattering in

beam pipe sets fundamental limits

“Dream” Detector Thickness 240 µm Si

equivalent Position resolution 8

µm

Study D0 measurement Multiple scattering in

beam pipe sets fundamental limits

“Dream” Detector Thickness 240 µm Si

equivalent Position resolution 8

µm


star micro vertex detectorstar micro vertex detector

Two layers 1.5 cm radius 4.5 cm radius

24 ladders 2 cm 20 cm each < 0.3% X0

~ 100 Mega Pixels

Two layers 1.5 cm radius 4.5 cm radius

24 ladders 2 cm 20 cm each < 0.3% X0

~ 100 Mega Pixels


close-up viewclose-up view


sensorsensor

Efficiency for min ionization 98%

Accidental rate < 100 /cm2

Position resolution < 10 m

Pixel dimension 30 m 30 m

Detector chip active area 19.2 mm 19.2 mm

Detector chip pixel array 640 640

•Sensor under development at IReS•First prototype made using 0.25 µm process by TSMC•Second version in production using 0.35 µm by AMS


ladderladder

10 thinned APS detectors Top of a matching row of

thinned readout chips Three-layer aluminum

Kapton cable Silicon cable structure is

bonded to a carbon composite v, closing the beam to make a rigid structure

Wire bonding to the cable

10 thinned APS detectors Top of a matching row of

thinned readout chips Three-layer aluminum

Kapton cable Silicon cable structure is

bonded to a carbon composite v, closing the beam to make a rigid structure

Wire bonding to the cable


ladderladder2 carrier candidates – X0 =0.11 %

Top layer = 50 µm CFC

Middle layer = 3.2 mm RVC

Bottom layer = 50 µm CFC

Outer shell = 100 µm CFC (carbon fiber composite)

Fill = RVC (reticulated vitreous carbon foam)

RDO Chip

APS

Cable

Carrier


ladder prototypesladder prototypes

Mechanical Prototype with 4 MIMOSA-5 detectors glued to the Kapton cable assembly. Tested for Vibration Stiffness

• A prototype cable (Cu) has been designed, constructed and tested.

• Prototype ladder using thinned 50 µm MIMOSA-5 detectors. Currently under test with DAQ

Mechanical Prototype with 4 MIMOSA-5 detectors glued to the Kapton cable assembly. Tested for Vibration Stiffness

• A prototype cable (Cu) has been designed, constructed and tested.

• Prototype ladder using thinned 50 µm MIMOSA-5 detectors. Currently under test with DAQ


heavy flavor tracker (hft) parametersheavy flavor tracker (hft) parameters

Total number of pixels 98 106

Number of pixels per chip 640 x 640

Pixel Readout rate 100 ns

Readout time per frame 4 ms

Dynamic range of the ADC 10 bits

Raw data from one sensor using a 10 bit ADC 1 Gb/s

Fixed pattern noise 2000 e

Noise after Correlated Double Sampling 10 e

Maximum signal 900 e

Dynamic range after Correlated Double Sampling 8 bits

Total power consumption 90 W


mechanical requirementsmechanical requirements

Geometry Maintain position resolution of ~ 10 µm Low mass / radiation length (X0~ 0.3% / layer) Coverage of -1 < < 1

Function

• Easy to calibrate

• Easy to align

• Easy to remove, repair and replace electronics (ladders will need to have a local survey)

• Fit easily into the existing detector and infrastructure at STAR

Geometry Maintain position resolution of ~ 10 µm Low mass / radiation length (X0~ 0.3% / layer) Coverage of -1 < < 1

Function

• Easy to calibrate

• Easy to align

• Easy to remove, repair and replace electronics (ladders will need to have a local survey)

• Fit easily into the existing detector and infrastructure at STAR


conceptual mechanical designconceptual mechanical design

•Mounted to SVT cone

•Slides in and out on one end

•Ladders moves as beam pipe diameter increases


kinematic support structurekinematic support structure

•Support bolts unto STAR

•Green structure provides stable support for the ladder

•Three point kinematic mounts assure accurate positioning

•Can move detector in and out with reproducibility


studies with scanning electron microscopestudies with scanning electron microscope

12 µm

Access to 5 - 30 keV scanning electron microscopeThought needed to punch through 2-3 µm Believed could detect these electrons

PART II - APS RESEARCHPART II - APS RESEARCH

30 keV electrons


cross sectional view(Tilt at 520)

cross sectional view(Tilt at 520)

Pt Layer

Top of ICArtifact dueto charge

Epi-layer

Top coating


element analysiselement analysis

AlAl

TiTi

WW

PtPt

SiSi

OOGaGa


30 kev electrons do not penetrate to the epilayer30 kev electrons do not penetrate to the epilayer


can detect “electrons” with reasonable accuracy

can detect “electrons” with reasonable accuracy

Can see microscope Measuring

Bremsstrahlung Maximum intensity

~3000 /frame

Evaluate charge sharing of cell

Evaluate position resolution algorithms Best

Can see microscope Measuring

Bremsstrahlung Maximum intensity

~3000 /frame

Evaluate charge sharing of cell

Evaluate position resolution algorithms Best

µm

x3 x1

x1 x2 /2 x3


track efficiency is critical with noise leveltrack efficiency is critical with noise level

Monte Carlo study two different algorithms with MIMOSA 5 Look for seed pixels Smooth data and then

look for seed pixels Real pedestal data with

imbedded electron spectrum Efficiency algorithm

dependent Algorithm choice dependent

on noise

Monte Carlo study two different algorithms with MIMOSA 5 Look for seed pixels Smooth data and then

look for seed pixels Real pedestal data with

imbedded electron spectrum Efficiency algorithm

dependent Algorithm choice dependent

on noise


how much signal do you get out of an aps sensor?how much signal do you get out of an aps sensor?

Calculations show that energy loss in thin materials much less than thicker Bichsel & Saxon, Phys.

Rev. A 11, 1286 (1975).

Observed in aluminum Perez & Sevely, Phys.

Rev. A 16, 1061 (1977).

Calculations show that energy loss in thin materials much less than thicker Bichsel & Saxon, Phys.

Rev. A 11, 1286 (1975).

Observed in aluminum Perez & Sevely, Phys.

Rev. A 16, 1061 (1977).

Energy Deposited - eV

Landau

Bichsel & Saxon

0.76 µm Al1 MeV e-


study at lbnl advanced light sourcestudy at lbnl advanced light source

Study 1.5 GeV/c electrons

Calculated expected energy Use Bichsel formalism 0.25 µm TSMC 8 µm epitaxial layer

Need to shift theory by 1.5 for good agreement

Study 1.5 GeV/c electrons

Calculated expected energy Use Bichsel formalism 0.25 µm TSMC 8 µm epitaxial layer

Need to shift theory by 1.5 for good agreement


some checkssome checks

Epitaxial (epi) layer 8 µm (error perhaps 1 µm)

Use Bichsel formalism on 8.5 µm aluminum data 1.66 keV scales to 1.43

keV silicon (most probable)

Bichsel predicts 1.43 keV

Total systematic error 10 - 20 %

Cannot explain 50% excess

Epitaxial (epi) layer 8 µm (error perhaps 1 µm)

Use Bichsel formalism on 8.5 µm aluminum data 1.66 keV scales to 1.43

keV silicon (most probable)

Bichsel predicts 1.43 keV

Total systematic error 10 - 20 %

Cannot explain 50% excess epitaxial layer

p++

substrate

P epitaxial layer

n-wellp-well MIP


a hypothesisa hypothesis

Extra charge equivalent to 4 µm

Electrons could be coming from upper p-well and p++ substrate

Check with Mimosa-5 data (AMS 0.6 µm) Most Probable - 996 e-

Bichsel - 746 e-

Equivalent to extra 4.7 µm over nominal 14 µm

Extra charge equivalent to 4 µm

Electrons could be coming from upper p-well and p++ substrate

Check with Mimosa-5 data (AMS 0.6 µm) Most Probable - 996 e-

Bichsel - 746 e-

Equivalent to extra 4.7 µm over nominal 14 µm

p++ substrate

P epitaxial layer

n-wellp-well MIP


scaling of cell sizescaling of cell size

UCI design a multi-spacing chip 5 µm, 10 µm, 20 µm and

30 µm All cell sizes on one chip

Minimize systematic errors

Charge sharing very similar Can see small absorption of

charge in epitaxial layer Good scaling

UCI design a multi-spacing chip 5 µm, 10 µm, 20 µm and

30 µm All cell sizes on one chip

Minimize systematic errors

Charge sharing very similar Can see small absorption of

charge in epitaxial layer Good scaling

5 10

20 30

Linear Scale

5 10

20 30

Log Scale


summarysummary

Proposal for a vertex detector with APS technology Awaiting funding Transmission scanning microscopes can be used

to probe sensors Software algorithms important to get high hit

reconstruction - choice very sensitive to absolute noise

Cell scales from 5 to 30 µm More charge then expected coming from APS

Proposal for a vertex detector with APS technology Awaiting funding Transmission scanning microscopes can be used

to probe sensors Software algorithms important to get high hit

reconstruction - choice very sensitive to absolute noise

Cell scales from 5 to 30 µm More charge then expected coming from APS


A Heavy Flavor Tracker for STAR

Z. XuBrookhaven National LaboratoryY. Chen, S. Kleinfelder, A. Koohi, S. Li University of California, IrvineH. Huang, A. TaiUniversity of California, Los AngelesV. Kushpil, M. SumberaNuclear Physics Institute AS CRC. Colledani, W. Dulinski, A. Himmi, C. Hu, A. Shabetai, M. Szelezniak, I. Valin, M. WinterInstitut de Recherches Subatomique, StrasbourgM. Miller, B. Surrow, G. Van NieuwenhuizenMassachusetts Institute of TechnologyF. Bieser, R. Gareus, L. Greiner, F. Lesser, H.S. Matis, M. Oldenburg, H.G. Ritter, L. Pierpoint, F. Retiere, A. Rose, K. Schweda, E. Sichtermann, J.H. Thomas, H. Wieman, E. YamamotoLawrence Berkeley National LaboratoryI. KotovOhio State University


endend


backup slidesbackup slides


precision tie points coupling the hft system to the star support coneprecision tie points coupling the hft system to the star support cone


thin beam pipethin beam pipe

Central beryllium region 14.5 mm radius

10 beam size 500 µm thick walls

Outer region 30 mm radius aluminum

Exoskeleton caries load

Central beryllium region 14.5 mm radius

10 beam size 500 µm thick walls

Outer region 30 mm radius aluminum

Exoskeleton caries load


end view showing the hft ladders between spokes of the inner beam pipe supportend view showing the hft ladders between spokes of the inner beam pipe support


data flow and processing stages in the readout chipdata flow and processing stages in the readout chip

Each stage can be bypassed to allow raw or partially unprocessed data to be routed to the DAQ

The first stage is a CDS preprocessor which is followed by pedestal subtraction and a pixel masking filter

Further processing allows us to sum up the value of 1, 4 or 9 pixels before a threshold cut is applied.

The last stage includes zero suppression and transcoding to hit positions.

Each stage can be bypassed to allow raw or partially unprocessed data to be routed to the DAQ

The first stage is a CDS preprocessor which is followed by pedestal subtraction and a pixel masking filter

Further processing allows us to sum up the value of 1, 4 or 9 pixels before a threshold cut is applied.

The last stage includes zero suppression and transcoding to hit positions.


readout layoutreadout layout sketch of the

readout-topology on a detector ladder

one of ten APS and the corresponding readout chip layout.

sketch of the readout-topology on a detector ladder

one of ten APS and the corresponding readout chip layout.


rdo asicrdo asic

• ADC – 10 bit ADC for signals from sensor chip

• CDS – Chip will perform correlated double sampling

• High speed LVDS output

• Configuration, control, clock, synch functions

• ADC – 10 bit ADC for signals from sensor chip

• CDS – Chip will perform correlated double sampling

• High speed LVDS output

• Configuration, control, clock, synch functions

• Both chips thinned to 50 µm thickness.

• X0 = 0.053 % each


daqdaq

Figure5:

ladders can be combined to one optical link.


hit loadinghit loading Au+Au Luminosity 1 1027 cm-2s-1

dN/d (min bias) 170

Min bias cross section 10 barns

Interaction diamond size, σ

30 cm

Outer Layer Inner Layer

Radius 5 cm 1.5 cm

Hit Flux 4.3 kHz/cm2 18 kHz/cm2

Hit Density 4 ms Integration 17/cm2 72/cm2

Projected Tracking Window Area 0.6 mm2 0.15 mm2

Probability of Tracking Window Pileup

10 % 10 %

HFT Hit Resolving Area 0.001 mm2 0.001 mm2

Probability of HFT Pileup 0.14% 0.58%


Comparison with mimosa-5Comparison with mimosa-5

Parameter Detector MIMOSA-5

Detection efficiency 98% @30 – 40 C ~ 99% ≤ 20 C

resolution < 10 µm ~ 2 µm

pixel pitch) 30 µm 17 µm

Read-out time 4 – 10 ms 24 ms ( 20 ms possible)

Ionizing radiation tolerance

2.6 kRad/yr 100 kRad

Fluence tolerance 2 1010 neq/cm2 ≤ 1012 neq/cm2

Power dissipation 100 mW/cm2 ~ 10 mW/cm2

Chip size ~2 2 cm2 1.9 1.7 cm2

Chip thickness 50 m 120 m


material budgetmaterial budget

MaterialMaterial Thickness

(µm of Si)% X0

Beryllium beam pipe 500 µm of Be 0.1417

MIMOSA detector 50 0.0534

Adhesive 13 0.0143

RDO chip 50 0.0534

Adhesive 13 0.0143

Cable assembly 84 0.0896

Adhesive 13 0.0143

Carbon fiber / RVC beam 103 0.1100

Total for the ladder components

327 0.349


using an aps as a camerausing an aps as a camera

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physics motivation for a thin vertex detector